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Sample records for alumina nanoparticles composites

  1. Aluminum matrix composites reinforced with alumina nanoparticles

    CERN Document Server

    Casati, Riccardo

    2016-01-01

    This book describes the latest efforts to develop aluminum nanocomposites with enhanced damping and mechanical properties and good workability. The nanocomposites exhibited high strength, improved damping behavior and good ductility, making them suitable for use as wires. Since the production of metal matrix nanocomposites by conventional melting processes is considered extremely problematic (because of the poor wettability of the nanoparticles), different powder metallurgy routes were investigated, including high-energy ball milling and unconventional compaction methods. Special attention was paid to the structural characterization at the micro- and nanoscale, as uniform nanoparticle dispersion in metal matrix is of prime importance. The aluminum nanocomposites displayed an ultrafine microstructure reinforced with alumina nanoparticles produced in situ or added ex situ. The physical, mechanical and functional characteristics of the materials produced were evaluated using different mechanical tests and micros...

  2. Solid state reaction in alumina nanoparticles/LZSA glass-ceramic composites

    International Nuclear Information System (INIS)

    Montedo, O.K.; Oliveira, A.N. de; Raupp-Pereira, F.

    2016-01-01

    Full text: The aim of this work is to present results related to solid state reactions on LZSA glass-ceramic composites containing alumina reinforcement nano-particles. A LZSA (Li2O-ZrO2-SiO2-Al2O3) glass-ceramic has been prepared by sintering of powders and characterized. Composites containing 0 to 77 vol.% of alumina nanoparticles (27-43 nm APS, 35 m2.g-1 SSA) and a 16.9Li2O•5.0ZrO2•65.1SiO2•8.6Al2O3 glass-ceramic matrix have been prepared. X-ray diffractometry studies have been performed in order of investigating the solid state reactions occurring in LZSA-based composites. Results of the XRD patterns have been related to the coefficient of thermal expansion (CTE), Young modulus, and dielectric constant, showing that, in comparison with the glass-ceramic composition, the composites showed a decrease of CTE with the alumina concentration increasing, due to the increasing of beta-spodumeness formation (solid solution of beta-spodumene, Li2O.Al2O3.4-10SiO2). The performance of the glass-ceramic was improved with the alumina nano-particles addition, showing potential of using in the preparation of Low Thermal Co-fired Ceramics (LTCC). (author)

  3. Alumina Matrix Composites with Non-Oxide Nanoparticle Addition and Enhanced Functionalities

    Directory of Open Access Journals (Sweden)

    Dušan Galusek

    2015-01-01

    Full Text Available The addition of SiC or TiC nanoparticles to polycrystalline alumina matrix has long been known as an efficient way of improving the mechanical properties of alumina-based ceramics, especially strength, creep, and wear resistance. Recently, new types of nano-additives, such as carbon nanotubes (CNT, carbon nanofibers (CNF, and graphene sheets have been studied in order not only to improve the mechanical properties, but also to prepare materials with added functionalities, such as thermal and electrical conductivity. This paper provides a concise review of several types of alumina-based nanocomposites, evaluating the efficiency of various preparation methods and additives in terms of their influence on the properties of composites.

  4. Microstructural characterisation of electrodeposited coatings of metal matrix composite with alumina nanoparticles

    International Nuclear Information System (INIS)

    Indyka, P; Beltowska-Lehman, E; Bigos, A

    2012-01-01

    In the present work a nanocrystalline Ni-W metallic matrix was used to fabricate Ni-W/Al 2 O 3 composite coatings. The MMC (metal matrix composite) coatings with inert α-Al 2 O 3 particles (30 - 90 nm) were electrodeposited from aqueous electrolytes under direct current (DC) and controlled hydrodynamic conditions in a system with a rotating disk electrode (RDE). The chemical composition and microstructure of electrodeposited composites mainly control their functional properties; however, the particles must be uniformly dispersed to exhibit the dispersion-hardening effect. In order to increase the alumina particles incorporation as well as to promote the uniform distribution of the ceramic phase in a matrix, outer ultrasonic field was applied during electrodeposition. The influence of embedded alumina nanoparticles on structural characteristics (morphology, phase composition, residual stresses) of the resulting Ni-W/Al 2 O 3 coatings was investigated in order to obtain a nanocomposite with high hardness and relatively low residual stresses. Surface and cross-section morphology and the chemical composition of deposits was examined in the scanning electron microscope, the EDS technique was used. Microstructure and phase composition were determined by transmission electron microscopy and X-ray diffraction. Based on microstructural and micromechanical properties of the coatings, the optimum conditions for obtaining crack-free homogeneous Ni-W/Al 2 O 3 composite coatings have been determined.

  5. Alumina-Reinforced Zirconia Composites

    Science.gov (United States)

    Choi, Sung R.; Bansal, Narottam P.

    2003-01-01

    Alumina-reinforced zirconia composites, used as electrolyte materials for solid oxide fuel cells, were fabricated by hot pressing 10 mol percent yttria-stabilized zirconia (10-YSZ) reinforced with two different forms of alumina particulates and platelets each containing 0 to 30 mol percent alumina. Major mechanical and physical properties of both particulate and platelet composites including flexure strength, fracture toughness, slow crack growth, elastic modulus, density, Vickers microhardness, thermal conductivity, and microstructures were determined as a function of alumina content either at 25 C or at both 25 and 1000 C. Flexure strength and fracture toughness at 1000 C were maximized with 30 particulate and 30 mol percent platelet composites, respectively, while resistance to slow crack growth at 1000 C in air was greater for 30 mol percent platelet composite than for 30 mol percent particulate composites.

  6. Fabrication and Enhanced Thermoelectric Properties of Alumina Nanoparticle-Dispersed Bi0.5Sb1.5Te3 Matrix Composites

    Directory of Open Access Journals (Sweden)

    Kyung Tae Kim

    2013-01-01

    Full Text Available Alumina nanoparticle-dispersed bismuth-antimony-tellurium matrix (Al2O3/BST composite powders were fabricated by using ball milling process of alumina nanoparticle about 10 nm and p-type bismuth telluride nanopowders prepared from the mechanochemical process (MCP. The fabricated Al2O3/BST composite powders were a few hundreds of nanometer in size, with a clear Bi0.5Sb1.5Te3 phase. The composite powders were consolidated into p-type bulk composite by spark plasma sintering process. High-resolution TEM images reveal that alumina nanoparticles were dispersed among the grain boundary or in the matrix grain. The sintered 0.3 vol.% Al2O3/BST composite exhibited significantly improved power factor and reduced thermal conductivity in the temperature ranging from 293 to 473 K compared to those of pure BST. From these results, the highly increased ZT value of 1.5 was obtained from 0.3 vol.% Al2O3/BST composite at 323 K.

  7. Microstructure, mechanical analysis and optimal selection of 7075 aluminum alloy based composite reinforced with alumina nanoparticles

    International Nuclear Information System (INIS)

    Ezatpour, H.R.; Torabi Parizi, M.; Sajjadi, S.A.; Ebrahimi, G.R.; Chaichi, A.

    2016-01-01

    Aluminum metal-matrix nanocomposites (AMMNCs) fabricated by conventional stir-casting process usually show high porosity and poor distribution of nanoparticles within the matrix. In the current study, for the improvement of nanoparticles distribution in the aluminum matrix and enhancement of the mechanical properties, a mixture of Al/nano-Al 2 O 3 powders were injected by pure argon gas into the molten 7075 aluminum alloy and this mixture was extruded at high temperature. Mechanical behavior of the final product was investigated by tensile and compression tests, hardness measurements, Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM) and Optical Microscopy. This nanocomposite exhibited some superior properties such as a fine grain microstructure and a reasonable uniform distribution of nanoparticles in the matrix. Mechanical experiments results confirmed that the addition of Al 2 O 3 nanoparticles and the extrusion process effectively improved ultimate tensile strength, compression strength and hardness. In next step, we used a Preference Selection Index (PSI) materials selection method to select best combination of strength and workability of Al7075−Al 2 O 3 nanocomposites. By this method, extruded Al7075/0.4 and 0.8 wt % Al 2 O 3 has best combination of strength and workability. - Highlights: • Injection Al/Al 2 O 3 powder is benefit way for improving nanoparticles distribution. • Nanocomposites present superior mechanical properties. • Extrusion process improved significantly mechanical properties of nanocomposites. • Preference Selection Index is a simple and benefit method in material selection.

  8. Microstructure, mechanical analysis and optimal selection of 7075 aluminum alloy based composite reinforced with alumina nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ezatpour, H.R., E-mail: H.R.Ezatpour@gmail.com [Faculty of Engineering, Sabzevar University of New Technology, Sabzevar (Iran, Islamic Republic of); Torabi Parizi, M. [Dept. of Materials Science and Metallurgical Engineering, Engineering Faculty, Semnan University of Semnan, Semnan (Iran, Islamic Republic of); Sajjadi, S.A. [Dept. of Materials Science and Metallurgical Engineering, Engineering Faculty, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Ebrahimi, G.R. [Department of Materials and Polymer Engineering, Hakim Sabzevari University, Sabzevar (Iran, Islamic Republic of); Chaichi, A. [Dept. of Materials Science and Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

    2016-08-01

    Aluminum metal-matrix nanocomposites (AMMNCs) fabricated by conventional stir-casting process usually show high porosity and poor distribution of nanoparticles within the matrix. In the current study, for the improvement of nanoparticles distribution in the aluminum matrix and enhancement of the mechanical properties, a mixture of Al/nano-Al{sub 2}O{sub 3} powders were injected by pure argon gas into the molten 7075 aluminum alloy and this mixture was extruded at high temperature. Mechanical behavior of the final product was investigated by tensile and compression tests, hardness measurements, Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM) and Optical Microscopy. This nanocomposite exhibited some superior properties such as a fine grain microstructure and a reasonable uniform distribution of nanoparticles in the matrix. Mechanical experiments results confirmed that the addition of Al{sub 2}O{sub 3} nanoparticles and the extrusion process effectively improved ultimate tensile strength, compression strength and hardness. In next step, we used a Preference Selection Index (PSI) materials selection method to select best combination of strength and workability of Al7075−Al{sub 2}O{sub 3} nanocomposites. By this method, extruded Al7075/0.4 and 0.8 wt % Al{sub 2}O{sub 3} has best combination of strength and workability. - Highlights: • Injection Al/Al{sub 2}O{sub 3} powder is benefit way for improving nanoparticles distribution. • Nanocomposites present superior mechanical properties. • Extrusion process improved significantly mechanical properties of nanocomposites. • Preference Selection Index is a simple and benefit method in material selection.

  9. Dynamic tensile response of alumina-Al composites

    International Nuclear Information System (INIS)

    Atisivan, R.; Bandyopadhyay, A.; Gupta, Y. M.

    2002-01-01

    Plate impact experiments were carried out to examine the high strain-rate tensile response of alumina-aluminum (Al) composites with tailored microstructures. A novel processing technique was used to fabricate interpenetrating phase alumina-aluminum composites with controlled microstructures. Fused deposition modeling (FDM), a commercially available rapid prototyping technique, was used to produce the controlled porosity mullite ceramic preforms. Alumina-Al composites were then processed via reactive metal infiltration of porous mullite ceramics. With this approach, both the micro as well as the macro structures can be designed via computer aided design (CAD) to tailor the properties of the composites. Two sets of dynamic tensile experiments were performed. In the first, the metal content was varied between 23 and 39 wt. percent. In the second, the microstructure was varied while holding the metal content nearly constant. Samples with higher metal content, as expected, displayed better spall resistance. For a given metal content, samples with finer metal diameter showed better spall resistance. Relationship of the microstructural parameters on the dynamic tensile response of the structured composites is discussed here

  10. Size dependent phase and morphological transformation of alumina nanoparticles

    Science.gov (United States)

    Dommisa, D. B.; Dash, R. K.

    2018-03-01

    The size effect of the alumina nanoparticles on the phase and morphological transition by thermal treatment at various temperatures is investigated by choosing two different sizes alumina nanoparticles. Our experimental results revealed that phase and morphological transformation behavior is significantly different for smaller size alumina nanoparticles than that of larger size. The more stable alpha phase transformation occurs at a higher temperature for smaller size alumina nanoparticles in comparison to that of the larger size alumina nanoparticles. Moreover, the experimental facts also elucidated that the nucleation and growth process at the nanoscale for the phase transition is also size dependent. Our experimental result from the FESEM and TEM analysis also revealed that there is a direct correlation between phase and morphological transition of alumina nanoparticles size which is consistent with the XRD results. Therefore, we believe that our experimental findings can be extended to other complex nanomaterials for understanding the size-dependent phase and morphological transformation at the nanoscale.

  11. Processing of Alumina-Toughened Zirconia Composites

    Science.gov (United States)

    Bansal, Narottam P.; Choi, Sung R.

    2003-01-01

    Dense and crack-free 10-mol%-yttria-stabilized zirconia (10YSZ)-alumina composites, containing 0 to 30 mol% of alumina, have been fabricated by hot pressing. Release of pressure before onset of cooling was crucial in obtaining crack-free material. Hot pressing at 1600 C resulted in the formation of ZrC by reaction of zirconia with grafoil. However, no such reaction was observed at 1500 C. Cubic zirconia and -alumina were the only phases detected from x-ray diffraction indicating no chemical reaction between the composite constituents during hot pressing. Microstructure of the composites was analyzed by scanning electron microscopy and transmission electron microscopy. Density and elastic modulus of the composites followed the rule-of-mixtures. Addition of alumina to 10YSZ resulted in lighter, stronger, and stiffer composites by decreasing density and increasing strength and elastic modulus.

  12. The effect of alumina nanofillers size and shape on mechanical behavior of PMMA matrix composite

    Directory of Open Access Journals (Sweden)

    Ben Hasan Somaya Ahmed

    2014-01-01

    Full Text Available Composites with the addition of alumina nanofillers show improvement in mechanical properties. The PMMA polymer was used as a matrix and two different types of nanofillers, having extremely different shapes were added in the matrix to form the composite. Reinforcements were based on alumina nanoparticles having either spherical shape or whiskers having the length to diameter ratio of 100. The influence of alumina fillers size, shape and fillers loading on mechanical properties of prepared composite were studied using the nanoindentation measurements and dynamic mechanical analysis. It was observed that both alumina whiskers and alumina spherical nanoparticles added in the PMMA matrix improved the mechanical properties of the composite but the improvement was significantly higher with alumina whisker reinforcement. The concentration of the reinforcing alumina spherical nanoparticles and alumina whiskers in PMMA matrix varied up to 5 wt. %. The best performance was obtained by the addition of 3 wt. % of alumina whiskers in the PMMA matrix with regard to mechanical properties of the obtained composite.

  13. Viscosity of aqueous and cyanate ester suspensions containing alumina nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lawler, Katherine [Iowa State Univ., Ames, IA (United States)

    2009-01-01

    The viscosities of both aqueous and cyanate ester monomer (BECy) based suspensions of alumina nanoparticle were studied. The applications for these suspensions are different: aqueous suspensions of alumina nanoparticles are used in the production of technical ceramics made by slip casting or tape casting, and the BECy based suspensions are being developed for use in an injection-type composite repair resin. In the case of aqueous suspensions, it is advantageous to achieve a high solids content with low viscosity in order to produce a high quality product. The addition of a dispersant is useful so that higher solids content suspensions can be used with lower viscosities. For BECy suspensions, the addition of nanoparticles to the BECy resin is expected to enhance the mechanical properties of the cured composite. The addition of saccharides to aqueous suspensions leads to viscosity reduction. Through DSC measurements it was found that the saccharide molecules formed a solution with water and this resulted in lowering the melting temperature of the free water according to classic freezing point depression. Saccharides also lowered the melting temperature of the bound water, but this followed a different rule. The shear thinning and melting behaviors of the suspensions were used to develop a model based on fractal-type agglomeration. It is believed that the structure of the particle flocs in these suspensions changes with the addition of saccharides which leads to the resultant viscosity decrease. The viscosity of the BECy suspensions increased with solids content, and the viscosity increase was greater than predicted by the classical Einstein equation for dilute suspensions. Instead, the Mooney equation fits the viscosity behavior well from 0-20 vol% solids. The viscosity reduction achieved at high particle loadings by the addition of benzoic acid was also investigated by NMR. It appears that the benzoic acid interacts with the surface of the alumina particle which may

  14. Thermal Conductivity of Alumina-Toughened Zirconia Composites

    Science.gov (United States)

    Bansal, Narottam P.; Zhu, Dong-Ming

    2003-01-01

    10-mol% yttria-stabilized zirconia (10YSZ)-alumina composites containing 0 to 30 mol% alumina were fabricated by hot pressing at 1500 C in vacuum. Thermal conductivity of the composites, determined at various temperatures using a steady-state laser heat flux technique, increased with increase in alumina content. Composites containing 0, 5, and 10-mol% alumina did not show any change in thermal conductivity with temperature. However, those containing 20 and 30-mol% alumina showed a decrease in thermal conductivity with increase in temperature. The measured values of thermal conductivity were in good agreement with those calculated from simple rule of mixtures.

  15. Sintering behaviour of spinel–alumina composites

    Indian Academy of Sciences (India)

    % alumina dissolves in spinel (MgAl2O4) at 1600°C. Solid solubility of alumina in spinel decreases rapidly with decreasing temperature, which causes exsolution of alumina from spinel phase. Previous work of one of the authors revealed that ...

  16. Sintering behaviour of spinel–alumina composites

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Study of alumina–magnesia binary phase diagram reveals that around 40–50 wt% alumina dis- solves in spinel (MgAl2O4) at 1600°C. Solid solubility of alumina in spinel decreases rapidly with decreasing temperature, which causes exsolution of alumina from spinel phase. Previous work of one of the authors.

  17. Thermal Conductivity of Alumina-reinforced Zirconia Composites

    Science.gov (United States)

    Bansal, Narottam P.

    2005-01-01

    10-mol% yttria-stabilized zirconia (10SZ) - alumina composites containing 0-30 mol% alumina were fabricated by hot pressing at 1500 C in vacuum. Thermal conductivity was determined at various temperatures using a steady-state laser heat flux technique. Thermal conductivity of the composites increased with increase in alumina content. Composites containing 0, 5, and 10-mol% alumina did not show any change in thermal conductivity with temperature. However, those containing 20 and 30-mol% alumina showed a decrease in thermal conductivity with increase in temperature. The measured values of thermal conductivity were in good agreement with those calculated from the Maxwell-Eucken model where one phase is uniformly dispersed within a second major continuous phase.

  18. Fabrication of Ceramic Matrix Composite Tubes Using a Porous Mullite/Alumina Matrix and Alumina/Mullite Fiber

    National Research Council Canada - National Science Library

    Radsick, Timothy

    2001-01-01

    ... or from inadequate oxide-based ones. A porous mullite/alumina matrix combined with alumina/mullite fiber reinforcement eliminates the need for an interface coating while producing a strong, tough and oxidation resistant composite...

  19. Glycine functionalized alumina nanoparticles stabilize collagen in ...

    Indian Academy of Sciences (India)

    perse well in organic solvents rather than in water. SiO2 nanoparticles were used to crosslink the collagen and enhance the thermal stability significantly [14]. The use of functionalized iron oxide nanoparticles for collagen stabi- lization both in aqueous and non-aqueous media was in recent times [15,16]. Castaneda et al ...

  20. Glycine functionalized alumina nanoparticles stabilize collagen in ...

    Indian Academy of Sciences (India)

    2016-08-26

    Aug 26, 2016 ... ... with collagen fibres was demonstrated using HRSEM, EDX, differential scanning calorimetry and FT-IR analysis. The thermal stability of collagen is enhanced to 74°C upon interaction with Gly@Al2O3 nanoparticles thereby suggesting applications in leather making, biomedicine and cosmetic fields.

  1. Thermal stability and microstructure of catalytic alumina composite support with lanthanum species

    Science.gov (United States)

    Ozawa, Masakuni; Nishio, Yoshitoyo

    2016-09-01

    Lanthanum (La) modified γ-alumina composite was examined for application toward thermostable catalytic support at elevated temperature. La added alumina was prepared through an aqueous process using lanthanum (III) nitrate and then characterized by surface area measurement, X-ray powder diffraction (XRD), differential thermal analysis (DTA), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoemission spectroscopy (XPS) and surface desorption of CO2. It was found that the properties depended on the La content and heat treatment temperatures. The characterization of the surface, structural and chemical properties of La-Al2O3 showed the existence of a strong interaction between the La species and alumina via formation of new phase and modified surface in Al2O3 samples. LaAlO3 nanoparticle formed among alumina particles by the solid phase reaction of Al2O3 and La2O3. The increase of the surface basicity of La modified alumina was demonstrated using CO2 temperature programmed desorption experiments. The controlled surface interaction between La oxide and alumina provide the unique surface and structural properties of the resulting mixed oxides as catalysts and catalytic supports.

  2. Antimicrobial Properties of Chitosan-Alumina/f-MWCNT Nano composites

    International Nuclear Information System (INIS)

    Masheane, M.; Nthunya, L.; Malinga, S.; Masheane, M.; Nthunya, L.; Nxumalo, E.; Mhlanga, S.; Barnard, T.

    2016-01-01

    Antimicrobial chitosan-alumina/functionalized-multi walled carbon nano tube (f-MWCNT) nano composites were prepared by a simple phase inversion method. Scanning electron microscopy (SEM) analyses showed the change in the internal morphology of the composites and energy dispersive spectroscopy (EDS) confirmed the presence of alumina and f-MWCNTs in the chitosan polymer matrix. Fourier transform infrared (FTIR) spectroscopy showed the appearance of new functional groups from both alumina and f-MWCNTs, and thermogravimetric analysis (TGA) revealed that the addition of alumina and f-MWCNTs improved the thermal stability of the chitosan polymer. The presence of alumina and f-MWCNTs in the polymer matrix was found to improve the thermal stability and reduced the solubility of chitosan polymer. The prepared chitosan-alumina/f-MWCNT nano composites showed inhibition of twelve strains of bacterial strains that were tested. Thus, the nano composites show a potential for use as a biocides in water treatment for the removal of bacteria at different environmental conditions.

  3. Simple Synthesis Method for Alumina Nanoparticle

    OpenAIRE

    Daniel Damian; Florentina Cziple; Adina Segneanu; Ioan Grozescu

    2017-01-01

    Globally, the human population steady increase, expansion of urban areas, excessive industrialization including in agriculture, caused not only decrease to depletion of non-renewable resources, a rapid deterioration of the environment with negative impact on water quality, soil productivity and of course quality of life in general. This paper aims to prepare size controlled nanoparticles of aluminum oxide using a simple synthesis method. The morphology and dimensions of n...

  4. Synthesis and characterization of alumina precursor and alumina to be used as nano composite; Sintese e caracterizacao de precursores de alumina e alumina para uso em nanocompositos

    Energy Technology Data Exchange (ETDEWEB)

    Antunes, M.L.P., E-mail: malu@sorocaba.unesp.b [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Sorocaba, SP (Brazil); Santos, H. Souza [Universidade de Sao Paulo (IF/USP), SP (Brazil). Inst. de Fisica; Santos, P. Souza [Universidade de Sao Paulo (EP/USP), SP (Brazil). Escola Politecnica

    2009-07-01

    With the evolution of nanomaterials technology, mainly in the 90s, it was possible to observe produced composites with alumina matrix and nanomaterial as reinforcing materials. It results in a significant improvement of mechanical proprieties of these composites. Thenceforth the study of synthesis and characterization of nanostructured materials has attracted great scientific interest. In this perspective, the aim of this work is to present an experimental procedure to obtain nordstrandite (aluminum hydroxide) with nanometric dimensions. Nordstrandite synthesis, obtained by the reaction of slightly amalgamated aluminum foil with aqueous ethylene glycol, which allows the control of the size of crystal produced. This control could be confirmed by X-Ray Diffraction and Electron Microscopy. Thermal transformation study is also presented. This study allowed the identification of transition aluminas that have potential to produce nanometric aluminas. (author)

  5. Simple Synthesis Method for Alumina Nanoparticle

    Directory of Open Access Journals (Sweden)

    Daniel Damian

    2017-11-01

    Full Text Available Globally, the human population steady increase, expansion of urban areas, excessive industrialization including in agriculture, caused not only decrease to depletion of non-renewable resources, a rapid deterioration of the environment with negative impact on water quality, soil productivity and of course quality of life in general. This paper aims to prepare size controlled nanoparticles of aluminum oxide using a simple synthesis method. The morphology and dimensions of nanomaterial was investigated using modern analytical techniques: SEM/EDAX and XRD spectroscopy.

  6. Microstructural design in alumina-alumina/zirconia layered composites

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Herencia, A.J.; Moya, J.S. [CSIC, Madrid (Spain). Inst. de Ceramica y Vidrio; Tomsia, A.P. [Lawrence Berkeley Lab., CA (United States). Materials Sciences Div.

    1997-12-18

    Very recently several authors have pointed out the extremely important role of microstructural design in developing structural ceramic materials for long term high temperature applications. In this sense Raj has identified several boundary conditions: (1) Resistance to oxidation, (ii) Resistance to grain boundary sliding and cavitation, (iii) Good strength and toughness at room temperature. The aspiration is to eliminate grain boundaries which can act as cavitation sites, without using single crystals which typically exhibit low toughness. In this regard ceramics with single crystal-like morphologies, e.g., large elongated grains, with good fracture toughness and high bending strength have been proposed. One route to find these apparently contradictory characteristic is by building up layered microarchitectures where layers with high toughness and high bending strength coexist with layers with high creep resistance. These conditions can be met in the case of Al{sub 2}O{sub 3}/Al{sub 2}O{sub 3}-ZrO{sub 2} laminates. The present work was directed to the study of the microstructural features and properties of Al{sub 2}O{sub 3}/Al{sub 2}O{sub 3} + unstabilized ZrO{sub 2} and Al{sub 2}O{sub 3}/Al{sub 2}O{sub 3} + t-ZrO{sub 2} (3 mol% Y{sub 2}O{sub 3}) layered composites.

  7. Graphene coated with alumina and its utilization as a thermal conductivity enhancer for alumina sphere/thermoplastic polyurethane composite

    International Nuclear Information System (INIS)

    Kim, Ki Tae; Dao, Trung Dung; Jeong, Han Mo; Anjanapura, Raghu V.; Aminabhavi, Tejraj M.

    2015-01-01

    Graphene was oxidized with H 2 O 2 to introduce additional anchoring sites for effective alumina coating on graphene by the sol–gel method. The X-ray photoelectron spectroscopy studies showed that the oxygen-containing groups such as hydroxyl group useful for coating were introduced by the oxidation. The transmission electron microscopy images and thermogravimetric analysis data demonstrated that the additional anchoring sites enhanced the efficiency of the alumina coating. A small amount of alumina-coated graphene synergistically improved the thermal conductivity of the alumina sphere/thermoplastic polyurethane (TPU) composite without any increase in the electrical conductivity, because the electrical conductivity of graphene effectively decreased by the alumina coating. Moreover, the synergistic effect of a small amount of graphene was enhanced by the alumina coating, and the stiffening of the alumina sphere/TPU composite due to the added graphene was alleviated by the alumina coating. - Highlights: • Oxidation of graphene with H 2 O 2 introduced anchoring sites for alumina coating. • The anchoring sites improved the efficiency of alumina coating on graphene. • The alumina-coated graphene synergistically enhanced the thermal conductivity

  8. Lysosomes involved in the cellular toxicity of nano-alumina: combined effects of particle size and chemical composition.

    Science.gov (United States)

    Zhang, Q; Xu, L; Wang, J; Sabbioni, E; Piao, L; Di Gioacchino, M; Niu, Q

    2013-01-01

    Nowadays, manufactured nano-particles of aluminum oxide (nano-alumina) have been widely used in many fields with the rapidly developed nano-technology, but their basic toxic data are scarce. It is believed that the smaller nano-particles are able to easily cross the bio-membrane and quickly reach cellular compartments rather than micro-size particles, thus showing more toxic effects. The aim of this study was to compare the toxicity of nano- and micro- particles of alumina for detecting particle size related toxicity, and to compare the toxicity of nano-alumina and nano-carbon with the same particle size for determining chemical composition related toxicity. The present study revealed that nano-particles of alumina were much toxic than micro-alumina particles, indicating a particle size related toxicity; and were much more toxic than nano-carbon particles as well, manifesting a chemical related toxicity. The mechanism might be concerned with the involvement of the lysosomes. In conclusion, toxicity of nano-alumina is a combination of the toxic effects of its particle size and chemical composition.

  9. Macroporous silica–alumina composites with mesoporous walls

    Indian Academy of Sciences (India)

    Macroporous silica–alumina composites with mesopores have been prepared by employing polymethylmethacrylate beads as templates in the presence of the cationic surfactant, N-cetyl-N,N,N-trimethylammonium bromide. The Si/Al ratio in the composites has been varied between 4.5 and 48 and the occurrence of ...

  10. Zirconia-alumina composites of high mechanical strength

    International Nuclear Information System (INIS)

    Pyda, W.; Pyda, A.

    2004-01-01

    Commercial zirconia (stabilized with 3 mol% yttria) and alumina powders of submicron size were used to produce ceramic matrix composites in the ZrO 2 -Al 2 O 3 system. Homogeneous mixtures of both constituent powders were prepared by means pf physical mixing in water exploiting a heterofloculation effect. The mixtures were consolidated using two methods: (i). Cold isostatic pressing of the samples under 300 MPa followed by pressureless sintering in air, (ii). hot pressing under 25 MPa in argon. The samples were sintered for 2 h at 1500-1650 o C. Detailed characterization was made with respect of the powder properties, packing of the particles in green compacts and microstructure of the consolidated composites. Studied was an influence of alumina content and the consolidation method on mechanical properties of the composites. A bending strength of 17±0.2 GPa was measured for the TZP material which contained 5 vol.% of alumina particles. (author)

  11. Synergistic effect in the oxidation of benzyl alcohol using citrate-stabilized gold bimetallic nanoparticles supported on alumina

    Science.gov (United States)

    Gómez-Villarraga, Fernando; Radnik, Jörg; Martin, Andreas; Köckritz, Angela

    2016-06-01

    Bimetallic nanoparticles (NPs) containing gold and various second metals ( M = Pd, Pt, Cu, and Ag) supported on alumina (AuM/Alumina) were prepared using sodium citrate as stabilizer. In addition, supported monometallic Au/Alumina and Pd/Alumina were synthesized and tested to reveal synergistic effects in the catalytic evaluation of the bimetallic catalysts. The monometallic and bimetallic NPs revealed average sizes below 10 nm. The oxidation of benzyl alcohol with molecular oxygen as oxidant at mild conditions in liquid phase in the absence and presence (toluene or NaOH aqueous solution, 0.2 M) of a solvent was selected as test reaction to evaluate the catalytic properties of the above-mentioned solids. AuPd/Alumina exhibited the best catalytic activity among all bimetallic catalysts using toluene as solvent and under solvent-free conditions, respectively. In comparison to the monometallic catalysts, a synergistic effect with AuPd/Alumina was only evident in the solvent-free reaction. The AuPd/Alumina catalyst was able to oxidize benzyl alcohol selectively depending on the reaction medium into benzaldehyde (toluene or solvent-free) or benzoic acid (NaOH aqueous solution, 0.2 M). However, the catalyst deactivated due to particle growth of the bimetallic AuPd NPs by Ostwald ripening and leaching was not observed in the oxidation using toluene as solvent. The size of the catalytically active NPs, the metal composition of the particles, and the reaction conditions greatly influenced the catalytic oxidation results.

  12. Macroporous silica–alumina composites with mesoporous walls

    Indian Academy of Sciences (India)

    Unknown

    surfactant N-cetyl-N,N,N-trimethylammonium bromide. (CTAB). We describe the macroporous–mesoporous silica– alumina composites with satisfactory/high surface areas. 2. Experimental. Polymethylmethacrylate (PMMA) spheres of diameter. 275 nm were obtained from Soken Chemicals, Japan. These were taken as 1% ...

  13. Effect of chemical composition and alumina content on structure and ...

    Indian Academy of Sciences (India)

    Abstract. In the present work, six electrical porcelain compositions with different amount of alumina and silica have been prepared and fired in an industrial furnace at 1300 ◦C. Density, porosity, bending strength and electrical strength were measured in the samples. In order to find a relationship between properties and ...

  14. Fractography of Alumina Fibre Reinforced Ex-polysiloxane Matrix Composites

    Czech Academy of Sciences Publication Activity Database

    Rudnayová, E.; Glogar, Petr

    2002-01-01

    Roč. 223, - (2002), s. 119-124 ISSN 1013-9826. [Fractography of Advanced Ceramic s 2001. Stará Lesná, 13.05.2001-16.05.2001] R&D Projects: GA ČR GA104/00/1140; GA ČR GA106/99/0096 Institutional research plan: CEZ:AV0Z3046908 Keywords : alumina fibre * fibrous composite * fracture features Subject RIV: JI - Composite Materials Impact factor: 0.497, year: 2002

  15. Synthesis and characterization of aluminium–alumina micro- and nano-composites by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Dash, K., E-mail: khushbudash@gmail.com; Chaira, D.; Ray, B.C.

    2013-07-15

    Graphical abstract: The evolution of microstructure by varying the particle size of reinforcement in the matrix employing spark plasma sintering has been demonstrated here in Al–Al{sub 2}O{sub 3} system. An emphasis has been laid on varying the reinforcement particle size and evaluating the microstructural morphologies and their implications on mechanical performance of the composites. Nanocomposites of 0.5, 1, 3, 5, 7 volume % alumina (average size < 50 nm) reinforced in aluminium matrix were fabricated by powder metallurgy route using spark plasma sintering technique technique at a temperature of 773 K and pressure of 50 MPa. Another set of specimens having composition 1, 5, 20 vol.% of alumina (average size ∼ 10 μm) had been fabricated to compare the physical as well as mechanical attributes of the microcomposite as well as the nanocomposites. These micro- and nano-composites have been characterized using X-ray diffraction, scanning electron microscopy and transmission electron microscopy followed by density, microhardness and nanoindentation measurements. The alumina nanoparticles revealed an interface showing appreciable physical intimacy with the aluminium matrix compared to that of the alumina microparticles. The interfacial integrity in case of nanocomposites is better than in the microcomposite which has been studied using microscopic techniques. Spark plasma sintering imparts enhanced densification as well as matrix-reinforcement proximity which has been corroborated with the experimental results. - Highlights: • The Al–Al{sub 2}O{sub 3} micro- and nano-composites fabricated by spark plasma sintering. • Better matrix-reinforcement integrity in nanocomposites than microcomposites. • Spark plasma sintering method results in higher density and hardness values. • High density and hardness values of nanocomposites than microcomposites. • High dislocation density in spark plasma sintered Al–Al{sub 2}O{sub 3} composites. - Abstract: In the

  16. Synergistic effect in the oxidation of benzyl alcohol using citrate-stabilized gold bimetallic nanoparticles supported on alumina

    Energy Technology Data Exchange (ETDEWEB)

    Gómez-Villarraga, Fernando, E-mail: ferchogomezv@gmail.com; Radnik, Jörg; Martin, Andreas; Köckritz, Angela [Leibniz-Institut für Katalyse e.V. an der Universität Rostock (Germany)

    2016-06-15

    Bimetallic nanoparticles (NPs) containing gold and various second metals (M = Pd, Pt, Cu, and Ag) supported on alumina (AuM/Alumina) were prepared using sodium citrate as stabilizer. In addition, supported monometallic Au/Alumina and Pd/Alumina were synthesized and tested to reveal synergistic effects in the catalytic evaluation of the bimetallic catalysts. The monometallic and bimetallic NPs revealed average sizes below 10 nm. The oxidation of benzyl alcohol with molecular oxygen as oxidant at mild conditions in liquid phase in the absence and presence (toluene or NaOH aqueous solution, 0.2 M) of a solvent was selected as test reaction to evaluate the catalytic properties of the above-mentioned solids. AuPd/Alumina exhibited the best catalytic activity among all bimetallic catalysts using toluene as solvent and under solvent-free conditions, respectively. In comparison to the monometallic catalysts, a synergistic effect with AuPd/Alumina was only evident in the solvent-free reaction. The AuPd/Alumina catalyst was able to oxidize benzyl alcohol selectively depending on the reaction medium into benzaldehyde (toluene or solvent-free) or benzoic acid (NaOH aqueous solution, 0.2 M). However, the catalyst deactivated due to particle growth of the bimetallic AuPd NPs by Ostwald ripening and leaching was not observed in the oxidation using toluene as solvent. The size of the catalytically active NPs, the metal composition of the particles, and the reaction conditions greatly influenced the catalytic oxidation results.Graphical Abstract.

  17. Dielectric properties of alumina/zirconia composites at millimeter wavelengths

    International Nuclear Information System (INIS)

    Molla, J.; Heidinger, R.; Ibarra, A.; Link, G.

    1994-01-01

    Alumina-zirconia composites with ZrO 2 contents up to 20% and negligible porosity were investigated at millimeter (mm) wavelengths to determine the changes appearing in the dielectric properties of pure alumina ceramics when unstabilized or partially stabilized ZrO 2 is added to improve the mechanical strength. It is demonstrated that it essential to distinguish between the contributions of the monoclinic and the tetragonal phase of zirconia (m-ZrO 2 , t-ZrO 2 ). Permittivity is raised with increasing content of either phases; the effective permittivity can be assessed by the rule of mixtures (Maxwell-Garnett formulation of the generalized Clasussius-Mossotti relation) using permittivity values of 10 for Al 2 O 3 , 14-21 for m-ZrO 2 and 40-45 for t-ZrO 2 . The permittivity data show only a small variation in the investigated range of 9-145 GHz. For the dielectric loss, there is evidence of a predominant contribution of m-ZrO 2 ; in addition, the marked increase in loss with frequency becomes sharper. The t-ZrO 2 , which is responsible for strengthening, does not show any significant influence on losses. It is therefore concluded, that ZrO 2 strengthening of alumina is feasible without affecting mm-wave losses at room temperature as long as the presence of m-ZrO 2 is avoided

  18. High-frequency characteristics of glass/ceramic composite and alumina multilayer structures

    International Nuclear Information System (INIS)

    Niwa, K.; Suzuki, H.; Yokoyama, H.; Kamechara, N.; Tsubone, K.; Tanisawa, H.; Sugiki, H.

    1990-01-01

    This paper reports the transmission characteristics of glass/ceramic composite (borosilicate glass/alumina) and alumina multilayer structures examined. The triplate stripline formed in the glass/ceramic multilayer shows low conductor and dielectric loss. Alumina multilayer, however, has twice the transmission loss at 10 GHz, because the resistivity of W in the alumina multilayer is higher than the Cu in the glass/ceramic multilayer. Crosstalk between striplines in the glass/ceramics is less than -80 dB up to 11 GHz and 9 GHz for alumina

  19. Surface modification of nanoporous alumina layers by deposition of Ag nanoparticles. Effect of alumina pore diameter on the morphology of silver deposit and its influence on SERS activity

    Energy Technology Data Exchange (ETDEWEB)

    Pisarek, Marcin, E-mail: mpisarek@ichf.edu.pl [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, Warsaw, 01-224 (Poland); Nowakowski, Robert [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, Warsaw, 01-224 (Poland); Kudelski, Andrzej [Faculty of Chemistry, University of Warsaw, Pasteur 1, Warsaw, 02-093 (Poland); Holdynski, Marcin; Roguska, Agata; Janik-Czachor, Maria [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, Warsaw, 01-224 (Poland); Kurowska-Tabor, Elżbieta; Sulka, Grzegorz D. [Department of Physical Chemistry and Electrochemistry, Jagiellonian University, Ingardena 3, Cracow, 30-060 (Poland)

    2015-12-01

    Graphical abstract: - Highlights: • Magnetron sputtering of Ag is a suitable method of producing a SERS-active substrate. • Morphology of nanoporous substrate is crucial in the resulting of SERS activity. • Free Ag-NPs act as surface nanoresonators for pyridine molecules. - Abstract: Self-organized Al{sub 2}O{sub 3} nanoporous/nanotubular (Al{sub 2}O{sub 3}-NP) oxide layers decorated with silver nanoparticles (Ag-NPs) exhibiting specific properties may serve as attractive SERS substrates for investigating the interactions between an adsorbate and adsorbent, or as stable platforms for detecting various organic compounds. This article presents the influence of the size of the alumina nanopores with a deposit of silver nanoparticles obtained by the magnetron sputtering technique on the morphology of silver film. Moreover, the effect of pore diameter on the intensity of SERS spectra in Ag-NPs/Al{sub 2}O{sub 3}-NP/Al composites has also been estimated. For such investigations we used pyridine as a probe molecule, since it has a large cross-section for Raman scattering. To characterize the morphology of the composite oxide layer Ag-NPs/Al{sub 2}O{sub 3}-NP/Al, before and after deposition of Ag-NPs by PVD methods (Physical Vapor Deposition), we used scanning electron microscopy (SEM) and atomic force microscopy (AFM). The surface analytical technique of surface-enhanced Raman spectroscopy (SERS) was used to investigate the surface activity of the composite. The results obtained show that, for a carefully controlled amount of Ag (0.020 mg/cm{sup 2} - deposited on the top of alumina nanopores whose average size varies from ∼86 nm up to ∼320 nm) in the composites investigated, pore size significantly affects SERS enhancement. We obtained distinctly higher intensities of SERS spectra for substrates with an Ag-NPs deposit having a larger diameter of the alumina nanopores. AFM results suggest that both the lateral and perpendicular distribution of Ag-NPs within and on

  20. Silver nanoparticles supported on alumina-​a highly efficient and selective nanocatalyst for imine reduction

    DEFF Research Database (Denmark)

    Poreddy, Raju; Garcia-Suarez, Eduardo J.; Riisager, Anders

    2014-01-01

    organic synthesis. Due to the mild reaction conditions and high conversion as well as high selectivity, we consider that the utilization of silver nanoparticles supported on alumina represents an attractive and environmentally friendly alternative to the current synthesis of N-alkyl amines.......Silver nanoparticles supported on alumina were prepared and tested in the catalytic reduction of various imines to primary and secondary amines and were shown to be exceptionally active and chemoselective. Furthermore, the catalytic activity of the prepared nanocatalyst was also tested...

  1. Effective coating of titania nanoparticles with alumina via atomic layer deposition

    Science.gov (United States)

    Azizpour, H.; Talebi, M.; Tichelaar, F. D.; Sotudeh-Gharebagh, R.; Guo, J.; van Ommen, J. R.; Mostoufi, N.

    2017-12-01

    Alumina films were deposited on titania nanoparticles via atomic layer deposition (ALD) in a fluidized bed reactor at 180 °C and 1 bar. Online mass spectrometry was used for real time monitoring of effluent gases from the reactor during each reaction cycle in order to determine the optimal dosing time of precursors. Different oxygen sources were used to see which oxygen source, in combination with trimethyl aluminium (TMA), provides the highest alumina growth per cycle (GPC). Experiments were carried out in 4, 7 and 10 cycles using the optimal dosing time of precursors. Several characterization methods, such as high resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR), X-ray diffraction (XRD) and instrumental neutron activation analysis (INAA), were conducted on the products. Formation of the alumina film was confirmed by EDX mapping and EDX line profiling, FTIR and TEM. When using either water or deuterium oxide as the oxygen source, the thickness of the alumina film was greater than that of ozone. The average GPC measured by TEM for the ALD of TMA with water, deuterium oxide and ozone was about 0.16 nm, 0.15 nm and 0.11 nm, respectively. The average GPC calculated using the mass fraction of aluminum from INAA was close to those measured from TEM images. Excess amounts of precursors lead to a higher average growth of alumina film per cycle due to insufficient purging time. XRD analysis demonstrated that amorphous alumina was coated on titania nanoparticles. This amorphous layer was easily distinguished from the crystalline core in the TEM images. Decrease in the photocatalytic activity of titania nanoparticles after alumina coating was confirmed by measuring degradation of Rhodamine B by ultraviolet irradiation.

  2. Zirconia / Alumina Composite Foams with Calcium Phosphate Coating

    Directory of Open Access Journals (Sweden)

    Lenka Novotná

    2016-06-01

    Full Text Available In this study, mechanical properties of calcium phosphate foams were enhanced by zirconia/alumina porous cores prepared by polymer replica technique. This technique was chosen to ensure interconnected pores of optimal size for cell migration and attachment. The porosity of ZA cores (50 – 99% was controlled by multistep impregnation process, the size of pore windows was 300 – 500 μm. Sintered ZA cores were impregnated by hydroxyapatite or β-tricalcium phosphate slurry to improve bioactivity. The bone like apatite layer was formed on coatings when immersed in a simulated body fluid. Neither of tested materials was cytotoxic. Thus, the composite foam can be potentially used as a permanent substitute of cancellous bone.

  3. Interactions between SIRT1 and AP-1 reveal a mechanistic insight into the growth promoting properties of alumina (Al2O3) nanoparticles in mouse skin epithelial cells.

    Science.gov (United States)

    Dey, Swatee; Bakthavatchalu, Vasudevan; Tseng, Michael T; Wu, Peng; Florence, Rebecca L; Grulke, Eric A; Yokel, Robert A; Dhar, Sanjit Kumar; Yang, Hsin-Sheng; Chen, Yumin; St Clair, Daret K

    2008-10-01

    The physicochemical properties of nanomaterials differ from those of the bulk material of the same composition. However, little is known about the underlying effects of these particles in carcinogenesis. The purpose of this study was to determine the mechanisms involved in the carcinogenic properties of nanoparticles using aluminum oxide (Al(2)O(3)/alumina) nanoparticles as the prototype. Well-established mouse epithelial JB6 cells, sensitive to neoplastic transformation, were used as the experimental model. We demonstrate that alumina was internalized and maintained its physicochemical composition inside the cells. Alumina increased cell proliferation (53%), proliferating cell nuclear antigen (PCNA) levels, cell viability and growth in soft agar. The level of manganese superoxide dismutase, a key mitochondrial antioxidant enzyme, was elevated, suggesting a redox signaling event. In addition, the levels of reactive oxygen species and the activities of the redox sensitive transcription factor activator protein-1 (AP-1) and a longevity-related protein, sirtuin 1 (SIRT1), were increased. SIRT1 knockdown reduces DNA synthesis, cell viability, PCNA levels, AP-1 transcriptional activity and protein levels of its targets, JunD, c-Jun and BcL-xl, more than controls do. Immunoprecipitation studies revealed that SIRT1 interacts with the AP-1 components c-Jun and JunD but not with c-Fos. The results identify SIRT1 as an AP-1 modulator and suggest a novel mechanism by which alumina nanoparticles may function as a potential carcinogen.

  4. Effects of Variable Aspect-Ratio Inclusions on the Electrical Impedance of an Alumina Zirconia Composite at Intermediate Temperatures

    Science.gov (United States)

    Goldsby, Jon C.

    2010-01-01

    A series of alumina-yttria-stabilized zirconia composites containing either a high aspect ratio (5 and 30 mol%) hexagonal platelet alumina or an alumina low aspect ratio (5 and 30 mol%) spherical particulate was used to determine the effect of the aspect ratio on the temperature-dependent impedance of the composite material. The highest impedance across the temperature range of 373 to 1073 K is attributed to the grain boundary of the hexagonal platelet second phase in this alumina zirconia composite.

  5. Obtaining alumina-mullite-zirconia composites using alternative raw materials; Avaliacao microestrural de compositos alumina-mulita-zirconia preparados a partir de bauxita como fonte alternativa de alumina

    Energy Technology Data Exchange (ETDEWEB)

    Nakachima, P.M., E-mail: peter.nakachima@curimbaba.com.br [Mineracao Curimbaba Ltda, Pocos de Caldas, MG (Brazil); Universidade Federal de Sao Carlos (UFSCar), SP (Brazil); Rodrigues, J.A. [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil)

    2016-07-01

    Traditionally, ceramic composites of alumina-mullite-zirconia are obtained by the sintering of a mixture of alumina and zircon powders at temperatures above 1570°C. Due to the high purity of these raw materials, the cost of this composite is relatively high and sometimes prohibitive for certain applications. This fact motivated the development of a composite using zircon and bauxite (as an alternative source of alumina). The work herein demonstrates the feasibility of using these raw materials to obtain the desired phases, together with other contaminant phases due to the presence of other oxides in the bauxite, in addition to the SiO{sub 2} and Al{sub 2}O{sub 3}. However, the procedure used was not successful on obtaining the desired amount of ZrO{sub 2}, since the dissociation of the zircon was not complete. Composites were chemically and mineralogically characterized using the X-ray fluorescence and the Rietveld method with X-ray diffraction data, respectively, besides the scanning electron microscopy for the microstructure evaluation. (author)

  6. Zirconia toughened SiC whisker reinforced alumina composites small business innovation research

    Science.gov (United States)

    Loutfy, R. O.; Stuffle, K. L.; Withers, J. C.; Lee, C. T.

    1987-01-01

    The objective of this phase 1 project was to develop a ceramic composite with superior fracture toughness and high strength, based on combining two toughness inducing materials: zirconia for transformation toughening and SiC whiskers for reinforcement, in a controlled microstructure alumina matrix. The controlled matrix microstructure is obtained by controlling the nucleation frequency of the alumina gel with seeds (submicron alpha-alumina). The results demonstrate the technical feasibility of producing superior binary composites (Al2O3-ZrO2) and tertiary composites (Al2O3-ZrO2-SiC). Thirty-two composites were prepared, consolidated, and fracture toughness tested. Statistical analysis of the results showed that: (1) the SiC type is the key statistically significant factor for increased toughness; (2) sol-gel processing with a-alumina seed had a statistically significant effect on increasing toughness of the binary and tertiary composites compared to the corresponding mixed powder processing; and (3) ZrO2 content within the range investigated had a minor effect. Binary composites with an average critical fracture toughness of 6.6MPam sup 1/2, were obtained. Tertiary composites with critical fracture toughness in the range of 9.3 to 10.1 MPam sup 1/2 were obtained. Results indicate that these composites are superior to zirconia toughened alumina and SiC whisker reinforced alumina ceramic composites produced by conventional techniques with similar composition from published data.

  7. Atomic-scale non-contact AFM studies of alumina supported nanoparticles

    DEFF Research Database (Denmark)

    Jensen, Thomas Nørregaard; Meinander, Kristoffer; Simonsen, Søren Bredmose

    in the society today, both as the means for environmental protection and as the backbone technology for most of the chemical industries. Among important processes based on heterogeneous catalysis are biomass conversion, steam reforming of methane and the synthesis of synthetic fuel from hydrocarbons, coal...... conducting or non-conducting [2]. We use nc-AFM to study the growth, shape and size of nanoparticles on spinel and alumina surfaces. In addition to this, we have grown a transition alumina thin film on a spinel surface in order to characterize such a film as well as studying the catalytic properties...

  8. Effects of pH and calcination temperature on structural and optical properties of alumina nanoparticles

    Science.gov (United States)

    Amirsalari, A.; Farjami Shayesteh, S.

    2015-06-01

    In this study, we describe the synthesis of alumina nanoparticles using a chemical wet method in at varying pH. The optimized prepared particles with pH equals to 9 were calcined at various temperatures. For characterization of structural and optical properties of nanoparticles had been used X-ray diffraction, Infrared Fourier transform spectroscopy, field effect-scanning electron microscopy, photoluminescence and ultraviolet-visible spectroscopy. The results revealed that the nanoparticles calcined at 500 °C consist of an Al2O3 tetragonal structure and tetragonal distortion decreases with increasing calcination temperature up to 750 °C then increased with increasing temperature. Another phase similar to γ-Al2O3 was formed instead of δ-Al2O3 in the transition sequence from the γ to θ phase. FT-IR analysis; suggests that there are a few different types of functional groups on the surface of the alumina nanoparticles such as hydroxy groups and oxy groups. The transmittance spectra showed that the absorption bands in the UV region strongly depend on the calcination temperature. Moreover, the results showed that alumina has an optical direct band gap and that the energy gap decreases with increasing the calcination temperature and pH of the reaction. Luminescence spectra showed that some luminescent centers such as OH-related radiative centers and oxygen vacancies (F, F22+ and F2 centers) centers exist in the nanoparticles.

  9. Microwave-Assisted Synthesis of Alumina Nanoparticles Using Some Plants Extracts

    Directory of Open Access Journals (Sweden)

    Meisam Hasanpoor

    2017-01-01

    Full Text Available In present study we used five green plants for microwave assisted synthesis of Alumina nanoparticles from Aluminum nitrate. Structural characterization was studied using x-ray diffraction that showed semi- crystalline and possibly, amorphous structure. Fourier infrared spectroscopy was used to determine Al-O bond and functional groups responsible for synthesis of nanoparticles. FTIR confirmed existence of Al-O band and bio-functional groups, originated from plant extract. Morphology and size of nanoparticles were investigated using scanning electron microscopy, transmission electron microscopy and atomic force microscopy techniques. It was observed that nanoparticles have near-spherical shape. Average size of clusters of nanoparticles varied with different routes from of 60 nm to 300 nm. AFM images showed that Individual nanoparticles were less than 10 nm.

  10. EFFECTIVE ELASTIC PROPERTIES OF ALUMINA-ZIRCONIA COMPOSITE CERAMICS - PART 4. TENSILE MODULUS OF POROUS ALUMINA AND ZIRCONIA

    Directory of Open Access Journals (Sweden)

    W. Pabst

    2004-12-01

    Full Text Available In this fourth paper of a series on the effective elastic properties of alumina-zirconia composite ceramics the influence of porosity on the effective tensile modulus of alumina and zirconia ceramics is discussed. The examples investigated are alumina and zirconia ceramics prepared from submicron powders by starch consolidation casting using two different types of starch, potato starch (median size D50 =47.2 µm and corn starch (median size D50 =13.7 µm. The dependence of effective tensile moduli E, on the porosity f, measured for porosities in the ranges of approx. 19-55 vol.% and 10-42 vol.% for alumina and zirconia, respectively, using a resonant frequency technique, was evaluated by fitting with various model relations, including newly developed ones. A detailed comparison of the fitting results suggests the superiority of the new relation E/E0 = (1 - f·(1 - f/fC, developed by the authors (with the tensile modulus of the dense ceramic material E0 and the critical porosity fC, over most other existing fit models. Only for special purposes and well-behaved data sets the recently proposed exponential relation E/E0 = exp [-Bf/(1 - f] and the well-known Phani-Niyogi relation E/E0 = (1 - f/fCN might be preferable.

  11. Feasibility study of use alumina waste in compositions containing clay for the mullite synthesis

    International Nuclear Information System (INIS)

    Silva, V.J.; Dias, G.; Goncalves, W.P.; Santana, L.N.L.

    2016-01-01

    The reuse of alumina residue in addition to reducing environmental impacts can be used as raw material in ceramic masses to mullite produce. This study aims to obtain mullite from compositions containing clays and alumina residue used heating in a conventional oven. The raw materials were processed and characterized. Subsequently, these compositions were formulated containing precursors in appropriate proportions based on the stoichiometry of the mullite 3:2. Then, heat treatment was performed at temperatures of 1300 to 1400°C and 5°C rate/min. The products obtained were characterized by XRD, analyzing qualitatively and quantitatively the phases formed. The results showed that is possible, from compositions containing clays and alumina residue to obtain mullite as major phase (>70%) and high crystallinity (> 80%) The percentage of mullite approached the values obtained with the compositions containing alumina and clays. (author)

  12. Spark plasma sintering of ceramic matrix composite based on alumina, reinforced by carbon nanotubes

    Science.gov (United States)

    Leonov, A. A.; Khasanov, A. O.; Danchenko, V. A.; Khasanov, O. L.

    2017-12-01

    Alumina composites reinforced with 3 vol.% multi-walled carbon nanotubes (MWCNTs) were prepared by spark plasma sintering (SPS). The influence of sintering temperature (1400-1600 °C) on the composites microstructure and mechanical properties was investigated. Microstructure observations of the composite shows that some CNTs site along alumina grains boundary, while others embed into the alumina grains and shows that CNTs bonded strongly with the alumina matrix contributing to fracture toughness and microhardness increase. MWCNTs reinforcing mechanisms including CNT pull-out and crack deflection were directly observed by scanning electron microscope (SEM). For Al2O3/CNT composite sintered at 1600 °C, fracture toughness and microhardness are 4.93 MPa·m1/2 and 23.26 GPa respectively.

  13. Experimental Investigations on Tribological Behaviour of Alumina Added Acrylonitrile Butadiene Styrene (ABS Composites

    Directory of Open Access Journals (Sweden)

    T. Panneerselvam

    2016-09-01

    Full Text Available Composite materials are multifunctional in nature, which can be custom-made based on the nature of the applications. The challenge of composite materials lie on complementing the properties of one another i.e. materials which go in the making of composites strengthen each other by inhibiting their weaknesses. Polymers are one of the widely used materials which serve a wide spectrum of engineering needs. In the present work, the tribological behaviour of a composite containing Acrylonitrile Butadiene Styrene (ABS and traces of Alumina is experimentally investigated. Alumina is added to ABS in various percentages such as 1%, and 3% by weight in order to improve the wear resistance of the polymer. Central Composite Design was used to design the experiments and a standard Pin-On-Disk apparatus was used to conduct the experiments. It is observed from the test results that the addition of alumina significantly enhances the wear behavior of the polymer. However, adding more percentage of alumina has led to adverse effect on wear resistance of polymer materials. Abrasive wear mechanism is found to be predominant in the case of alumina added composite materials. It is also found that 1% alumina added composite exhibits excellent wear properties compared to other materials.

  14. Radiation degradation in the mechanical properties of Polyetheretherketone–alumina composites

    International Nuclear Information System (INIS)

    Lawrence, Falix; Mallika, C.; Kamachi Mudali, U.; Natarajan, R.; Ponraju, D.; Seshadri, S.K.; Sampath Kumar, T.S.

    2012-01-01

    Polyetheretherketone (PEEK) is extensively employed in corrosive and radiation environments. To improve the radiation tolerance of PEEK in the presence of high energetic radiation, PEEK was reinforced with micron sized alumina powder (5–25% by weight) and PEEK–alumina composite sheets fabricated were irradiated to 10 MGy. Mechanical properties of the irradiated composites revealed significant reduction in the degradation of PEEK with addition of alumina as the polymer reinforced with ceramic additives is expected to increase the interface area of the constituents in the system resulting in an improvement in the performance of the reinforced material.

  15. Agglomeration, sedimentation, and cellular toxicity of alumina nanoparticles in cell culture medium

    International Nuclear Information System (INIS)

    Yoon, Dokyung; Woo, Daekwang; Kim, Jung Heon; Kim, Moon Ki; Kim, Taesung; Hwang, Eung-Soo; Baik, Seunghyun

    2011-01-01

    The cytotoxicity of alumina nanoparticles (NPs) was investigated for a wide range of concentration (25–200 μg/mL) and incubation time (0–72 h) using floating cells (THP-1) and adherent cells (J774A.1, A549, and 293). Alumina NPs were gradually agglomerated over time although a significant portion of sedimentation occurred at the early stage within 6 h. A decrease of the viability was found in floating (THP-1) and adherent (J774A.1 and A549) cells in a dose-dependent manner. However, the time-dependent decrease in cell viability was observed only in adherent cells (J774A.1 and A549), which is predominantly related with the sedimentation of alumina NPs in cell culture medium. The uptake of alumina NPs in macrophages and an increased cell-to-cell adhesion in adherent cells were observed. There was no significant change in the viability of 293 cells. This in vitro test suggests that the agglomeration and sedimentation of alumina NPs affected cellular viability depending on cell types such as monocytes (THP-1), macrophages (J774A.1), lung carcinoma cells (A549), and embryonic kidney cells (293).

  16. Effects of pore structure and distribution on strength of porous Cu-Sn-Ti alumina composites

    Directory of Open Access Journals (Sweden)

    Biao ZHAO

    2017-12-01

    Full Text Available Porous Cu-Sn-Ti alumina composites were fabricated by sintering Cu-Sn-Ti alloy powders, graphite particles, and alumina hollow particles agent. The effects of the pore structure and distribution on the composites strength were evaluated. Different pore distributions were modeled by using finite element analysis to investigate the tensile strength of the composites. Furthermore, a fractal analysis-based box-covering algorithm was used on the Cu-Sn-Ti alumina composites topology graphs to better investigate the pore structure and distribution. Results obtained show that different sizes and concentrations of alumina hollow particles could result in different porosities from 20% to 50%. A larger pore size and a higher pore concentration reduce the strength, but provide more space for chip formation as a bonding material of a grinding wheel. The body-centered pore structure of the composites shows the highest stress under a tension load. The original composites topology graphs have been transformed to ordered distributed pore graphs based on the total pore area conservation. The information dimension magnitude difference between the original topology graphs and the ordered distributed circulars graphs is found to be linear with the Cu-Sn-Ti alumina composites strength. A larger difference renders a lower flexural strength, which indicates that uniform ordered distributed pores could benefit the composites strength. Keywords: Finite element analysis (FEA, Metal-matrix composites (MMCs, Microstructural analysis, Pore structure, Strength

  17. The ultrasonic machining of silicon carbide / alumina composites

    Science.gov (United States)

    Nicholson, Garth Martyn John

    Silicon carbide fibre reinforced alumina is a ceramic composite which was developed in conjunction with the Rolls-Royce Aerospace Group. The material is intended for use in the latest generation of jet engines, specifically for high temperature applications such as flame holders, combustor barrel segments and turbine blade tip seals. The material in question has properties which have been engineered by optimizing fibre volume fractions, weaves and fibre interface materials to meet the following main requirements : high thermal resistance, high thermal shock resistance and low density.Components intended for manufacture using this material will use the "direct metal oxidation" (DIMOX) method. This process involves manufacturing a near net shape component from the woven fibre matting, and infiltrating the matting with the alumina matrix material. Some of the components outlined require high tolerance features to be included in their design. The combustor barrel segments for example require slots to be formed within them for sealing purposes, the dimensions of these features preclude their formation using DIMOX, and therefore require a secondary process to be performed. Conventional machining techniques such as drilling, turning and milling cannot be used because of the brittle nature of the material. Electrodischarge machining (E.D.M.) cannot be used since the material is an insulator. Electrochemical machining (E.C.M.) cannot be used since the material is chemically inert. One machining method which could be used is ultrasonic machining (U.S.M.).The research programme investigated the feasibility of using ultrasonic machining as a manufacturing method for this new fibre reinforced composite. Two variations of ultrasonic machining were used : ultrasonic drilling and ultrasonic milling. Factors such as dimensional accuracy, surface roughness and delamination effects were examined. Previously performed ultrasonic machining experimental programmes were reviewed, as well

  18. Influence of current density on microstructure and properties of electrodeposited nickel-alumina composite coatings

    International Nuclear Information System (INIS)

    Góral, Anna; Nowak, Marek; Berent, Katarzyna; Kania, Bogusz

    2014-01-01

    Highlights: • Current density of the electrodeposition affects the incorporation of Al 2 O 3 in Ni matrix. • Ni/Al 2 O 3 composite coatings exhibit changes in crystallographic texture. • The pitting corrosion effects were observed in Ni/Al 2 O 3 coatings. • Residual stresses were decreased with increasing current density and coating thickness. - Abstract: Electrodeposition process is a very promising method for producing metal matrix composites reinforced with ceramic particles. In this method insoluble particles suspended in an electrolytic bath are embedded in a growing metal layer. This paper is focused on the investigations of the nickel matrix nanocomposite coatings with hard α-Al 2 O 3 nano-particles, electrochemically deposited from modified Watts-type baths on steel substrates. The influence of various current densities on the microstructure, residual stresses, texture, hardness and corrosion resistance of the deposited nickel/alumina coatings was investigated. The surface morphology, cross sections of the coatings and distribution of the ceramic particles in the metal matrix were examined by scanning electron microscopy. The phase composition, residual stresses and preferred grain orientation of the coatings were characterized using X-ray diffraction techniques. The coating morphology revealed that α-Al 2 O 3 particles show a distinct tendency to form agglomerates, approximately uniformly distributed into the nickel matrix

  19. On the drop-weight testing of alumina/aluminum laminated composites

    Indian Academy of Sciences (India)

    In this study, DWT of alumina/aluminum laminated composites was done in order to investigate the effects of lamination type, density with respect to area and mechanical property of backing material on the low velocity ballistic performance of these composites. The experimental results showed that the laminated composite ...

  20. One-pot organometallic synthesis of alumina-embedded Pd nanoparticles.

    Science.gov (United States)

    Costa, Natália J S; Vono, Lucas L R; Wojcieszak, Robert; Teixiera-Neto, Érico; Philippot, Karine; Rossi, Liane M

    2017-10-24

    Herein we report a one pot organometallic strategy to access alumina-embedded Pd nanoparticles. Unexpectedly, the decomposition of the organometallic complex tris(dibenzylideneacetone)dipalladium(0), Pd 2 (dba) 3 , by dihydrogen in the presence of aluminum isopropoxide, Al(iPrO) 3 , and without extra stabilizers, was found to be an efficient method to generate a Pd colloidal solution. Careful characterization studies revealed that the so-obtained Pd nanoparticles were stabilized by an aluminum isopropoxide tetramer and 1,5-diphenyl-pentan-3-one, which was produced after reduction of the dba ligand from the organometallic precursor. Moreover, calcination of the obtained nanomaterial in air at 773 K for 2 h resulted in a nanocomposite material containing Pd nanoparticles embedded in Al 2 O 3 . This stabilization strategy opens new possibilities for the preparation of transition metal nanoparticles embedded in oxides.

  1. Processing, structure, and mechanical properties of alumina-nanofilled polystyrene composites

    Science.gov (United States)

    Siengchin, S.

    2010-11-01

    Binary composites composed of polystyrene (PS) and a synthetic boehmite alumina were produced by using the water-mediated melt compounding (WMC) and direct melt compounding (DMC) techniques. The alumina particles were dispersed in water at ambient temperature. The aqueous alumina suspension was injected into molten PS in a twin-screw extruder to prepare reinforced polymer composites. The dispersion of the alumina was studied by transmission and scanning electron microcopy techniques (TEM and SEM, respectively). The mechanical and thermomechanical properties of the composites were determined by employing a dynamic-mechanical thermal analysis (DMTA) and short-time creep and uniaxial static tensile tests. It was found that the direct melt compounding of the alumina with PS resulted in microcomposites, whereas the water-mediated melt compounding technique gave rise to nanocomposites. The incorporation of alumina into the PS nanocomposites increased their stiffness, tensile strength, and creep resistance. However, the elongation of the PS nanocomposites at break was smaller than that of the PS microcomposites.

  2. Oxidation resistance of YSZ-alumina composites compared to normal YSZ TBC coatings at 1100 deg. C

    Energy Technology Data Exchange (ETDEWEB)

    Keyvani, A., E-mail: akeyvani@ut.ac.ir [School of Metallurgy and Materials, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Saremi, M., E-mail: saremi@ut.ac.ir [School of Metallurgy and Materials, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Sohi, M. Heydarzadeh, E-mail: mhsohi@ut.ac.ir [School of Metallurgy and Materials, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of)

    2011-08-18

    Highlights: > This work aims to study the oxidation behavior of plasma sprayed YSZ-alumina composites coatings. > The composites TBC coatings of YSZ-alumina showed better oxidation resistance than normal YSZ. > The durability of composite coating with alumina is a novel method and has not been reported before. - Abstract: In the present work oxidation behavior of plasma sprayed YSZ-alumina composite TBC coatings on Ni-base (IN-738LC) super alloy substrate was studied and compared to normal YSZ. Cyclic oxidation process in 4 h intervals was performed in an air electrical furnace at 1100 deg. C and the specimens were cooled in the furnace during each cycle. Preliminary checking was done with naked eye and further investigation was achieved using scanning electron microscopy. If there were any cracks or spallation in the coating's edge, the tests were stopped, the time was recorded and coating microstructure was studied. YSZ-alumina composites were made by applying alumina layer at the top of YSZ or mixed with YSZ as a TBC layer on the bond coat. Composite coatings of YSZ-alumina having alumina as a top coat and the mixed YSZ-alumina layer, showed better resistance than normal YSZ in oxidation test. It was observed that alumina overlay on YSZ has promoted the oxidation resistance of the coatings for longer times by preventing infiltration of oxygen through YSZ layer.

  3. Alumina and Zirconia Based Layered Composites:Part 1 Preparation

    Czech Academy of Sciences Publication Activity Database

    Hadraba, Hynek; Maca, K.; Chlup, Zdeněk

    2009-01-01

    Roč. 412, - (2009), s. 221-226 ISSN 1013-9826 R&D Projects: GA ČR(CZ) GA106/06/0724 Institutional research plan: CEZ:AV0Z20410507 Keywords : electrophoretic deposition * alumina * zirconia Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

  4. Microstructure-mechanical behaviour relationship in alumina-calcium exaluminate composites; Relaciones microestructura-comportamiento mecanico en materiales de alumina-hexaluminato calcico

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Herencia, A. J.; Moreno, R.; Baudin, C.

    2001-07-01

    The grain growth behaviour of dense alumina materials has been modified by the addition of calcium hexaluminate particles. Maximum dispersion has been obtained by colloidal processing routes. The influence of sintering temperature (1500-1600 degree centigree) on the size and shape of the alumina grains has been established. The mechanical behaviour of three composite materials with the same composition ({approx}10 vol% CA{sub 6}) and large microstructural differences has been studied in comparison with that of monophasic alumina of the same grain size. The influence of grain size and shape on toughness has been established. R-curve behaviour has been detected during fracture of the material with the alumina grains presenting the largest shape factor. (Author) 18 refs.

  5. Probing colloidal forces between a Si3N4 AFM tip and single nanoparticles of silica and alumina.

    Science.gov (United States)

    Drelich, J; Long, J; Xu, Z; Masliyah, J; White, C L

    2006-11-15

    The atomic force microscope (AFM) has been used to measure surface forces between silicon nitride AFM tips and individual nanoparticles deposited on substrates in 10(-4) and 10(-2) M KCl solutions. Silica nanoparticles (10 nm diameter) were deposited on an alumina substrate and alumina particles (5 to 80 nm diameter) were deposited on a mica substrate using aqueous suspensions. Ionic concentrations and pH were used to manage attractive substrate-particle electrostatic forces. The AFM tip was located on deposited nanoparticles using an operator controlled offset to achieve stepwise tip movements. Nanoparticles were found to have a negligible effect on long-range tip-substrate interactions, however, the forces between the tip and nanoparticle were detectable at small separations. Exponentially increasing short-range repulsive forces, attributed to the hydration forces, were observed for silica nanoparticles. The effective range of hydration forces was found to be 2-3 nm with the decay length of 0.8-1.3 nm. These parameters are in a good agreement with the results reported for macroscopic surfaces of silica obtained using the surface force apparatus suggesting that hydration forces for the silica nanoparticles are similar to those for flat silica surfaces. Hydration forces were not observed for either alumina substrates or alumina nanoparticles in both 10(-4) M KCl solution at pH 6.5 and 10(-2) M KCl at pH 10.2. Instead, strong attractive forces between the silicon nitride tip and the alumina (nanoparticles and substrate) were observed.

  6. Can zinc aluminate-titania composite be an alternative for alumina as microelectronic substrate?

    Science.gov (United States)

    Roshni, Satheesh Babu; Sebastian, Mailadil Thomas; Surendran, Kuzhichalil Peethambharan

    2017-01-13

    Alumina, thanks to its superior thermal and dielectric properties, has been the leading substrate over several decades, for power and microelectronics circuits. However, alumina lacks thermal stability since its temperature coefficient of resonant frequency (τ f ) is far from zero (-60 ppmK -1 ). The present paper explores the potentiality of a ceramic composite 0.83ZnAl 2 O 4 -0.17TiO 2 (in moles, abbreviated as ZAT) substrates for electronic applications over other commercially-used alumina-based substrates and synthesized using a non-aqueous tape casting method. The present substrate has τ f of + 3.9 ppmK -1 and is a valuable addition to the group of thermo-stable substrates. The ZAT substrate shows a high thermal conductivity of 31.3 Wm -1 K -1 (thermal conductivity of alumina is about 24.5 Wm -1 K -1 ), along with promising mechanical, electrical and microwave dielectric properties comparable to that of alumina-based commercial substrates. Furthermore, the newly-developed substrate material shows exceptionally good thermal stability of dielectric constant, which cannot be met with any of the alumina-based HTCC substrates.

  7. [Development and property study of zirconia toughened nano-composite alumina ceramic powder for dental application].

    Science.gov (United States)

    Zhao, Ke; Chao, Yong-lie; Yang, Zheng

    2003-09-01

    To prepare zirconia toughened nano-composite alumina ceramic powder for dental application. Physical and chemical property of the prepared material were tested, and the effect of development technology on composite powder was also studied in this study. Nano-composite alumina powder was prepared by surface-induced precipitation method. The effect of pH value and dispersing agent content on volume of alumina suspension sediment was recorded. The effect of ultrasonic time on agglomeration was measured also. X ray diffraction (XRD) was used to analyze powder phase before and after the stabilizer was added. Scanning electronic microscope (SEM) was applied for characterizing the specimen. The dispersion was better at pH=9 and wt (dispersing agent) = 0.2% approximately 0.3%. Selecting proper ultrasonic time can decrease the agglomeration of powders and lower the average particle size. XRD analysis indicated that the phase composition of the prepared nano-composite ceramic powder was shown as alpha-Al2O3, t-ZrO2 and a small amount of m-ZrO2 after the addition of stabilizer. Through SEM observation, nanometer-sized ZrO2 particles (80 approximately 100 nm) were uniformly located on the surface of submicrometer alumina grains. By choosing appropriate preparation method, weakly agglomerated powders with fine particle size can be obtained. The zirconia part of nano-composite powder was transmitted to partially stabled zirconia after the use of stabilizer.

  8. Magnetic field effect on nanoparticles migration and heat transfer of water/alumina nanofluid in a channel

    Energy Technology Data Exchange (ETDEWEB)

    Malvandi, A., E-mail: amirmalvandi@aut.ac.ir [Department of Mechanical Engineering, Amirkabir University of Technology (Tehran Polytechnic), 424 Hafez Avenue, Tehran (Iran, Islamic Republic of); Ganji, D.D., E-mail: ddg_davood@yahoo.com [Mechanical Engineering Department, Babol Noshirvani University of Technology, Babol (Iran, Islamic Republic of)

    2014-08-01

    The present study is a theoretical investigation of the laminar flow and convective heat transfer of water/alumina nanofluid inside a parallel-plate channel in the presence of a uniform magnetic field. A modified two-component, four-equation, nonhomogeneous equilibrium model was employed for the alumina/water nanofluid, which fully accounted for the effect of the nanoparticle volume fraction distribution. The no-slip condition of the fluid–solid interface is abandoned in favor of a slip condition which appropriately represents the non-equilibrium region near the interface at micro/nano channels. The results obtained indicated that nanoparticles move from the heated walls (nanoparticles depletion) toward the core region of the channel (nanoparticles accumulation) and construct a non-uniform nanoparticles distribution. Moreover, in the presence of the magnetic field, the near wall velocity gradients increase, enhancing the slip velocity and thus the heat transfer rate and pressure drop increase. - Highlights: • Force convection of alumina/water nanofluid inside a parallel-plate channel. • Magnetic field effects on nanoparticles' migration. • Effects of Brownian motion and thermophoresis diffusivities on nanoparticle migration. • Different mechanisms of heat transfer rate based on nanoparticles' diameter.

  9. Structural, Optical, and Electronic Characterization of Fe-Doped Alumina Nanoparticles

    Science.gov (United States)

    Heiba, Zein K.; Mohamed, Mohamed Bakr; Wahba, Adel Maher; Imam, N. G.

    2018-01-01

    The effects of iron doping on the structural, optical, and electronic properties of doped alumina have been studied. Single-phase iron-doped alumina Al2- x Fe x O3 ( x = 0.00 to 0.30) nanoparticles were synthesized via citrate-precursor method. Formation of single-phase hexagonal corundum structure with no other separate phases was demonstrated by x-ray diffraction (XRD) analysis and Fourier-transform infrared spectroscopy. The effects of iron doping on the α-Al2O3 structural parameters, viz. atomic coordinates, lattice parameters, crystallite size, and microstrain, were estimated from XRD data by applying the Rietveld profile fitting method. Transmission electron microscopy further confirmed the nanosize nature of the prepared samples with size ranging from 12 nm to 83 nm. The electronic band structure was investigated using density functional theory calculations to explain the decrease in the energy gap of Al2- x Fe x O3 as the amount of Fe was increased. The colored emission peaks in the visible region (blue, red, violet) of the electromagnetic spectrum obtained for the Fe-doped α-Al2O3 nanoparticles suggest their potential application as ceramic nanopigments.

  10. Experimental investigation of nano-alumina effect on the filling time ...

    African Journals Online (AJOL)

    In this research, by producing composite samples made of glass fibers and epoxy resin with different percentages of nanoparticles (Nano-alumina), the adding effect of nanoparticles of alumina Alpha and Gamma grade on filling time in the vacuum assistant resin transfer molding process (VARTM) is investigated. The grade ...

  11. Measurements on hydrophobic and hydrophilic surfaces using a porous gamma alumina nanoparticle aggregate mounted on Atomic Force Microscopy cantilevers

    NARCIS (Netherlands)

    Das, Theerthankar; Becker, Thomas; Nair, Balagopal N.

    2010-01-01

    Atomic Force Microscopy (AFM) measurements are extensively used for a detailed understanding of molecular and surface forces. In this study, we present a technique for measuring such forces, using an AFM cantilever attached with a porous gamma alumina nanoparticle aggregate. The modified cantilever

  12. Synthesis and Thermal Conductivity of Exfoliated Hexagonal Boron Nitride/Alumina Ceramic Composite

    Science.gov (United States)

    Hung, Ching-cheh; Hurst, Janet; Santiago, Diana; Lizcano, Maricela; Kelly, Marisabel

    2017-01-01

    Exfoliated hexagonal boron nitride (hBN)/alumina composite can be fabricated by following the process of (1) heating a mixture of hBN, AlCl3, and NaF in nitrogen for intercalation; (2) heating the intercalated product in air for exfoliation and at the same time converting the intercalate (AlCl3) into Al2O3, (3) rinsing the oxidized product, (4) coating individual exfoliated hBN platelets that contain Al2O3 with new layers of aluminum oxide, and finally, (5) hot pressing the product into the composite. The composite thus obtained has a composition of approximately 60 percent by weight hBN and 40 percent by weight alumina. Its in-plane and through-plane thermal conductivity were measured to be 86 and 18 watts per meter Kelvin, respectively, at room temperature.

  13. Alumina matrix ceramic-nickel composites formed by centrifugal slip casting

    Directory of Open Access Journals (Sweden)

    Justyna Zygmuntowicz

    2015-12-01

    Full Text Available The paper is focused on the possibility of fabricating the alumina matrix ceramic-nickel composites with gradient concentration of metal particles. Centrifugal slip casting method was chosen for the composite fabrication. This method allows fabrication of the graded distribution of nickel particles in the hollow cylinder composites. The horizontal rotation axis was applied. The samples were characterized by XRD, SEM and quantitative description of the microstructure. The macroscopic as well as SEM observations of the prepared composites confirmed the gradient concentration of Ni particles in the composite materials. The application of the centrifugal slip casting method allows for the graded distribution of metal particles in the samples.

  14. Synthesis and ceramic processing of zirconia alumina composites for application as solid oxide fuel cell electrolytes

    International Nuclear Information System (INIS)

    Garcia, Rafael Henrique Lazzari

    2007-01-01

    The global warmness and the necessity to obtain clean energy from alternative methods than petroleum raises the importance of developing cleaner and more efficient systems of energy generation, among then, the solid oxide fuel cell (SOFC). Cubic stabilized zirconia (CSZ) has been the most studied material as electrolyte in SOFC, due to its ionic conductivity and great stability at operation conditions. However, its low fracture toughness difficulties its application as a thin layer, what could lead to an improvement of cell efficiency. In this sense, the alumina addition in CSZ forms a composite, which can shift its mechanical properties, without compromising its electrical properties. In this work, coprecipitation synthesis route and ceramic processing of zirconia-alumina composites were studied, in order to establish optimum conditions to attain high density, homogeneous microstructure, and better mechanical properties than CSZ, without compromising ionic conductivity. For this purpose, composites containing up to 40 wt % of alumina, in a 9 mol % yttria-stabilized zirconia (9Y-CSZ) matrix were evaluated. In order to optimize the synthesis of the composites, a preliminary study of powder obtaining and processing were carried out, at compositions containing 20 wt % of alumina, in 9Y-CSZ. The ceramic powders were characterized by helium picnometry, X-ray diffraction, scanning electronic microscopy, transmission electronic microscopy, thermogravimetry, differential scanning calorimetry, granulometry by laser diffraction and gas adsorption (BET). The characterization of sinterized compacts were performed by X-ray diffraction, scanning electron microscopy, optical microscopy, density measurements, Vickers indentation and impedance spectroscopy. The obtained results show that the alumina addition, in the 9Y-CSZ matrix powders, raises the specific surface area, promotes deagglomeration of powders and elevates the oxides crystallization temperature, requiring higher

  15. Fabrication, microstructural characterization and wear characteristics of A380 alloy-alumina composites

    KAUST Repository

    Nurani, Sheikh Jaber

    2016-03-10

    To obtain better mechanical and tribological properties than aluminium alloys aluminium is reinforced with alumina particles making aluminium metal matrix composites. In this work scrap piston A380 alloy was used as the matrix alloy. Alumina particles were added by 5%, 10% and 15% into matrix alloy respectively to form desired composites by stir casting technique. Pin on disc wear testing machine with counter surface as steel disc of hardness HRC 32 and surface roughness of 0.62 μm was used to conduct the wear test. In result composites showed superior wear resistance property over A380 alloy. The effect of load, sliding speed and sliding distance on wear behaviour were also examined in this study. Wear mechanism was identified from the worn surface. Both optical and scanning electron microscope (SEM) of the composites was performed to determine the microstructures. Optical micrograph shows grain size decreases with addition of alumina particles. EDS analysis was performed to confirm the presence of α-Al matrix, primary Si particles and intermetallic. As a general method, phase compositions were analyzed by using a scanning electron microscope (SEM) equipped with an energy dispersive spectroscopy (EDS). Optical microstructures were consistent with the SEM micrographs. © 2015 IEEE.

  16. Viscoelastic behaviour and fracture toughness of linear-low-density polyethylene reinforced with synthetic boehmite alumina nanoparticles

    Directory of Open Access Journals (Sweden)

    D. Pedrazzoli

    2013-08-01

    Full Text Available Aim of the present study is to investigate how synthetic boehmite alumina (BA nanoparticles modify the viscoleastic and fracture behaviour of linear low-density polyethylene. Nanocomposites containing up to 8 wt% of untreated and octyl silane-functionalized BA nanoparticles, were prepared by melt compounding and hot pressing. The BA nanoparticles were finely and unformly dispersed within the matrix according to scanning electron microscopy inspection. The results of quasi-static tensile tests indicated that nanoparticles can provide a remarkable stiffening effect at a rather low filler content. Short term creep tests showed that creep stability was significatively improved by nanofiller incorporation. Concurrently, both storage and loss moduli were enhanced in all nanocomposites, showing better result for surface treated nanoparticles. The plane-stress fracture toughness, evaluated by the essential work of fracture approach, manifested a dramatic increase (up to 64% with the BA content, with no significant differences among the various types of BA nanoparticles.

  17. Alternative Processing Method Leads to Stronger Sapphire-Reinforced Alumina Composites

    Science.gov (United States)

    Jaskowiak, Martha H.

    1997-01-01

    The development of advanced engines for aerospace applications depends on the availability of strong, tough materials that can withstand increasingly higher temperatures under oxidizing conditions. The need for such materials led to the study of an oxide-based composite composed of an alumina matrix reinforced with zirconia-coated sapphire fibers. Because the nonbrittle behavior of this system depends on the interface and its ability to prevent fiber-to-matrix bonding and reduce interfacial shear stress, the microstructure of the zirconia must be carefully controlled during both coating application and composite processing. When it was both porous and unstabilized, zirconia (which does not react easily with alumina) was found to be the most effective material tested in reducing interfacial shear strength between the fiber and matrix.

  18. Preparation and characterization of porous alumina-zirconia composite ceramics

    Czech Academy of Sciences Publication Activity Database

    Pabst, W.; Gregorová, E.; Sedlářová, I.; Černý, Martin

    2011-01-01

    Roč. 31, č. 14 (2011), s. 2721-2731 ISSN 0955-2219. [International Conference on Ceramic Processing Science /11./. Zürich, 29.08.2010-01.09.2010] Institutional research plan: CEZ:AV0Z30460519 Keywords : sintering * slip casting * composites Subject RIV: JI - Composite Materials Impact factor: 2.353, year: 2011

  19. Mechanical, thermal, and fire properties of biodegradable polylactide/boehmite alumina composites

    CSIR Research Space (South Africa)

    Das, K

    2013-05-01

    Full Text Available -Smith‡ †Department of Applied Chemistry, University of Johannesburg, Doornforntein 2028, Johannesburg, South Africa ‡DST/CSIR National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, Pretoria 0001, South Africa §Polymer... and Composites, Materials Science and Manufacturing, Council for Scientific and Industrial Research, Port Elizabeth 6000, South Africa Abstract Boehmite alumina (BAl) was investigated in terms of its use as an filler to improve the inherent properties...

  20. Thermal exposure effects on the mechanical properties of a polycrystalline alumina fiber/aluminum matrix composite

    Science.gov (United States)

    Olsen, G. C.

    1979-01-01

    The effects of thermal exposures and elevated test temperature on the mechanical properties of a unidirectional polycrystalline alumina fiber reinforced aluminum matrix composite were investigated. Test temperatures up to 590 K and 2500 hours exposures at 590 K did not significantly affect fiber dominated properties but did severely degrade matrix dominated properties. Fiber strength, degraded by the fabrication process, was restored by post fabrication thermal exposures. Possible degradation mechanisms are discussed.

  1. Mechanical properties of hybrid composites prepared by ice-templating of alumina

    Czech Academy of Sciences Publication Activity Database

    Roleček, J.; Salamon, D.; Chlup, Zdeněk

    2017-01-01

    Roč. 37, č. 14 (2017), s. 4279-4286 ISSN 0955-2219 R&D Projects: GA MŠk(CZ) LQ1601 Institutional support: RVO:68081723 Keywords : fracture-toughness * ceramics * matrix * laminate * behavior * fibers * Ice-templating * Alumina * Epoxide * Hybrid composite s * Strength Subject RIV: JH - Ceramics, Fire-Resistant Material s and Glass OBOR OECD: Ceramics Impact factor: 3.411, year: 2016

  2. Mechanical properties of alumina-PEEK unidirectional composite - Compression, shear, and tension

    Science.gov (United States)

    Kriz, R. D.; Mccolskey, J. D.

    1990-01-01

    An Al2O3 (alumina)-fiber composite with high strain to failure was fabricated with a thermal plastic PEEK (poly-ether-ether-ketone). The Al2O3-PEEK composite shows a marked improvement over thermally setting composite in that it absorbs 150 percent more elastic-strain energy at 76 K than at room temperature. This increase in fracture toughness at low temperatures can provide improved fatigue performance for thermal isolation straps at low temperature. Other mechanical property results suggest improvements for applications where graphite-epoxy materials are presently being used at low temperatures and where light weight is not a critical issue.

  3. Development of ceramic composites from mixture of alumina and ceramic precursor polymer poly (silsesquioxane))

    International Nuclear Information System (INIS)

    Machado, Glauson Aparecido Ferreira

    2009-01-01

    Processing of ceramics materials, by polymer precursors pyrolysis, has been intensively researched over the past decades, due to advantages that this path provides, such as: lower temperature process compared to conventional techniques; structure control at molecular level; synthesis possibility of a wide range of ceramic compounds; obtaining parts with dimensions of the final product etc. The active filler controlled polymer pyrolysis (AFCOP) process, enables the synthesis of ceramic composites, by reaction between added filler (oxides, metals, intermetallic etc.) and solid and gaseous products, from polymer decomposition. In this study, based on this process, samples of alumina, with addition of 10 and 20 mass% of poly silsesquioxane polymer precursor, were manufactured. These samples were pyrolyzed at 900 degree C and thermal treated at temperatures of 1100, 1300 and 1500 degree C. The samples were characterized for bulk density, porosity and hardness, after each stage of thermal treatment. Structural transformations were analyzed by X-ray diffraction, scanning electron microscopy and infrared spectroscopy. Samples treated until 1300 degree C resulted in composites of alumina and silicon oxycarbide, while those treated at 1500 degree C, formed composites of mullite and alumina. The samples with 20% of polymer added started to density around 800 degree C and high retraction rate was observed at 1400 degree C. (author)

  4. Microstructural stability of zirconia-alumina composite coatings during hot corrosion test at 1050 {sup o}C

    Energy Technology Data Exchange (ETDEWEB)

    Keyvani, A., E-mail: akeyvani@ut.ac.i [School of Metallurgy and Materials, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Saremi, M., E-mail: saremi@ut.ac.i [School of Metallurgy and Materials, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Heydarzadeh Sohi, M., E-mail: mhsohi@ut.ac.i [School of Metallurgy and Materials, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of)

    2010-09-10

    In the present work hot corrosion behavior of plasma sprayed zirconia-alumina coatings on Ni-base, IN-738, super alloy substrate was studied compared with normal zirconia. Hot corrosion resistance of the coatings was measured at 1050 {sup o}C using an atmospheric electrical furnace and a fused mixture of vanadium pentoxide and sodium sulfate salt. The hot corrosion test duration was 4 h in each cycle, while the specimens were cooled in the furnace. The general and peripheral conditions of the specimens were inspected. If there were any cracks or spallation in coating wedge the test was stopped, the time was recorded and coating microstructure was studied. Composite coatings of zirconia-alumina having alumina as a top coat or a mixed zirconia-alumina layer, showed better resistance in hot corrosion tests. It was concluded that alumina overlay on zirconia has promoted the hot corrosion resistance of the coatings.

  5. Analysis of Material Removal and Surface Characteristics in Machining Multi Walled Carbon Nanotubes Filled Alumina Composites by WEDM Process

    Directory of Open Access Journals (Sweden)

    Annebushan Singh Meinam

    2017-01-01

    Full Text Available The reinforcement of ceramic materials with electrically conductive particles increases the overall conductivity of the ceramic material. This allows the ceramic material to be more readily machined using wire electrical discharge machining process. The current work is an approach to identify the machinability of multi walled carbon nanotubes filled alumina composites in wire electrical discharge machining process. Alumina samples of 5 vol. % and 10 vol. % multi walled carbon nanotubes are machined and analysed for material removal rate and the surface characteristics. An increase in material removal rate is observed with increase in filler concentrations. At the same time, better surface roughness is observed. The surface characteristics of composite alumina are further compared with Monel 400 alloy. It has been observed that spalling action is the dominating material removal mechanism for alumina composites, while melting and evaporation is for the Monel 400 alloy.

  6. Molten salt based nanofluids based on solar salt and alumina nanoparticles: An industrial approach

    Science.gov (United States)

    Muñoz-Sánchez, Belén; Nieto-Maestre, Javier; Guerreiro, Luis; Julia, José Enrique; Collares-Pereira, Manuel; García-Romero, Ana

    2017-06-01

    Thermal Energy Storage (TES) and its associated dispatchability is extremely important in Concentrated Solar Power (CSP) plants since it represents the main advantage of CSP technology in relation to other renewable energy sources like photovoltaic (PV). Molten salts are used in CSP plants as a TES material because of their high operational temperature and stability of up to 600°C. Their main problems are their relative poor thermal properties and energy storage density. A simple cost-effective way to improve the thermal properties of molten salts is to dope them with nanoparticles, thus obtaining the so-called salt-based nanofluids. Additionally, the use of molten salt based nanofluids as TES materials and Heat Transfer Fluid (HTF) has been attracting great interest in recent years. The addition of tiny amounts of nanoparticles to the base salt can improve its specific heat as shown by different authors1-3. The application of these nano-enhanced materials can lead to important savings on the investment costs in new TES systems for CSP plants. However, there is still a long way to go in order to achieve a commercial product. In this sense, the improvement of the stability of the nanofluids is a key factor. The stability of nanofluids will depend on the nature and size of the nanoparticles, the base salt and the interactions between them. In this work, Solar Salt (SS) commonly used in CSP plants (60% NaNO3 + 40% KNO3 wt.) was doped with alumina nanoparticles (ANPs) at a solid mass concentration of 1% wt. at laboratory scale. The tendency of nanoparticles to agglomeration and sedimentation is tested in the molten state by analyzing their size and concentration through the time. The specific heat of the nanofluid at 396 °C (molten state) is measured at different times (30 min, 1 h, 5 h). Further research is needed to understand the mechanisms of agglomeration. A good understanding of the interactions between the nanoparticle surface and the ionic media would provide

  7. Fast mass interdiffusion in ceria/alumina composite

    DEFF Research Database (Denmark)

    Teocoli, Francesca; Ni, De Wei; Sanna, Simone

    2015-01-01

    Gadolinium-doped ceria (CGO) presents unique processes at low oxygen partial pressure (pO2 < 1012 atm) and low temperatures (T > 800 C) such as faster mass diffusion, which are not observed in conventional sintering under ambient air conditions. In CGO/Al2O3 composites the resulting effects drive...

  8. Poly(Butylene Terephthalate Based Composites Containing Alumina Whiskers: Influence of Filler Functionalization on Dielectric Properties

    Directory of Open Access Journals (Sweden)

    Pietro Russo

    2014-01-01

    Full Text Available Poly(butylene terephthalate (PBT is one of the most widely used semicrystalline thermoplastics polyester because of its superior thermal and mechanical properties, high dimensional stability and excellent processability. In this research PBT-based nanocomposites, including various amounts (up to 10 wt% of commercial alumina whiskers, have been prepared by using a Brabender internal chamber mixer and analysed in terms of morphological features and dielectric properties. Specific attention has been focused on the effect of the filler functionalization considering 3-glycidoxy propylmethoxysilane (GPS or 3-methacryloxypropyltrimethoxysilane (MPS as coupling agents. Tests, performed on compounds filled with neat and functionalized alumina whiskers, show a clear dependence of relative dielectric permittivity εr, invariance of dissipation factor (tgδ, and a sensible increase of volume electrical resistivity (ρv with the filler’s content and are encouraging for a future introduction of such composites in many electrical applications.

  9. Combustion chemical vapor deposition (CCVD) of LaPO4 monazite and beta-alumina on alumina fibers for ceramic matrix composites

    International Nuclear Information System (INIS)

    Hwang, T.J.; Hendrick, M.R.; Shao, H.; Hornis, H.G.; Hunt, A.T.

    1998-01-01

    This research used the low cost, open atmosphere combustion chemical vapor deposition (CCVD SM ) method to efficiently deposit protective coatings onto alumina fibers (3M Nextel TM 610) for use in ceramic matrix composites (CMCs). La-monazite (LaPO 4 ) and beta-alumina were the primary candidate debonding coating materials investigated. The coated fibers provide thermochemical stability, as well as desired debonding/sliding interface characteristics to the CMC. Dense and uniform La-phosphate coatings were obtained at deposition temperatures as low as 900-1000 C with minimal degradation of fibers. However, all of the β-alumina phases required high deposition temperatures and, thus, could not be applied onto the Nextel TM 610 alumina fibers. The fibers appeared to have complete and relatively uniform coatings around individual filaments when 420 and 1260 filament tows were coated via the CCVD process. Fibers up to 3 feet long were fed through the deposition flame in the laboratory of MicroCoating Technologies (MCT). TEM analyses performed at Wright-Patterson AFB on the CCVD coated fibers showed a 10-30 nm thick La-rich layer at the fiber/coating interface, and a layer of columnar monazite 0.1-1 μm thick covered with sooty carbon of <50 nm thick on the outside. A single strength test on CCVD coated fibers performed by 3M showed that the strength value fell in the higher end of data from other CVD coated samples. (orig.)

  10. Laminated alumina/zirconia ceramic composites prepared by electrophoretic

    Czech Academy of Sciences Publication Activity Database

    Hadraba, Hynek; Drdlík, D.; Chlup, Zdeněk; Maca, K.; Dlouhý, Ivo; Cihlář, J.

    2012-01-01

    Roč. 32, č. 9 (2012), s. 2053-2056 ISSN 0955-2219. [Engineering Ceramics 2011 - from Materials to Components. Smolenice, 09.05.2011-12.05.2011] R&D Projects: GA ČR(CZ) GAP108/11/1644 Institutional research plan: CEZ:AV0Z20410507 Institutional support: RVO:68081723 Keywords : electrophoretic deposition * composites * hardness * Al2O3 * ZrO2 Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 2.360, year: 2012

  11. A New Phase Change Material Based on Potassium Nitrate with Silica and Alumina Nanoparticles for Thermal Energy Storage.

    Science.gov (United States)

    Chieruzzi, Manila; Miliozzi, Adio; Crescenzi, Tommaso; Torre, Luigi; Kenny, José M

    2015-12-01

    In this study different nanofluids with phase change behavior were developed by mixing a molten salt base fluid (KNO3 selected as phase change material) with nanoparticles using the direct synthesis method. The thermal properties of the nanofluids obtained were investigated. Following the improvement in the specific heat achieved, these nanofluids can be used in concentrating solar plants with a reduction of storage material. The nanoparticles used (1.0 wt.%) were silica (SiO2), alumina (Al2O3), and a mix of silica-alumina (SiO2-Al2O3) with an average diameter of 7, 13, and 2-200 nm respectively. Each nanofluid was prepared in water solution, sonicated, and evaporated. Measurements of the thermophysical properties were performed by DSC analysis, and the dispersion of the nanoparticles was analyzed by SEM microscopy. The results obtained show that the addition of 1.0 wt.% of nanoparticles to the base salt increases the specific heat of about 5-10 % in solid phase and of 6 % in liquid phase. In particular, this research shows that the addition of silica nanoparticles has significant potential for enhancing the thermal storage characteristics of KNO3. The phase-change temperature of potassium nitrate was lowered up to 3 °C, and the latent heat was increased to 12 % with the addition of silica nanoparticles. These results deviated from the predictions of theoretical simple mixing model used. The stored heat as a function of temperature was evaluated for the base salt, and the nanofluids and the maximum values obtained were 229, 234, 242, and 266 J/g respectively. The maximum total gain (16 %) due to the introduction of the nanoparticles (calculated as the ratio between the total stored heat of the nanofluids and the base salt in the range of temperatures 260-390 °C) was also recorded with the introduction of silica. SEM and EDX analysis showed the presence of aggregates in all nanofluids: with silica nanoparticles they were homogenously present while with

  12. Optical characterization of poly (ethylene oxide)/alumina composites

    Energy Technology Data Exchange (ETDEWEB)

    Elimat, Z.M., E-mail: ziad_elimat@yahoo.co [Department of Applied Science, Ajloun University College, Al-Balqa' Applied University, Amman (Jordan); Zihlif, A.M. [Physics Department, University of Jordan, Amman (Jordan); Ragosta, G. [Institute of Chemistry and Technology of Polymers (ICTP), CNR-Possouli, Napoli (Italy)

    2010-09-01

    The optical properties in the UV-visible region of poly (ethylene oxide) polymer containing 0%, 5%, 10% and 15% by weight aluminum oxide (Al{sub 2}O{sub 3}) are reported. The optical results obtained were analyzed in terms of the absorption formula for non-crystalline materials. The absorption coefficient {alpha}({nu}) and the optical band energy gap (E{sub opt}) have been obtained from direct allowed transitions in k-space at room temperature. The tail widths ({Delta}E) of the tail of localized states in the band gap were evaluated using the Urbach-edges method. It was found that both (E{sub opt}) and ({Delta}E) vary with the concentration of the aluminum oxide complex dispersed in the polymer matrix, and the measured optical energy gap for the poly (ethylene oxide) is greater than the PEO/Al{sub 2}O{sub 3} composites. The refractive index (n) for the composites was determined from the collected transmittance and reflectance spectra. The dispersion of the refractive index is discussed in terms of the single oscillator model. The optical energy gaps E{sub opt}, and the optical constants such as refractive index, extinction coefficient and dielectric constant were estimated.

  13. Thermal analysis and in vitro bioactivity of bioactive glass-alumina composites

    Energy Technology Data Exchange (ETDEWEB)

    Chatzistavrou, Xanthippi, E-mail: x.chatzistavrou@imperial.ac.uk [Solid State Physics Section, Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Kantiranis, Nikolaos, E-mail: kantira@geo.auth.gr [School of Geology, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Kontonasaki, Eleana, E-mail: kont@dent.auth.gr [School of Dentistry, Department of Fixed Prosthesis and Implant Prosthodontics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Chrissafis, Konstantinos, E-mail: hrisafis@physics.auth.gr [Solid State Physics Section, Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Papadopoulou, Labrini, E-mail: lambrini@geo.auth.gr [School of Geology, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Koidis, Petros, E-mail: pkoidis@dent.auth.gr [School of Dentistry, Department of Fixed Prosthesis and Implant Prosthodontics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Boccaccini, Aldo R., E-mail: a.boccaccini@imperial.ac.uk [Department of Materials, Faculty of Engineering, Imperial College, SW7 2AZ London (United Kingdom); Paraskevopoulos, Konstantinos M., E-mail: kpar@auth.gr [Solid State Physics Section, Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)

    2011-01-15

    Bioactive glass-alumina composite (BA) pellets were fabricated in the range 95/5-60/40 wt.% respectively and were heat-treated under a specific thermal treatment up to 950 {sup o}C. Control (unheated) and heat-treated pellets were immersed in Simulated Body Fluid (SBF) for bioactivity testing. All pellets before and after immersion in SBF were studied by Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM-EDS) and X-ray Diffraction (XRD) analysis. All composite pellets presented bioactive response. On the surface of the heat-treated pellets the development of a rich biological hydroxyapatite (HAp) layer was delayed for one day, compared to the respective control pellets. Independent of the proportion of the two components, all composites of each group (control and heat-treated) presented the same bioactive response as a function of immersion time in SBF. It was found that by the applied methodology, Al{sub 2}O{sub 3} can be successfully applied in bioactive glass composites without obstructing their bioactive response. - Research Highlights: {yields} Isostatically pressed glass-alumina composites presented apatite-forming ability. {yields} The interaction with SBF resulted in an aluminium phosphate phase formation. {yields} The formation of an aluminium phosphate phase enhanced the in vitro apatite growth.

  14. Thermal analysis and in vitro bioactivity of bioactive glass-alumina composites

    International Nuclear Information System (INIS)

    Chatzistavrou, Xanthippi; Kantiranis, Nikolaos; Kontonasaki, Eleana; Chrissafis, Konstantinos; Papadopoulou, Labrini; Koidis, Petros; Boccaccini, Aldo R.; Paraskevopoulos, Konstantinos M.

    2011-01-01

    Bioactive glass-alumina composite (BA) pellets were fabricated in the range 95/5-60/40 wt.% respectively and were heat-treated under a specific thermal treatment up to 950 o C. Control (unheated) and heat-treated pellets were immersed in Simulated Body Fluid (SBF) for bioactivity testing. All pellets before and after immersion in SBF were studied by Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM-EDS) and X-ray Diffraction (XRD) analysis. All composite pellets presented bioactive response. On the surface of the heat-treated pellets the development of a rich biological hydroxyapatite (HAp) layer was delayed for one day, compared to the respective control pellets. Independent of the proportion of the two components, all composites of each group (control and heat-treated) presented the same bioactive response as a function of immersion time in SBF. It was found that by the applied methodology, Al 2 O 3 can be successfully applied in bioactive glass composites without obstructing their bioactive response. - Research Highlights: → Isostatically pressed glass-alumina composites presented apatite-forming ability. → The interaction with SBF resulted in an aluminium phosphate phase formation. → The formation of an aluminium phosphate phase enhanced the in vitro apatite growth.

  15. Synthesis and Characterization of Nickel-Alumina Composites from Recycled Nickel Powder

    Directory of Open Access Journals (Sweden)

    V. G. Karayannis

    2012-01-01

    Full Text Available The recycling of metallic waste to create more valuable materials and their valorization into upgraded metal-based composites constitutes an important field of study. The composite industry nowadays considers environmental improvements as important as other properties of the materials. In the present paper, nickel powder was recycled from ferrous scrap, a low-cost and largely available material, by an effective hydrometallurgical recovery process. Then, this recycled powder was successfully used along with particulate α-alumina to prepare oblong nickel-based composite specimens with ceramic reinforcement loadings ranging from 0 to 30 wt.% by applying powder processing manufacturing techniques including cold isostatic pressing (CIP and sintering. The microstructures obtained were characterized, the specimens were subjected to three-point bend tests, and their fracture behaviour was evaluated. By increasing the % ceramic reinforcement content, density clearly decreases while strengthening is achieved, thus leading to development of lightweight and enhanced oblong nickel-alumina composites. The composite microstructure, and particularly the metal-ceramic interface bonding, has a strong impact on fracture behaviour upon external loading.

  16. Mechanical and physical properties of calcium silicate/alumina composite for biomedical engineering applications.

    Science.gov (United States)

    Shirazi, F S; Mehrali, M; Oshkour, A A; Metselaar, H S C; Kadri, N A; Abu Osman, N A

    2014-02-01

    The focus of this study is to investigate the effect of Al2O3 on α-calcium silicate (α-CaSiO3) ceramic. α-CaSiO3 was synthesized from CaO and SiO2 using mechanochemical method followed by calcinations at 1000°C. α-CaSiO3 and alumina were grinded using ball mill to create mixtures, containing 0-50w% of Al2O3 loadings. The powders were uniaxially pressed and followed by cold isostatic pressing (CIP) in order to achieve greater uniformity of compaction and to increase the shape capability. Afterward, the compaction was sintered in a resistive element furnace at both 1150°C and 1250°C with a 5h holding time. It was found that alumina reacted with α-CaSiO3 and formed alumina-rich calcium aluminates after sintering. An addition of 15wt% of Al2O3 powder at 1250°C were found to improve the hardness and fracture toughness of the calcium silicate. It was also observed that the average grain sizes of α-CaSiO3 /Al2O3 composite were maintained 500-700nm after sintering process. © 2013 Published by Elsevier Ltd.

  17. Wear properties of alumina/zirconia composite ceramics for joint prostheses measured with an end-face apparatus.

    Science.gov (United States)

    Morita, Yusuke; Nakata, Kenichi; Kim, Yoon-Ho; Sekino, Tohru; Niihara, Koichi; Ikeuchi, Ken

    2004-01-01

    While only alumina is applied to all-ceramic joint prostheses at present, a stronger ceramic is required to prevent fracture and chipping due to impingement and stress concentration. Zirconia could be a potential substitute for alumina because it has high strength and fracture toughness. However, the wear of zirconia/zirconia combination is too high for clinical use. Although some investigations on composite ceramics revealed that mixing of different ceramics was able to improve the mechanical properties of ceramics, there are few reports about wear properties of composite ceramics for joint prosthesis. Since acetabular cup and femoral head of artificial hip joint are finished precisely, they indicate high geometric conformity. Therefore, wear test under flat contact was carried out with an end-face wear testing apparatus for four kinds of ceramics: alumina monolith, zirconia monolith, alumina-based composite ceramic, and zirconia based composite ceramic. Mean contact pressure was 10 MPa and sliding velocity was 40 mm/s. The wear test continued for 72 hours and total sliding distance was 10 km. After the test, the wear factor was calculated. Worn surfaces were observed with a scanning electron micrograph (SEM). The results of this wear test show that the wear factors of the both composite ceramics are similarly low and their mechanical properties are much better than those of the alumina monolith and the zirconia monolith. According to these results, it is predicted that joint prostheses of the composite ceramics are safer against break down and have longer lifetime compared with alumina/alumina joint prostheses.

  18. Porous hydroxyapatite composite with alumina for bone repair

    International Nuclear Information System (INIS)

    Rusnah Mustaffa; Mohd Reusmaazran Mohd Yusof; Idris Besar

    2010-01-01

    Porous fabrications, a number of techniques were investigated using polyurethane foam as the scaffold. These techniques involve dipping of the foam into a slurry prepared by mixing of HA+Al 2 O 3 powder with PVA and Sago as binder and subjecting to burn off procedure to get the porous products. Sintering parameter was studied at 1100, 1200 and 1300 degree Celsius. Initially HA powder was prepared by the sol-gel precipitation method using calcium hydroxide and ortho-phosphoric acid meanwhile Al 2 O 3 powder from supplier (MERK). The fine HA powder, measuring 2 O 3 . These techniques also produce the uniformity pore shape. Characterization of the physical analysis, porosity, surface morphology by Scanning Electron Microscopy analysis (SEM) and compression strength were studied. Mechanical properties showing that the composite of porous HA+Al 2 O 3 gives higher maximum compression strength compared to the porous hydroxyapatite itself. Observation from this studied the increasing of temperature will increase the strength. (author)

  19. Synthesis and characterization of aluminium–alumina micro- and nano-composites by spark plasma sintering

    International Nuclear Information System (INIS)

    Dash, K.; Chaira, D.; Ray, B.C.

    2013-01-01

    Graphical abstract: The evolution of microstructure by varying the particle size of reinforcement in the matrix employing spark plasma sintering has been demonstrated here in Al–Al 2 O 3 system. An emphasis has been laid on varying the reinforcement particle size and evaluating the microstructural morphologies and their implications on mechanical performance of the composites. Nanocomposites of 0.5, 1, 3, 5, 7 volume % alumina (average size 2 O 3 micro- and nano-composites fabricated by spark plasma sintering. • Better matrix-reinforcement integrity in nanocomposites than microcomposites. • Spark plasma sintering method results in higher density and hardness values. • High density and hardness values of nanocomposites than microcomposites. • High dislocation density in spark plasma sintered Al–Al 2 O 3 composites. - Abstract: In the present study, an emphasis has been laid on evaluation of the microstructural morphologies and their implications on mechanical performance of the composites by varying the reinforcement particle size. Nanocomposites of 0.5, 1, 3, 5, 7 volume % alumina (average size 2 O 3 nancomposites respectively. Spark plasma sintering imparts enhanced densification and matrix-reinforcement proximity which have been corroborated with the experimental results

  20. Study of the mechanical properties of hybrid composite basalt / alumina / shells for brake lining pads

    Science.gov (United States)

    Adi Atmika, I. K.; Ary Subagia, IDG.; Surata, I. W.; Sutantra, I. N.

    2017-05-01

    Brake lining pad as one of the active safety components in motor vehicles has been studied thoroughly. Asbestos is the main material forming the brake in addition to other alloy materials that have a negative impact on health and the environment. This paper explain the behavior of hybrid composites phenolic resin with basalt/alumina/clamshell powder reinforced on brake lining pad. This materials has been manufactured use compaction and sintering process through any steps, that an emphasis of 2,000 kg for 30 minutes at a constant temperature of 150° C. The research aims to investigate hardness characteristic of hybrid composite that test using the vickers according to standard ASTM E-384. The reinforced materials and phenolic resin composition is 60%: 40%. The results show for the average hardness VHN to 24.18, 25.11, 26.34, 27.21 and 28.83. The average hardness hybrid composite shows the hardness harder than asbestos materials.

  1. Effect of high thermal expansion glass infiltration on mechanical properties of alumina-zirconia composite

    International Nuclear Information System (INIS)

    Balakrishnan, A.; Panigrahi, B.B.; Chu, Min-Cheol; Cho, Seong-Jai; Sanosh, K.P.; Kim, T.N.

    2009-01-01

    This work studies the effect on the mechanical properties of alumina-10 wt% zirconia (3 mol % yttria stabilized) composite by infiltrating glass of a higher thermal expansion (soda lime glass) on the surface at high temperature. The glass improved the strength of composite at room temperature as well as at high temperature. This could be attributed to the drastic drop in the coefficient of thermal expansion due to the compositional change in the soda lime glass during infiltration. There was a significant improvement in the Weibull modulus after glass infiltration. Glass infiltrated samples showed better thermal shock resistance. The magnitude of strength increment was found to be in the order of the surface residual stress generated by thermo-elastic properties mismatch between the composite and the penetrated glass. (author)

  2. The Effect of surface Treatment of Alumina NanoParticles with a Silane Coupling Agent on the Mechanical Properties of Polymer Nanocomposites

    Science.gov (United States)

    Amirchakhmaghi, S.; Nia, A. Alavi; Azizpour, G.; Bamdadi, H.

    2015-07-01

    Surface-treated and untreated alumina nanoparticles were mixed with a polycarbonate matrix at different weight percentages and the mechanical properties of the nanocomposites produced were determined by subjecting them to quasi-static tension and Charpy impact tests. The results obtained showed that the surface treatment of nanoparticles had improved their mechanical properties.

  3. Optimization of Alumina Slurry for Oxide-Oxide Ceramic Composites Manufactured by Injection Molding

    Directory of Open Access Journals (Sweden)

    Catherine Billotte

    2017-01-01

    Full Text Available This paper focuses on the rheological study of an alumina suspension intended for the manufacturing of oxide-oxide composites by flexible injection. Given the production constraints, it is required to have stable suspension with low viscosity and a Newtonian behavior. This is achieved with a concentration of nitric acid between 0.08 wt% and 0.2 wt% and amount of 3 wt% of PVA binder. The maximum loading of the suspension of 47 vol% suggests that there is no structure development within the suspension with optimized concentration of acid and PVA.

  4. Machining parameters optimization during machining of Al/5 wt% alumina metal matrix composite by fiber laser

    Science.gov (United States)

    Ghosal, Arindam; Patil, Pravin

    2017-06-01

    This experimental work presents the study of machining parameters of Ytterbium fiber laser during machining of 5 mm thick Aluminium/5wt%Alumina-MMC (Metal Matrix Composite). Response surface methodology (RSM) is used to achieve the optimization i.e. minimize hole tapering and maximize Material Removal Rate (MRR). A mathematical model has been developed and ANOVA has been done for correlating the interactive and higher-order influences of Ytterbium fiber laser machining parameters (laser power, modulation frequency, gas pressure, wait time, pulse width) on Material Removal Rate (MRR) and hole tapering during machining process.

  5. Synthesis and characterization of copper–alumina metal matrix composite by conventional and spark plasma sintering

    International Nuclear Information System (INIS)

    Dash, K.; Ray, B.C.; Chaira, D.

    2012-01-01

    Graphical abstract: The evolution of microstructure, density and hardness of Cu–Al 2 O 3 metal matrix composites with different techniques of sintering has been demonstrated here. The effect of sintering atmosphere has also been discussed. Synthesis of microcomposites was carried out by reinforcing 5, 10 and 15 vol.% of alumina powder particle (average size ∼5.71 μm) in copper matrix via conventional sintering using H 2 and N 2 atmospheres. Nanocomposites of 1, 5, 7 vol.% alumina (average size 2 O 3 metal matrix microcomposites and nanocomposites via conventional route and spark plasma sintering routes are studied and compared. Maximum Vickers hardness of 60 and 80 are obtained when the Cu–15 vol.% Al 2 O 3 is conventionally sintered in N 2 and H 2 atmosphere respectively. However, maximum hardness value of 125 is achieved for the Cu–5 vol.% Al 2 O 3 nanocomposite prepared by spark plasma sintering. It has been observed that Cu–Al 2 O 3 metal matrix composite (MMC) shows poor mechanical properties when it is conventionally sintered in N 2 atmosphere than H 2 atmosphere. Highlights: ► Better matrix–reinforcement interfacial bonding and compatibility in hydrogen atmosphere than nitrogen atmosphere. ► An improvement in density and hardness under hydrogen atmosphere than in nitrogen atmosphere is manifested. ► Spark plasma sintering method results in higher density and hardness values than conventional sintering. - Abstract: The evolution of microstructure, density and hardness of Cu–Al 2 O 3 metal matrix composites with different techniques of sintering have been demonstrated here. The effect of sintering atmosphere on the interfacial compatibility of matrix and reinforcement has also been discussed. Synthesis of microcomposites was carried out by reinforcing 5, 10 and 15 vol.% of alumina powder particles (average size ∼5.71 μm) in copper matrix via conventional sintering using N 2, H 2 and Ar atmospheres. Nanocomposites of 1, 5, 7 vol

  6. Correlation between fracture toughness, work of fracture and fractal dimensions of Alumina-mullite-zirconia composites

    Directory of Open Access Journals (Sweden)

    Santos Sérgio Francisco dos

    2003-01-01

    Full Text Available The purpose of this work is to show the correlation between the fractal dimension, D, and mechanical properties such as work of fracture, gammawof, and fracture toughness, K Ic. Alumina-mullite-zirconia composites were characterized by the slit-island method, SIM, to obtain values of D and its fractional part, D*. The fracture surface roughness was also evaluated using a cyclic voltametric method. It will be shown that there is a positive experimental dependency of gammawof on D* and that there is not an evident correlation between K Ic and D*.

  7. Preparation of α-alumina nanoparticles with various shapes via hydrothermal phase transformation under supercritical water conditions

    Science.gov (United States)

    Hakuta, Y.; Nagai, N.; Suzuki, Y.-H.; Kodaira, T.; Bando, K. K.; Takashima, H.; Mizukami, F.

    2013-12-01

    Alumina (Al2O3) fine particles are widely used as industrial materials including fillers for metal or plastics, paints, polisher, cosmetics and electric substrates, due to its high hardness, chemical stability, and high thermal conductivity. The performance of those industrial products is closely related to the particle size or shape of the alumina particles used, and thus a new synthetic method to control size, shape, and crystal structure of the aluminum oxide is desired for the improvement of the performance. Hydrothermal phase transformation using various aluminum compounds such as oxide, hydroxide, and salt as a staring material, is known as one of the synthetic methods for producing alumina fine particles; however, the influence about the size and shape of the starting aluminum compounds has been little mentioned, although they strongly affect the size and shape of the final products. In this study, we investigated the influence of the shape, size and crystal structure of the starting aluminum compounds on those of the products, and newly succeeded in the production of rod-like α-Al2O3 nanoparticles from fibrous boehmite nanoparticles using hydrothermal phase transformation under supercritical water conditions.

  8. Probability of failure of veneered glass fiber-reinforced composites and glass-infiltrated alumina with or without zirconia reinforcement.

    Science.gov (United States)

    Chong, Kok-Heng; Chai, John

    2003-01-01

    The probability of failure under flexural load of veneered specimens of a unidirectional glass fiber-reinforced composite (FibreKor/Sculpture), a bidirectional glass fiber-reinforced composite (Vectris/Targis), a glass-infiltrated alumina (In-Ceram Alumina/Vita alpha), and a zirconia-reinforced glass-infiltrated alumina (In-Ceram Zirconia/Vita alpha) was investigated; a metal-ceramic (PG200/Vita omega) system served as a control. Ten uniform beams of the veneered core materials were fabricated for each system and subjected to a three-point bending test. The data were analyzed using the Weibull method. The failure load of specimens at a 10% probability of failure (B10 load) was compared. The mode of failure was analyzed. The B10 load of the systems investigated was not significantly different from that of the metal-ceramic system. FibreKor possessed significantly higher B10 load than Vectris, In-Ceram Alumina, and In-Ceram Zirconia. The B10 strength loads of Vectris, In-Ceram Alumina, and In-Ceram Zirconia were not significantly different from one another. The probability of FibreKor to fracture under a flexural load was significantly lower than that of Vectris, In-Ceram Alumina, or In-Ceram Zirconia.

  9. Bending Strength and Fracture Investigations of Cu Based Composite Materials Strengthened with δ-Alumina Fibres

    Directory of Open Access Journals (Sweden)

    Kaczmar J.W.

    2013-06-01

    Full Text Available Bending strength, thermal and electric conductivity and microstructure examinations of Cu based composite materials reinforced with Saffil alumina fibres are presented. Materials were produced by squeeze casting method applying the designed device and specially elaborated production parameters. Applying infiltration pressure of 90MPa and suitable temperature parameters provided manufacturing of copper based composite materials strengthened with Saffil alumina fibres characterized by the low rest porosity and good fibre-matrix interface. Three point bending tests at temperatures of 25, 100 and 300ºC were performed on specimens reinforced with 10, 15 and 20% of Saffil fibres. Introduced reinforcement effected on the relatively high bending strengths at elevated temperatures. In relation to unreinforced Cu casting strength of composite material Cu - 15vol.% Saffil fibres increase by about 25%, whereas at the highest applied test temperature of 300oC the improvement was almost 100%. Fibres by strengthening of the copper matrix and by transferring loads from the matrix reduce its plastic deformation and hinder the micro-crack developed during bending tests. Decreasing of thermal and electrical conductivity of Cu after incorporating fibres in the matrix are relatively small and these properties can be acceptable for electric and thermal applications.

  10. Density control of electrodeposited Ni nanoparticles/nanowires inside porous anodic alumina templates by an exponential anodization voltage decrease.

    Science.gov (United States)

    Marquardt, B; Eude, L; Gowtham, M; Cho, G; Jeong, H J; Châtelet, M; Cojocaru, C S; Kim, B S; Pribat, D

    2008-10-08

    Porous alumina templates have been fabricated by applying an exponential voltage decrease at the end of the anodization process. The time constant η of the exponential voltage function has been used to control the average thickness and the thickness distribution of the barrier layer at the bottom of the pores of the alumina structure. Depending on the η value, the thickness distribution of the barrier layer can be made very uniform or highly scattered, which allows us to subsequently fine tune the electrodeposition yield of nickel nanoparticles/nanowires at low voltage. As an illustration, the pore filling percentage with Ni has been varied, in a totally reproducible manner, between ∼3 and 100%. Combined with the ability to vary the pore diameter and repetition step over ∼2 orders of magnitude (by varying the anodization voltage and electrolyte type), the control of the pore filling percentage with metal particles/nanowires could bring novel approaches for the organization of nano-objects.

  11. Synthesis of Ru nanoparticles confined in magnesium oxide-modified mesoporous alumina and their enhanced catalytic performance during ammonia decomposition

    KAUST Repository

    Tan, Hua

    2012-09-01

    In this work, Ru nanoparticles confined in the channels of ordered mesoporous alumina (MA) and magnesium oxide-modified ordered MA are prepared for the first time via a two-solvent technique, combined with the amorphous citrate route. Structural characterizations reveal that uniform 2-3 nm Ru nanoparticles are highly dispersed in the blockage-free channels of mesoporous supports. The Ru nanoparticles confined in MA modified with 20% molar ratio magnesium oxide exhibited a high catalytic activity and stability during ammonia decomposition due to the optimized particle size, basic support, lack of chlorine, and confined space provided by the channels of the mesoporous supports. © 2012 Elsevier B.V. All rights reserved.

  12. Recycling of Coal Fly Ash for the Fabrication of Porous Mullite/Alumina Composites

    Directory of Open Access Journals (Sweden)

    Kyu H. Kim

    2014-08-01

    Full Text Available Coal fly ash with the addition of Al2O3 was recycled to produce mullite/alumina composites and the camphene-based freeze casting technique was processed to develop a controlled porous structure with improved mechanical strength. Many rod-shaped mullite crystals, formed by the mullitization of coal fly ash in the presence of enough silicate, melt. After sintering at 1300–1500 °C with the initial solid loadings of 30–50 wt.%, interconnected macro-sized pore channels with nearly circular-shaped cross-sections developed along the macroscopic solidification direction of camphene solvent used in freeze casting and a few micron-sized pores formed in the walls of the pore channels. The macro-pore size of the mullite/alumina composites was in the range 20–25 μm, 18–20 μm and 15–17 μm with reverse dependence on the sintering temperature at 30, 40 and 50 wt.% solid loading, respectively. By increasing initial solid loading and the sintering temperature, the sintered porosity was reduced from 79.8% to 31.2%, resulting in an increase in the compressive strength from 8.2 to 80.4 MPa.

  13. Novel calcium hexaluminate/spinel-alumina composites with graded microstructures and mechanical properties

    Science.gov (United States)

    Yi, Shuai; Huang, Zhaohui; Huang, Juntong; Fang, Minghao; Liu, Yan'gai; Zhang, Shaowei

    2014-03-01

    Calcium hexaluminate (CA6) was incorporated into the matrix of magnesio aluminate spinel-alumina (MA-A) via infiltration of a porous preform fabricated from α-Al2O3 and MgO powders with a saturated calcium acetate solution and subsequent firing, forming CA6/(MA-A) functionally composites with graded fracture toughness. Actually, the porous preform was partially and perpendicularly immersed (1/4 of its length) in the solution. Owing to the capillary action, the calcium acetate solution was absorbed into the porous preform, and the different absorption distance led to the graded solution concentration in the height direction of the porous preform. The in-situ formation of CA6 conferred graded microstructures, as well as improved mechanical properties on the resultant composites. The CA6 content decreased gradually along the solution absorption direction, i.e., from one end [CA6/(MA-A) region] immersed in solution to the other end [MA-A region], reducing evidently the formation of layered structure along the direction, while increasing gradually the formation of spherical alumina particles. The CA6/(MA-A) region had a better toughness that could prevent the crack propagation and improve the spalling resistance. Meanwhile, the MA-A region could provide structural support, because of the higher Vickers hardness and density.

  14. Feasibility study of use alumina waste in compositions containing clay for the mullite synthesis; Estudo da viabilidade do uso de residuo de alumina em composicoes contendo argilas destinadas a sintese de mulita

    Energy Technology Data Exchange (ETDEWEB)

    Silva, V.J.; Dias, G.; Goncalves, W.P.; Santana, L.N.L., E-mail: valmir_jspb@yahoo.com.br [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Unidade Academica de Engenharia de Materiais

    2016-07-01

    The reuse of alumina residue in addition to reducing environmental impacts can be used as raw material in ceramic masses to mullite produce. This study aims to obtain mullite from compositions containing clays and alumina residue used heating in a conventional oven. The raw materials were processed and characterized. Subsequently, these compositions were formulated containing precursors in appropriate proportions based on the stoichiometry of the mullite 3:2. Then, heat treatment was performed at temperatures of 1300 to 1400°C and 5°C rate/min. The products obtained were characterized by XRD, analyzing qualitatively and quantitatively the phases formed. The results showed that is possible, from compositions containing clays and alumina residue to obtain mullite as major phase (>70%) and high crystallinity (> 80%) The percentage of mullite approached the values obtained with the compositions containing alumina and clays. (author)

  15. Ceria nanoparticles vis-à-vis cerium nitrate as corrosion inhibitors for silica-alumina hybrid sol-gel coating

    Energy Technology Data Exchange (ETDEWEB)

    Lakshmi, R.V. [Surface Engineering Division, Council of Scientific and Industrial Research – National Aerospace Laboratories, HAL Airport Road, Kodihalli, Bengaluru 560017 (India); Aruna, S.T., E-mail: staruna194@gmail.com [Surface Engineering Division, Council of Scientific and Industrial Research – National Aerospace Laboratories, HAL Airport Road, Kodihalli, Bengaluru 560017 (India); Sampath, S. [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bengaluru 560012 (India)

    2017-01-30

    Highlights: • Corrosion protection efficiency comparison of ceria nanoparticles and cerium nitrate. • Silica-alumina hybrid coating exhibited good barrier protection. • Detailed XPS study confirm the hybrid structure and presence of Ce species in coating. • Loss of cerium ions not prevalent in ceria doped coating unlike that of cerium nitrate. • Ceria increased the coating integrity, corrosion inhibition and barrier protection. - Abstract: The present work provides a comparative study on the corrosion protection efficiency of defect free sol-gel hybrid coating containing ceria nanoparticles and cerium nitrate ions as corrosion inhibitors. Less explored organically modified alumina-silica hybrid sol-gel coatings are synthesized from 3-glycidoxypropyltrimethoxysilane and aluminium-tri-sec-butoxide. The microemulsion derived nanoparticles and the hybrid coatings are characterized and compared with coatings containing cerium nitrate. Corrosion inhibiting capability is assessed using electrochemical impedance spectroscopy. Scanning Kelvin probe measurements are also conducted on the coatings for identifying the apparent corrosion prone regions. Detailed X-ray photoelectron spectroscopy (XPS) analysis is carried out to comprehend the bonding and corrosion protection rendered by the hybrid coatings.

  16. Effect of Oxide Additives on Phase Evolution and Tribological Behavior of Zirconia-Toughened Alumina Composite

    Science.gov (United States)

    Dey, Ashis Kumar; Chatterjee, Subrata; Biswas, Koushik

    2017-12-01

    Four different zirconia-toughened alumina added with different pairs of oxides (CeO2, TiO2, CuO, ZnO and SnO2) were prepared through the co-precipitation technique. Conventional sintering resulted in relative densities ≥96%. Phase analyses of these composites were performed by x-ray diffraction. Vicker's hardness and tribological behavior of all ZTA composites were studied. Microstructure analysis of polished and worn surfaces was carried out to understand and correlate the mechanical/tribological behavior with the microstructure. A different wear mechanism is observed in ZTA containing CeO2 and TiO2 which resulted in considerable improvement in tribological behavior with a minimum specific wear rate of 9 × 10-7 mm3/Nm.

  17. Effects of alumina nanoparticles on the microstructure, strength and wear resistance of poly(methyl methacrylate)-based nanocomposites prepared by friction stir processing.

    Science.gov (United States)

    Aghajani Derazkola, Hamed; Simchi, Abdolreza

    2018-03-01

    In this study, alumina-reinforced poly(methyl methacrylate) nanocomposites (PMMA/Al 2 O 3 ) containing up to 20vol% nanoparticles with an average diameter of 50nm were prepared by friction stir processing. The effects of nanoparticle volume fraction on the microstructural features and mechanical properties of PMMA were studied. It is shown that by using a frustum pin tool and employing an appropriate processing condition, i.e. a rotational speed of 1600rpm/min and transverse velocity of 120mm/min, defect free nanocomposites at microscale with fine distribution of the nanoparticles can successfully been prepared. Mechanical evaluations including tensile, flexural, hardness and impact tests indicate that the strength and toughness of the material gradually increases with the nanoparticle concentration and reach to a flexural strength of 129MPa, hardness of 101 Shore D, and impact energy 2kJ/m 2 for the nanocomposite containing 20vol% alumina. These values are about 10% and 20% better than untreated and FSP-treated PMMA (without alumina addition). Fractographic studies indicate typical brittle features with crack deflection around the nanoparticles. More interestingly, the sliding wear rate in a pin-on-disk configuration and the friction coefficient are reduced up to 50% by addition of alumina nanoparticles. The worn surfaces exhibit typical sliding and ploughing features. Copyright © 2018 Elsevier Ltd. All rights reserved.

  18. Antifungal activity of fabricated mesoporous alumina nanoparticles against root rot disease of tomato caused by Fusarium oxysporium.

    Science.gov (United States)

    Shenashen, Mohamed; Derbalah, Aly; Hamza, Amany; Mohamed, Ahmed; El Safty, Sherif

    2017-06-01

    The present work involved the synthesis and characterisation of mesoporous alumina sphere (MAS) nanoparticles to evaluate their biological activity against tomato root rot caused by Fusarium oxysporium, as compared with the recommended fungicide, tolclofos-methyl, under laboratory and greenhouse conditions. The effects of MAS nanoparticles on the growth of tomato plants were also evaluated and compared with those of tolclofos-methyl. The physical characteristics and structural features of MAS nanoparticles, such as their large surface-area-to-volume ratio, active surface sites and open channel pores, caused high antifungal efficacy against F. oxysporium. MAS nanoparticles presented an antifungal potential similar to that of tolclofos-methyl and much greater than that of the control under both laboratory and greenhouse conditions. The highest growth parameters were recorded in tomato plants treated with MAS nanoparticles, followed by those treated with tolclofos-methyl. Our study demonstrated the possible use of cylindrically cubic MAS nanoparticles as an effective alternative for the control of Fusarium root rot in tomato. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  19. An Alumina Toughened Zirconia Composite for Dental Implant Application: In Vivo Animal Results

    Science.gov (United States)

    Schierano, Gianmario; Faga, Maria Giulia; Menicucci, Giulio; Sabione, Cristian; Genova, Tullio; von Degerfeld, Mitzy Mauthe; Peirone, Bruno; Cassenti, Adele; Cassoni, Paola; Carossa, Stefano

    2015-01-01

    Ceramic materials are widely used for biomedical applications because of their remarkable biological and mechanical properties. Composites made of alumina and zirconia are particularly interesting owing to their higher toughness with respect to the monolithic materials. On this basis, the present study is focused on the in vivo behavior of alumina toughened zirconia (ATZ) dental implants treated with a hydrothermal process. A minipig model was implemented to assess the bone healing through histology and mRNA expression at different time points (8, 14, 28, and 56 days). The novel ATZ implant was compared to a titanium clinical standard. The implants were analyzed in terms of microstructure and surface roughness before in vivo tests. The most interesting result deals with a statistically significant higher digital histology index for ATZ implants with respect to titanium standard at 56 days, which is an unprecedented finding, to the authors' knowledge. Even if further investigations are needed before proposing the clinical use in humans, the tested material proved to be a promising candidate among the possible ceramic dental implants. PMID:25945324

  20. An Alumina Toughened Zirconia Composite for Dental Implant Application: In Vivo Animal Results

    Directory of Open Access Journals (Sweden)

    Gianmario Schierano

    2015-01-01

    Full Text Available Ceramic materials are widely used for biomedical applications because of their remarkable biological and mechanical properties. Composites made of alumina and zirconia are particularly interesting owing to their higher toughness with respect to the monolithic materials. On this basis, the present study is focused on the in vivo behavior of alumina toughened zirconia (ATZ dental implants treated with a hydrothermal process. A minipig model was implemented to assess the bone healing through histology and mRNA expression at different time points (8, 14, 28, and 56 days. The novel ATZ implant was compared to a titanium clinical standard. The implants were analyzed in terms of microstructure and surface roughness before in vivo tests. The most interesting result deals with a statistically significant higher digital histology index for ATZ implants with respect to titanium standard at 56 days, which is an unprecedented finding, to the authors’ knowledge. Even if further investigations are needed before proposing the clinical use in humans, the tested material proved to be a promising candidate among the possible ceramic dental implants.

  1. Effect of lateral size of graphene nano-sheets on the mechanical properties and machinability of alumina nano-composites

    Czech Academy of Sciences Publication Activity Database

    Porwal, H.; Saggar, Richa; Tatarko, P.; Grasso, S.; Saunders, T.; Dlouhý, Ivo; Reece, M. J.

    2016-01-01

    Roč. 42, č. 6 (2016), s. 7533-7542 ISSN 0272-8842 EU Projects: European Commission(XE) 264526 Institutional support: RVO:68081723 Keywords : Alumina * Graphene nano-sheets * Nano-composites * Mechanical properties * Machinability Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.986, year: 2016

  2. Highly fluorescent silver nanoclusters in alumina-silica composite optical fiber

    Energy Technology Data Exchange (ETDEWEB)

    Halder, A.; Chattopadhyay, R.; Majumder, S.; Paul, M. C.; Das, S.; Bhadra, S. K., E-mail: skbhadra@cgcri.res.in [Fiber Optics and Photonics Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Road, Kolkata 700032 (India); Bysakh, S.; Unnikrishnan, M. [Material Characterization Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Road, Kolkata 700032 (India)

    2015-01-05

    An efficient visible fluorescent optical fiber embedded with silver nanoclusters (Ag-NCs) having size ∼1 nm, uniformly distributed in alumina-silica composite core glass, is reported. Fibers are fabricated in a repetitive controlled way through modified chemical vapour deposition process associated with solution doping technique. Fibers are drawn from the transparent preforms by conventional fiber drawing process. Structural characteristics of the doped fibers are studied using transmission electron microscopy and electron probe micro analysis. The oxidation state of Ag within Ag-NCs is investigated by X-ray photo electron spectroscopy. The observed significant fluorescence of the metal clusters in fabricated fibers is correlated with electronic model. The experimentally observed size dependent absorption of the metal clusters in fabricated fibers is explained with the help of reported results calculated by ab-initio density functional theory. These optical fibers may open up an opportunity of realizing tunable wavelength fiber laser without the help of rare earth elements.

  3. Quantitative phase analysis of alumina/calcium-hexaluminate composites using neutron diffraction data and the Rietveld method

    International Nuclear Information System (INIS)

    Asmi, D.; Low, I.M.; O'Connor, B.H.; Kennedy, S.J.

    2000-01-01

    Full text: The Al 2 O 3 -CaO system is the basis of an important class of high-temperature refractories in the steel industry. It contains a number of stable intermediate compounds which include C 3 A, C 12 A 7 , CA, CA 2 , and CA 6 . These calcium aluminates are also important constituents of high alumina cement and have been used to produce high-strength and high-toughness ceramic-polymer composite materials. More recently, alumina composites containing 30 wt% CA 6 platelets have been developed by An et al which show characteristics of self-reinforcement and enhanced toughening through crack-bridging. In this paper, we describe the use of high-temperature neutron diffraction to monitor the in-situ phase formation and abundances of calcium aluminates (CA, CA 2 , and CA 6 ) in alumina composites containing 5-50 wt % CA 6 .at temperatures in the range 1000 - 1600 deg C. These composites were produced using reaction sintering of alumina and calcium oxide. For comparison purposes, control samples of pure α-alumina and CA 6 were also produced. Determination of relative phase abundances in these materials has been performed using the standardless Rietveld refinement method. Results show that the relative phase abundance of calcium aluminates in the composites increased with temperature and in proportion with the amount of calcium oxide present. The formation temperatures of CA, CA 2 , and CA 6 have been observed to occur at 1000 deg , 1200 deg, and ∼1350 deg C respectively, which agree well with results obtained from x-ray diffraction, synchrotron radiation diffraction and differential thermal analysis

  4. Properties and electronic structures of titanium aluminides-alumina composites from in-situ SHS process

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Y.F., E-mail: dinahyfsh@hotmail.com [School of Chemistry and Chemical Engineering, Guangxi University, Nanning, Guangxi 530000 (China); Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, Ministry of Education, Guilin University of Technology, Guilin, Guangxi 541004 (China); Zou, Z.G., E-mail: zouzg@glite.edu.cn [Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, Ministry of Education, Guilin University of Technology, Guilin, Guangxi 541004 (China); Xiao, Z.G.; Liu, K.; Long, F.; Wu, Y. [Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, Ministry of Education, Guilin University of Technology, Guilin, Guangxi 541004 (China)

    2011-02-25

    Research highlights: {yields} In-situ SHS processing method plus vacuum hot-pressing process were applied. {yields} Mechanical and electronic properties and microscopic structures were studied. {yields} First principle pseudopotential plane-wave-based DFT calculations were performed. - Abstract: Titanium aluminides-alumina composite was synthesized by in-situ self-propagating high-temperature synthesis (SHS) method, followed by hot-pressing process. To understand the fundamental differences between the composite and A1{sub 2}O{sub 3} ceramic, a comparative study was carried out using first-principles plane-wave pseudopotential method based on density functional theory (DFT). XRD analysis of final products confirmed the formation of TiAl, A1{sub 2}O{sub 3} and a small amount of Ti{sub 3}Al phases in the composites and the reaction mechanisms of the process were proposed. SEM observation revealed that a two-phase ({gamma} + {alpha}{sub 2}) TiAl-Ti{sub 3}Al lamellar structure was formed, and the composites exhibited a homogeneous microstructure. Moreover, density of states (DOS), band structure, charge density difference and Mulliken population analysis showed that metallic, covalent and ionic bonding were produced at the interfaces of the composite. O-Al interface bonds showed more covalent character with respect to pure Al{sub 2}O{sub 3}. Therefore, interface combination of the composite was improved, making the composite tougher (a toughness as high as 7.9 MPa m{sup 1/2}) than monophase Al{sub 2}O{sub 3} ceramic.

  5. Perfluoropolyether-Impregnated Mesoporous Alumina Composites Overcome the Dewetting-Tribological Properties Trade-Off.

    Science.gov (United States)

    Rowthu, Sriharitha; Hoffmann, Patrik

    2018-03-28

    Conventional omniphobic surfaces suffer from wear-sensitivity due to soft apolar coatings or substrates and protruding surface features that are eroded even for mild abrasion treatments, leading to the loss of dewetting properties after wear. Evidently, there was a trade-off between dewetting and tribological properties. Here, we show the establishment of self-healing slippery properties post severe abrasion by utilizing perfluoropolyether-impregnated mesoporous Al 2 O 3 (MPA) composites. The hard polar alumina matrix provides the optimal tribological properties, and the liquid lubricant in the porous network contributes to both tribological and self-healing dewetting properties. These composites sustained normal pressures up to 350 MPa during reciprocating sliding contacts. The severely abraded surfaces are capable of self-replenishing in ambient environment, driven by capillarity and surface diffusion processes, and regained their slippery properties toward water and hexadecane after 15 h of self-healing. Eventually, a dewetting-tribology diagram has been introduced to show different regimes, namely-optimal slippery properties, optimal tribological properties, and a mixed regime). We found out that the microstructural expression [Formula: see text] is a robust guiding tool to predict the regime of interest. This dewetting-tribological diagram may be marked as an inception to designing abrasion-resistant slippery liquid impregnated composites for overcoming the dewetting tribological properties trade-off. Such surfaces may potentially find applications in paint industries and as anti-icing surfaces.

  6. Influence of Collector Surface Composition and Water Chemistry on the Deposition of Cerium Dioxide Nanoparticles: QCM-D and Column Experiment Approaches

    Science.gov (United States)

    The deposition behavior of cerium dioxide (CeO2) nanoparticles (NPs) in dilute NaCl solutions was investigated as a function of collector surface composition, pH, ionic strength, and organic matter (OM). Sensors coated separately with silica, iron oxide, and alumina were applied ...

  7. Effect of Solution Treatment Process on Hardness of Alumina Reinforced Al-9Zn Composite Produced by Squeeze Casting

    Directory of Open Access Journals (Sweden)

    Dwi Rahmalina

    2014-10-01

    Full Text Available Characteristics of aluminium matrix composites reinforced by alumina have been developed to improve mechanical properties. One of the determining factors in the development of this material is parameter of solution treatment process. This study discusses the performance of the composite matrix of Al-9Zn-6Mg-3Si reinforced by alumina powder of 5 % volume fraction. Composite are manufactured by squeeze casting process with the pressure of 20 Ton in the metal mould. To improve mechanical properties, the precipitation hardening process is conducted through variation of temperature of solution treatment of 450, 475 and 500 °C and holding time of solution treatment of 30, 60 and 90 minutes. Materials are characterized by hardness testing and microstructure observation. The results showed that the optimum condition of hardness was produced by solution treatment temperature of 500 °C and 90 minutes holding time of 86 HRB.

  8. Removal of Hexavalent Chromium from Aqueous Solutions Using Magnetic Nanoparticles Coated with Alumina and Modified by Cetyl Trimethyl Ammonium Bromide

    Directory of Open Access Journals (Sweden)

    Mohammad Malakootian

    2015-12-01

    Full Text Available Introduction: The development of an effective method regarding chromium removal from the environment is of great importance. Therefore, the present study aimed to examiner magnetic nanoparticles coated with alumina modified by Cetyl Trimethyl Ammonium Bromide (CTAB in the removal of Cr6+ through magnetic solid phase extraction method. Materials & Methods: At first, iron oxide nanoparticles were synthesized, coated with alumina, modified with CTAB and characterized with suitable instruments. The factors affecting the process of chromium removal were investigated, including the concentration of CTAB, the pH, the amount of nanoparticles, the sample volume, a proper eluent, the adsorption and desorption time, and the effect of interfering ions. Moreover, the chromium concentration was determined by flame atomic absorption spectrometric (FAAS technique. The adsorption isotherm, adsorption capacity, and recoverability of the adsorbent were further examined. Results: The modified magnetic nanoparticles were demonstrated to be homogeneous, spherical, with a size lower than 20 nanometer having a magnetic property. The optimal conditions for chromium removal entailed 7*10-6 mol/L concentration of CTAB, pH range of 6-8, 0.1 g of the nanoparticles, 10 mL volume of the chromium sample (5 &mug mL-1, nitric acid 2 M as a suitable eluent, 15 minutes of adsorption and desorption, and no interference of interfering ions in the process of chromium separation. The process efficiency under optimal conditions was determined to be over 95%, which this process followed the Langmuir adsorption isotherm. The adsorption capacity proved to be 23.8 mg/g. Reusing after four times of adsorbent recovering was effective in the chromium removal (80%. The method accuracy for five measurement times was 4.155% and the method’s LOD was 0.081 mg/L. Conclusion: The method enjoys the benefits of convenient preparation of the adsorbent, high selectivity, high accuracy, short process

  9. Catalytic Properties of Alumina-Supported Ruthenium, Platinum, and Cobalt Nanoparticles towards the Oxidation of Cyclohexane to Cyclohexanol and Cyclohexanone

    Directory of Open Access Journals (Sweden)

    Ilhem Rekkab-Hammoumraoui

    2018-01-01

    Full Text Available A series of metal-loaded (Ru, Pt, Co alumina catalysts were evaluated for the catalytic oxidation of cyclohexane using tertbutylhydroperoxide (TBHP as oxidant and acetonitrile or acetic acid as solvent. These materials were prepared by the impregnation method and then characterized by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES, H2 chemisorption, Fourier Transformed Infrared Spectroscopy (FTIR, High-Resolution Transmission Electron Microscopy (HRTEM, and X-ray Diffraction (XRD. All the prepared materials acted as efficient catalysts. Among them, Ru/Al2O3 was found to have the best catalytic activity with enhanced cyclohexane conversion of 36 %, selectivity to cyclohexanol and cyclohexanone of 96 % (57.6 mmol, and cyclohexane turnover frequency (TOF of 288 h-1. Copyright © 2018 BCREC Group. All rights reserved Received: 26th May 2017; Revised: 17th July 2017; Accepted: 18th July 2017; Available online: 22nd January 2018; Published regularly: 2nd April 2018 How to Cite: Rekkab-Hammoumraoui, I., Choukchou-Braham, A. (2018. Catalytic Properties of Alumina-Supported Ruthenium, Platinum, and Cobalt Nanoparticles towards the Oxidation of Cyclohexane to Cyclohexanol and Cyclohexanone. Bulletin of Chemical Reaction Engineering & Catalysis, 13(1: 24-36 (doi:10.9767/bcrec.13.1.1226.24-35

  10. Low-cost fabrication and polar-dependent switching uniformity of memory devices using alumina interfacial layer and Ag nanoparticle monolayer

    Directory of Open Access Journals (Sweden)

    Peng Xia

    2017-11-01

    Full Text Available A facile and low-cost process was developed for fabricating write-once-read-many-times (WORM Cu/Ag NPs/Alumina/Al memory devices, where the alumina passivation layer formed naturally in air at room temperature, whereas the Ag nanoparticle monolayer was in situ prepared through thermal annealing of a 4.5 nm Ag film in air at 150°C. The devices exhibit irreversible transition from initial high resistance (OFF state to low resistance (ON state, with ON/OFF ratio of 107, indicating the introduction of Ag nanoparticle monolayer greatly improves ON/OFF ratio by four orders of magnitude. The uniformity of threshold voltages exhibits a polar-dependent behavior, and a narrow range of threshold voltages of 0.40 V among individual devices was achieved upon the forward voltage. The memory device can be regarded as two switching units connected in series. The uniform alumina interfacial layer and the non-uniform distribution of local electric fields originated from Ag nanoparticles might be responsible for excellent switching uniformity. Since silver ions in active layer can act as fast ion conductor, a plausible mechanism relating to the formation of filaments sequentially among the two switching units connected in series is suggested for the polar-dependent switching behavior. Furthermore, we demonstrate both alumina layer and Ag NPs monolayer play essential roles in improving switching parameters based on comparative experiments.

  11. Low-cost fabrication and polar-dependent switching uniformity of memory devices using alumina interfacial layer and Ag nanoparticle monolayer

    Science.gov (United States)

    Xia, Peng; Li, Luman; Wang, Pengfei; Gan, Ying; Xu, Wei

    2017-11-01

    A facile and low-cost process was developed for fabricating write-once-read-many-times (WORM) Cu/Ag NPs/Alumina/Al memory devices, where the alumina passivation layer formed naturally in air at room temperature, whereas the Ag nanoparticle monolayer was in situ prepared through thermal annealing of a 4.5 nm Ag film in air at 150°C. The devices exhibit irreversible transition from initial high resistance (OFF) state to low resistance (ON) state, with ON/OFF ratio of 107, indicating the introduction of Ag nanoparticle monolayer greatly improves ON/OFF ratio by four orders of magnitude. The uniformity of threshold voltages exhibits a polar-dependent behavior, and a narrow range of threshold voltages of 0.40 V among individual devices was achieved upon the forward voltage. The memory device can be regarded as two switching units connected in series. The uniform alumina interfacial layer and the non-uniform distribution of local electric fields originated from Ag nanoparticles might be responsible for excellent switching uniformity. Since silver ions in active layer can act as fast ion conductor, a plausible mechanism relating to the formation of filaments sequentially among the two switching units connected in series is suggested for the polar-dependent switching behavior. Furthermore, we demonstrate both alumina layer and Ag NPs monolayer play essential roles in improving switching parameters based on comparative experiments.

  12. Fabrication of Ceramic Matrix Composite Tubes Using a Porous Mullite/Alumina Matrix and Alumina/Mullite Fiber

    National Research Council Canada - National Science Library

    Radsick, Timothy

    2001-01-01

    Continuous fiber ceramic composites show promise for applications in high-temperature oxidizing environments, but their actual use has been limited in part due to unstable non-oxide-based constituents...

  13. Compressive Creep Behavior of NEXTEL(TradeMark) 720/Alumina Ceramic Matrix Composite at 1200 Degrees C in Air and in Steam Environment

    National Research Council Canada - National Science Library

    Szymczak, Neil R

    2006-01-01

    ...) 720/Alumina ceramic matrix composite at 1200 deg. C in air and 100% steam environments. The effects of creep loading history on the tensile and compressive material behavior will also be examined...

  14. Functionalization of γ-alumina cores by polyvinylpirrolidone: properties of the resulting biocompatible nanoparticles in aqueous suspension

    International Nuclear Information System (INIS)

    Fernandez, L.; Arranz, G.; Palacio, L.; Soria, C.; Sanchez, M.; Perez, G.; Lozano, A. E.; Hernandez, A.; Pradanos, P.

    2009-01-01

    A biocompatible polymer has been used to functionalize 45-50 nm diameter γ-alumina nanoparticles. Because the target was to use these systems in real applications, polyvinylpirrolidone (PVP) was chosen due to the characteristics of non-toxicity, biocompatibility, and feasibility of this polymer to form complexes with many cations and chemical species. This approach allows the use of these materials in medicine and food, textile, or pharmaceutical industry. The functionalization process required a previous attachment of an active group on the surface of the nanoparticles. Subsequently, a polymer chain was generated in situ, using vinyltrimethoxysilane (VTMS) and 1-vinyl-2-pyrrolidone (VP) as reactives. The morphology and topology of the nanocompound has been characterized in aqueous suspensions, attending to possible applications in this medium. The results obtained from the different techniques show that the polymer chain was successfully grafted to the nanoparticle surface, and allow an estimation of the size of the modified particle. Their electrical and conformational behavior have also been studied in different aqueous chemical environments.

  15. Functionalization of {gamma}-alumina cores by polyvinylpirrolidone: properties of the resulting biocompatible nanoparticles in aqueous suspension

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, L. [Universidad Nacional del Comahue, Dpto de Quimica, Facultad de Ingenieria (Argentina); Arranz, G.; Palacio, L. [Universidad de Valladolid, Dpto. Fisica Aplicada, Facultad de Ciencias (Spain); Soria, C.; Sanchez, M.; Perez, G. [Universidad Nacional del Comahue, Dpto de Quimica, Facultad de Ingenieria (Argentina); Lozano, A. E. [UA-CSIC-UVA, Surface and Porous Materials (SMAP) (Spain); Hernandez, A.; Pradanos, P., E-mail: pradanos@termo.uva.e [Universidad de Valladolid, Dpto. Fisica Aplicada, Facultad de Ciencias (Spain)

    2009-02-15

    A biocompatible polymer has been used to functionalize 45-50 nm diameter {gamma}-alumina nanoparticles. Because the target was to use these systems in real applications, polyvinylpirrolidone (PVP) was chosen due to the characteristics of non-toxicity, biocompatibility, and feasibility of this polymer to form complexes with many cations and chemical species. This approach allows the use of these materials in medicine and food, textile, or pharmaceutical industry. The functionalization process required a previous attachment of an active group on the surface of the nanoparticles. Subsequently, a polymer chain was generated in situ, using vinyltrimethoxysilane (VTMS) and 1-vinyl-2-pyrrolidone (VP) as reactives. The morphology and topology of the nanocompound has been characterized in aqueous suspensions, attending to possible applications in this medium. The results obtained from the different techniques show that the polymer chain was successfully grafted to the nanoparticle surface, and allow an estimation of the size of the modified particle. Their electrical and conformational behavior have also been studied in different aqueous chemical environments.

  16. Synthesis and Characterization of Cobalt Containing Nanoparticles on Alumina A Potential Catalyst for Gas to Liquid Fuels Production

    Science.gov (United States)

    Cowen, Jonathan; Hepp, Aloysius F.

    2016-01-01

    Fisher-Tröpsch synthesis (FTS) is a century-old gas-to-liquid (GTL) technology that commonly employs cobalt (Co, on an oxide support) or iron (supported or not) species catalysts. It has been well established that the activity of the Co catalyst depends directly upon the number of surface Co atoms. The addition of promoter (mainly noble) metals has been widely utilized to increase the fraction of Co that is available for surface catalysis. Direct synthesis of Co nanoparticles is a possible alternative approach; our preliminary synthesis and characterization efforts are described. Materials were characterized by various transmission microscopies and energy dispersive spectroscopy. Tri-n-octylphosphine oxide (TOPO) and dicobalt octacarbonyl were heated under argon to a temperature of 180 deg with constant stirring for 1 hr. Quenching the reaction in toluene produced Co-containing nanoparticles with a diameter of 5 to 10 nm. Alternatively, an alumina support (SBA-200 Al2O3) was added; the reaction was further stirred and the temperature was decreased to 140 deg to reduce the rate of further growth/ripening of the nucleated Co nanoparticles. A typical size of Co-containing NPs was also found to be in the range of 5 to 10 nm. This can be contrasted with a range of 50 to 200 nm for conventionally-produced Co-Al2O3 Fischer-Tröpsch catalysts. This method shows great potential for production of highly dispersed catalysts that are either supported or unsupported.

  17. Effect of friction time on the properties of friction welded YSZ‐alumina composite and 6061 aluminium alloy

    Directory of Open Access Journals (Sweden)

    Uday M. Basheer

    2012-03-01

    Full Text Available The aim of this work was to study the effect of friction time on the microstructure and mechanical properties of alumina 0, 25, 50 wt% yttria stabilized zirconia (YSZ composite and 6061 aluminium alloy joints formed by friction welding. The alumina-YSZ composites were prepared through slip casting in plaster of Paris molds (POP and subsequently sintered at 1600°C, while the aluminium rods were machined down using a lathe machine to the dimension required. The welding process was carried out under different rotational speeds and friction times, while friction force (0.5 ton-force was kept constant. Scanning electron microscopy was used to characterize the interface of the joints structure. The experimental results showed that the friction time has a significant effect on joint structure and mechanical properties.

  18. Effect of Alumina Addition to Zirconia Nano-composite on Low Temperature Degradation Process and Biaxial Strength

    Directory of Open Access Journals (Sweden)

    Moluk Aivazi

    2016-12-01

    Full Text Available Ceramic dental materials have been considered as alternatives to metals for dental implants application. In this respect, zirconia tetragonal stabilized with %3 yttrium, is of great importance among the ceramic materials for endosseous dental implant application. Because of its good mechanical properties and color similar to tooth. The aim and novelty of this study was to design and prepare Y-TZP nano-composite to reduce the degradation process at low temperature by alumina addition and maintaining submicron grain sized. Also, flexural strength of nano-composite samples was evaluated. Toward this purpose, alumina-Y-TZP nano-composites containing 0–30 vol% alumina (denoted as A-Y-TZP 0-30 were fabricated using α-alumina and Y-TZP nano-sized by sintering pressure less method. The synthesized samples were characterized using x-ray diffraction, field emission scanning electron microscopy equipped with energy dispersive x-ray spectroscopy techniques. Nano-composite samples with high density (≥96% and grain sized of ≤ 400 nm was obtained by sintering at 1270 °C for 170 min. After low temperature degradation test (LTD, A-Y-TZP20 and A-Y-TZP30 not showed monoclinic phase and the flexural strength in all of samples were higher than A-Y-TZP0. It was concluded that the grains were remained in submicron sized and A-Y-TZP20 and A-Y-TZP30 did not present biaxial strength reduction after LTD test.

  19. Epoxy based photoresist/carbon nanoparticle composites

    DEFF Research Database (Denmark)

    Lillemose, Michael; Gammelgaard, Lauge; Richter, Jacob

    2008-01-01

    We have fabricated composites of SU-8 polymer and three different types of carbon nanoparticles (NPs) using ultrasonic mixing. Structures of composite thin films have been patterned on a characterization chip with standard UV photolithography. Using a four-point bending probe, a well defined stress...... is applied to the composite thin film and we have demonstrated that the composites are piezoresistive. Stable gauge factors of 5-9 have been measured, but we have also observed piezoresistive responses with gauge factors as high as 50. As SU-8 is much softer than silicon and the gauge factor of the composite...

  20. The control mechanism of surface traps on surface charge behavior in alumina-filled epoxy composites

    International Nuclear Information System (INIS)

    Li, Chuanyang; Hu, Jun; Lin, Chuanjie; He, Jinliang

    2016-01-01

    To investigate the role surface traps play in the charge injection and transfer behavior of alumina-filled epoxy composites, surface traps with different trap levels are introduced by different surface modification methods which include dielectric barrier discharges plasma, direct fluorination, and Cr 2 O 3 coating. The resulting surface physicochemical characteristics of experimental samples were observed using atomic force microscopy, scanning electron microscopy and fourier transform infrared spectroscopy. The surface potential under dc voltage was detected and the trap level distribution was measured. The results suggest that the surface morphology of the experimental samples differs dramatically after treatment with different surface modification methods. Different surface trap distributions directly determine the charge injection and transfer property along the surface. Shallow traps with trap level of 1.03–1.11 eV and 1.06–1.13 eV introduced by plasma and fluorination modifications are conducive for charge transport along the insulating surface, and the surface potential can be modified, producing a smoother potential curve. The Cr 2 O 3 coating can introduce a large number of deep traps with energy levels ranging from 1.09 to 1.15 eV. These can prevent charge injection through the reversed electric field formed by intensive trapped charges in the Cr 2 O 3 coatings. (paper)

  1. Microstructural characterization of a zirconia-toughened alumina fiber reinforced niobium aluminide composite

    International Nuclear Information System (INIS)

    Nourbakhsh, S.; Sahin, O.; Rhee, W.H.; Margolin, H.

    1992-01-01

    This paper reports on an NbAl 3 + Nb 2 Al composite reinforced with continuous zirconia-toughened alumina, PRD-166 fibers, that was produced by pressure casing and was examined by optical and transmission electron microscopy and energy dispersive spectroscopy. Exposure of the fiber to the molten metal resulted in ZrO 2 and Al; 2 O 3 grain growth, formation of a thin layer of an amorphous phase on the grain boundaries of Al 2 O 3 and transformation of ZrO 2 . Preferential Al 2 O 3 grain growth near the surface of the fiber led to the rejection of ZrO 2 from this region into the molten metal. In NbAl 3 slip occurred by the glide of a left-angle 110 right-angle superdislocations and to a lesser extent by the glide of a pair of left-angle 11 bar 1 right-angle + left-angle 3 bar 1 bar 1 right-angle dislocations on the (112) planes and a/2 left-angle 110 right-angle superpartial dislocations on the (001) plane. The operating slip system in Nb 2 Al was identified as {010 left-angle 100 right-angle. A left-angle 100 right-angle dislocations were dissociated into a/x left-angle 100 right-angle partial dislocations joined together by a stacking fault

  2. Microstructure and high-temperature mechanical behavior of alumina/alumina-yttria-stabilized tetragonal zirconia multilayer composites

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez-Melendo, M.; Clauss, C.; Dominguez-Rodriguez, A. [Dept. de Fisica de la Materia Condensada, Sevilla (Spain); Sanchez-Herencia, A.J.; Moya, J.S. [CSIC, Madrid (Spain). Inst. de Ciencias de Materiales

    1997-08-01

    Layered composites of alternate layers of pure Al{sub 2}O{sub 3} (thickness of 125 {micro}m) and 85 vol% Al{sub 2}O{sub 3}-15 vol% ZrO{sub 2} that was stabilized with 3 mol% Y{sub 2}O{sub 3} (thickness of 400 {micro}m) were obtained by sequential slip casting and then fired at either 1,550 or 1,700 C. Constant-strain-rate tests were conducted on these materials in air at 1,400 C at an initial strain rate of 2 {times} 10{sup {minus}5} s{sup {minus}1}. The load axis was applied both parallel and perpendicular to the layer interfaces. Catastrophic failure occurred for the composite that was fired at 1,700 C, because of the coalescence of cavities that had developed in grain boundaries of the Al{sub 2}O{sub 3} layers. In comparison, the composite that was fired at 1,550 C demonstrated the ductility of the Al{sub 2}O{sub 3} + YTZP layer, but at a flow stress level that was determined by the Al{sub 2}O{sub 3} layer.

  3. Al6061 Hybrid Metal Matrix Composite Reinforced with Alumina and Molybdenum Disulphide

    Directory of Open Access Journals (Sweden)

    G. Pitchayyapillai

    2016-01-01

    Full Text Available Aluminum Hybrid Reinforcement Technology is a response to the dynamic ever-increasing service requirement of industries such as transportation, aerospace, automobile, and marine, due to its attractive properties like high ductility, highly conductivity, light weight, and high strength to weight ratio. In this evolution, an attempt has been made to investigate the wear rate of Al6061 hybrid metal matrix composite reinforced with the hard ceramic alumina (4, 8, and 12 wt.% of Al2O3 and soft solid lubricant of molybdenum disulphide (2, 4, and 6 wt.% of MoS2 is fabricated by using stir casting method. The unlubricated pins on disc wear tests were conducted to examine the wear behaviour of Al6061/12 wt.% of Al2O3/MoS2 composites. The sliding wear tests were carried out at various loads of 15, 30, and 45 N, sliding velocity (1.25, 2.50, and 3.25 m/sec, and different MoS2 wt.% (2, 4, and 6 wt.%. In addition, the CNC turning experiments were conducted on Al6061/12 wt.% Al2O3/6 wt.% MoS2 using CNMG 120408 uncoated carbide cutting tool under cutting of 100, 150, and 200 m/min, feed of 0.1, 0.2, and 0.3 mm/rev, and depth of cut of 1, 1.5, and 2 mm.

  4. Silver nanoparticles with an armor layer embedded in the alumina matrix to form nanocermet thin films with sound thermal stability.

    Science.gov (United States)

    Gao, Junhua; Tu, Chengjun; Liang, Lingyan; Zhang, Hongliang; Zhuge, Fei; Wu, Liang; Cao, Hongtao; Yu, Ke

    2014-07-23

    In this article, we demonstrate that the Al-alloyed Ag nanoparticle-embedded alumina nanocermet films lead to excellent thermal stability, even at 500 °C for 130 h under an ambient nitrogen atmosphere. The outward diffusion of Al atoms from the AgAl bimetallic alloy nanoparticles and their easy oxidation create an armor layer to suppress the mobility of Ag atoms. Then, the AlAg particles or/and agglomerates with a uniform spherical shape favor higher dispersion concentration within the host matrix, which is beneficial both for high absorptance in the visible range and for the solid localized surface plasmon absorption features in the AgAl-Al2O3 nanocermet films. Based on the AgAl-Al2O3 absorbing layer with sound optical and microstructural stability, we successfully constructed a high-temperature-endurable solar selective absorber. The multilayer stacked absorber demonstrates a high solar absorptance of ∼94.2% and a low thermal emittance of ∼15% (@ 673 K) after annealing at 450 °C for 70 h in an ambient nitrogen atmosphere.

  5. Sub-100-nm nanoparticle arrays with perfect ordering and tunable and uniform dimensions fabricated by combining nanoimprinting with ultrathin alumina membrane technique.

    Science.gov (United States)

    Zhan, Zhibing; Lei, Yong

    2014-04-22

    This work reports a nonlithographic nanopatterning approach to fabricate perfectly ordered nanoparticle arrays with tunable and uniform dimensions from about 30 to 80 nm and strict periods of 100 nm in a square lattice on large-area substrates by combining nanoimprinting with ultrathin alumina membrane technique. There is no requirement of any organic layer to support an ultrathin membrane in our novel route, which totally addressed the problems of nonuniform pores in prepatterned alumina templates and contamination during sample preparation, and thus is indispensable for our fabrication of ideally regular nanoparticle arrays on various kinds of substrates (such as flexible plastic). The effect of imprinted pressure on the prepatterning of Al foil was also studied in order to ensure the reusability of the precious imprinting stamps. This simple but efficient method provides a cost-effective platform for the fabrication of perfectly ordered nanostructures on substrates for various applications in nanotechnology.

  6. Electro-oxidation of some non-steroidal anti-inflammatory drugs on an alumina nanoparticle-modified glassy carbon electrode

    OpenAIRE

    TABESHNIA, Mahla; HELI, Hossein; JABBARI, Ali

    2010-01-01

    The electro-oxidation of mefenamic acid, diclofenac, and indomethacin on glassy carbon and alumina nanoparticle-modified glassy carbon electrodes in a phosphate buffer solution at physiological pH was studied. The techniques of cyclic voltammetry, chronoamperometry, impedance spectroscopy, and steady state polarization measurements were applied. The drugs were irreversibly oxidized on bath electrodes via an anodic peak and the process was controlled by diffusion in the bulk of soluti...

  7. Study on the toxicity of inhaled alumina nanoparticles: impact of physicochemical properties and adsorption artifacts on the measurement of biological responses

    Energy Technology Data Exchange (ETDEWEB)

    Pailleux, M; Pourchez, J; Boudard, D; Cottier, M [LINA Laboratoire Interdisciplinaire d' etude des Nanoparticules Aerosolisees, F-42023, Saint-Etienne (France); Grosseau, P, E-mail: pailleux@emse.fr [Ecole Nationale Superieure des Mines de Saint-Etienne, Centre SPIN, LPMG, UMR CNRS 5148, F-42023, Saint-Etienne (France)

    2011-07-06

    This work aims at developping a multidisciplinary approach to highlight the correlation between the toxicity of alumina engineered nanoparticles (NP) and their physicochemical characteristics. Accuracy of measurements depends on cell production after contact with particles, but also depends on the ability of biomolecules to get adsorbed on the NP. That's why, mechanisms of biomolecules adsorption on NP must be fully understood to avoid misinterpretation of data.

  8. Comportamento da viscosidade de um compósito vidro-partícula de alumina Viscosity behaviour of a glass-alumina particle composite

    Directory of Open Access Journals (Sweden)

    J. A. Rodrigues

    2003-04-01

    Full Text Available O aumento na produção de concretos refratários de alto desempenho tem demandado proporcional acréscimo no entendimento do comportamento reológico de suspensões concentradas de sólidos. Os concretos podem ser considerados como sistemas contendo agregados cujo diâmetro médio de partícula é superior a 100 mm e partículas finas que constituem a matriz. A reologia desse sistema é determinada, predominantemente, pela viscosidade da matriz, porém influenciada por parâmetros associados aos agregados. Este trabalho simula um sistema fluido-partícula, empregando um compósito vidro-partícula de alumina, caracterizando-o quanto à sua viscosidade em temperaturas em torno de 600 °C. Um viscosímetro de flexão foi empregado para medir as altas viscosidades do compósito. São mostrados resultados de viscosidade para diferentes teores de partículas de alumina. O sistema vidro-partícula apresentou um máximo na viscosidade para teores em torno de 50%-vol de partículas. Até aproximadamente 40%-vol de partículas, o compósito se comporta como um sistema newtoniano entre 560 ºC e 670 °C. Os resultados deste trabalho indicam a possibilidade de simulação da reologia na preparação de concretos refratários e da fluência do concreto operando em alta temperatura.Basic knowledge on rheological behaviour of highly concentrated suspensions is nowadays a very important issue in the refractory industry, regarding the production of high-performance castables. Refractory castables can be considered as a system containing aggregates and particles larger than 100 mm and finer ones constituting a matrix. In that system, the rheological behaviour is mainly determined by the viscosity of the matrix, although it is affected by parameters related to the aggregates. This work simulates a fluid-particle system through the use of a glass-alumina particle composite which viscosity was evaluated at temperatures close to 600 ºC. A beam-bending viscometer

  9. From Coating to Dopant: How the Transition Metal Composition Affects Alumina Coatings on Ni-Rich Cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Han, Binghong [Chemical; Key, Baris [Chemical; Lapidus, Saul H. [Chemical; Garcia, Juan C. [Chemical; Iddir, Hakim [Chemical; Vaughey, John T. [Chemical; Dogan, Fulya [Chemical

    2017-11-14

    Surface alumina coatings have been shown to be an effective way to improve the stability and cyclability of cathode materials. However, a detailed understanding of the relationship between the surface coatings and the bulk layered oxides is needed to better define the critical cathode–electrolyte interface. In this paper, we systematically studied the effect of the composition of Ni-rich LiNixMnyCo1–x–yO2 (NMC) on the surface alumina coatings. Changing cathode composition from LiNi0.5Mn0.3Co0.2O2 (NMC532) to LiNi0.6Mn0.2Co0.2O2 (NMC622) and LiNi0.8Mn0.1Co0.1O2 (NMC811) was found to facilitate the diffusion of surface alumina into the bulk after high-temperature annealing. By use of a variety of spectroscopic techniques, Al was seen to have a high bulk compatibility with higher Ni/Co content, and low bulk compatibility was associated with Mn in the transition metal layer. It was also noted that the cathode composition affected the observed morphology and surface chemistry of the coated material, which has an effect on electrochemical cycling. The presence of a high surface Li concentration and strong alumina diffusion into the bulk led to a smoother surface coating on NMC811 with no excess alumina aggregated on the surface. Structural characterization of pristine NMC particles also suggests surface Co segregation, which may act to mediate the diffusion of the Al from the surface to the bulk. The diffusion of Al into the bulk was found to be detrimental to the protection function of surface coatings leading to poor overall cyclability, indicating the importance of compatibility between surface coatings and bulk oxides on the electrochemical performance of coated cathode materials. These results are important in developing a better coating method for synthesis of next-generation cathode materials for lithium-ion batteries.

  10. Effects of β-spodumene on the phase development and densification of alumina/aluminium-titanate composites

    International Nuclear Information System (INIS)

    Manurunga, P.; Low, I.M.; O'Connor, B.H.; Kennedy, S.J.

    2000-01-01

    Full text: Spodumene (Li 2 O.Al 2 O 3 .4SiO 2 ) has a monoclinic α polymorph which is stable under ambient conditions and it transforms irreversibly at 1080 deg C to a tetragonal β polymorph which melts at 1423 deg C. Spodumene has been widely used in the glass and ceramic industry for decades as a lithia-bearing flux and low-expansion filler in whiteware bodies. It is also commonly used for making glasses and ceramics which are harder, smoother, chemical and thermal shock resistant. Recently, spodumene has been used as a liquid-phase sintering aid for the densification of alumina, mullite, and aluminium-titanate (AT). In this paper, we describe the use of dilatometry and high temperature neutron diffraction to study respectively the effect of β-spodumene additions (0-15 wt %) on the densification, and in-situ phase formation and abundances in alumina composites containing 30 wt% at temperatures in the range 1000-1400 deg C. These composites were produced using reaction sintering of alumina and rutile. Determination of relative phase abundances in these materials has been performed using the Rietveld refinement method. Results show that β-spodumene began to decompose by phase separation and partial melting at 1290 deg C, followed by complete melting at 1330 deg C. Formation of AT was observed to occur at 1310 deg C and its abundance increased with temperature. The presence of β-spodumene did not react with alumina or rutile to form additional phases. Up to 5 wt% β-spodumene was involved in the liquid-phase-sintering and densification of the alumina-AT composite. Addition of β-spodumene in excess of 5 wt% resulted in pronounced vitrification which partly recrystallised when cooled to room temperature. The presence of glassy phase has been verified by selected-area diffraction in transmission electron microscopy. Dilatometry results show that the presence of up to 5 wt% β-spodumene resulted in a lower onset of sintering temperature and improved densification

  11. Study of the Effects of Ethanol As an Additive with a Blend of Poultry Litter Biodiesel and Alumina Nanoparticles on a Diesel Engine

    Directory of Open Access Journals (Sweden)

    Ramesha D. K.

    2017-12-01

    Full Text Available With the increasing population and rise in industrialization, the demand for petroleum reserves is increasing almost daily. This is causing depletion of the non-renewable energy resources. This work aims to find an alternative fuel for diesel engines. The use of poultry litter oil biodiesel obtained from poultry industry waste, which is a non-edible source for biodiesel, is very encouraging as an alternative fuel for diesel engines. The aim of this study is to observe and maximize the performance of poultry litter oil biodiesel by adding alumina nanoparticles and ethanol. The biodiesel is prepared with acid and the base catalysed transesterification of poultry litter oil with methanol using concentrated sulphuric acid and potassium hydroxide as catalysts. The experimentation is carried out on a CI engine with three different blends - B20 biodiesel blend, B20 biodiesel blend with 30 mg/L alumina nanoparticles, and B20 biodiesel blend with 30 mg/L alumina nanoparticles and 15 ml/L ethanol. The performance, combustion and emission characteristics of all three blends are compared with neat diesel. The results of the experiment show that ethanol as an additive improves the combustion and performance characteristics. It increases the brake thermal efficiency and peak cylinder pressure. It also reduces CO and UBHC emissions and there is a marginal increase in NOx emissions as compared to neat diesel.

  12. Synthesis and ceramic processing of zirconia alumina composites for application as solid oxide fuel cell electrolytes; Sintese e processamento de compositos de zirconia-alumina para aplicacao como eletrolito em celulas a combustivel de oxido solido

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Rafael Henrique Lazzari

    2007-07-01

    The global warmness and the necessity to obtain clean energy from alternative methods than petroleum raises the importance of developing cleaner and more efficient systems of energy generation, among then, the solid oxide fuel cell (SOFC). Cubic stabilized zirconia (CSZ) has been the most studied material as electrolyte in SOFC, due to its ionic conductivity and great stability at operation conditions. However, its low fracture toughness difficulties its application as a thin layer, what could lead to an improvement of cell efficiency. In this sense, the alumina addition in CSZ forms a composite, which can shift its mechanical properties, without compromising its electrical properties. In this work, coprecipitation synthesis route and ceramic processing of zirconia-alumina composites were studied, in order to establish optimum conditions to attain high density, homogeneous microstructure, and better mechanical properties than CSZ, without compromising ionic conductivity. For this purpose, composites containing up to 40 wt % of alumina, in a 9 mol % yttria-stabilized zirconia (9Y-CSZ) matrix were evaluated. In order to optimize the synthesis of the composites, a preliminary study of powder obtaining and processing were carried out, at compositions containing 20 wt % of alumina, in 9Y-CSZ. The ceramic powders were characterized by helium picnometry, X-ray diffraction, scanning electronic microscopy, transmission electronic microscopy, thermogravimetry, differential scanning calorimetry, granulometry by laser diffraction and gas adsorption (BET). The characterization of sinterized compacts were performed by X-ray diffraction, scanning electron microscopy, optical microscopy, density measurements, Vickers indentation and impedance spectroscopy. The obtained results show that the alumina addition, in the 9Y-CSZ matrix powders, raises the specific surface area, promotes deagglomeration of powders and elevates the oxides crystallization temperature, requiring higher

  13. The Effect of Alumina and Magnesia Supported Germanium Nanoparticles on the Growth of Carbon Nanotubes in the Chemical Vapor Deposition Method

    Directory of Open Access Journals (Sweden)

    Ghazaleh Allaedini

    2015-01-01

    Full Text Available The effect of alumina and magnesia supported germanium (Ge nanoparticles on the synthesis of carbon nanotubes (CNTs using the chemical vapor deposition (CVD method in atmospheric pressure was investigated. The TEM micrographs confirmed the formation of carbon nanotubes, and the field emission scanning electron microscopy (FESEM analysis suggested a tip-growth mechanism for the grown carbon nanotubes. The X-ray diffraction (XRD pattern indicated a graphitic nature of the carbon nanotubes. The obtained CNTs using Ge nanoparticles supported by MgO resulted in a higher degree of graphitization than the CNTs obtained using Ge nanoparticles supported by Al2O3. Raman spectroscopy analysis of the CNTs confirmed the presence of radial breathing modes (RBM, which verified the formation of CNTs. High frequency Raman analysis demonstrated that the degree of graphitization of the synthesized CNTs using magnesia supported Ge nanoparticles is higher than that of the alumina supported Ge nanoparticles with the values of (ID/IG ratios equal to 0.45 and 0.73, respectively.

  14. Sprayable Elastic Conductors Based on Block Copolymer Silver Nanoparticle Composites

    OpenAIRE

    Vural, Mert; Behrens, Adam M.; Ayyub, Omar B.; Ayoub, Joseph J.; Kofinas, Peter

    2014-01-01

    Block copolymer silver nanoparticle composite elastic conductors were fabricated through solution blow spinning and subsequent nanoparticle nucleation. The reported technique allows for conformal deposition onto nonplanar substrates. We additionally demonstrated the ability to tune the strain dependence of the electrical properties by adjusting nanoparticle precursor concentration or localized nanoparticle nucleation. The stretchable fiber mats were able to display electrical conductivity val...

  15. Influence of coprecipitation and mechanical mixture methods on the characteristics of nickel oxide-alumina composites

    International Nuclear Information System (INIS)

    Cordeiro, G.L.; Yoshito, W.K.; Ussui, V.; Lima, N.B. de; Lazar, D.R.R.

    2014-01-01

    Alumina-supported nickel catalysts are currently used in the reforming process due to low cost and high activity for hydrogen production from alcohols. In this work, the effect of preparation methods on nickel oxide-alumina based materials has been investigated. Nickel content was fixed at 15 wt%. Ceramic powders were obtained by coprecipitation in ammonia medium and mechanical mixture. Coprecipitated materials were calcined in air at 750 deg C to obtain the corresponding oxides. Materials obtained by mechanical mixture were prepared by wet milling of nickel oxide and alumina powders, both synthesized by precipitation and calcination in air at 450 and 750 deg C, respectively. Powders were characterized by X-ray diffraction, nitrogen gas sorption by applying the BET method, laser diffraction, scanning electron microscopy, electrophoretic mobility measurements for zeta potential determination and infrared spectroscopy. The results showed that coprecipitation method allowed the production of mixed oxides with high surface area (232,7 ± 3,2 m 2 .g -1 ) and normal granulometric distribution while mechanical mixture led to the formation of materials constituted by gamma alumina and nickel oxide phases, with low surface area (136,2 ± 0,5 m 2 .g -1 ) and bimodal granulometric distribution. (author)

  16. Repair bond strength of a resin composite to alumina-reinforced feldspathic ceramic

    NARCIS (Netherlands)

    Goia, Tamiye Simone; Pereira Leite, Fabiola Pessoa; Valandro, Luiz Felipe; Oezcan, Mutlu; Bottino, Marco Antonio

    2006-01-01

    This study compared the microtensile bond strength of a repair resin to an alumina-reinforced feldspathic ceramic (Vitadur-alpha, Vita) after 3 surface conditioning methods: Group 1, etching with 9.6% hydrofluoric acid for 1 minute plus rinsing and drying, followed by application of silane for 5

  17. Blocking of grain reorientation in self-doped alumina materials

    International Nuclear Information System (INIS)

    Suarez, M.; Fernandez, A.; Menendez, J.L.; Ramirez-Rico, J.; Torrecillas, R.

    2011-01-01

    Alumina nanoparticles 10-20 nm in diameter were nucleated on alumina particles, 150 nm average diameter, by a colloidal route followed by calcination. It is shown that after sintering, the final grain size is up to 20% smaller due to the addition of the alumina nanoparticles. Electron backscattered diffraction analysis shows that whereas a correlation in the relative crystalline orientations between neighbouring grains exists in the pure materials, the addition of alumina nanoparticles results in a random crystalline orientation.

  18. Cyclic Creep and Recovery Behavior of Nextel(Trademark) 720/Alumina Ceramic Matrix Composite at 1200deg C in Air and in Steam Environments

    Science.gov (United States)

    2007-09-01

    cement . Composites today are everyday items. As technology advances so does the need for composites for advanced materials. Aerospace has taken...Furthermore, microstructural deformational failure mechanisms present in air and in steam environments are explored. 4 II. Background 2.1...is processed at high temperatures [6, 2]. Common types of ceramic matrix materials being studied are alumina, silicon nitride and silicon carbide

  19. Flexible Nanocellulose - Nanoparticle Composites: Structures and Properties

    OpenAIRE

    UTHPALA MANAVI GARUSINGHE

    2018-01-01

    Nanocellulose is biodegradable and renewable and has many attractive properties of technological interest. Therefore, nanocellulose can be converted into thin films, which is used in wide range of applications. However, the property range achievable with nanocellulose by itself still has limitations. This thesis focuses on the production of nanocellulose-inorganic nanoparticle composites to combine the advantage associated with both individual components together to extend the range of proper...

  20. Microstructural changes in copper-graphite-alumina nanocomposites produced by mechanical alloying.

    Science.gov (United States)

    Rodrigues, Ivan; Guedes, Mafalda; Ferro, Alberto C

    2015-02-01

    Microstructural features of nanostructured copper-matrix composites produced via high-energy milling were studied. Copper-graphite-alumina batches were planetary ball milled up to 16 h; copper-graphite batches were also prepared under the same conditions to evaluate the effect of contamination from the milling media. The microstructure of the produced materials was characterized by field emission gun scanning electron microscopy/energy-dispersive spectroscopy and related to Raman, X-ray diffraction, and particle size analysis results. Results showed that alumina was present in all milled powders. However, size reduction was effective at shorter times in the copper-graphite-alumina system. In both cases the produced powders were nanostructured, containing graphite and alumina nanoparticles homogeneously distributed in the copper matrix, especially for longer milling times and in the presence of added alumina. Copper crystallite size was significantly affected above 4 h milling; nanographite size decreased and incipient amorphization occurred. A minimum size of 15 nm was obtained for the copper crystallite copper-alumina-graphite composite powders, corresponding to 16 h of milling. Contamination from the media became more significant above 8 h. Results suggest that efficient dispersion and bonding of graphite and alumina nanoparticles in the copper matrix is achieved, envisioning high conductivity, high strength, and thermal stability.

  1. Synthesis of alumina/YAG 20 vol% composite by co-precipitation

    Directory of Open Access Journals (Sweden)

    Radosław Lach

    2011-12-01

    Full Text Available Co-precipitation of alumina/YAG precursor from aluminum and yttrium nitrate solution with ammonium carbonate results in dawsonite. Its crystallographic parameters differ from the compound precipitated with no yttrium additive. It suggests that yttrium ions become incorporated into the dawsonite structure. The DSC/TG and X-ray diffraction measurements show decomposition of dawsonite at elevated temperatures resulting in γ-Al2O3 and then δ- and θ-alumina modifications. Full transformation to α-Al2O3 and YAG occurs at temperatures higher than 1230°C. Starting powder for the sintering experiments was prepared using the coprecipitated precursor calcined at 600°C. Seeding of such powder with 5 wt.% α-Al2O3 results in material of 98% density at 1500°C. Much lower densification show compacts of unseeded powder.

  2. Tribological studies of composite material based on CuZn38Al2Mn1Fe brass strengthened with δ-alumina fibres

    Directory of Open Access Journals (Sweden)

    J. W. Kaczmar

    2010-10-01

    Full Text Available The results of tribological studies (friction coefficient, wear resistance of the frictional couple of composite material based on CuZn38Al2Mn1Fe brass strengthened with δ-alumina fibres (Saffil and cast iron are shown in this paper. The wear investigations were conducted applying the tribological pin-on-disc tester and the friction forces between composite materials containing 10 and 20 vol. % of δ-alumina fibres (Saffil and cast iron were registered. Wear was determined on the base of the specimen mass loss after 1, 3,5 and 8.5 km of friction distance.

  3. Composite reinforced alumina ceramics with titan and lantana for use in coating storage tanks and transport of crude oil

    International Nuclear Information System (INIS)

    Mendes, C.E.; Rego, S.A.B.C.; Oliveira, J.C.S.; Ferreira, R.A. Sanguinetti; Yadava, Y.P.

    2011-01-01

    The objective of this work is to use ceramics to improve the performance of the tanks that store and transport crude oil and which use metallic materials for their manufacture. These tanks in contact with crude oil undergo a process of degradation on their surfaces, since crude oil is a highly corrosive substance. And in turn ceramic materials have good stability in hostile environments. However, they are inherently fragile for display little plastic deformation. Therefore, the choice of a ceramic composite alumina-titania-lantana has high mechanical strength and high toughness which were produced by thermo-mechanical processing. These composites were sintered at 1350 ° C for 36 hours, and it was held Vickers hardness testing and microstructural characterization to assess their surfaces before and after the attack by crude to use such material as ceramic coating. These results will be presented at the congress. (author)

  4. Dynamic Response and Simulations of Nanoparticle-Enhanced Composites

    National Research Council Canada - National Science Library

    Mantena, P. R; Al-Ostaz, Ahmed; Cheng, Alexander H

    2007-01-01

    ...) molecular dynamics simulations of nanoparticle-enhanced composites and fly- ash based foams that are being considered for the future generation naval structures or retrofitting of existing ones...

  5. Composite-Nanoparticles Thermal History Sensors

    Science.gov (United States)

    2014-05-01

    developing composite nanostructure-based (core-shell nanoparticles, heterostructure nanowires , and nano-flakes) temperature history sensors for recording the...shell microspheres …………………………………….. 72 7.2 Ga2O3 nanowires …………………………………………….. 76 7.3 GaN porous microtubes …………………………………….. 79 7.4 Coated CNTs...HRTEM experiments of nanoparticles and holey Al2O3 supporting films for high temperature experiments of nanowires . The sandwiched carbon films or

  6. Part I. Corrosion studies of continuous alumina fiber reinforced aluminum-matrix composites. Part II. Galvanic corrosion between continuous alumina fiber reinforced aluminum-matrix composites and 4340 steel

    Science.gov (United States)

    Zhu, Jun

    Part I. The corrosion performance of continuous alumina fiber reinforced aluminum-matrix composites (CF-AMCs) was investigated in both the laboratory and field environments by comparing them with their respective monolithic matrix alloys, i.e., pure Al, A1-2wt%Cu T6, and Al 6061 T6. The corrosion initiation sites were identified by monitoring the changes in the surface morphology. Corrosion current densities and pH profiles at localized corrosion sites were measured using the scanning-vibrating electrode technique and the scanning ion-selective electrode technique, respectively. The corrosion damage of the materials immersed in various electrolytes, as well as those exposed in a humidity chamber and outdoor environments, was evaluated. Potentiodynamic polarization behavior was also studied. The corrosion initiation for the composites in 3.15 wt% NaCl occurred primarily around the Fe-rich intermetallic particles, which preferentially existed around the fiber/matrix interface on the composites. The corrosion initiation sites were also caused by physical damage (e.g., localized deformation) to the composite surface. At localized corrosion sites, the buildup of acidity was enhanced by the formation of micro-crevices resulting from fibers left in relief as the matrix corroded. The composites that were tested in exposure experiments exhibited higher corrosion rates than their monolithic alloys. The composites and their monolithic alloys were subjected to pitting corrosion when anodically polarized in the 3.15 wt% NaCl, while they passivated when anodically polarized in 0.5 M Na2SO4. The experimental results indicated that the composites exhibited inferior corrosion resistance compared to their monolithic matrix alloys. Part II. Galvanic corrosion studies were conducted on CF-AMCs coupled to 4340 steel since CF-AMCs have low density and excellent mechanical properties and are being considered as potential jacketing materials for reinforcing steel gun barrels. Coupled and

  7. Highly selective formation of imines catalyzed by silver nanoparticles supported on alumina

    DEFF Research Database (Denmark)

    Mielby, Jerrik Jørgen; Poreddy, Raju; Engelbrekt, Christian

    2014-01-01

    -2 in the gas phase. The use of an efficient and selective Ag catalyst for the oxidative dehydrogenation of alcohol in the presence of amines gives a new green reaction protocol for imine synthesis. (C) 2014, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B......The oxidative dehydrogenation of alcohols to aldehydes catalyzed by Ag nanoparticles supported on Al2O3 was studied. The catalyst promoted the direct formation of imines by tandem oxidative dehydrogenation and condensation of alcohols and amines. The reactions were performed under mild conditions...... and afforded the imines in high yield (up to 99%) without any byproducts other than H2O. The highest activity was obtained over 5 wt% Ag/Al2O3 in toluene with air as oxidant. The reactions were also performed under oxidant-free conditions where the reaction was driven to the product side by the production of H...

  8. Composite Materials with Magnetically Aligned Carbon Nanoparticles Having Enhanced Electrical Properties and Methods of Preparation

    Science.gov (United States)

    Hong, Haiping (Inventor); Peterson, G.P. (Bud) (Inventor); Salem, David R. (Inventor)

    2016-01-01

    Magnetically aligned carbon nanoparticle composites have enhanced electrical properties. The composites comprise carbon nanoparticles, a host material, magnetically sensitive nanoparticles and a surfactant. In addition to enhanced electrical properties, the composites can have enhanced mechanical and thermal properties.

  9. Nanoparticle-Liquid Crystalline Elastomer Composites

    Directory of Open Access Journals (Sweden)

    Yan Ji

    2012-01-01

    Full Text Available Liquid crystalline elastomers (LCEs exhibit a number of remarkable physical effects, including a uniquely high-stroke reversible mechanical actuation triggered by external stimuli. Fundamentally, all such stimuli affect the degree of liquid crystalline order in the polymer chains cross-linked into an elastic network. Heat and the resulting thermal actuation act by promoting entropic disorder, as does the addition of solvents. Photo-isomerization is another mechanism of actuation, reducing the orientational order by diminishing the fraction of active rod-like mesogenic units, mostly studied for azobenzene derivatives incorporated into the LCE composition. Embedding nanoparticles provides a new, promising strategy to add functionality to LCEs and ultimately enhance their performance as sensors and actuators. The motivation for the combination of nanoparticles with LCEs is to provide better-controlled actuation stimuli, such as electric and magnetic fields, and broad-spectrum light, by selecting and configuring the appropriate nanoparticles in the LCE matrix. Here we give an overview of recent advances in this area with a focus on preparation, physical properties and actuation performance of the resultant nanocomposites.

  10. Nucleation and growth characteristics of cavities during the early stages of tensile creep deformation in a superplastic zirconia-20 wt% alumina composite

    International Nuclear Information System (INIS)

    Owen, D.M.; Chokshi, A.H.; Nutt, S.R.

    1997-01-01

    Constant-stress tensile creep experiments on a superplastic 3-mol%-yttria-stabilized tetragonal zirconia composite with 20 wt% alumina revealed that cavities nucleate relatively early during tensile deformation. The number of cavities nucleated increases with increasing imposed stress. The cavities nucleate at triple points associated largely with an alumina grain, and then grow rapidly in a cracklike manner to attain dimensions on the order of the grain facet size. It is suggested that coarser-grained superplastic ceramics exhibit lower ductility due to the ease in formation of such grain boundary facet-cracks and their interlinkage to form a macroscopic crack of critical dimensions

  11. Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials

    Science.gov (United States)

    2015-12-18

    electric circuits from a composite material of silver nanoparticles and elastomeric fibres. Nat Nanotechnol... Conductors Based on Block Copolymer Silver Nanoparticle Composites. Acs Nano 2015, 9 (1), 336-344. 2. (a) Yang, T. I.; Brown, R. N. C.; Kempel, L. C...Stretchable nanoparticle conductors with self-organized conductive pathways. Abstr Pap Am Chem S 2014, 248; (c) Balazs, A. C.; Emrick, T.;

  12. Method of producing zeolite encapsulated nanoparticles

    DEFF Research Database (Denmark)

    2015-01-01

    The invention therefore relates to a method for producing zeolite, zeolite-like or zeotype encapsulated metal nanoparticles, the method comprises the steps of: 1) Adding one or more metal precursors to a silica or alumina source; 2) Reducing the one or more metal precursors to form metal...... nanoparticles on the surface of the silica or alumina source; 3) Passing a gaseous hydrocarbon, alkyl alcohol or alkyl ether over the silica or alumina supported metal nanoparticles to form a carbon template coated zeolite, zeolite-like or zeotype precursor composition; 4a) Adding a structure directing agent...... to the carbon template coated zeolite, zeolite-like or zeotype precursor composition thereby creating a zeolite, zeolite-like or zeotype gel composition; 4b) Crystallising the zeolite, zeolite-like or zeotype gel composition by subjecting said composition to a hydrothermal treatment; 5) Removing the carbon...

  13. Effect of nanoparticles and nanofibers on Mode I fracture toughness of fiber glass reinforced polymeric matrix composites

    International Nuclear Information System (INIS)

    Kelkar, Ajit D.; Mohan, Ram; Bolick, Ronnie; Shendokar, Sachin

    2010-01-01

    Graphical abstract: Use of alumina nanoparticles and TEOS electrospun nanofibers at the interfaces of glass fiber plies to develop delamination resistant epoxy polymeric composites and compare their Mode I fracture toughness characteristics. - Abstract: In the recent past, the research involving the fabrication and processing of reinforced polymer nanocomposites has increased significantly. These new materials are enabling in the discovery, development and incorporation of improved nanocomposite materials with effective manufacturing methodologies for several defense and industrial applications. These materials eventually will allow the full utilization of nanocomposites in not only reinforcing applications but also in multifunctional applications where sensing and the unique optical, thermal, electrical and magnetic properties of nanoparticles can be combined with mechanical reinforcement to offer the greatest opportunities for significant advances in material design and function. This paper presents two methods and material systems for processing and integration of the nanomaterial constituents, namely: (a) dispersing alumina nanoparticles using high energy mixing (using ultrasonication, high shear mixing and pulverization) and (b) electrospinning technique to manufacture nanofibers. These reinforced polymer nanocomposites and the processing methodologies are likely to provide effective means of improving the interlaminar properties of woven fiber glass composites compared to the traditional methods such as stitching and Z-pinning. The electrospinning technology relies on the creation of nanofibers with improved molecular orientation with reduced concentration of fiber imperfections and crystal defects. Electrospinning process utilizes surface tension effects created by electrostatic forces acting on liquid droplets, creating numerous nanofibers. These nanofibers thus have potential to serve as through-the-thickness reinforcing agents in woven composites. While

  14. Adsorptive removal of oil spill from oil-in-fresh water emulsions by hydrophobic alumina nanoparticles functionalized with petroleum vacuum residue.

    Science.gov (United States)

    Franco, Camilo A; Cortés, Farid B; Nassar, Nashaat N

    2014-07-01

    Oil spills on fresh water can cause serious environmental and economic impacts onshore activities affecting those who exploit freshwater resources and grassland. Alumina nanoparticles functionalized with vacuum residue (VR) were used as a low-cost and high hydrophobic nanosorbents. The nanomaterial resulting showed high adsorption affinity and capacity of oil from oil-in-freshwater emulsion. The effects of the following variables on oil removal were investigated, namely: contact times, solution pH, initial oil concentrations, temperature, VR loadings and salinity. Kinetic studies showed that adsorption was fast and equilibrium was achieved in less than 30 min. The amount adsorbed of oil was higher for neutral system compared to acidic or basic medium. Increasing the VR loading on nanoparticle surface favored the adsorption. Results of this study showed that oil removal for all systems evaluated had better performance at pH value of 7 using nano-alumina functionalized with 4 wt% VR. Adsorption equilibrium and kinetics were evaluated using the Polanyi theory-based Dubinin-Ashtakhov (DA) model, and pseudo-first and pseudo-second order-models, respectively. Copyright © 2014 Elsevier Inc. All rights reserved.

  15. Terahertz acoustic phonon detection from a compact surface layer of spherical nanoparticles powder mixture of aluminum, alumina and multi-walled carbon nanotube

    Science.gov (United States)

    Abouelsayed, A.; Ebrahim, M. R.; El hotaby, W.; Hassan, S. A.; Al-Ashkar, Emad

    2017-10-01

    We present terahertz spectroscopy study on spherical nanoparticles powder mixture of aluminum, alumina, and MWCNTs induced by surface mechanical attrition treatment (SMAT) of aluminum substrates. Surface alloying of AL, Al2O3 0.95% and MWCNTs 0.05% powder mixture was produced during SMAT process, where a compact surface layer of about 200 μm due to ball bombardment was produced from the mixture. Al2O3 alumina powder played a significant role in MWCNTs distribution on surface, those were held in deformation surface cites of micro-cavities due to SMAT process of Al. The benefits are the effects on resulted optical properties of the surface studied at the terahertz frequency range due to electrical isolation confinement effects and electronic resonance disturbances exerted on Al electronic resonance at the same range of frequencies. THz acoustic phonon around 0.53-0.6 THz (17-20 cm-1) were observed at ambient conditions for the spherical nanoparticles powder mixture of Al, Al2O3 and MWCNTs. These results suggested that the presence of Al2O3 and MWCNTs during SMAT process leads to the optically detection of such acoustic phonon in the THz frequency range.

  16. Chemically Derived Dense Alumina-Zirconia Composites for Improved Mechanical and Wear Erosion Properties

    Science.gov (United States)

    1998-01-01

    As a result of this funded project high purity Zirconia-Toughened Alumina (ZTA) ceramic powders with and without yttria were produced using metal alkoxide precursors. ZTA ceramic powders with varying volume percents of zirconia were prepared (7, 15, and 22%). Aluminum tri-sec butoxide, zirconium propoxide, and yttrium isopropoxide were the reagents used. Synthesis conditions were varied to control the hydrolysis and the aging conditions for the sol to gel transition. FTIR analysis and rheological characterization were used to follow the structural evolution during the sol to gel transition. The greater extent of hydrolysis and the build-up of structure measured from viscoelastic properties were consistent. Heat treatment was conducted to produce submicron grain fully crystalline ZTA ceramic powders. This improved materials should have enhanced properties such strength, toughness, and wear resistance for advanced structural applications, for example engine components in high technology aerospace applications.

  17. Phase stability and dynamics of entangled polymer-nanoparticle composites.

    KAUST Repository

    Mangal, Rahul

    2015-06-05

    Nanoparticle-polymer composites, or polymer-nanoparticle composites (PNCs), exhibit unusual mechanical and dynamical features when the particle size approaches the random coil dimensions of the host polymer. Here, we harness favourable enthalpic interactions between particle-tethered and free, host polymer chains to create model PNCs, in which spherical nanoparticles are uniformly dispersed in high molecular weight entangled polymers. Investigation of the mechanical properties of these model PNCs reveals that the nanoparticles have profound effects on the host polymer motions on all timescales. On short timescales, nanoparticles slow-down local dynamics of the host polymer segments and lower the glass transition temperature. On intermediate timescales, where polymer chain motion is typically constrained by entanglements with surrounding molecules, nanoparticles provide additional constraints, which lead to an early onset of entangled polymer dynamics. Finally, on long timescales, nanoparticles produce an apparent speeding up of relaxation of their polymer host.

  18. Synthesis of Core-Shell Nanoparticle Composites

    Science.gov (United States)

    2010-08-17

    monodispersed gold nanoparticles , which were produced from reducing a HAuCl4 solution, in a suspension of pre- prepared Gd2O3 nanoparticles . 1...produced from reducing a HAuCl4 solution, in a suspension of pre- prepared Gd2O3 nanoparticles . 15. SUBJECT TERMS nanoparticles , Polymer Chemistry 16...known that nanoparticles of materials such as gold, silver, and magnetite can interact with electromagnetic waves (surface plasmon resonance) in the

  19. Effect of low-dimensional alumina structures on viability of L 929 cells

    Energy Technology Data Exchange (ETDEWEB)

    Fomenko, Alla N., E-mail: alserova@ispms.tsc.ru; Korovin, Matvey S., E-mail: msk@ispms.tsc.ru; Bakina, Olga V., E-mail: ovbakina@ispms.tsc.ru; Kazantsev, Sergey O., E-mail: kzso@ispms.tsc.ru; Glazkova, Elena A., E-mail: eagl@ispms.tsc.ru; Svarovskaya, Natalia V., E-mail: nvsv@ispms.tsc.ru; Lozhkomoev, Aleksandr S., E-mail: asl@ispms.tsc.ru [National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation)

    2015-10-27

    In the study, we estimated the cytotoxicity of alumina nanoparticles differing in shape (nanofibers, nanoplates, nanosheets, agglomerates of nanosheets) and close in physicochemical properties (particle size, specific surface area, phase composition, and zeta potential). The alumina structures were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) data, low-temperature nitrogen adsorption, and dynamic light scattering (DLS). The cytotoxicity was estimated on fibroblast cells of the L929 line. It was found that a more adverse effect on the cells was exerted by alumina nanofibers and nanosheets. The action of nanosheets on the cells was inhibitory and was of about the same level, irrespective of the observation period. The effect of alumina nanosheet agglomerates and nanoplates on the cell proliferation was weak even at an exposure time of 72 h.

  20. The Possibility of Using Composite Nanoparticles in High Energy Materials

    Science.gov (United States)

    Komarova, M. V.; Vorozhtsov, A. B.; Wakutin, A. G.

    2017-01-01

    The effect of nanopowders on the burning rate varying with the metal content in mixtures of different high energy composition is investigated. Experiments were performed on compositions based on an active tetrazol binder and electroexplosive nanoaluminum with addition of copper, nickel, or iron nanopowders, and of Al-Ni, Al-Cu, or Al-Fe composite nanoparticles produced by electrical explosion of heterogeneous metal wires. The results obtained from thermogravimetric analysis of model metal-based compositions are presented. The advantages of the composite nanoparticles and the possibility of using them in high energy materials are discussed.

  1. Engineering durable hydrophobic surfaces on porous alumina ceramics using in-situ formed inorganic-organic hybrid nanoparticles

    NARCIS (Netherlands)

    Gu, Jianqiang; Wang, Junwei; Li, Yanan; Xu, Xin; Chen, Chusheng; Winnubst, Louis

    2017-01-01

    Hydrophobic surfaces are required for a variety of applications owing to their water repellent and self-cleaning properties. In this work, we present a novel approach to prepare durable hydrophobic surfaces on porous ceramics. A polydimethylsiloxane (PDMS) film was applied to a porous alumina wafer,

  2. A comparative approach to synthesis and sintering of alumina/yttria nanocomposite powders using different precipitants

    Energy Technology Data Exchange (ETDEWEB)

    Kafili, G. [Department of Nanotechnology Engineering, Faculty of Advanced Sciences and Technologies, University of Isfahan, Isfahan, 81746-73441 (Iran, Islamic Republic of); Movahedi, B., E-mail: b.movahedi@ast.ui.ac.ir [Department of Nanotechnology Engineering, Faculty of Advanced Sciences and Technologies, University of Isfahan, Isfahan, 81746-73441 (Iran, Islamic Republic of); Milani, M. [Faculty of Advanced Materials and Renewable Energy Research Center, Tehran (Iran, Islamic Republic of)

    2016-11-01

    Alumina/yttria nanocomposite powder as an yttrium aluminum garnet (YAG) precursor was synthesized via partial wet route using urea and ammonium hydrogen carbonate (AHC) as precipitants, respectively. The products were characterized using X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and energy dispersive spectroscopy. The use of urea produced very tiny spherical Y-compounds with chemical composition of Y{sub 2}(CO{sub 3}){sub 3}·nH{sub 2}O, which were attracted to the surface of alumina nanoparticles and consequently, a core-shell structure was obtained. The use of ammonium hydrogen carbonate produced sheets of Y-compounds with chemical composition of Y(OH)CO{sub 3} covering the alumina nanoparticles. A fine-grained YAG ceramic (about 500 nm), presenting a non-negligible transparency (45% RIT at IR range) was obtained by the spark plasma sintering (SPS) of alumina-yttria nanocomposite synthesized in the urea system. This amount of transmission was obtained by only the sintering of the powder specimen without any colloidal forming process before sintering or adding any sintering aids or dopant elements. However, by spark plasma sintering of alumina-yttria nanocomposite powder synthesized in AHC system, an opaque YAG ceramic with an average grain size of 1.2 μm was obtained. - Highlights: • Urea proved to be an appropriate precipitant for obtaining a core-shell alumina/yttria nanocomposite. • Alumina/yttria nanocomposite powders with more appropriate morphology and highly sinterability. • A fine-grained YAG ceramic was obtained by SPS of alumina-yttria nanocomposite.

  3. On the drop-weight testing of alumina/aluminum laminated composites

    Indian Academy of Sciences (India)

    Laminated composites with ceramic front layers and metallic or composite backing layers have gained attractiveness as lightweight armours, as they exhibit the same ballistic performance with lower areal densities as compared to steels. Drop-weight testing (DWT) has potential for evaluating the low velocity impact ...

  4. Magnetic Nano-particle Based Composite Materials/Magnets

    Data.gov (United States)

    National Aeronautics and Space Administration — This project seeks to develop and evaluate novel advanced composite materials which contain magnetic nano-particles. The primary goal is to develop a new class of...

  5. Ca stabilized zirconia based composites by wet consolidation of zirconia and high alumina cement mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Bruni, Y.L.; Garrido, L.B.; Aglietti, E.F., E-mail: lgarrido@cetmic.unlp.edu.ar [Centro de Tecnologia de Recursos Minerales y Ceramica (CETMIC/CIC-CONICET La Plata), Buenos Aires (Argentina)

    2012-07-01

    Composites of the CaO-Al{sub 2}O{sub 3}-ZrO{sub 2} system are widely used in many industrial applications. In this study, porous Ca stabilized ZrO{sub 2} composites were developed from a starting mixture of m-ZrO{sub 2} and calcium aluminate cement. Ceramics were produced by wet consolidation of aqueous suspensions with and without corn starch as pore former agent and sintering at 1000-1500 °C. The influence of processing parameters on crystalline phases, sintering behavior and textural characteristics was examined. Stabilized c-ZrO{sub 2} formed with the composition of Ca{sub 0.15}Zr{sub 0.85}O{sub 1.85}. The sintering of the mixtures lead to porous composites materials. Textural properties were analyzed considering the initial composition and the present crystalline phases. (author)

  6. Polymer-Nanoparticle Composites: From Synthesis to Modern Applications

    Directory of Open Access Journals (Sweden)

    Thomas Hanemann

    2010-05-01

    Full Text Available The addition of inorganic spherical nanoparticles to polymers allows the modification of the polymers physical properties as well as the implementation of new features in the polymer matrix. This review article covers considerations on special features of inorganic nanoparticles, the most important synthesis methods for ceramic nanoparticles and nanocomposites, nanoparticle surface modification, and composite formation, including drawbacks. Classical nanocomposite properties, as thermomechanical, dielectric, conductive, magnetic, as well as optical properties, will be summarized. Finally, typical existing and potential applications will be shown with the focus on new and innovative applications, like in energy storage systems.

  7. Two Glass Transitions Associated to Different Dynamic Disorders in the Nematic Glassy State of a Non-Symmetric Liquid Crystal Dimer Dopped with γ-Alumina Nanoparticles

    Science.gov (United States)

    Diez-Berart, Sergio; López, David O.; Salud, Josep; Diego, José Antonio; Sellarès, Jordi; Robles-Hernández, Beatriz; de la Fuente, María Rosario; Ros, María Blanca

    2015-01-01

    In the present work, the nematic glassy state of the non-symmetric LC dimer α-(4-cyanobiphenyl-4′-yloxy)-ω-(1-pyrenimine-benzylidene-4′-oxy) undecane is studied by means of calorimetric and dielectric measurements. The most striking result of the work is the presence of two different glass transition temperatures: one due to the freezing of the flip-flop motions of the bulkier unit of the dimer and the other, at a lower temperature, related to the freezing of the flip-flop and precessional motions of the cyanobiphenyl unit. This result shows the fact that glass transition is the consequence of the freezing of one or more coupled dynamic disorders and not of the disordered phase itself. In order to avoid crystallization when the bulk sample is cooled down, the LC dimer has been confined via the dispersion of γ-alumina nanoparticles, in several concentrations.

  8. Two Glass Transitions Associated to Different Dynamic Disorders in the Nematic Glassy State of a Non-Symmetric Liquid Crystal Dimer Dopped with g-Alumina Nanoparticles

    Directory of Open Access Journals (Sweden)

    Sergio Diez-Berart

    2015-06-01

    Full Text Available In the present work, the nematic glassy state of the non-symmetric LC dimer α-(4-cyanobiphenyl-4′-yloxy-ω-(1-pyrenimine-benzylidene-4′-oxy undecane is studied by means of calorimetric and dielectric measurements. The most striking result of the work is the presence of two different glass transition temperatures: one due to the freezing of the flip-flop motions of the bulkier unit of the dimer and the other, at a lower temperature, related to the freezing of the flip-flop and precessional motions of the cyanobiphenyl unit. This result shows the fact that glass transition is the consequence of the freezing of one or more coupled dynamic disorders and not of the disordered phase itself. In order to avoid crystallization when the bulk sample is cooled down, the LC dimer has been confined via the dispersion of γ-alumina nanoparticles, in several concentrations.

  9. Synthesis and Characterization of Nickel-Alumina Composites from Recycled Nickel Powder

    OpenAIRE

    Karayannis, V. G.; Moutsatsou, A. K.

    2012-01-01

    The recycling of metallic waste to create more valuable materials and their valorization into upgraded metal-based composites constitutes an important field of study. The composite industry nowadays considers environmental improvements as important as other properties of the materials. In the present paper, nickel powder was recycled from ferrous scrap, a low-cost and largely available material, by an effective hydrometallurgical recovery process. Then, this recycled powder was successfully u...

  10. Modeling and multi-objective optimization of powder mixed electric discharge machining process of aluminum/alumina metal matrix composite

    Directory of Open Access Journals (Sweden)

    Gangadharudu Talla

    2015-09-01

    Full Text Available Low material removal rate (MRR and high surface roughness values hinder large-scale application of electro discharge machining (EDM in the fields like automobile, aerospace and medical industry. In recent years, however, EDM has gained more significance in these industries as the usage of difficult-to-machine materials including metal matrix composites (MMCs increased. In the present work, an attempt has been made to fabricate and machine aluminum/alumina MMC using EDM by adding aluminum powder in kerosene dielectric. Results showed an increase in MRR and decrease in surface roughness (Ra compared to those for conventional EDM. Semi empirical models for MRR and Ra based on machining parameters and important thermo physical properties were established using a hybrid approach of dimensional and regression analysis. A multi response optimization was also performed using principal component analysis-based grey technique (Grey-PCA to determine optimum settings of process parameters for maximum MRR and minimum Ra within the experimental range. The recommended setting of process parameters for the proposed process has been found to be powder concentration (Cp = 4 g/l, peak current (Ip = 3 A, pulse on time (Ton = 150 μs and duty cycle (Tau = 85%.

  11. Nanoparticles with tunable shape and composition fabricated by nanoimprint lithography

    International Nuclear Information System (INIS)

    Alayo, Nerea; Bausells, Joan; Pérez-Murano, Francesc; Conde-Rubio, Ana; Labarta, Amilcar; Batlle, Xavier; Borrisé, Xavier

    2015-01-01

    Cone-like and empty cup-shaped nanoparticles of noble metals have been demonstrated to provide extraordinary optical properties for use as optical nanoanntenas or nanoresonators. However, their large-scale production is difficult via standard nanofabrication methods. We present a fabrication approach to achieve arrays of nanoparticles with tunable shape and composition by a combination of nanoimprint lithography, hard-mask definition and various forms of metal deposition. In particular, we have obtained arrays of empty cup-shaped Au nanoparticles showing an optical response with distinguishable features associated with the excitations of localized surface plasmons. Finally, this route avoids the most common drawbacks found in the fabrication of nanoparticles by conventional top-down methods, such as aspect ratio limitation, blurring, and low throughput, and it can be used to fabricate nanoparticles with heterogeneous composition. (paper)

  12. Novel manufacturing process of nanoparticle/Al composite filler metals of tungsten inert gas welding by accumulative roll bonding

    Energy Technology Data Exchange (ETDEWEB)

    Fattahi, M., E-mail: fattahi.put@gmail.com [Technical Inspection Engineering Department, Petroleum University of Technology, Abadan (Iran, Islamic Republic of); Noei Aghaei, V. [Aerospace Engineering Department, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Dabiri, A.R. [Technical Inspection Engineering Department, Petroleum University of Technology, Abadan (Iran, Islamic Republic of); Amirkhanlou, S. [Young Researchers and Elite Club, Najafabad Branch, Islamic Azad University, Najafabad (Iran, Islamic Republic of); Akhavan, S.; Fattahi, Y. [Materials Engineering Department, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of)

    2015-11-11

    In the present work, accumulative roll bonding (ARB) was used as an effective method for manufacturing nanoparticle/Al composite filler metals of tungsten inert gas (TIG) welding. After welding, the distribution of ceramic nanoparticles and mechanical properties of welds were investigated. By applying ARB, ceramic nanoparticles were uniformly dispersed in the composite filler metals. Consequently, the welds produced by these filler metals had a uniform dispersion of ceramic nanoparticles in their compositions. The test results showed that the yield strength of welds was greatly increased when using the nanoparticle/Al composite filler metals. The improvement in the yield strength was attributed to the coefficient of thermal expansion mismatch and Orowan strengthening mechanisms. Therefore, according to the results presented in this paper, it can be concluded that the nanoparticle/Al composite filler metals can serve as a novel filler metal for TIG welding of aluminum and its alloys.

  13. Exceptionally strong and robust millimeter-scale graphene–alumina composite membranes

    International Nuclear Information System (INIS)

    Berdova, Maria; Franssila, Sami; Perros, Alexander Pyymaki; Kim, Wonjae; Riikonen, Juha; Li, Changfeng; Lipsanen, Harri; Ylitalo, Tuomo; Kassamakov, Ivan; Hæggström, Edward; Heino, Jouni

    2014-01-01

    Graphene has attracted attention as a potential strengthening material and functional component in suspended membranes as utilized in micro and nanosystems. Development of a practical and scalable fabrication process is a necessary step to allow the exceptional material properties of graphene to be fully exploited in composite structures. Using standard and scalable microfabrication processes, we fabricated free-standing chemical vapor deposition monolayer graphene-reinforced Al 2 O 3 composite membranes, 0.5 mm in diameter, that are strong and robust. Bulge tests revealed that the graphene reinforcement increased the membrane fracture strength by a factor of at least three and maximum sustainable strain from 0.28% to at least 0.69%. We show that the graphene-reinforced membranes are even tolerant to significant cracking without loss of membrane integrity. The graphene composite membranes’ freestanding area of ∼200 000 μm 2 is almost a thousand times larger than suspended graphene membranes reported elsewhere. The presented graphene composite membranes may be seen as representing an interesting new class of durable composite materials warranting further study and having potential for broad applicability in a variety of fields. (paper)

  14. Antibacterial effect of composite resins containing quaternary ammonium polyethyleneimine nanoparticles

    International Nuclear Information System (INIS)

    Yudovin-Farber, Ira; Beyth, Nurit; Weiss, Ervin I.; Domb, Abraham J.

    2010-01-01

    Quaternary ammonium polyethyleneimine (QA-PEI)-based nanoparticles were synthesized by crosslinking with dibromopentane followed by N-alkylation with various alkyl halides and further N-methylation with methyl iodide. Insoluble pyridinium-type particles were prepared by suspension polymerization of 4-vinyl pyridine followed by N-alkylation with alkyl halides. Polyamine-based nanoparticles embedded in restorative composite resin at 1% w/w were tested for antibacterial activity against Streptococcus mutans using direct contact test. Activity analysis revealed that the alkyl chain length of the QA-PEI nanoparticles plays a significant role in antibacterial activity of the reagent. The most potent compound was octyl-alkylated QA-PEI embedded in restorative composite resin at 1% w/w that totally inhibited S. mutans growth in 3-month-aged samples. This data indicates that restorative composite resin with antibacterial properties can be produced by the incorporation of QA-PEI nanoparticles.

  15. Antibacterial effect of composite resins containing quaternary ammonium polyethyleneimine nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Yudovin-Farber, Ira [Hebrew University of Jerusalem, Department of Medicinal Chemistry and Natural Products, School of Pharmacy, Faculty of Medicine (Israel); Beyth, Nurit; Weiss, Ervin I. [Hebrew University of Jerusalem, Department of Prosthodontics, Faculty of Dentistry (Israel); Domb, Abraham J., E-mail: avid@ekmd.huji.ac.i [Hebrew University of Jerusalem, Department of Medicinal Chemistry and Natural Products, School of Pharmacy, Faculty of Medicine (Israel)

    2010-02-15

    Quaternary ammonium polyethyleneimine (QA-PEI)-based nanoparticles were synthesized by crosslinking with dibromopentane followed by N-alkylation with various alkyl halides and further N-methylation with methyl iodide. Insoluble pyridinium-type particles were prepared by suspension polymerization of 4-vinyl pyridine followed by N-alkylation with alkyl halides. Polyamine-based nanoparticles embedded in restorative composite resin at 1% w/w were tested for antibacterial activity against Streptococcus mutans using direct contact test. Activity analysis revealed that the alkyl chain length of the QA-PEI nanoparticles plays a significant role in antibacterial activity of the reagent. The most potent compound was octyl-alkylated QA-PEI embedded in restorative composite resin at 1% w/w that totally inhibited S. mutans growth in 3-month-aged samples. This data indicates that restorative composite resin with antibacterial properties can be produced by the incorporation of QA-PEI nanoparticles.

  16. Fabrication of a segmented composite stainless steel-alumina discharge tube for a theta-pinch coil

    International Nuclear Information System (INIS)

    Dickinson, J.M.; Stoddard, S.D.; Muller, J.F.

    1975-11-01

    An 80-mm-diam segmented discharge tube that simulated in a simplified way the blanket and first wall of the Reference Theta-Pinch Reactor (RTPR) has been constructed. The segments were fabricated by plasma-arc spraying an alumina coating on tubular stainless steel trapezoids. These were laid up to form a cylinder that was contained in a fully dense alumina vacuum tube. The fabrication processes are discussed in detail

  17. Mechanical and Thermal Transport Properties of Suspension Thermal-Sprayed Alumina-Zirconia Composite Coatings

    Czech Academy of Sciences Publication Activity Database

    Oberste-Berghaus, J.; Legoux, J.-G.; Moreau, C.; Tarasi, F.; Chráska, Tomáš

    2008-01-01

    Roč. 17, č. 1 (2008), s. 91-104 ISSN 1059-9630 Institutional research plan: CEZ:AV0Z20430508 Keywords : thermal spraying * nanocrystalline composites * wear Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 1.200, year: 2008

  18. Effect of platelet orientation on the properties of alumina platelet zirconia matrix composites

    DEFF Research Database (Denmark)

    Toft Sørensen, O.; Li, W.-Y.

    1996-01-01

    Platelet alignment in Al2O3pl - TZ3YS composites formed by injection moulding, slip casting, and tape casting, has been examined. Mechanical properties have been determined in terms of flexural strength and fracture toughness, with respect to materials formed by different techniques...

  19. Effects of air abrasion with alumina or glass beads on surface characteristics of CAD/CAM composite materials and the bond strength of resin cements

    Directory of Open Access Journals (Sweden)

    ARAO Nobuaki

    2015-12-01

    Full Text Available ABSTRACT Objective The study aimed to evaluate effects of air abrasion with alumina or glass beads on bond strengths of resin cements to CAD/CAM composite materials. Material and Methods CAD/CAM composite block materials [Cerasmart (CS and Block HC (BHC] were pretreated as follows: (a no treatment (None, (b application of a ceramic primer (CP, (c alumina-blasting at 0.2 MPa (AB, (d AB followed by CP (AB+CP, and (e glass-beads blasting at 0.4 MPa (GBB followed by CP (GBB+CP. The composite specimens were bonded to resin composite disks using resin cements [G-CEM Cerasmart (GCCS and ResiCem (RC]. The bond strengths after 24 h (TC 0 and after thermal cycling (TC 10,000 at 4–60°C were measured by shear tests. Three-way ANOVA and the Tukey compromise post hoc tests were used to analyze statistically significant differences between groups (α=0.05. Results For both CAD/CAM composite materials, the None group exhibited a significant decrease in bond strength after TC 10,000 (p0.05. The AB+CP group showed a significantly higher bond strength after TC 10,000 than did the AB group for RC (p<0.05, but not for GCCS. The GBB+CP group showed the highest bond strength for both thermal cyclings (p<0.05. Conclusions Air abrasion with glass beads was more effective in increasing bond durability between the resin cements and CAD/CAM composite materials than was using an alumina powder and a CP.

  20. Effect of platelet orientation on the properties of alumina platelet zirconia matrix composites

    DEFF Research Database (Denmark)

    Toft Sørensen, O.; Li, W.-Y.

    1996-01-01

    Platelet alignment in Al2O3pl - TZ3YS composites formed by injection moulding, slip casting, and tape casting, has been examined. Mechanical properties have been determined in terms of flexural strength and fracture toughness, with respect to materials formed by different techniques, and to the p...... 220 and 300 degrees C, which is approximately in the same range as for the matrix....

  1. In situ surface reduction of a NiO-YSZ-alumina composite using scanning probe microscopy

    DEFF Research Database (Denmark)

    Hansen, Karin Vels; Jacobsen, Torben; Thydén, Karl Tor Sune

    2014-01-01

    In situ surface reductions of NiO-YSZ-Al2O3 composites into Ni-YSZ-Al2O3 cermets were carried out at 312–525 °C in a controlled atmosphere high-temperature scanning probe microscope (CAHT-SPM) in dry and humidified 9 % H2 in N2. The reduction of NiO was followed by contact mode scanning of topogr...

  2. Toughening effects quantification in glass matrix composite reinforced by alumina platelets

    Czech Academy of Sciences Publication Activity Database

    Kotoul, M.; Pokluda, J.; Šandera, P.; Dlouhý, Ivo; Chlup, Zdeněk; Boccaccini, A. R.

    2008-01-01

    Roč. 56, č. 12 (2008), s. 2908-2918 ISSN 1359-6454 R&D Projects: GA ČR(CZ) GA106/06/0724 Institutional research plan: CEZ:AV0Z20410507 Keywords : glass matrix composites * crack deflection * fracture surface toughness * residual stresses Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 3.729, year: 2008

  3. Composite Coatings of Alumina-based Ceramics and Stainless Steel Manufactured by Plasma Spraying

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Ageorges, H.; Neufuss, Karel; Zahálka, F.

    2009-01-01

    Roč. 15, č. 2 (2009), s. 108-114 ISSN 1392-1320 R&D Projects: GA AV ČR 1QS200430560 Institutional research plan: CEZ:AV0Z20430508 Keywords : Cermet * plasma spraying * microstructure * elastic modulus * wear resistance Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.299, year: 2009 http://internet.ktu.lt/en/science/journals/medz/medz0-97.html#Composite_Coatings_

  4. Aluminium Matrix Composites Reinforced with Co-continuous Interlaced Phases Aluminium-alumina Needles

    Directory of Open Access Journals (Sweden)

    Elvio de Napole Gregolin

    2002-09-01

    Full Text Available An Al-5SiO2 (5 wt% of SiO2 aluminium matrix fiber composite was produced where the reinforcement consists of fossil silica fibers needles. After being heat-treated at 600 °C, the original fiber morphology was retained but its microstructure changed from solid silica to an interconnected (Al-Si/Al2O3 interlaced structure named co-continuous composite. A technique of powder metallurgy, using commercial aluminium powder and the silica fibers as starting materials, followed by hot extrusion, was used to produce the composite. The co-continuous microstructure was obtained partially or totally on the fibers as a result of the reaction, which occurs during the heat treatment, first by solid diffusion and finally by the liquid Al-Si in local equilibrium, formed with the silicon released by reaction. The internal structure of the fibers was characterized using field emission electron microscope (FEG-SEM and optical microscopy on polished and fractured samples.

  5. Anodization Mechanism on SiC Nanoparticle Reinforced Al Matrix Composites Produced by Power Metallurgy.

    Science.gov (United States)

    Ferreira, Sonia C; Conde, Ana; Arenas, María A; Rocha, Luis A; Velhinho, Alexandre

    2014-12-19

    Specimens of aluminum-based composites reinforced by silicon carbide nanoparticles (Al/SiC np ) produced by powder metallurgy (PM) were anodized under voltage control in tartaric-sulfuric acid (TSA). In this work, the influence of the amount of SiC np on the film growth during anodizing was investigated. The current density versus time response and the morphology of the porous alumina film formed at the composite surface are compared to those concerning a commercial aluminum alloy (AA1050) anodized under the same conditions. The processing method of the aluminum alloys influences the efficiency of the anodizing process, leading to a lower thicknesses for the unreinforced Al-PM alloy regarding the AA1050. The current density versus time response is strongly dependent on the amount of SiC np . The current peaks and the steady-state current density recorded at each voltage step increases with the SiC np volume fraction due to the oxidation of the SiC np . The formation mechanism of the anodic film on Al/SiC np composites is different from that occurring in AA1050, partly due the heterogeneous distribution of the reinforcement particles in the metallic matrix, but also to the entrapment of SiC np in the anodic film.

  6. Microstructural analysis and mechanical characterization of aluminum matrix nanocomposites reinforced with uncoated and Cu-coated alumina particles

    Energy Technology Data Exchange (ETDEWEB)

    Beygi, H., E-mail: hossein.beygi@stu-mail.um.ac.ir; Sajjadi, S.A.; Zebarjad, S.M.

    2014-06-01

    Aluminum matrix composites used in the aerospace, military and automotive industries are typically fabricated by a stir casting method. However, when nanoparticles are used for reinforcement, fabrication of composite materials by this method leads to the formation of a large number of structural defects. In this study, copper coating of alumina reinforcement particles is investigated as a technique for improving the structure of Al-Al{sub 2}O{sub 3} composites. Microstructural investigations by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersion spectroscopy (EDS) and transmission electron microscopy (TEM) showed that the alumina particles were coated uniformly with copper shells. Copper coating of the reinforcing particles significantly increased their wettability in the molten aluminum alloy, strengthened the matrix-particle interfaces and improved the distribution of reinforcing particles within the matrix. Due to these microstructural improvements, the hardness, compressive strength, yield stress, tensile strength and elongation of the composites were enhanced by copper coating of the alumina particles.

  7. Radiation-induced synthesis of gold, iron-oxide composite nanoparticles

    International Nuclear Information System (INIS)

    Seino, Satoshi; Yamamoto, Takao; Nakagawa, Takashi; Kinoshita, Takuya; Kojima, Takao; Taniguchi, Ryoichi; Okuda, Shuichi

    2007-01-01

    Composite nanoparticles consisting of magnetic iron oxide nanoparticles and gold nanoparticles were synthesized using gamma-rays or electron beam. Ionizing irradiation induces the generation of reducing species inside the aqueous solution, and gold ions are reduced to form metallic Au nanoparticles. The size of Au nanoparticles depended on the dose rate and the concentration of support iron oxide. The gold nanoparticles on iron oxide nanoparticles selectively adsorb biomolecules via Au-S bonding. By using magnetic property of the support iron oxide nanoparticles, the composite nanoparticles are expected as a new type of magnetic nanocarrier for biomedical applications. (author)

  8. Process to Produce Iron Nanoparticle Lunar Dust Simulant Composite

    Science.gov (United States)

    Hung, Ching-cheh; McNatt, Jeremiah

    2010-01-01

    A document discusses a method for producing nanophase iron lunar dust composite simulant by heating a mixture of carbon black and current lunar simulant types (mixed oxide including iron oxide) at a high temperature to reduce ionic iron into elemental iron. The product is a chemically modified lunar simulant that can be attracted by a magnet, and has a surface layer with an iron concentration that is increased during the reaction. The iron was found to be -iron and Fe3O4 nanoparticles. The simulant produced with this method contains iron nanoparticles not available previously, and they are stable in ambient air. These nanoparticles can be mass-produced simply.

  9. Fabrication and characterization of magnetic nanoparticle composite membranes

    Science.gov (United States)

    Cruickshank, Akeem Armand

    To effectively and accurately deliver drugs within the human body, both new designs and components for implantable micropumps are being studied. Designs must ensure high biocompatibility, drug compatibility, accuracy and small power consumption. The focus of this thesis was to fabricate a prototype magnetic nanoparticle membrane for eventual incorporation into a biomedical pump and then determine the relationship between this membrane deflection and applied pneumatic or magnetic force. The magnetic nanoparticle polymer composite (MNPC) membranes in this study were composed of crosslinked polydimethylsiloxane (PDMS) and iron oxide nanoparticles (IONPs). An optimal iron oxide fabrication route was identified and particle size in each batch was approximately 24.6 nm. Once these nanoparticles were incorporated into a membrane (5 wt. %), the nanoparticle formed agglomerates with an average diameter of 2.26 +/-1.23 microm. Comparisons between the 0 and 5 wt. % loading of particles into the membranes indicated that the elastic modulus of the composite decreased with increasing particle concentration. The pressure- central deflection of the membranes could not be predicated by prior models and variation between magnetic and pneumatic pressure-deflection curves was quantified. Attempts to fabricate membranes with above 5 wt. % nanoparticles were not successful (no gelation). Fourier Transform Infrared (FTIR) spectroscopy results suggest that excess oleic acid on the nanoparticles prior to mixing might have prevented crosslinking.

  10. Transport properties of alumina nanofluids

    International Nuclear Information System (INIS)

    Wong, Kau-Fui Vincent; Kurma, Tarun

    2008-01-01

    Recent studies have showed that nanofluids have significantly greater thermal conductivity compared to their base fluids. Large surface area to volume ratio and certain effects of Brownian motion of nanoparticles are believed to be the main factors for the significant increase in the thermal conductivity of nanofluids. In this paper all three transport properties, namely thermal conductivity, electrical conductivity and viscosity, were studied for alumina nanofluid (aluminum oxide nanoparticles in water). Experiments were performed both as a function of volumetric concentration (3-8%) and temperature (2-50 deg. C). Alumina nanoparticles with a mean diameter of 36 nm were dispersed in water. The effect of particle size was not studied. The transient hot wire method as described by Nagaska and Nagashima for electrically conducting fluids was used to test the thermal conductivity. In this work, an insulated platinum wire of 0.003 inch diameter was used. Initial calibration was performed using de-ionized water and the resulting data was within 2.5% of standard thermal conductivity values for water. The thermal conductivity of alumina nanofluid increased with both increase in temperature and concentration. A maximum thermal conductivity of 0.7351 W m -1 K -1 was recorded for an 8.47% volume concentration of alumina nanoparticles at 46.6 deg. C. The effective thermal conductivity at this concentration and temperature was observed to be 1.1501, which translates to an increase in thermal conductivity by 22% when compared to water at room temperature. Alumina being a good conductor of electricity, alumina nanofluid displays an increasing trend in electrical conductivity as volumetric concentration increases. A microprocessor-based conductivity/TDS meter was used to perform the electrical conductivity experiments. After carefully calibrating the conductivity meter's glass probe with platinum tip, using a standard potassium chloride solution, readings were taken at various

  11. Transport properties of alumina nanofluids.

    Science.gov (United States)

    Wong, Kau-Fui Vincent; Kurma, Tarun

    2008-08-27

    Recent studies have showed that nanofluids have significantly greater thermal conductivity compared to their base fluids. Large surface area to volume ratio and certain effects of Brownian motion of nanoparticles are believed to be the main factors for the significant increase in the thermal conductivity of nanofluids. In this paper all three transport properties, namely thermal conductivity, electrical conductivity and viscosity, were studied for alumina nanofluid (aluminum oxide nanoparticles in water). Experiments were performed both as a function of volumetric concentration (3-8%) and temperature (2-50 °C). Alumina nanoparticles with a mean diameter of 36 nm were dispersed in water. The effect of particle size was not studied. The transient hot wire method as described by Nagaska and Nagashima for electrically conducting fluids was used to test the thermal conductivity. In this work, an insulated platinum wire of 0.003 inch diameter was used. Initial calibration was performed using de-ionized water and the resulting data was within 2.5% of standard thermal conductivity values for water. The thermal conductivity of alumina nanofluid increased with both increase in temperature and concentration. A maximum thermal conductivity of 0.7351 W m(-1) K(-1) was recorded for an 8.47% volume concentration of alumina nanoparticles at 46.6 °C. The effective thermal conductivity at this concentration and temperature was observed to be 1.1501, which translates to an increase in thermal conductivity by 22% when compared to water at room temperature. Alumina being a good conductor of electricity, alumina nanofluid displays an increasing trend in electrical conductivity as volumetric concentration increases. A microprocessor-based conductivity/TDS meter was used to perform the electrical conductivity experiments. After carefully calibrating the conductivity meter's glass probe with platinum tip, using a standard potassium chloride solution, readings were taken at

  12. Preparation of alumina-coated magnetite nanoparticle for extraction of trimethoprim from environmental water samples based on mixed hemimicelles solid-phase extraction.

    Science.gov (United States)

    Sun, Lei; Zhang, Chuanzhou; Chen, Ligang; Liu, Jun; Jin, Haiyan; Xu, Haoyan; Ding, Lan

    2009-04-13

    In this study, a new type of alumina-coated magnetite nanoparticles (Fe(3)O(4)/Al(2)O(3) NPs) modified by the surfactant sodium dodecyl sulfate (SDS) has been successfully synthesized and applied for extraction of trimethoprim (TMP) from environmental water samples based on mixed hemimicelles solid-phase extraction (MHSPE). The coating of alumina on Fe(3)O(4) NPs not only avoids the dissolving of Fe(3)O(4) NPs in acidic solution, but also extends their application without sacrificing their unique magnetization characteristics. Due to the high surface area of these new sorbents and the excellent adsorption capacity after surface modification by SDS, satisfactory concentration factor and extraction recoveries can be produced with only 0.1g Fe(3)O(4)/Al(2)O(3) NPs. Main factors affecting the adsolubilization of TMP such as the amount of SDS, pH value, standing time, desorption solvent and maximal extraction volume were optimized. Under the selected conditions, TMP could be quantitatively extracted. The recoveries of TMP by analyzing the four spiked water samples were between 67 and 86%, and the relative standard deviation (RSD) ranged from 2 to 6%. Detection and quantification limits of the proposed method were 0.09 and 0.24 microg L(-1), respectively. Concentration factor of 1000 was achieved using this method to extract 500 mL of different environmental water samples. Compared with conventional SPE methods, the advantages of this new Fe(3)O(4)/Al(2)O(3) NPs MHSPE method still include easy preparation and regeneration of sorbents, short times of sample pretreatment, high extraction yields, and high breakthrough volumes. It shows great analytical potential in preconcentration of organic compounds from large volume water samples.

  13. One-Pot Synthesis of Size- and Composition-Controlled Ni-Rich NiPt Alloy Nanoparticles in a Reverse Microemulsion System and Their Application

    KAUST Repository

    Biausque, Gregory

    2017-08-16

    Bimetallic nanoparticles have been the subject of numerous research studies in the nanotechnology field, in particular for catalytic applications. Control of the size, morphology, and composition has become a key challenge due to the relationship between these parameters and the catalytic behavior of the particles in terms of activity, selectivity, and stability. Here, we present a one-pot air synthesis of 2 nm NiPt nanoparticles with a narrow size distribution. Control of the size and composition of the alloy particles is achieved at ambient temperature, in the aqueous phase, by the simultaneous reduction of nickel and platinum precursors with hydrazine, using a reverse microemulsion system. After deposition on an alumina support, this Ni-rich nanoalloy exhibits unprecedented stability under the harsh conditions of methane dry reforming.

  14. The Effect of Multi-pass Equal-Channel Angular Pressing (ECAP) for Consolidation of Aluminum-Nano Alumina Composite Powder on Wear Resistance

    Science.gov (United States)

    Derakhshandeh-Haghighi, Reza; Jenabali Jahromi, Seyed Ahmad

    2016-02-01

    The wear behavior of aluminum matrix composite powder with varying concentration of nano alumina particles, which was consolidated by equal-channel angular pressing (ECAP) at different passes, was determined by applying, 10 and 46 N loads, using a pin-on-disk machine. Optical and electronic microscopy, EDX analysis, and hardness measurement were performed in order to characterize the worn samples. The relative density of the samples after each pass of ECAP was determined using Archimedes principle. Within the studied range of loads, the wear loss decreased by increasing the number of ECAP passes.

  15. Lump Kinetic Analysis of Syngas Composition Effect on Fischer-Tropsch Synthesis over Cobalt and Cobalt-Rhenium Alumina Supported Catalyst

    Directory of Open Access Journals (Sweden)

    Dewi Tristantini

    2016-03-01

    Received: 10th November 2015; Revised: 10th February 2016; Accepted: 16th February 2016 How to Cite: Tristantini, D., Suwignjo, R.K. (2016. Lump Kinetic Analysis of Syngas Composition Effect on Fischer-Tropsch Synthesis over Cobalt and Cobalt-Rhenium Alumina Supported Catalyst. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (1: 84-92. (doi:10.9767/bcrec.11.1.424.84-92 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.11.1.424.84-92

  16. SERS of semiconducting nanoparticles (TIO{sub 2} hybrid composites).

    Energy Technology Data Exchange (ETDEWEB)

    Rajh, T.; Musumeci, A.; Gosztola, D.; Schiller, T.; Dimitrijevic, N. M.; Mujica, V.; Martin, D.; Center for Nanoscale Materials

    2009-05-06

    Raman scattering of molecules adsorbed on the surface of TiO{sub 2} nanoparticles was investigated. We find strong enhancement of Raman scattering in hybrid composites that exhibit charge transfer absorption with TiO{sub 2} nanoparticles. An enhancement factor up to {approx}10{sup 3} was observed in the solutions containing TiO{sub 2} nanoparticles and biomolecules, including the important class of neurotransmitters such as dopamine and dopac (3,4-dihydroxy-phenylacetic acid). Only selected vibrations are enhanced, indicating molecular specificity due to distinct binding and orientation of the biomolecules coupled to the TiO{sub 2} surface. All enhanced modes are associated with the asymmetric vibrations of attached molecules that lower the symmetry of the charge transfer complex. The intensity and the energy of selected vibrations are dependent on the size and shape of nanoparticle support. Moreover, we show that localization of the charge in quantized nanoparticles (2 nm), demonstrated as the blue shift of particle absorption, diminishes SERS enhancement. Importantly, the smallest concentration of adsorbed molecules shows the largest Raman enhancements suggesting the possibility for high sensitivity of this system in the detection of biomolecules that form a charge transfer complex with metal oxide nanoparticles. The wavelength-dependent properties of a hybrid composite suggest a Raman resonant state. Adsorbed molecules that do not show a charge transfer complex show weak enhancements probably due to the dielectric cavity effect.

  17. Glass transition temperature of PMMA/modified alumina nanocomposite: Molecular dynamic study

    OpenAIRE

    Mohammadi, Maryam; Davoodi, Jamal; Javanbakht, Mahdi; Rezaei, Hamidreza

    2017-01-01

    In this study, the effect of alumina and modified alumina nanoparticles in a PMMA/alumina nanocomposite was investigated. To attain this goal, the glass transition behavior of poly methyl methacrylate (PMMA), PMMA/alumina and PMMA/hydroxylated alumina nanocomposites were investigated by molecular dynamic simulations (MD). All the MD simulations were performed using the Materials Studio 6.0 software package of Accelrys. To obtain the glass transition temperature, the variation of density vs. t...

  18. Size and compositionally controlled manganese ferrite nanoparticles with enhanced magnetization

    International Nuclear Information System (INIS)

    Vamvakidis, K.; Sakellari, D.; Angelakeris, M.; Dendrinou-Samara, C.

    2013-01-01

    A facile solvothermal approach was used to synthesize stable, superparamagnetic manganese ferrite nanoparticles with relatively small sizes ( 2 to Mn(acac) 3 , different sizes, 8 and 5 nm, of MnFe 2 O 4 nanoparticles were obtained respectively, while by tailoring the synthetic conditions iron-rich Mn 0.77 Fe 2.23 O 4 nanoparticles have been isolated with identical sizes and enhanced saturation magnetization. The magnetization values increased from 58.2 to 68.3 Am 2 /kg and from 53.3 to 60.2 Am 2 /kg for the nanoparticles of 8 and 5 nm, respectively. Blocking temperature (T B ), ranging from 80 to 180 K, and anisotropy constant (K eff ), ranging from 1.5 × 10 5 to 4.9 × 10 5 J/m 3 , were found higher for the iron-rich samples and associated with size and composition effects.

  19. Sprayable elastic conductors based on block copolymer silver nanoparticle composites.

    Science.gov (United States)

    Vural, Mert; Behrens, Adam M; Ayyub, Omar B; Ayoub, Joseph J; Kofinas, Peter

    2015-01-27

    Block copolymer silver nanoparticle composite elastic conductors were fabricated through solution blow spinning and subsequent nanoparticle nucleation. The reported technique allows for conformal deposition onto nonplanar substrates. We additionally demonstrated the ability to tune the strain dependence of the electrical properties by adjusting nanoparticle precursor concentration or localized nanoparticle nucleation. The stretchable fiber mats were able to display electrical conductivity values as high as 2000 ± 200 S/cm with only a 12% increase in resistance after 400 cycles of 150% strain. Stretchable elastic conductors with similar and higher bulk conductivity have not achieved comparable stability of electrical properties. These unique electromechanical characteristics are primarily the result of structural changes during mechanical deformation. The versatility of this approach was demonstrated by constructing a stretchable light emitting diode circuit and a strain sensor on planar and nonplanar substrates.

  20. Composite nanoparticles containing rare earth metal and methods of preparation thereof

    Energy Technology Data Exchange (ETDEWEB)

    Kandapallil, Binil Itty Ipe; Krishnan, Lakshmi; Johnson, Francis

    2018-04-10

    The present invention is directed to composite nanoparticles comprising a metal, a rare earth element, and, optionally, a complexing ligand. The invention is also directed to composite nanoparticles having a core-shell structure and to processes for preparation of composite nanoparticles of the invention.

  1. Crack growth resistance of alumina, zirconia and zirconia toughened alumina ceramics for joint prostheses.

    Science.gov (United States)

    De Aza, A H; Chevalier, J; Fantozzi, G; Schehl, M; Torrecillas, R

    2002-02-01

    Mono-phase bio-ceramics (alumina and zirconia) are widely used as femoral heads in total hip replacements (THR) as an alternative to metal devices. Unfortunately, the orthopaedic community reports significant in-vivo failures. Material scientists are already familiar with composites like alumina zirconia. Since both are biocompatible, this could prove to be a new approach to implants. This paper deals with a new generation of alumina-zirconia nano-composites having a high resistance to crack propagation, and as a consequence may offer the option to improve lifetime and reliability of ceramic joint prostheses. The reliability of the above mentioned three bio-ceramics (alumina, zirconia and zirconia toughened alumina) for THR components is analysed based on the study of their slow crack-growth behaviour. The influence of the processing conditions on the microstructure development, of the zirconia toughened alumina composites and the effect of these microstructures, on its mechanical properties, are discussed.

  2. Antimicrobial Bacterial Cellulose-Silver Nanoparticles Composite Membranes

    Directory of Open Access Journals (Sweden)

    Hernane S. Barud

    2011-01-01

    Full Text Available Antimicrobial bacterial cellulose-silver nanoparticles composite membranes have been obtained by “in situ” preparation of Ag nanoparticles from hydrolytic decomposition of silver nitrate solution using triethanolamine as reducing and complexing agent. The formation of silver nanoparticles was evidenced by the X-ray diffraction, scanning electron microscopy (SEM, transmission electron microscopy (TEM, and absorption in the UV-Visible (350 nm to 600 nm. Thermal and mechanical properties together with swelling behavior for water were considered. TEA concentration was observed to be important in order to obtain only Ag particles and not a mixture of silver oxides. It was also observed to control particle size and amount of silver contents in bacterial cellulose. The composite membranes exhibited strong antimicrobial activity against Gram-negative and Gram-positive bacteria.

  3. Development and characterization of ceramic composites alumina-titania based reinforced with lanthanum oxide for fabrication of inert coatings for metallic tanks of the oil industry

    International Nuclear Information System (INIS)

    Bandeira, J.M.; Yadava, Y.P.; Silva, N.D.G.; Ferreira, R.A.S.

    2016-01-01

    Crude petroleum is highly corrosive causing superficial degradation in metallic tanks used for storage and transportation of this material, which causes a serious problem in the oil industry. An alternative to solve this problem is to use some kind of coating that is inert to this kind of corrosion. Alumina and titania are interesting materials for several engineering applications because, when compared with other ceramic materials, they present superior mechanical properties, e.g. high mechanical strength, good chemical stability and high fracture toughness combined with good wear resistance and a coefficient of thermal expansion close to the iron's, which makes them fit to use in ceramic hardening process and coating. In this paper, alumina-titania ceramic composites with 5%, 10%, 15% and 20% of titania (TiO2) and reinforced with 2% of lanthanum oxide of were produced by thermo-mechanical processing and sintering techniques at 1350 deg C. In these composites, microstructure and mechanical properties were analyzed using X-ray spectroscopy, optical microscopy, scanning electron microscopy and Vickers hardness in order to evaluate their applicability. X-ray spectroscopy showed the formation of composite without the presence of other phases. Optical microscopy and scanning electron microscopy showed a homogeneous microstructure in terms of particle size and distribution. Vickers hardness test showed a gradual decrease in hardness with the addition of titania. The composite with 5% of titania and 2% of lanthanum oxide is the best choice for structural applications. The composites were submerged in crude petroleum for 30 days to study their stability in such environment. Through the analysis of X-ray spectroscopy, optical microscopy and Vickers hardness before and after the submersion in crude petroleum, it was not observed structural or microstructural degradation nether alterations in mechanical properties. This way, it was concluded that these composites have

  4. Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials

    Science.gov (United States)

    2016-06-15

    at higher than 1GHz. 15. SUBJECT TERMS Magnetoresistance , Metamaterials, Nanocomposites, Nanoparticles 16. SECURITY CLASSIFICATION OF: 17. LIMITATION...magnetic loss values limited to 0.11. The resulting composites can also be stretched up to 165% strain before failure due to good adhesion between the

  5. TXRF and ICP-OES analysis of liquid-phase laser-ablated (LP-LA) nanoparticles of cryolite-alumina solutions

    Science.gov (United States)

    Castell, Ricardo; Greaves, Eduardo D.; Abdala, Lyzeth; Barros, Haydn

    2012-10-01

    A new procedure with minimum sample preparation has been developed for a fast and serial analysis of cryolite with varying concentrations of dissolved alumina by liquid-phase laser ablation followed by Total Reflection X-Ray Fluorescence and induced coupled plasma optical emission spectroscopy. The analysis supplies the sodium/aluminium ratio of bath samples taken from industrial Hall-Herault reduction cells, as well as trace element relative concentrations. Two different types of molten samples taken directly from the aluminium production plant were placed under distilled de-ionized water in a quartz cell and subjected to pulsed laser ablation using the beam from a third harmonic Nd:YAG laser. Scanning electron microscopy examination shows the nanoparticles nature of the ablated material. The water-suspension is deposited on quartz reflectors for Total Reflection X-ray Fluorescence analysis or directly aspirated to the induced coupled plasma yielding the aluminium and sodium signals. Instrument quantification of the elements is performed by the use of aqueous standards. Validation tests were done with cryolite sample digestion and standard methods of sample quantification. The procedure can provide the aluminium/sodium ratio with adequate precision for aluminium production plant cell diagnostics and reveals the trace elements that could be considered as contamination.

  6. Polymer composites with plasmonic metal nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Dammer, Ondřej; Vlčková, B.; Podhájecká, Klára; Procházka, M.; Pfleger, Jiří

    2008-01-01

    Roč. 268, č. 1 (2008), s. 91-95 ISSN 1022-1360. [Microsymposium on Advanced Polymer Materials for Photonics and Electronics /47./. Prague, 15.07.2007-19.07.2007] R&D Projects: GA AV ČR IAA4050406 Institutional research plan: CEZ:AV0Z40500505 Keywords : metal nanoparticles * nanocomposites * .pi.-conjugated polymers Subject RIV: CD - Macromolecular Chemistry

  7. Adsorption of TX-100 and SDBS on the surface of alumina and maghemite nanoparticles from aqueous solutions

    Directory of Open Access Journals (Sweden)

    R. R. Mansurov

    2014-11-01

    Full Text Available Adsorption equilibriums in aqueous aluminum and iron oxides nanosuspensions stabilized by SDBS and TX-100 were investigated using UV spectrophotometry. It was established that the non-ionic surfactant TritonX-100 is not adsorbed from aqueous solution on a hydrophilic surface of both aluminum and iron oxide nanoparticles. At the same time adsorption of the anionic surfactant SDBS was observed in both oxides nanoparticles. In the investigated range of concentrations adsorption isotherms SDBS from aqueous solution on the surfaces of nanoparticles Al2O3 and γ-Fe2O3 not reach saturation. The share of the particles surface occupied by surfactant molecules were estimated based on the value of an area of molecules SDBS in the adsorption layer, which was derived from the isotherm of surface tension (0.10 nm2. The calculations showed that at the investigated concentrations SDBS Al2O3 employed approximately 30 % of surface of nanoparticles, and for γ-Fe2O3 – up to 10%.

  8. Effect of Alumina Nanoparticles on the Rheological Behavior of Aluminum-Binder Mixtures for Powder Injection Molding

    Directory of Open Access Journals (Sweden)

    Hassan Abdoos

    2014-10-01

    Full Text Available Preparation of appropriate powder-binder mixtures is the crucial step of powder injection molding process. Hence, the rheological properties of powder-binder mixture are important factors in production of sound parts using powder injection molding. Nowadays, the use of nanoparticles in powder injection molding is increasing due to the improved properties and dimensional precision of the final parts. On the other hand, nanoparticles can initiate problems such as agglomeration and loss of rheological properties and homogeneity. In the present study, the rheological behavior of aluminum mixtures containing nanoalumina particles was investigated. Two powder loadings of aluminum powder (54 vol% and 60 vol%, in which 0, 3, 6 and 9 wt% of aluminum was replaced with nanoalumina, were used. The powder systems were blended with the molten binder system in a banbury internal mixer and the rheological properties of the resulting mixtures were evaluated. All feedstocks showed pseudo-plastic behavior. The presence of nanoparticles increased the viscosity of feedstocks. Due to overwhelming particles cohesion by hydrodynamic forces, the viscosity of the mixtures decreased at high shear rates. Tap density results confirmed an improvement in packing compressibility of the mentioned powders. Shear rate sensitivity decreased with incorporation of nanoparticles into the mixtures. This phenomenon improved the injection capability through further reduction in viscosity.

  9. Entrapment of Radionuclides in Nanoparticle Compositions

    DEFF Research Database (Denmark)

    2012-01-01

    The present invention is directed to the technical field of imaging compositions useful for diagnosing cancer and other diseases in a subject. In particular, the invention relates to a class of diagnostic compounds comprising a novel liposome composition with encapsulated metal entities such as r......The present invention is directed to the technical field of imaging compositions useful for diagnosing cancer and other diseases in a subject. In particular, the invention relates to a class of diagnostic compounds comprising a novel liposome composition with encapsulated metal entities...

  10. Synthesis and ceramic processing of alumina and zirconia based composites infiltrated with glass phase for dental applications

    International Nuclear Information System (INIS)

    Duarte, Daniel Gomes

    2009-01-01

    The interest for the use of ceramic materials for dental applications started due to the good aesthetic appearance promoted by the similarity to natural teeth. However, the fragility of traditional ceramics was a limitation for their use in stress conditions. The development of alumina and zirconia based materials, that associate aesthetic results, biocompatibility and good mechanical behaviour, makes possible the employment of ceramics for fabrication of dental restorations. The incorporation of vitreous phase in these ceramics is an alternative to minimize the ceramic retraction and to improve the adhesion to resin-based cements, necessary for the union of ceramic frameworks to the remaining dental structure. In the dentistry field, alumina and zirconia ceramic infiltrated with glassy phase are represented commercially by the In-Ceram systems. Considering that the improvement of powder's synthesis routes and of techniques of ceramic processing contributes for good performance of these materials, the goal of the present work is the study of processing conditions of alumina and/or 3 mol% yttria-stabilized zirconia ceramics infiltrated with aluminum borosilicate lanthanum glass. The powders, synthesized by hydroxide coprecipitation route, were pressed by uniaxial compaction and pre-sintered at temperature range between 950 and 1650 degree C in order to obtain porous ceramics bodies. Vitreous phase incorporation was performed by impregnation of aluminum borosilicate lanthanum powder, also prepared in this work, followed by heat treatment between 1200 and 1400 degree C .Ceramic powders were characterized by thermogravimetry, X-ray diffraction, scanning and transmission electron microscopy, gaseous adsorption (BET) and laser diffraction. Sinterability of alumina and /or stabilized zirconia green pellets was evaluated by dilatometry. Pre-sintered ceramics were characterized by apparent density measurements (Archimedes method), X-ray diffraction and scanning electron

  11. Radiation induced synthesis of gold/iron-oxide composite nanoparticles using high-energy electron beam

    International Nuclear Information System (INIS)

    Seino, Satoshi; Kinoshita, Takuya; Nakagawa, Takashi; Kojima, Takao; Taniguci, Ryoichi; Okuda, Shuichi; Yamamoto, Takao A.

    2008-01-01

    Composite nanoparticles consisting of gold and iron oxide were synthesized in aqueous solution systems by using a high-energy electron beam. The electron irradiation induces radiation-chemical reaction to form metallic gold nanoparticles. These gold nanoparticles were firmly immobilized on the surface of the support iron oxide nanoparticles. Surface of the support iron oxide nanoparticles are almost fully coated with fine gold nanoparticles. The size of these gold nanoparticles depended on the concentrations of gold ions, polymers and iron oxide nanoparticles in the solutions before the irradiation.

  12. Understanding and Quantifying the Reactivity of Energetic NanoParticles and NanoComposites

    Science.gov (United States)

    2015-01-05

    The Effects of Aluminum Hydride as a Fuel Supplement on the Performance of Traditional NanoThermites, Journal of Propulsion and Power (06 2013...Sullivan, , K-S. Lee,, Y. H. Kim, , R. Zahaf, , M. R. Zachariah, D. Lee . Microstructural Behavior of the Alumina Shell and Aluminum CoreBefore and...After Melting of Aluminum Nanoparticles, J Phys Chem , (01 2012): 404. doi: N. Piekiel, M.R. Zachariah. N.W. Piekiel and M.R. ZachariahDecomposition

  13. Composite proton exchange membrane based on sulfonated organic nanoparticles

    Science.gov (United States)

    Pitia, Emmanuel Sokiri

    As the world sets its sight into the future, energy remains a great challenge. Proton exchange membrane (PEM) fuel cell is part of the solution to the energy challenge because of its high efficiency and diverse application. The purpose of the PEM is to provide a path for proton transport and to prevent direct mixing of hydrogen and oxygen at the anode and the cathode, respectively. Hence, PEMs must have good proton conductivity, excellent chemical stability, and mechanical durability. The current state-of-the-art PEM is a perfluorosulfonate ionomer, Nafion®. Although Nafion® has many desirable properties, it has high methanol crossover and it is expensive. The objective of this research was to develop a cost effective two-phase, composite PEM wherein a dispersed conductive organic phase preferentially aligned in the transport direction controls proton transport, and a continuous hydrophobic phase provides mechanical durability to the PEM. The hypothesis that was driving this research was that one might expect better dispersion, higher surface to volume ratio and improved proton conductivity of a composite membrane if the dispersed particles were nanometer in size and had high ion exchange capacity (IEC, = [mmol sulfonic acid]/gram of polymer). In view of this, considerable efforts were employed in the synthesis of high IEC organic nanoparticles and fabrication of a composite membrane with controlled microstructure. High IEC, ~ 4.5 meq/g (in acid form, theoretical limit is 5.4 meq/g) nanoparticles were achieved by emulsion copolymerization of a quaternary alkyl ammonium (QAA) neutralized-sulfonated styrene (QAA-SS), styrene, and divinylbenzene (DVB). The effects of varying the counterion of the sulfonated styrene (SS) monomer (alkali metal and QAA cations), SS concentration, and the addition of a crosslinking agent (DVB) on the ability to stabilize the nanoparticles to higher IECs were assessed. The nanoparticles were ion exchanged to acid form. The extent of ion

  14. Deposition kinetics of quantum dots and polystyrene latex nanoparticles onto alumina: role of water chemistry and particle coating.

    Science.gov (United States)

    Quevedo, Ivan R; Olsson, Adam L J; Tufenkji, Nathalie

    2013-03-05

    A clear understanding of the factors controlling the deposition behavior of engineered nanoparticles (ENPs), such as quantum dots (QDs), is necessary for predicting their transport and fate in natural subsurface environments and in water filtration processes. A quartz crystal microbalance with dissipation monitoring (QCM-D) was used to study the effect of particle surface coatings and water chemistry on the deposition of commercial QDs onto Al2O3. Two carboxylated QDs (CdSe and CdTe) with different surface coatings were compared with two model nanoparticles: sulfate-functionalized (sPL) and carboxyl-modified (cPL) polystyrene latex. Deposition rates were assessed over a range of ionic strengths (IS) in simple electrolyte (KCl) and in electrolyte supplemented with two organic molecules found in natural waters; namely, humic acid and rhamnolipid. The Al2O3 collector used here is selected to be representative of oxide patches found on the surface of aquifer or filter grains. Deposition studies showed that ENP deposition rates on bare Al2O3 generally decreased with increasing salt concentration, with the exception of the polyacrylic-acid (PAA) coated CdTe QD which exhibited unique deposition behavior due to changes in the conformation of the PAA coating. QD deposition rates on bare Al2O3 were approximately 1 order of magnitude lower than those of the polystyrene latex nanoparticles, likely as a result of steric stabilization imparted by the QD surface coatings. Adsorption of humic acid or rhamnolipid on the Al2O3 surface resulted in charge reversal of the collector and subsequent reduction in the deposition rates of all ENPs. Moreover, the ratio of the two QCM-D output parameters, frequency and dissipation, revealed key structural information of the ENP-collector interface; namely, on bare Al2O3, the latex particles were rigidly attached as compared to the more loosely attached QDs. This study emphasizes the importance of considering the nature of ENP coatings as well

  15. Detection of Nanoparticles Released at Finishing of Dental Composite Materials.

    Czech Academy of Sciences Publication Activity Database

    Bradna, P.; Ondráčková, Lucie; Ždímal, Vladimír; Navrátil, Tomáš; Pelclová, D.

    2017-01-01

    Roč. 148, č. 3 (2017), s. 531-537 ISSN 0026-9247. [International Conference on Modern Electrochemical Methods /36./. Jetřichovice, 23.05.2016-27.05.2016] Institutional support: RVO:67985858 ; RVO:61388955 Keywords : dental composite * grinding * nanoparticles * aerosol * health risk Subject RIV: DN - Health Impact of the Environment Quality; CF - Physical ; Theoretical Chemistry (UFCH-W) OBOR OECD: Public and environmental health ; Physical chemistry (UFCH-W) Impact factor: 1.282, year: 2016

  16. Detection of Nanoparticles Released at Finishing of Dental Composite Materials.

    Czech Academy of Sciences Publication Activity Database

    Bradna, P.; Ondráčková, Lucie; Ždímal, Vladimír; Navrátil, Tomáš; Pelclová, D.

    2017-01-01

    Roč. 148, č. 3 (2017), s. 531-537 ISSN 0026-9247. [International Conference on Modern Electrochemical Methods /36./. Jetřichovice, 23.05.2016-27.05.2016] Institutional support: RVO:67985858 ; RVO:61388955 Keywords : dental composite * grinding * nanoparticles * aerosol * health risk Subject RIV: DN - Health Impact of the Environment Quality; CF - Physical ; Theoretical Chemistry (UFCH-W) OBOR OECD: Public and environmental health; Physical chemistry (UFCH-W) Impact factor: 1.282, year: 2016

  17. Polyvinylpyrrolidone Matrix as an Effective Reducing Agent and Stabilizer during Reception of Silver Nanoparticles in Composites

    OpenAIRE

    Semenyuk, Nataliya; Kostiv, Ulyana; Dudok, Galyna; Nechay, Jaroslav; Skorokhoda, Volodymyr

    2013-01-01

    The use of polyvinylpyrrolidone matrix as an effective reducing agent and stabilizer during reception of silver nanoparticles in composites is substantiated. The influence of various factors on patterns of obtaining silver nanoparticles and their size.

  18. Influences of glass content on the microstructure and properties of BaO-CaO-Al2O3-SiO2 glass/alumina composite for LTCC applications

    Science.gov (United States)

    Li, Z. X.; Mao, H. J.; Zhang, Y. W.; Zhang, W. J.

    2018-01-01

    In this paper, a new amorphous Ba-Ca-Al-Si glass was prepared and the composites with different glass/alumina ratios, which ranged from 40 wt. % glass to 60 wt. % glass, have been studied. According to XRD patterns, the main crystalline phases of the composites are Al2O3 and BaAl2Si2O8, and BaAl2Si2O8 is generated by the reaction between glass and alumina. With regard to dielectric and mechanical properties, both the dielectric constant and the bending strength of the samples show positive relationships with glass content, and then the values tend to decline when the glass content exceeds 55 wt. %, which can be explained by the results of sintering shrinkage curves, bulk densities and SEM images. The optimal composition of 55 wt. % glass-45 wt. % alumina was developed, exhibiting good dielectric properties (εr =5.882, tanδ=2.75× 10-3) and high bending strength (σ=169 MPa). Finally, the 55 wt. % glass/alumina composite was chosen for tape casting, showing a well chemical compatibility with silver.

  19. Temperature and composition dependent structural evolution of AgPd bimetallic nanoparticle: phase diagram of (AgPd)151 nanoparticle.

    Science.gov (United States)

    Kim, Hyun You; Kim, Da Hye; Lee, Hyuck Mo

    2011-03-01

    We study the structural evolution of a 151 atom Ag-Pd bimetallic nanoparticle with composition and temperature. The solid-to-liquid transition region was investigated using molecular dynamics simulations with an improved collision method, and the solid-state structure of the nanoparticle was explored with a combination of molecular dynamics and density functional theory. Results show that an fcc-to-icosahedron transformation occurs at high temperature in all composition range and that a composition of nanoparticles concerns the atomic distribution of the (AgPd)151 nanoparticle. As a result, we constructed a phase diagram of the (AgPd)151 nanoparticle. Our phase diagram offers guidance on the application of Ag-Pd nanoparticles.

  20. Photocatalytic Cementitious Composites containing Mesoporous Titanium Dioxide Nanoparticles

    Directory of Open Access Journals (Sweden)

    FALIKMAN Vyacheslav Ruvimovich

    2014-02-01

    Full Text Available The advanced method to produce nanoparticles of anatase mesoporous TiO₂ with high specific surface 300 m²/g has been developed. It was shown that titanium nanodioxide can be used in cement and gypsum composites as a highly efficient photocatalyst in the conversion processes of nitric oxide and volatile organic substances. Influence of radiation intensity, relative humidity, and concentration of contaminant and its stream speed on photocatalysis was studied. It was determined that efficiency of the composites with synthesized samples is 1,5–1,7 times higher than that of the commercial sample of the titanium nanodioxide.

  1. Novel hybrid coatings with controlled wettability by composite nanoparticle aggregation

    Energy Technology Data Exchange (ETDEWEB)

    Hritcu, Doina, E-mail: dhritcu@ch.tuiasi.ro; Dodi, Gianina; Iordache, Mirabela L.; Draganescu, Dan; Sava, Elena; Popa, Marcel I.

    2016-11-30

    Highlights: • Magnetite-grafted chitosan composite nanoparticles were synthesized. • The particles are able to assemble under the influence of a silane derivative. • Thin films containing composites, chitosan and hydrolyzed silane were optimized. • The novel hybrid coatings show hierarchical roughness and high wetting angle. - Abstract: The aim of this study is to evaluate novel hybrid materials as potential candidates for producing coatings with hierarchical roughness and controlled wetting behaviour. Magnetite (Fe{sub 3}O{sub 4}) nanoparticles obtained by co-precipitation were embedded in matrices synthesized by radical graft co-polymerization of butyl acrylate (BA), butyl methacrylate (BMA), hexyl acrylate (HA) or styrene (ST) with ethylene glycol di-methacrylate (EGDMA) onto previously modified chitosan bearing surface vinyl groups. The resulting composite particles were characterized regarding their average size, composition and magnetic properties. Hybrid thin films containing suspension of composite particles in ethanol and pre-hydrolysed hexadecyltrimethoxysilane (HDTS) as a coupling/crosslinking agent were deposited by spin coating or spraying. The films were cured by heating and subsequently characterized regarding their morphology (scanning electron microscopy), contact angle with water and adhesion to substrate (scratch test). The structure-property relationship is discussed.

  2. Study of microstructure and mechanical properties of ceramics composites alumina-zirconia reinforced with yttria for inert coating of metal matrices used in the petroleum industry

    International Nuclear Information System (INIS)

    Pontual, J.O.; Silva, N.D.G.; Ferreira, R.A.S.; Yadava, Y.P.

    2014-01-01

    The storage and transportation of crude oil is complicated due to the hostile environment provided by this. Under these conditions, it is imperative to search for alternative solutions, using an inert coating to protect from corrosion caused by crude oil. In this work, alumina-zirconia ceramic composites with 5-20%w zirconia and 1 - 2%w yttria were produced through thermomechanical process. The structural and microstructural characterization of the sintered material was carried out by X-ray diffraction and scanning electron microscopy. Mechanical properties were analyzed by Vickers hardness tests. Currently, the pads are submerged in crude oil and after 30-60 days will be removed and sent for stability test.(author)

  3. Characterization of Piezoelectric PDMS-Nanoparticle Composites

    Science.gov (United States)

    Borsa, C. J.; Mionic Ebersold, M.; Bowen, P.; Farine, P.-A.; Briand, D.

    2015-12-01

    In this work, the novel fabrication and characterization of elastomeric piezoelectric nanocomposites are explored. Fabrication methods explored herein utilize ball milled barium titanate powder dispersions, along with double walled carbon nanotubes which are dispersed in toluene though the use of an ultrasonic probe. Test devices are then constructed with electrodes made from evaporated gold on polyimide foils and protective dielectrics of pristine PDMS. Two different device construction methods are explored utilizing both direct contact bonding and plasma bonding of the active composite layers to the dielectric/electrode. Test samples are evaluated through the use of a dedicated Berlincourt type piezoelectric d33 meter.

  4. Characterization of silane coated hollow sphere alumina-reinforced

    Indian Academy of Sciences (India)

    Silane coated hollow sphere alumina ceramic particles were moulded with ultra high molecular weight polyethylene (UHMWPE) to form a series of composites with alumina weight percent in the range from 15 to 50. The composites were prepared in a cylindrical mould using powder-processing technique. The composites ...

  5. Characterization of silane coated hollow sphere alumina-reinforced ...

    Indian Academy of Sciences (India)

    Silane coated hollow sphere alumina ceramic particles were moulded with ultra high molecular weight polyethylene (UHMWPE) to form a series of composites with alumina weight percent in the range from 15 to 50. The composites were prepared in a cylindrical mould using powder-processing technique. The composites ...

  6. Synthesis of Fe nanoparticles-graphene composites for environmental applications

    International Nuclear Information System (INIS)

    Guo, Juan; Wang, Ruiyu; Tjiu, Weng Weei; Pan, Jisheng; Liu, Tianxi

    2012-01-01

    Graphical abstract: Fe nanoparticles-graphene composites (FGC) are successfully synthesized by forming a complex Fe 3+ -GO and further reducing it with NaBH4 as one step at ambient condition. The morphology and structure studies of FGC indicate that Fe nanoparticles with size of about 5 nm are finely dispersed on graphene sheets. Decolorization experiments show that the FGC hybrids display better removal capacities to decolorize methyl blue (MB), a model dye in the dyeing and printing industry, compared with bare Fe particles. On the other hand, FGC hybrids exhibit superparamagnetic properties and can be separated from MB solution leaving a colorless solution by using a magnet. All of these suggest FGC an excellent candidate for dye removal. Highlights: ► Graphene oxide (GO) and Fe 3+ are used as precursors. ► By adding NaBH 4 , Fe 3+ and GO are in situ reduced to Fe and graphene, respectively, thus forming FGC hybrids. ► Fe nanoparticles with size of about 5 nm are finely dispersed on graphene sheets. ► FGC hybrids have better decolorization capacities than bare Fe nanoparticles. - Abstract: Fe nanoparticles-graphene composites (FGC) are successfully synthesized by using graphene oxide (GO) as a supporting matrix. GO is first treated with Fe 3+ to form Fe 3+ -GO complexes. Then, by adding NaBH 4 solution, Fe 3+ and GO are simultaneously reduced in situ to Fe and graphene respectively, forming FGC hybrid composites. The structures, properties and applications of the hybrids thus obtained are investigated by X-ray diffraction, Raman spectroscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, thermogravimetric analysis and magnetization measurements. The hybrids are also evaluated for decolorization of methyl blue solution, a model dye in wastewater of dyeing industry. Compared with bare Fe particles, the high removal capacities of FGC are due to the

  7. Harnessing Compositional Marangoni Flows in Depositing Nanoparticle Films

    Science.gov (United States)

    Majumder, Mainak; Pasquali, Matteo; Monash University/Rice University Team

    2012-11-01

    Attempts at depositing uniform films of nanoparticles by drop-drying have been frustrated by the ``coffee-stain'' effect, arising from the convective macroscopic flow into the solid-liquid-vapor contact line of a droplet. We have recently demonstrated that uniform deposition of nanoparticles from aqueous suspensions can be obtained by drying the droplet in an ethanol vapor atmosphere.(.).............(Majumder et al., 2012). This technique allows the particle-laden water droplets to spread on a variety of surfaces such as glass, silicon, mica, PDMS, and even Teflon® due to absorption of ethanol from the vapor. Visualization of droplet shape and internal flow shows initial droplet spreading and strong re-circulating flow during spreading and shrinkage. During the drying phase, the vapor is saturated in ethanol, leading to preferential evaporation of water at the contact line; thereby generating a surface tension gradient (or Marangoni forces) that drive a strong recirculating flow. We show that this method can be used for depositing catalyst nanoparticles for the growth of single-walled carbon nanotubes as well as to manufacture plasmonic films of well-spaced, unaggregated gold nanoparticles. MAJUMDER, M., RENDALL, C. S., PASQUALI, M. et al. 2012. Overcoming the ``Coffee-Stain'' Effect by Compositional Marangoni-Flow-Assisted Drop-Drying. J.Phys.Chem.B, 116, 6536-6542.

  8. Synthesis of berberine loaded polymeric nanoparticles by central composite design

    Science.gov (United States)

    Mehra, Meenakshi; Sheorain, Jyoti; Kumari, Santosh

    2016-04-01

    Berberine is an isoquinoline alkaloid which is extracted from bark and roots of Berberis vulgaris plant. It has been used in ayurvedic medicine as it possess antimicrobial, antidiabetic, anticancer, antioxidant properties etc. But poor solubility of berberine leads to poor stability and bioavailability in medical formulations decreasing its efficacy. Hence nanoformulations of berberine can help in removing the limiting factors of alkaloid enhancing its utilization in pharmaceutical industry. Sodium alginate polymer was used to encapsulate berberine within nanoparticles by emulsion solvent evaporation method using tween 80 as a surfactant. Two factors and three level in central composite design was used to study the formulation. The optimized formulation (1% v/v of Tween 80 and 0.01% w/v of sodium alginate) of polymeric nanoparticles was taken for further evaluations. The size of synthesized nanoparticles was found to be 71.18 nm by particle size analysis (PSA). The berberine loaded polymeric nanoparticles showed better antibacterial activity compared to aqueous solution of berberine by well diffusion assay.

  9. Composite Scaffolds Based on Silver Nanoparticles for Biomedical Applications

    Directory of Open Access Journals (Sweden)

    Jenel Marian Patrascu

    2015-01-01

    Full Text Available This paper presents the synthesis, characterisation, and in vitro testing of homogenous and heterogeneous materials containing silver nanoparticles (nanoAg. Three types of antiseptic materials based on collagen (COLL, hydroxyapatite (HA, and collagen/hydroxyapatite (COLL/HA composite materials were obtained. The synthesis of silver nanoparticles was realized by chemical reaction as well as plasma sputtering deposition. The use of chemical reduction allows the synthesis of homogenous materials while the plasma sputtering deposition can be easily used for the synthesis of homogeneous and heterogeneous support. Based on the in vitro assays clear antiseptic activity against Escherichia coli was relieved even at low content of nanoAg (10 ppm.

  10. The evaluation of prepared microgroove pattern by femtosecond laser on alumina-zirconia nano-composite for endosseous dental implant application.

    Science.gov (United States)

    Aivazi, Moluk; Hossein Fathi, Mohammad; Nejatidanesh, Farahnaz; Mortazavi, Vajihesadat; HashemiBeni, Batoul; Matinlinna, Jukka Pekka; Savabi, Omid

    2016-12-01

    Ceramic dental materials, especially alumina (20 %vol)-yttrium stabilized tetragonal zirconia poly crystal (A-Y-TZP20), have been considered as alternatives to metals for endosseous dental implant application. For increasing the bone-to-implant contact as well as the speed of bone formation, a new surface modification can be effective. The aim of this study was to design microgroove patterns by femtosecond laser on A-Y-TZP20 nano-composite disks for endosseous dental implant application. The phase composition and the morphology of the A-Y-TZP20 nano-composite samples were characterized using X-ray diffraction and Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy techniques. Statistical analysis was submitted to Kolmogorov-Smirnov test and Student's t test for independent variables, with a 5 % significance level. EDAX analysis revealed a significant decrease in the relative content of contaminants like carbon (p < 0.05) in laser surface-treated group as compared to non surface-treated group. X-ray diffraction did not show any change in the crystalline structure induced by laser processing. It was concluded that the femtosecond laser is a clean and safe method for surface modification of A-Y-TZP20.

  11. New composites of nanoparticle Cu (I) oxide and titania in a novel inorganic polymer (geopolymer) matrix for destruction of dyes and hazardous organic pollutants.

    Science.gov (United States)

    Falah, Mahroo; MacKenzie, Kenneth J D; Knibbe, Ruth; Page, Samuel J; Hanna, John V

    2016-11-15

    New photoactive composites to efficiently remove organic dyes from water are reported. These consist of Cu2O/TiO2 nanoparticles in a novel inorganic geopolymer matrix modified by a large tertiary ammonium species (cetyltrimethylammonium bromide, CTAB) whose presence in the matrix is demonstrated by FTIR spectroscopy. The CTAB does not disrupt the tetrahedral geopolymer structural silica and alumina units as demonstrated by (29)Si and (27)Al MAS NMR spectroscopy. SEM/EDS, TEM and BET measurements suggest that the Cu2O/TiO2 nanoparticles are homogenously distributed on the surface and within the geopolymer pores. The mechanism of removal of methylene blue (MB) dye from solution consists of a combination of adsorption (under dark conditions) and photodegradation (under UV radiation). MB adsorption in the dark follows pseudo second-order kinetics and is described by Freundlich-Langmuir type isotherms. The performance of the CTAB-modified geopolymer based composites is superior to composites based on unmodified geopolymer hosts, the most effective composite containing 5wt% Cu2O/TiO2 in a CTAB-modified geopolymer host. These composites constitute a new class of materials with excellent potential in environmental protection applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Enhancement of the Optoelectronic Properties of PEDOT: PSS-PbS Nanoparticles Composite Thin Films Through Nanoparticles' Capping Ligand Exchange

    Science.gov (United States)

    García-Gutiérrez, Diana F.; Hernández-Casillas, Laura P.; Sepúlveda-Guzmán, Selene; Vazquez-Rodriguez, Sofia; García-Gutiérrez, Domingo I.

    2018-02-01

    The influence of the capping ligand on nanoparticles' optical and electronic properties is a topic of great interest currently being investigated by several research groups in different countries. In the present study, PbS nanoparticles originally synthesized with oleic acid, myristic acid and hexanoic acid underwent a ligand exchange process to replace the original carboxylic acid for uc(l)-cysteine as the capping layer, and were thoroughly characterized by means of transmission electron microscopy and its related techniques, such as energy dispersive x-ray spectroscopy and scanning-transmission electron microscopy, and Fourier transform infrared, Raman and x-ray photoelectron spectroscopy. Afterwards, these PbS nanoparticles were dispersed into a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) matrix to fabricate a composite thin film which displayed the optical absorption properties of the PbS nanoparticles and the electrical transport properties of the PEDOT:PSS matrix, in order to evaluate the impact of the nanoparticles' capping ligand on the optoelectronic properties of the fabricated composite thin films. Composite thin films with PbS nanoparticles showing uc(l)-cysteine as the capping layer displayed clear photoresponse and a threefold increment in their conductivities compared to pristine PEDOT:PSS. The properties of PEDOT:PSS, known as a hole transport layer in most organic photovoltaic devices, were enhanced by adding PbS nanoparticles with different capping ligands, producing a promising composite material for optoelectronic applications by proper selection of the nanoparticles' capping layer.

  13. Monitoring Moisture Damage Propagation in GFRP Composites Using Carbon Nanoparticles

    Directory of Open Access Journals (Sweden)

    Ahmed Al-Sabagh

    2017-03-01

    Full Text Available Glass fiber reinforced polymer (GFRP composites are widely used in infrastructure applications including water structures due to their relatively high durability, high strength to weight ratio, and non-corrosiveness. Here we demonstrate the potential use of carbon nanoparticles dispersed during GFRP composite fabrication to reduce water absorption of GFRP and to enable monitoring of moisture damage propagation in GFRP composites. GFRP coupons incorporating 2.0 wt % carbon nanofibers (CNFs and 2.0 wt % multi-wall carbon nanotubes (MWCNTs were fabricated in order to study the effect of moisture damage on mechanical properties of GFRP. Water absorption tests were carried out by immersing the GFRP coupons in a seawater bath at two temperatures for a time period of three months. Effects of water immersion on the mechanical properties and glass transition temperature of GFRP were investigated. Furthermore, moisture damage in GFRP was monitored by measuring the electrical conductivity of the GFRP coupons. It was shown that carbon nanoparticles can provide a means of self-sensing that enables the monitoring of moisture damage in GFRP. Despite the success of the proposed technique, it might not be able to efficiently describe moisture damage propagation in GFRP beyond a specific threshold because of the relatively high electrical conductivity of seawater. Microstructural investigations using Fourier Transform Infrared (FTIR explained the significance of seawater immersion time and temperature on the different levels of moisture damage in GFRP.

  14. Hetero-modulus alumina matrix nanoceramics and CMCs with extreme dynamic strength

    Energy Technology Data Exchange (ETDEWEB)

    Goemze, Laszlo A [University of Miskolc, Department of Ceramics and Silicate Engineering, Miskolc-Egyetemvaros, H-3515 (Hungary); Goemze, Liudmila N, E-mail: femgomze@uni-miskolc.h [IGREX Engineering Service Ltd., Igrici, Rakoczi utca 2., H-3459 (Hungary)

    2011-10-29

    Applying the well-known alumina powders for matrix, different oxide and non-oxide ceramic submicron and nano-particles as additive materials, and investigating the impact of nitrogen atmosphere on sintering; the authors successfully developed new hetero-modulus alumina matrix ceramic composite materials, reinforced with submicron and nanoparticles of {alpha}-Si{sub 3}N{sub 4} {beta}-Si{sub 3}N{sub 4}, Si{sub 2}ON{sub 2}, SiAlON and AlN. Thanks to the new compacting technology with high speed flying punches in vacuumed N{sub 2} atmosphere developed by authors, phase transformation of {alpha}-Si{sub 3}N{sub 4} and {beta}-Si{sub 3}N{sub 4} into cubic c-Si{sub 3}N{sub 4} can be observed, creating so-called Si{sub 3}N{sub 4}-diamond submicron and nanoparticles in alumina matrix. The {alpha}-Si{sub 3}N{sub 4}, {beta}-Si{sub 3}N{sub 4}, Si{sub 2}ON{sub 2}, SiAlON, AlN and c-Si{sub 3}N{sub 4} diamond submicron and nanoparticles reinforced alumina matrix hetero-modulus nanoceramics have excellent mechanical properties and extreme dynamic strength. The dynamic strength was tested through collision with high density metallic flying bodies, with speed higher than 900 m/sec. Analytical methods applied in this research were laser granulometry, scanning electron microscopy, X-ray diffraction and energy dispersive spectrometry. Digital image analysis was applied to microscopy results, to enhance the results of transformation.

  15. Analysis of Composite Leaf Spring Enhanced With Nanoparticles

    Directory of Open Access Journals (Sweden)

    K. Ganesan

    2015-12-01

    Full Text Available Weight reduction is now the main issue in automobile industries. In this work due to reduce the weight of steel spring with composite leaf spring due to high strength ratio is need to improve. The main aim is to compare to the load carrying capacity, stiffness and weight savings of composite leaf spring with that of steel leaf spring at rated-load and over-load condition. The analysis has been carried out for the leaf spring made up of steel and Composite materials. Composite specimens are fabricated with two different staking sequences like the (resin with clay and enhanced with Nanoparticles. The thickness and width for constant cross section is maintained on the moulding techniques. The design of multi leaf spring was modeled in PRO-E and imported in ANSYS 14.5.the dimensions of an existing multi leaf spring is taken for modeling and analysis of a laminated composite multi leaf spring with different composite sequence materials subjected to the same load as that of steel spring.

  16. Influence of coprecipitation and mechanical mixture methods on the characteristics of nickel oxide-alumina composites; Influencia dos metodos de coprecipitacao e mistura mecanica nas caracteristicas de compositos oxido de niquel-alumina

    Energy Technology Data Exchange (ETDEWEB)

    Cordeiro, G.L.; Yoshito, W.K.; Ussui, V.; Lima, N.B. de; Lazar, D.R.R., E-mail: gcordeiro@usp.br [Instituto de Pesquisas Energeticas e Nucleares (CCTM/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Ciencia e Tecnologia de Materiais

    2014-07-01

    Alumina-supported nickel catalysts are currently used in the reforming process due to low cost and high activity for hydrogen production from alcohols. In this work, the effect of preparation methods on nickel oxide-alumina based materials has been investigated. Nickel content was fixed at 15 wt%. Ceramic powders were obtained by coprecipitation in ammonia medium and mechanical mixture. Coprecipitated materials were calcined in air at 750 deg C to obtain the corresponding oxides. Materials obtained by mechanical mixture were prepared by wet milling of nickel oxide and alumina powders, both synthesized by precipitation and calcination in air at 450 and 750 deg C, respectively. Powders were characterized by X-ray diffraction, nitrogen gas sorption by applying the BET method, laser diffraction, scanning electron microscopy, electrophoretic mobility measurements for zeta potential determination and infrared spectroscopy. The results showed that coprecipitation method allowed the production of mixed oxides with high surface area (232,7 ± 3,2 m{sup 2}.g{sup -1}) and normal granulometric distribution while mechanical mixture led to the formation of materials constituted by gamma alumina and nickel oxide phases, with low surface area (136,2 ± 0,5 m{sup 2}.g{sup -1}) and bimodal granulometric distribution. (author)

  17. Composite Polymer Electrolytes: Nanoparticles Affect Structure and Properties

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2016-11-01

    Full Text Available Composite polymer electrolytes (CPEs can significantly improve the performance in electrochemical devices such as lithium-ion batteries. This review summarizes property/performance relationships in the case where nanoparticles are introduced to polymer electrolytes. It is the aim of this review to provide a knowledge network that elucidates the role of nano-additives in the CPEs. Central to the discussion is the impact on the CPE performance of properties such as crystalline/amorphous structure, dielectric behavior, and interactions within the CPE. The amorphous domains of semi-crystalline polymer facilitate the ion transport, while an enhanced mobility of polymer chains contributes to high ionic conductivity. Dielectric properties reflect the relaxation behavior of polymer chains as an important factor in ion conduction. Further, the dielectric constant (ε determines the capability of the polymer to dissolve salt. The atom/ion/nanoparticle interactions within CPEs suggest ways to enhance the CPE conductivity by generating more free lithium ions. Certain properties can be improved simultaneously by nanoparticle addition in order to optimize the overall performance of the electrolyte. The effects of nano-additives on thermal and mechanical properties of CPEs are also presented in order to evaluate the electrolyte competence for lithium-ion battery applications.

  18. HI-SCALE Nanoparticle Composition and Precursors Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Smith, James [Univ. of California, Irvine, CA (United States); Stark, Harald [Aerodyne Research, Inc., Billerica, MA (United States); Browne, Eleanor [Univ. of Colorado, Boulder, CO (United States); Hanson, David [Augsburg College, Minneapolis, MN (United States)

    2017-06-15

    From 21 August to 27 September, 2016, during the second Intensive Operational Period (IOP) of the Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecoystems (HI-SCALE) field campaign, a suite of instruments were placed in the Guest Instrument Facility (GIF) at the Central Facility of the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility’s Southern Great Plains (SGP) site in Lamont, Oklahoma. The goal of these measurements was to fully characterize the formation and evolution of atmospheric aerosol particles through measurements of gas-phase precursor and ambient nanoparticle composition. Specifically, we sought to: 1. investigate the role of acid-base chemistry in new-particle growth through measurements of ammonia and amines as well as organic and inorganic acids in both atmospheric nanoparticles and the gas phase; 2. investigate the contribution of other surface-area or volume-controlled processes to nanoparticle formation and growth, such as the uptake of extremely low volatility organic compounds (ELVOCs); 3. evaluate the performance of a new instrument being developed with funding from the DOE Small Business Innovation Research (SBIR) program for measuring gas-phase amines and related compounds; and 4. together with colleagues measuring on the ground and onboard the ARM Gulfstream-1 (G-1) aircraft during HI-SCALE, create a comprehensive data set related to new particle formation and growth that can be used in modeling efforts by the research team as well as DOE collaborators.

  19. Visible luminescence in polyaniline/(gold nanoparticle) composites

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Renata F. S. [Universidade Federal de Pernambuco, Pos-Graduacao em Ciencia de Materiais (Brazil); Andrade, Cesar A. S. [Universidade Federal de Pernambuco, Departamento de Bioquimica (Brazil); Santos, Clecio G. dos [Instituto de Educacao, Ciencia e Tecnologia de Pernambuco (Brazil); Melo, Celso P. de, E-mail: celso@df.ufpe.br [Universidade Federal de Pernambuco, Pos-Graduacao em Ciencia de Materiais (Brazil)

    2013-01-15

    We describe the use of solution chemistry methods to prepare polyaniline/(gold nanoparticles)-PANI/AuNPs-composites as colloidal particles that exhibit an intense green fluorescence after excitation in the ultraviolet region. Measurements of the relative fluorescence quantum yield indicate that the intensity of the observed luminescence of these nanocomposites is a few orders of magnitude higher than the corresponding fluorescence of either the isolated polymer or the pure AuNPs. Hence, cooperative effects between the conducting polymer chains and the metallic particles must dominate the emission behavior of these materials. Transmission electron microscopy reveals the existence of metal nanoparticle aggregates with sizes in the 2-3 nm range dispersed in the polymer matrix. By implementing an experimental planning, we have been able to change the preparation parameters so as to vary in a controlled manner the intensity and the profile of the luminescence spectrum as well as the size and aggregation characteristics of the colloidal particles. We also show that when the pH of the medium is varied, the dielectric properties (such as the degree of conductivity) of the PANI/AuNPs colloidal solutions and the intensity of their luminescence change in a consistent manner. Due to the polycation nature of the doped PANI chains, we suggest that these composites may find interesting applications as fluorescent markers of biologic molecules.

  20. NiCrxFe2− xO4 ferrite nanoparticles and their composites with ...

    Indian Academy of Sciences (India)

    The XRD and FT-IR studies have confirmed the well crystalline phase of ferrite nanoparticles, and the presence of amorphous PPy in the composite samples. The SEM and TEM images have obviously clarified the coating of ferrite nanoparticles by PPy in the composite samples. The hysteresis loop of the samples has ...

  1. Determining the composition of gold nanoparticles: a compilation of shapes, sizes, and calculations using geometric considerations.

    Science.gov (United States)

    Mori, Taizo; Hegmann, Torsten

    2016-01-01

    Size, shape, overall composition, and surface functionality largely determine the properties and applications of metal nanoparticles. Aside from well-defined metal clusters, their composition is often estimated assuming a quasi-spherical shape of the nanoparticle core. With decreasing diameter of the assumed circumscribed sphere, particularly in the range of only a few nanometers, the estimated nanoparticle composition increasingly deviates from the real composition, leading to significant discrepancies between anticipated and experimentally observed composition, properties, and characteristics. We here assembled a compendium of tables, models, and equations for thiol-protected gold nanoparticles that will allow experimental scientists to more accurately estimate the composition of their gold nanoparticles using TEM image analysis data. The estimates obtained from following the routines described here will then serve as a guide for further analytical characterization of as-synthesized gold nanoparticles by other bulk (thermal, structural, chemical, and compositional) and surface characterization techniques. While the tables, models, and equations are dedicated to gold nanoparticles, the composition of other metal nanoparticle cores with face-centered cubic lattices can easily be estimated simply by substituting the value for the radius of the metal atom of interest.

  2. Beyond the Compositional Threshold of Nanoparticle-Based Materials.

    Science.gov (United States)

    Portehault, David; Delacroix, Simon; Gouget, Guillaume; Grosjean, Rémi; Chan-Chang, Tsou-Hsi-Camille

    2018-03-13

    The design of inorganic nanoparticles relies strongly on the knowledge from solid-state chemistry not only for characterization techniques, but also and primarily for choosing the systems that will yield the desired properties. The range of inorganic solids reported and studied as nanoparticles is however strikingly narrow when compared to the solid-state chemistry portfolio of bulk materials. Efforts to enlarge the collection of inorganic particles are becoming increasingly important for three reasons. First, they can yield materials more performing than current ones for a range of fields including biomedicine, optics, catalysis, and energy. Second, looking outside the box of common compositions is a way to target original properties or to discover genuinely new behaviors. The third reason lies in the path followed to reach these novel nano-objects: exploration and setup of new synthetic approaches. Indeed, willingness to access original nanoparticles faces a synthetic challenge: how to reach nanoparticles of solids that originally belong to the realm of solid-state chemistry and its typical protocols at high temperature? To answer this question, alternative reaction pathways must be sought, which may in turn provide tracks for new, untargeted materials. The corresponding strategies require limiting particle growth by confinement at high temperatures or by decreasing the synthesis temperature. Both approaches, especially the latter, provide a nice playground to discover metastable solids never reported before. The aim of this Account is to raise attention to the topic of the design of new inorganic nanoparticles. To do so, we take the perspective of our own work in the field, by first describing synthetic challenges and how they are addressed by current protocols. We then use our achievements to highlight the possibilities offered by new nanomaterials and to introduce synthetic approaches that are not in the focus of recent literature but hold, in our opinion

  3. Probing Au nanoparticle uptake by enzyme following the digestion of a starch-Au-nanoparticle composite.

    Science.gov (United States)

    Deka, Jashmini; Paul, Anumita; Ramesh, A; Chattopadhyay, Arun

    2008-09-16

    In this letter, we report on the digestion of starch, when present as a composite with Au nanoparticles (NPs), by alpha-amylase. It has been observed that the rate of digestion of free starch and that in the composite were identical. Also, the well-established iodine test could be carried out to investigate the kinetics in the presence of Au NPs. The investigations revealed that following the digestion of starch in the composite the NPs were released and subsequently attached to the enzyme only and not to the degraded products of starch. Also, the enzyme attached to NPs, following digestion, retained its catalytic activity. The particle sizes of the NPs were not affected in the process because no agglomeration was observed. Experimental observations indicated the possibility of oriented attachment of alpha-amylase to the NPs in comparison to amyloglucosidase, another digestive enzyme. Finally, we observed a change in the surface plasmon resonance (SPR) of the NPs following the digestion of starch in the composite, and thus we could demonstrate that the SPR of the NPs could be used as a direct probe for monitoring the digestion of the composite by the enzyme.

  4. Synthesis and ceramic processing of alumina and zirconia based composites infiltrated with glass phase for dental applications; Sintese e processamento de compositos a base de alumina e zirconia com infiltracao de fase vitrea para aplicacoes odontologicas

    Energy Technology Data Exchange (ETDEWEB)

    Duarte, Daniel Gomes

    2009-07-01

    The interest for the use of ceramic materials for dental applications started due to the good aesthetic appearance promoted by the similarity to natural teeth. However, the fragility of traditional ceramics was a limitation for their use in stress conditions. The development of alumina and zirconia based materials, that associate aesthetic results, biocompatibility and good mechanical behaviour, makes possible the employment of ceramics for fabrication of dental restorations. The incorporation of vitreous phase in these ceramics is an alternative to minimize the ceramic retraction and to improve the adhesion to resin-based cements, necessary for the union of ceramic frameworks to the remaining dental structure. In the dentistry field, alumina and zirconia ceramic infiltrated with glassy phase are represented commercially by the In-Ceram systems. Considering that the improvement of powder's synthesis routes and of techniques of ceramic processing contributes for good performance of these materials, the goal of the present work is the study of processing conditions of alumina and/or 3 mol% yttria-stabilized zirconia ceramics infiltrated with aluminum borosilicate lanthanum glass. The powders, synthesized by hydroxide coprecipitation route, were pressed by uniaxial compaction and pre-sintered at temperature range between 950 and 1650 degree C in order to obtain porous ceramics bodies. Vitreous phase incorporation was performed by impregnation of aluminum borosilicate lanthanum powder, also prepared in this work, followed by heat treatment between 1200 and 1400 degree C .Ceramic powders were characterized by thermogravimetry, X-ray diffraction, scanning and transmission electron microscopy, gaseous adsorption (BET) and laser diffraction. Sinterability of alumina and /or stabilized zirconia green pellets was evaluated by dilatometry. Pre-sintered ceramics were characterized by apparent density measurements (Archimedes method), X-ray diffraction and scanning

  5. Polymer nanocomposites for high-temperature composite repair

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, Xia [Iowa State Univ., Ames, IA (United States)

    2008-01-01

    A novel repair agent for resin-injection repair of advanced high temperature composites was developed and characterized. The repair agent was based on bisphenol E cyanate ester (BECy) and reinforced with alumina nanoparticles. To ensure good dispersion and compatibility with the BECy matrix in nanocomposites, the alumina nanoparticles were functionalized with silanes. The BECy nanocomposites, containing bare and functionalized alumina nanoparticles, were prepared and evaluated for their thermal, mechanical, rheological, and viscoelastic properties. The monomer of BECy has an extremely low viscosity at ambient temperature, which is good for processability. The cured BECy polymer is a highly cross-linked network with excellent thermal mechanical properties, with a high glass transition temperature (Tg) of 270 C and decomposition temperature above 350 C. The incorporation of alumina nanoparticles enhances the mechanical and rheological properties of the BECy nanocomposites. Additionally, the alumina nanoparticles are shown to catalyze the cure of BECy. Characterization of the nanocomposites included dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, rheological and rheokinetic evaluation, and transmission electron microscopy. The experimental results show that the BECy nanocomposite is a good candidate as repair agent for resin-injection repair applications.

  6. Experimental Determination of Ballistic Performance of Composite Material Kevlar 29 and Alumina Powder/ Epoxy by Spherical Projectile

    Directory of Open Access Journals (Sweden)

    Luay Hashem Abbud

    2016-12-01

    Full Text Available In this study, a response of hybrid composite laminate woven fiber Kevlar29 – Al2O3 Powder/ Epoxy subjected to high velocity impact loading is presented. The energy absorbed due to impact of small rigid projectile on composite materials targets is determined experimentally. The energy absorbed due to impact of hemispherical projectiles on the developed composite laminates is investigated. The results revealed the maximum ballistic limit at impact velocity is found to be 390.87 ± 6 m/s for an the 18 mm target thickness. The ballistic limit velocity predictions are based on the theoretical method presented from another article. The initial velocity and residual velocity results showed good is agreement compared with the predicted results of Ipson and Recht equations. With 5.4 % of accuracy based on the experimental value for the theoretical model for ballistic limit velocity.

  7. Particulate Composite Materials: Numerical Modeling of a Cross-Linked Polymer Reinforced With Alumina-Based Particles

    Czech Academy of Sciences Publication Activity Database

    Máša, Bohuslav; Náhlík, Luboš; Hutař, Pavel

    2013-01-01

    Roč. 49, č. 4 (2013), s. 421-428 ISSN 0191-5665. [Mechanics of Composite Materials. Riga, 28.05.2013-01.06.2012] R&D Projects: GA ČR GD106/09/H035; GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : particulate composite * cross-linked polymer * FEM * damage model * hyperelasticity Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.451, year: 2013 http://link.springer.com/article/10.1007%2Fs11029-013-9358-y

  8. Tuneable nanoparticle-nanofiber composite substrate for improved cellular adhesion.

    Science.gov (United States)

    Nicolini, Ariana M; Toth, Tyler D; Yoon, Jeong-Yeol

    2016-09-01

    This work presents a novel technique using a reverse potential electrospinning mode for fabricating nanoparticle-embedded composites that can be tailored to represent various fiber diameters, surface morphologies, and functional groups necessary for improved cellular adhesion. Polycaprolactone (PCL) nanofibers were electrospun in both traditional positive (PP) and reverse potential (RP) electrical fields. The fibers were incorporated with 300nm polystyrene (PS) fluorescent particles, which contained carboxyl, amine groups, and surfactants. In the unconventional RP, the charged colloidal particles and surfactants were shown to have an exaggerated effect on Taylor cone morphology and fiber diameter caused by the changes in charge density and surface tension of the bulk solution. The RP mode was shown to lead to a decrease in fiber diameter from 1200±100nm (diameter±SE) for the nanofibers made with PCL alone to 440±80nm with the incorporation of colloidal particles, compared to the PP mode ranging from 530±90nm to 350±50nm, respectively. The nanoparticle-nanofiber composite substrates were cultured with human umbilical vein endothelial cells (HUVECs) and evaluated for cellular viability and adhesion for up to 5 days. Adhesion to the nanofibrous substrates was improved by 180±10% with the addition of carboxylated particles and by 480±60% with the functionalization of an RGD ligand compared to the PCL nanofibers. The novel approach of electrospinning in the RP mode with the addition of colloids in order to alter charge density and surface tension could be utilized towards many applications, one being implantable biomaterials and tissue engineered scaffolds as demonstrated in this work. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. New composites of nanoparticle Cu (I) oxide and titania in a novel inorganic polymer (geopolymer) matrix for destruction of dyes and hazardous organic pollutants

    Energy Technology Data Exchange (ETDEWEB)

    Falah, Mahroo [MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington (New Zealand); MacKenzie, Kenneth J.D., E-mail: Kenneth.mackenzie@vuw.ac.nz [MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington (New Zealand); Knibbe, Ruth [Robinson Research Institute, Victoria University of Wellington (New Zealand); Page, Samuel J.; Hanna, John V. [Department of Physics, Warwick University, Coventry CV4 7AL (United Kingdom)

    2016-11-15

    Highlights: • Synthesis reported of new photoactive nano-oxide composites in a geopolymer matrix. • The novel aluminosilicate matrix is expanded with cetyltrimethylammonium bromide. • The photoactive component consists of a Cu(I) oxide and titania heterostructure. • Composites remove the model pollutant by both adsorption and photodegradation. • These new photocatalysts are extremely efficient and ecologically friendly. - Abstract: New photoactive composites to efficiently remove organic dyes from water are reported. These consist of Cu{sub 2}O/TiO{sub 2} nanoparticles in a novel inorganic geopolymer matrix modified by a large tertiary ammonium species (cetyltrimethylammonium bromide, CTAB) whose presence in the matrix is demonstrated by FTIR spectroscopy. The CTAB does not disrupt the tetrahedral geopolymer structural silica and alumina units as demonstrated by {sup 29}Si and {sup 27}Al MAS NMR spectroscopy. SEM/EDS, TEM and BET measurements suggest that the Cu{sub 2}O/TiO{sub 2} nanoparticles are homogenously distributed on the surface and within the geopolymer pores. The mechanism of removal of methylene blue (MB) dye from solution consists of a combination of adsorption (under dark conditions) and photodegradation (under UV radiation). MB adsorption in the dark follows pseudo second-order kinetics and is described by Freundlich-Langmuir type isotherms. The performance of the CTAB-modified geopolymer based composites is superior to composites based on unmodified geopolymer hosts, the most effective composite containing 5 wt% Cu{sub 2}O/TiO{sub 2} in a CTAB-modified geopolymer host. These composites constitute a new class of materials with excellent potential in environmental protection applications.

  10. Improvement of Thermal and Electrical Conductivity of Epoxy/boron Nitride/silver Nanoparticle Composite

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seungyong; Lim, Soonho [Korea Institute of Science and Technology, Wanju (Korea, Republic of)

    2017-06-15

    In this study, we investigated the effect of BN (boron nitride) on the thermal and the electrical conductivity of composites. In case of epoxy/BN composites, the thermal conductivity was increased as the BN contents were increased. Epoxy/AgNP (Ag nanoparticle) nanocomposites exhibited a slight change of thermal conductivity and showed a electrical percolation threshold at 20 vol% of Ag nanoparticles. At the fixed Ag nanoparticle content below the electrical percolation threshold, increasing the amount of BN enhanced the electrical conductivity as well as thermal conductivity for the epoxy/AgNP/BN composites.

  11. Conductive polymer and Si nanoparticles composite secondary particles and structured current collectors for high loading lithium ion negative electrode application

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Gao

    2017-07-11

    Embodiments of the present invention disclose a composition of matter comprising a silicon (Si) nanoparticle coated with a conductive polymer. Another embodiment discloses a method for preparing a composition of matter comprising a plurality of silicon (Si) nanoparticles coated with a conductive polymer comprising providing Si nanoparticles, providing a conductive polymer, preparing a Si nanoparticle, conductive polymer, and solvent slurry, spraying the slurry into a liquid medium that is a non-solvent of the conductive polymer, and precipitating the silicon (Si) nanoparticles coated with the conductive polymer. Another embodiment discloses an anode comprising a current collector, and a composition of matter comprising a silicon (Si) nanoparticle coated with a conductive polymer.

  12. Photoactive Donor-Acceptor Composite Nanoparticles Dispersed in Water.

    Science.gov (United States)

    Parrenin, Laurie; Laurans, Gildas; Pavlopoulou, Eleni; Fleury, Guillaume; Pecastaings, Gilles; Brochon, Cyril; Vignau, Laurence; Hadziioannou, Georges; Cloutet, Eric

    2017-02-14

    A major issue that inhibits the large-scale fabrication of organic solar modules is the use of chlorinated solvents considered to be toxic and hazardous. In this work, composite particles of poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2',1',3'-benzothiadiazole] (PCDTBT) and [6,6]-phenyl C71 butyric acid methyl ester (PC 71 BM) were obtained in water from a versatile and a ready-to-market methodology based on postpolymerization miniemulsification. Depending on the experimental conditions, size-controlled particles comprising both the electron donor and the electron acceptor were obtained and characterized using transmission electron microscopy (TEM), atomic force microscopy (AFM), small-angle neutron scattering (SANS), UV-visible absorption, and fluorescence spectroscopy. Intimate mixing of the two components was definitely asserted through PCDTBT fluorescence quenching in the composite nanoparticles. The water-based inks were used for the preparation of photovoltaic active layers that were subsequently integrated into organic solar cells.

  13. Development and characterization of ceramic composites alumina-titania based reinforced with lanthanum oxide for fabrication of inert coatings for metallic tanks of the oil industry; Desenvolvimento e caracterizacao de compositos ceramicos baseados em alumina-titania reforcados com oxido de lantanio para fabricacao de revestimentos inertes em tanques metalicos da industria petrolifera

    Energy Technology Data Exchange (ETDEWEB)

    Bandeira, J.M.; Yadava, Y.P.; Silva, N.D.G.; Ferreira, R.A.S., E-mail: julianamb91@gmail.com, E-mail: yadava@ufpe.br [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Centro de Tecnologia e Geociencias. Departamento de Engenharia Mecanica

    2016-07-01

    Crude petroleum is highly corrosive causing superficial degradation in metallic tanks used for storage and transportation of this material, which causes a serious problem in the oil industry. An alternative to solve this problem is to use some kind of coating that is inert to this kind of corrosion. Alumina and titania are interesting materials for several engineering applications because, when compared with other ceramic materials, they present superior mechanical properties, e.g. high mechanical strength, good chemical stability and high fracture toughness combined with good wear resistance and a coefficient of thermal expansion close to the iron's, which makes them fit to use in ceramic hardening process and coating. In this paper, alumina-titania ceramic composites with 5%, 10%, 15% and 20% of titania (TiO2) and reinforced with 2% of lanthanum oxide of were produced by thermo-mechanical processing and sintering techniques at 1350 deg C. In these composites, microstructure and mechanical properties were analyzed using X-ray spectroscopy, optical microscopy, scanning electron microscopy and Vickers hardness in order to evaluate their applicability. X-ray spectroscopy showed the formation of composite without the presence of other phases. Optical microscopy and scanning electron microscopy showed a homogeneous microstructure in terms of particle size and distribution. Vickers hardness test showed a gradual decrease in hardness with the addition of titania. The composite with 5% of titania and 2% of lanthanum oxide is the best choice for structural applications. The composites were submerged in crude petroleum for 30 days to study their stability in such environment. Through the analysis of X-ray spectroscopy, optical microscopy and Vickers hardness before and after the submersion in crude petroleum, it was not observed structural or microstructural degradation nether alterations in mechanical properties. This way, it was concluded that these composites have

  14. Silica Coating of Nonsilicate Nanoparticles for Resin-Based Composite Materials.

    Science.gov (United States)

    Kaizer, M R; Almeida, J R; Gonçalves, A P R; Zhang, Y; Cava, S S; Moraes, R R

    2016-11-01

    This study was designed to develop and characterize a silica-coating method for crystalline nonsilicate ceramic nanoparticles (Al 2 O 3 , TiO 2 , and ZrO 2 ). The hypothesis was that the coated nonsilicate nanoparticles would stably reinforce a polymeric matrix due to effective silanation. Silica coating was applied via a sol-gel method, with tetraethyl orthosilicate as a silica precursor, followed by heat treatment. The chemical and microstructural characteristics of the nanopowders were evaluated before and after silica coating through x-ray diffraction, BET (Brunauer-Emmett-Teller), energy-dispersive x-ray spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy analyses. Coated and noncoated nanoparticles were silanated before preparation of hybrid composites, which contained glass microparticles in addition to the nanoparticles. The composites were mechanically tested in 4-point bending mode after aging (10,000 thermal cycles). Results of all chemical and microstructural analyses confirmed the successful obtaining of silica-coated nanoparticles. Two distinct aspects were observed depending on the type of nanoparticle tested: 1) formation of a silica shell on the surface of the particles and 2) nanoparticle clusters embedded into a silica matrix. The aged hybrid composites formulated with the coated nanoparticles showed improved flexural strength (10% to 30% higher) and work of fracture (35% to 40% higher) as compared with composites formulated with noncoated nanoparticles. The tested hypothesis was confirmed: silanated silica-coated nonsilicate nanoparticles yielded stable reinforcement of dimethacrylate polymeric matrix due to effective silanation. The silica-coating method presented here is a versatile and promising novel strategy for the use of crystalline nonsilicate ceramics as a reinforcing phase of polymeric composite biomaterials.

  15. The local strength of individual alumina particles

    Science.gov (United States)

    Pejchal, Václav; Fornabaio, Marta; Žagar, Goran; Mortensen, Andreas

    2017-12-01

    We implement the C-shaped sample test method and micro-cantilever beam testing to measure the local strength of microscopic, low-aspect-ratio ceramic particles, namely high-purity vapor grown α-alumina Sumicorundum® particles 15-30 μm in diameter, known to be attractive reinforcing particles for aluminum. Individual particles are shaped by focused ion beam micromachining so as to probe in tension a portion of the particle surface that is left unaffected by ion-milling. Mechanical testing of C-shaped specimens is done ex-situ using a nanoindentation apparatus, and in the SEM using an in-situ nanomechanical testing system for micro-cantilever beams. The strength is evaluated for each individual specimen using bespoke finite element simulation. Results show that, provided the particle surface is free of readily observable defects such as pores, twins or grain boundaries and their associated grooves, the particles can achieve local strength values that approach those of high-perfection single-crystal alumina whiskers, on the order of 10 GPa, outperforming high-strength nanocrystalline alumina fibers and nano-thick alumina platelets used in bio-inspired composites. It is also shown that by far the most harmful defects are grain boundaries, leading to the general conclusion that alumina particles must be single-crystalline or alternatively nanocrystalline to fully develop their potential as a strong reinforcing phase in composite materials.

  16. The effect of silver nanoparticles on composite shear bond strength to dentin with different adhesion protocols

    Directory of Open Access Journals (Sweden)

    KOOHPEIMA Fatemeh

    Full Text Available Abstract In Dentistry, restorative materials and oral bacteria are believed to be responsible for restoration failure. To make long-lasting restorations, antibacterial agents should be made. Inorganic nanoparticles and their nano composites are applied as good antibacterial agents. Objective The purpose of this study was to investigate the effect of silver nanoparticles on composite shear bond strength using one etch and rinse and one self-etch adhesive systems. Material and Methods Silver nanoparticles were prepared. Transmission electron microscope and X-ray diffraction were used to characterize the structure of the particles. Nanoparticles were applied on exposed dentin and then different adhesives and composites were applied. All samples were tested by universal testing machine and shear bond strength was assesed. Results Particles with average diameter of about 20 nm and spherical shape were found. Moreover, it was shown that pretreatment by silver nanoparticles enhanced shear bond strength in both etch and rinse, and in self-etch adhesive systems (p≤0.05. Conclusions Considering the positive antibacterial effects of silver nanoparticles, using them is recommended in restorative dentistry. It seems that silver nanoparticles could have positive effects on bond strength of both etch-and-rinse and self-etch adhesive systems. The best results of silver nanoparticles have been achieved with Adper Single Bond and before acid etching.

  17. Reuse of activated alumina

    Energy Technology Data Exchange (ETDEWEB)

    Hobensack, J.E. [Martin Marietta Energy Systems, Inc., Piketon, OH (United States)

    1991-12-31

    Activated alumina is used as a trapping media to remove trace quantities of UF{sub 6} from process vent streams. The current uranium recovery method employs concentrated nitric acid which destroys the alumina pellets and forms a sludge which is a storage and disposal problem. A recently developed technique using a distilled water rinse followed by three dilute acid rinses removes on average 97% of the uranium, and leaves the pellets intact with crush strength and surface area values comparable with new material. Trapping tests confirm the effectiveness of the recycled alumina as UF{sub 6} trapping media.

  18. A study on synthesis and properties of Ag nanoparticles immobilized polyacrylamide hydrogel composites

    International Nuclear Information System (INIS)

    Saravanan, P.; Padmanabha Raju, M.; Alam, Sarfaraz

    2007-01-01

    Synthesis of Ag nanoparticles containing polyacrylamide (PAm) hydrogel composites was performed by free-radical cross-linking polymerization of acrylamide monomer in an aqueous medium containing Ag + ions. The Ag nanoparticle/PAm composites exhibit faint yellow colour and are found to stable under ambient conditions, without undergoing oxidation. TEM micrographs reveal the presence of nearly spherical and well-separated Ag nanoparticles with diameters in the range of 4-7 nm. UV-vis studies apparently show the characteristic surface plasmon band at ∼415 nm, for the existence of Ag nanoparticles within the hydrogel matrix. The effect of varying Ag + ion concentration within the PAm hydrogels on the amount of formation of Ag nanoparticles, as well as on the bulk properties of hydrogel nanocomposites such as equilibrium swelling, optical and electrical properties are studied. The Ag/PAm hydrogel nanocomposites have higher swelling ratio and lower electron transfer resistance than its corresponding conventional hydrogel

  19. Milling of Nanoparticles Reinforced Al-Based Metal Matrix Composites

    Directory of Open Access Journals (Sweden)

    Alokesh Pramanik

    2018-03-01

    Full Text Available This study investigated the face milling of nanoparticles reinforced Al-based metal matrix composites (nano-MMCs using a single insert milling tool. The effects of feed and speed on machined surfaces in terms of surface roughness, surface profile, surface appearance, chip surface, chip ratio, machining forces, and force signals were analyzed. It was found that surface roughness of machined surfaces increased with the increase of feed up to the speed of 60 mm/min. However, at the higher speed (100–140 mm/min, the variation of surface roughness was minor with the increase of feed. The machined surfaces contained the marks of cutting tools, lobes of material flow in layers, pits and craters. The chip ratio increased with the increase of feed at all speeds. The top chip surfaces were full of wrinkles in all cases, though the bottom surfaces carried the evidence of friction, adhesion, and deformed material layers. The effect of feed on machining forces was evident at all speeds. The machining speed was found not to affect machining forces noticeably at a lower feed, but those decreased with the increase of speed for the high feed scenario.

  20. Preparation of alumina-β'

    International Nuclear Information System (INIS)

    Casarini, J.R.; Souza, D.P.F.

    1984-01-01

    Alumina - (β + β') in powder, with composition of 8.85% Na 2 0 + 0.75% Li 2 0 + 90.40% Al 2 O 3 is obtained using the zeta process. The phase transformation β→β' can be seen with powder X-ray diffraction. It was observed that the efficiency of the transformation is related to the processing and purity of the raw material. Impurities as Ca and Si difficult the phase transformation β→β'. (E.G.) [pt

  1. 3D optical printing of piezoelectric nanoparticle-polymer composite materials.

    Science.gov (United States)

    Kim, Kanguk; Zhu, Wei; Qu, Xin; Aaronson, Chase; McCall, William R; Chen, Shaochen; Sirbuly, Donald J

    2014-10-28

    Here we demonstrate that efficient piezoelectric nanoparticle-polymer composite materials can be optically printed into three-dimensional (3D) microstructures using digital projection printing. Piezoelectric polymers were fabricated by incorporating barium titanate (BaTiO3, BTO) nanoparticles into photoliable polymer solutions such as polyethylene glycol diacrylate and exposing to digital optical masks that could be dynamically altered to generate user-defined 3D microstructures. To enhance the mechanical-to-electrical conversion efficiency of the composites, the BTO nanoparticles were chemically modified with acrylate surface groups, which formed direct covalent linkages with the polymer matrix under light exposure. The composites with a 10% mass loading of the chemically modified BTO nanoparticles showed piezoelectric coefficients (d(33)) of ∼ 40 pC/N, which were over 10 times larger than composites synthesized with unmodified BTO nanoparticles and over 2 times larger than composites containing unmodified BTO nanoparticles and carbon nanotubes to boost mechanical stress transfer efficiencies. These results not only provide a tool for fabricating 3D piezoelectric polymers but lay the groundwork for creating highly efficient piezoelectric polymer materials via nanointerfacial tuning.

  2. Surface modified carbon nanoparticle papers and applications on polymer composites

    Science.gov (United States)

    Ouyang, Xilian

    Free-standing paper like materials are usually employed as protective layers, chemical filters, components of electrical batteries or supercapacitors, adhesive layers, and electronic or optoelectric components. Free-standing papers made from carbon nanoparticles have drawn increased interest because they have a variety of superior chemical and physical characteristics, such as light weight, high intrinsic mechanical properties, and extraordinary high electrical conductivity. Nanopapers fabricated from 1- D shape carbon nanofibers (CNFs) and carbon nanotubes (CNTs) are promising reinforcing materials for polymer composites, because the highly porous CNF and CNT nanopapers (porosity ˜80% and ˜70% respectively) can be impregnated with matrix polymers. In the first part of this work, polyaniline (PANI) was used to functionalize the surface of CNFs, and the resultant carbon nanopapers presented impressive mechanical strength and electrical conductivity that it could be used in the in-mold coating (IMC)/ injection molding process to achieve high electromagnetic interference (EMI) shielding effectiveness. Aniline modified (AF) CNT nanopapers were used as a 3D network in gas separation membranes. The resultant composite membranes demonstrated better and stable CO2 permeance and CO 2/H2 selectivity in a high temperature (107°C) and high pressure (15-30 atm) gas separation process, not achievable by conventional polymer membranes. In the second part, we demonstrated that 2-D graphene (GP) or graphene oxide (GO) nanosheets could be tightly packed into a film which was impermeable to most gases and liquids. GP or GO nanopapers could be coated on polymer composites. In order to achieve well-dispersed single-layer graphene in aqueous medium, we developed a facile approach to synthesize functional GP bearing benzenesulfonic acid groups which allow the preparation of nanopapers by water based assembly. With the optimized processing conditions, our best GP nanopapers could reach

  3. The Composites of Graphene Oxide with Metal or Semimetal Nanoparticles and Their Effect on Pathogenic Microorganisms

    Directory of Open Access Journals (Sweden)

    Lukas Richtera

    2015-05-01

    Full Text Available The present experiment describes a synthesis process of composites based on graphene oxide, which was tested as a carrier for composites of metal- or metalloid-based nanoparticles (Cu, Zn, Mn, Ag, AgP, Se and subsequently examined as an antimicrobial agent for some bacterial strains (Staphylococcus aureus (S. aureus, methicillin-resistant Staphylococcus aureus (MRSA and Escherichia coli (E. coli. The composites were first applied at a concentration of 300 µM on all types of model organisms and their effect was observed by spectrophotometric analysis, which showed a decrease in absorbance values in comparison with the control, untreated strain. The most pronounced inhibition (87.4% of S. aureus growth was observed after the application of graphene oxide composite with selenium nanoparticles compared to control. Moreover, the application of the composite with silver and silver phosphate nanoparticles showed the decrease of 68.8% and 56.8%, respectively. For all the tested composites, the observed antimicrobial effect was found in the range of 26% to 87.4%. Interestingly, the effects of the composites with selenium nanoparticles significantly differed in Gram-positive (G+ and Gram-negative (G− bacteria. The effects of composites on bacterial cultures of S. aureus and MRSA, the representatives of G+ bacteria, increased with increasing concentrations. On the other hand, the effects of the same composites on G− bacteria E. coli was observed only in the highest applied concentration.

  4. Silver Nanoparticle-Deposited Boron Nitride Nanosheets as Fillers for Polymeric Composites with High Thermal Conductivity.

    Science.gov (United States)

    Wang, Fangfang; Zeng, Xiaoliang; Yao, Yimin; Sun, Rong; Xu, Jianbin; Wong, Ching-Ping

    2016-01-19

    Polymer composites with high thermal conductivity have recently attracted much attention, along with the rapid development of the electronic devices toward higher speed and performance. However, a common method to enhance polymer thermal conductivity through an addition of high thermally conductive fillers usually cannot provide an expected value, especially for composites requiring electrical insulation. Here, we show that polymeric composites with silver nanoparticle-deposited boron nitride nanosheets as fillers could effectively enhance the thermal conductivity of polymer, thanks to the bridging connections of silver nanoparticles among boron nitride nanosheets. The thermal conductivity of the composite is significantly increased from 1.63 W/m-K for the composite filled with the silver nanoparticle-deposited boron nitride nanosheets to 3.06 W/m-K at the boron nitride nanosheets loading of 25.1 vol %. In addition, the electrically insulating properties of the composite are well preserved. Fitting the measured thermal conductivity of epoxy composite with one physical model indicates that the composite with silver nanoparticle-deposited boron nitride nanosheets outperforms the one with boron nitride nanosheets, owning to the lower thermal contact resistance among boron nitride nanosheets' interfaces. The finding sheds new light on enhancement of thermal conductivity of the polymeric composites which concurrently require the electrical insulation.

  5. Electrochemically produced alumina as TL detector

    International Nuclear Information System (INIS)

    Osvay, M.

    1996-01-01

    The goal of this work was to compare the TL properties of various electrochemically produced alumina layers (E-AIO) in order to investigate the effect of the electrolyte and the Mg content on the alloys. It has been found that the TL sensitivity of oxidised layers is more influenced by the type of electrolyte, than by the composition of alloy. Hard oxide layer evolved in reduction electrolyte has rather different character compared to other alumina production investigated. The effect of reducing media seems to be very important during preparation of alumina layer. One of the advantages properties of E-AIO is, that it serve a promising method to increase the measuring range of TL method above 10 kGy as well. (author)

  6. Beta-alumina solid electrolyte separators

    Energy Technology Data Exchange (ETDEWEB)

    Duncan, J.H.; Stead, R.J.

    1989-06-14

    A method of making a composite beta-alumina artifact such as a separator tube for an electrochemical cell, comprising two beta-alumina portions which are sealed together in a sealing zone, namely an inner portion and an outer portion which extends peripherally around the inner portion and embraces it in the sealing zone, comprises pressing the inner and outer portions from powders which, when finally sintered, shrink and form integral beta-alumina artifacts. The portions are made so that the outer portion undergoes a greater degree of shrinkage during sintering than the inner portion and the portions are pressed so that the spacing between the portions where the outer portion extends around and embraces the inner portion is such that, upon sintering, the outer portion shrinks on to the inner portion to provide a hermetic peripheral seal between the portions. (author).

  7. Silver nanoparticle protein corona composition in cell culture media.

    Science.gov (United States)

    Shannahan, Jonathan H; Lai, Xianyin; Ke, Pu Chun; Podila, Ramakrishna; Brown, Jared M; Witzmann, Frank A

    2013-01-01

    The potential applications of nanomaterials as drug delivery systems and in other products continue to expand. Upon introduction into physiological environments and driven by energetics, nanomaterials readily associate proteins forming a protein corona (PC) on their surface. This PC influences the nanomaterial's surface characteristics and may impact their interaction with cells. To determine the biological impact of nanomaterial exposure as well as nanotherapeutic applications, it is necessary to understand PC formation. Utilizing a label-free mass spectrometry-based proteomics approach, we examined the composition of the PC for a set of four silver nanoparticles (AgNPs) including citrate-stabilized and polyvinlypyrrolidone-stabilized (PVP) colloidal silver (20 or 110 nm diameter). To simulate cell culture conditions, AgNPs were incubated for 1 h in Dulbecco's Modified Eagle Medium supplemented with 10% fetal bovine serum, washed, coronal proteins solubilized, and proteins identified and quantified by label-free LC-MS/MS. To determine which attributes influence PC formation, the AgNPs were characterized in both water and cell culture media with 10% FBS. All AgNPs associated a common subset of 11 proteins including albumin, apolipoproteins, keratins, and other serum proteins. 110 nm citrate- and PVP-stabilized AgNPs were found to bind the greatest number of proteins (79 and 85 respectively) compared to 20 nm citrate- and PVP-stabilized AgNPs (45 and 48 respectively), suggesting a difference in PC formation based on surface curvature. While no relationships were found for other protein parameters (isoelectric point or aliphatic index), the PC on 20 nm AgNPs (PVP and citrate) consisted of more hydrophobic proteins compared to 110 nm AgNPs implying that this class of proteins are more receptive to curvature-induced folding and crowding in exchange for an increased hydration in the aqueous environment. These observations demonstrate the significance of electrostatic

  8. Comparative analysis of the effect of low-dimensional alumina structures on cell lines L929 and Neuro-2a

    Energy Technology Data Exchange (ETDEWEB)

    Fomenko, A. N., E-mail: alserova@ispms.tsc.ru; Korovin, M. S., E-mail: msk@ispms.tsc.ru [National Research Tomsk Polytechnic University, Lenin Avenue 30, Tomsk, 634050 (Russian Federation)

    2016-08-02

    The paper presents the toxicity evaluation of nanostructures on the basis of alumina of different shape (nanofibers, nanoplates, nanosheets, nanosheet agglomerates) and with similar physical and chemical properties (particle size, specific surface area, phase composition, and zeta potential). The nanostructures were examined by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), low-temperature nitrogen adsorption, and dynamic light scattering (DLS). The cytotoxicity of nanostructures was estimated using L929 fibroblast cells and Neuro-2a tumor cells. It has been found that the L929 cells are less subject to the influence of alumina nanoparticles than the Neuro-2a tumor cells. Probably, the differences in the proliferation activity of normal and tumor cells in contact with the synthesized nanostructures are due to a change in the pH of the cell microenvironment.

  9. Comparative analysis of the effect of low-dimensional alumina structures on cell lines L929 and Neuro-2a

    Science.gov (United States)

    Fomenko, A. N.; Korovin, M. S.

    2016-08-01

    The paper presents the toxicity evaluation of nanostructures on the basis of alumina of different shape (nanofibers, nanoplates, nanosheets, nanosheet agglomerates) and with similar physical and chemical properties (particle size, specific surface area, phase composition, and zeta potential). The nanostructures were examined by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), low-temperature nitrogen adsorption, and dynamic light scattering (DLS). The cytotoxicity of nanostructures was estimated using L929 fibroblast cells and Neuro-2a tumor cells. It has been found that the L929 cells are less subject to the influence of alumina nanoparticles than the Neuro-2a tumor cells. Probably, the differences in the proliferation activity of normal and tumor cells in contact with the synthesized nanostructures are due to a change in the pH of the cell microenvironment.

  10. One-step synthesis of gold bimetallic nanoparticles with various metal-compositions

    International Nuclear Information System (INIS)

    Bratescu, Maria Antoaneta; Takai, Osamu; Saito, Nagahiro

    2013-01-01

    Highlights: ► Synthesis of bimetallic nanoparticles in an aqueous solution discharge. ► Alloying gold with divalent sp metals, trivalent sp metals, 3d or 4d metals. ► Formation mechanism of bimetallic nanoparticles by metal reduction and gold erosion. ► Blue and red shift of surface plasmon resonance. -- Abstract: A rapid, one-step process for the synthesis of bimetallic nanoparticles by simultaneous metal reduction and gold erosion in an aqueous solution discharge was investigated. Gold bimetallic nanoparticles were obtained by alloying gold with various types of metals belonging to one of the following categories: divalent sp metals, trivalent sp metals, 3d or 4d metals. The composition of the various gold bimetallic nanoparticles obtained depends on electrochemical factors, charge transfer between gold and other metal, and initial concentration of metal in solution. Transmission electron microscopy and energy dispersive spectroscopy show that the gold bimetallic nanoparticles were of mixed pattern, with sizes of between 5 and 20 nm. A red-shift of the surface plasmon resonance band in the case of the bimetallic nanoparticles Au–Fe, Au–Ga, and Au–In, and a blue-shift of the plasmon band of the Au–Ag nanoparticles was observed. In addition, the interaction of gold bimetallic nanoparticles with unpaired electrons, provided by a stable free radical molecule, was highest for those NPs obtained by alloying gold with a 3d metal

  11. Evaluation of the in vivo performance of composite aluminum/calcium phosphate (CAPs) as bone reconstruction material; Avaliacao in vivo do desempenho de compositos de alumina/fosfato de calcio (CaPs) como material de reconstrucao ossea

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, P.M.; Lima, M.G.; Costa, A.C. [Universidade Federal de Campina Grande (UFCG), PB (Brazil); Pallone, E.M. [Universidade de Sao Paulo (FZEA/USP), Pirassununga, SP (Brazil). Faculdade de Zootecnia e Engenharia de Alimentos; Kiminami, R.H. [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil)

    2016-07-01

    This study aims to evaluate the in vivo performance of composite aluminum/calcium phosphate (CAPs) as bone reconstruction material. To this end, mass CAPs relative to the total weight of Al2O3 prepared Al{sub 2}O{sub 3}/CAPs using percentage of 0, 10, 20 and 30% composites. The composites characterized were by X-ray diffraction, scanning electron microscopy with scanning. After implanted in rabbit tibia randomly divided were into two groups, each with nine rabbits, according to the euthanasia period (30 days after surgery). After euthanasia was performed radiographic and histological evaluation of the grafted areas. The results confirm that the compounds Al{sub 2}O{sub 3}/CAPs presented major phase of alumina and the second phase calcium pyrophosphate. Increasing the concentration of CAPs on alumina promoted with a reduction in density and increase in porosity, as well as an increase in grain size and heterogeneity in the microstructure. Upon radiographic examination of the tibiae of the nine (9) rabbits score was observed with grade 3, or similar radiopacity presented by the remaining cortical bone. It shown was that the tibiae of rabbits with the implant showed the presence of foreign material (composite), well delimited with bone formation and bone proliferation around the implants. At the point where the composite in 30 days' time of sacrifice, there was no observable sign of infection was established, since there were observed no cellular infiltration, no rejection of the implant, concluding that the biocompatible composite was studied. (author)

  12. Characterization and sintering of niobium-ATR alumina

    International Nuclear Information System (INIS)

    Sibuya, N.H.; Iwasaki, H.; Suzuki, C.K.; Pinatti, D.G.

    1987-01-01

    In the niobium aluminothermy a slag is produced, composed mostly of alumina and other compounds such as niobium oxide and silica. The phase composition of this ATR alumina was characterized by X-ray powder diffractometry, and afterwards this alumina was subjected to leaching processes. It was noticed that the original content of 70% α-alumina in slag rose to 95% after the calcination. ATR alumina (leached and calcined, and without any treatment) was used to make pressed bodies which were fired in air at 1200 to 1400 0 C for 1 to 10,5 hours; and in vacuum at 1550 to 1800$0C for 2 hours. Characterization was done by density measurements, X-ray diffractometry and ultrasonic analysis. Ultrasonic analysis of some vacuum fired bodies showed londitudinal velocities close to the value found in literature. Correlation of several techniques measurements disclosed the niobium oxide interference in sintering. (Author) [pt

  13. Synthesis and characterization of ZA-27 alloy matrix composites reinforced with zinc oxide nanoparticles

    Directory of Open Access Journals (Sweden)

    B.O. Fatile

    2017-06-01

    Full Text Available An investigation has been carried out on the synthesis and characterization of ZA-27 alloy composites reinforced with zinc oxide nanoparticles. This was aimed at developing high performance ZA-27 matrix nanocomposite with low density. The particle size and morphology of the zinc oxide (ZnO nanoparticles were investigated by Transmission Electron Microscope (TEM and the elemental composition was obtained from Energy Dispersive Spectroscopy (EDS attached to TEM and X-ray fluorescence spectroscopy (XRF. ZA-27 nanocomposite samples were developed using 0, 1, 2, 3, 4 and 5 wt% of ZnO nanoparticles by double steps stir casting technique. Mechanical properties and Microstructural examination were used to characterize the composite samples produced. The results show that hardness and ultimate tensile strength of the composite samples increased progressively with increase in weight percentage of ZnO nanoparticles. Increase in Ultimate tensile strength (UTS of 10.2%, 21.1%, 22.3%, 35.5%, 33.4% and increase in hardness value of 8.2%, 14.8%, 21.7%, 27.9%, 27.1% were observed for nanocomposites reinforced with 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 5 wt% ZnO nanoparticles respectively in comparison with unreinforced alloy. It was generally observed that composite sample containing 4 wt% of reinforcement has the highest tensile strength and hardness values. However, the fracture toughness and percent elongation of the composites samples slightly decreased with increase in ZnO nanoparticles content. Results obtained from the Microstructural examination using optical microscope and Scanning Electron Microscope (SEM show that the nanoparticles were well dispersed in the ZA-27 alloy matrix.

  14. Entropy driven spontaneous formation of highly porous films from polymer-nanoparticle composites

    International Nuclear Information System (INIS)

    Korampally, Venumadhav; Yun, Minseong; Rajagopalan, Thiruvengadathan; Gangopadhyay, Keshab; Gangopadhyay, Shubhra; Dasgupta, Purnendu K

    2009-01-01

    Nanoporous materials have become indispensable in many fields ranging from photonics, catalysis and semiconductor processing to biosensor infrastructure. Rapid and energy efficient process fabrication of these materials is, however, nontrivial. In this communication, we describe a simple method for the rapid fabrication of these materials from colloidal dispersions of Polymethyl Silsesquioxane nanoparticles. Nanoparticle-polymer composites above the decomposition temperature of the polymer are examined and the entropic gain experienced by the nanoparticles in this rubric is harnessed to fabricate novel highly porous films composed of nanoparticles. Optically smooth, hydrophobic films with low refractive indices (as low as 1.048) and high surface areas (as high as 1325 m 2 g -1 ) have been achieved with this approach. In this communication we address the behavior of such systems that are both temperature and substrate surface energy dependent. The method is applicable, in principle, to a variety of nanoparticle-polymer systems to fabricate custom nanoporous materials.

  15. Antimicrobial activity of composite nanoparticles consisting of titania photocatalytic shell and nickel ferrite magnetic core

    International Nuclear Information System (INIS)

    Rawat, Jagdish; Rana, Subhasis; Srivastava, Radhey; Misra, R. Devesh K.

    2007-01-01

    Reverse micelle and hydrolysis have been combined to synthesize composite nanoparticles consisting of anatase-titania photocatalytic shell and nickel ferrite magnetic core. The average particle size of the composite nanoparticles was in the range of 10-15 nm. The photocatalytic shell of titania is responsible for the photocatalytic and anti-microbial activity and nickel ferrite magnetic core is responsible for the magnetic behavior, studied by superconducting quantum interference device. The anatase TiO2 coated NiFe 2 O 4 nanoparticles retains the magnetic characteristics of uncoated nanocrystalline nickel ferrites, superparamagnetism (absence of hysteresis, remanence and coercivity at 300 K) and non-saturation of magnetic moments at high field. The magnetic measurements results encourage their application as removable anti-microbial photocatalysts. Bacterial inactivation with UV light in the presence of titania-coated NiFe 2 O 4 nanoparticles is faster than the action with UV light alone

  16. Antimicrobial activity of composite nanoparticles consisting of titania photocatalytic shell and nickel ferrite magnetic core

    Energy Technology Data Exchange (ETDEWEB)

    Rawat, Jagdish [Center for Structural and Functional Materials, University of Louisiana at Lafayette, LA 70504-4130 (United States); Department of Chemical Engineering, Center for Structural and Functional Materials, University of Louisiana at Lafayette, LA 70504-4130 (United States); Rana, Subhasis [Center for Structural and Functional Materials, University of Louisiana at Lafayette, LA 70504-4130 (United States); Department of Chemical Engineering, Center for Structural and Functional Materials, University of Louisiana at Lafayette, LA 70504-4130 (United States); Srivastava, Radhey [Department of Chemistry, University of Louisiana at Lafayette, LA 70504-4370 (United States); Misra, R. Devesh K. [Center for Structural and Functional Materials, University of Louisiana at Lafayette, LA 70504-4130 (United States) and Department of Chemical Engineering, Center for Structural and Functional Materials, University of Louisiana at Lafayette, LA 70504-4130 (United States)]. E-mail: dmisra@louisiana.edu

    2007-04-15

    Reverse micelle and hydrolysis have been combined to synthesize composite nanoparticles consisting of anatase-titania photocatalytic shell and nickel ferrite magnetic core. The average particle size of the composite nanoparticles was in the range of 10-15 nm. The photocatalytic shell of titania is responsible for the photocatalytic and anti-microbial activity and nickel ferrite magnetic core is responsible for the magnetic behavior, studied by superconducting quantum interference device. The anatase TiO2 coated NiFe{sub 2}O{sub 4} nanoparticles retains the magnetic characteristics of uncoated nanocrystalline nickel ferrites, superparamagnetism (absence of hysteresis, remanence and coercivity at 300 K) and non-saturation of magnetic moments at high field. The magnetic measurements results encourage their application as removable anti-microbial photocatalysts. Bacterial inactivation with UV light in the presence of titania-coated NiFe{sub 2}O{sub 4} nanoparticles is faster than the action with UV light alone.

  17. Magnetic Composite Thin Films of FexOy Nanoparticles and Photocrosslinked Dextran Hydrogels

    International Nuclear Information System (INIS)

    Brunsen, Annette; Utech, Stefanie; Maskos, Michael; Knoll, Wolfgang; Jonas, Ulrich

    2012-01-01

    Magnetic hydrogel composites are promising candidates for a broad field of applications from medicine to mechanical engineering. Here, surface-attached composite films of magnetic nanoparticles (MNP) and a polymeric hydrogel (HG) were prepared from magnetic iron oxide nanoparticles and a carboxymethylated dextran with photoreactive benzophenone substituents. A blend of the MNP and the dextran polymer was prepared by mixing in solution, and after spin-coating and drying the blend film was converted into a stable MNP–HG composite by photocrosslinking through irradiation with UV light. The bulk composite material shows strong mobility in a magnetic field, imparted by the MNPs. By utilizing a surface layer of a photoreactive adhesion promoter on the substrates, the MNP–HG films were covalently immobilized during photocrosslinking. The high stability of the composite was documented by rinsing experiments with UV–Vis spectroscopy, while surface plasmon resonance and optical waveguide mode spectroscopy was employed to investigate the swelling behavior in dependence of the nanoparticle concentration, the particle type, and salt concentration. - Highlights: ► blending of iron oxide nanoparticles with photocrosslinkable carboxymethyldextran. ► UV irradiation of blend yields surface-attached, magnetic hydrogel films. ► film characterization by surface plasmon resonance/optical waveguide spectroscopy. ► swelling decreases with increasing nanoparticle content. ► swelling decreases with increasing NaCl salt concentration in the aqueous medium.

  18. Superparamagnetic graphene oxide-magnetite nanoparticle composites for uptake of actinide ions from mildly acidic feeds.

    Science.gov (United States)

    Gadly, Trilochan; Mohapatra, Prasanta K; Patre, Dinesh K; Gujar, Rajesh B; Gupta, Alka; Ballal, Anand; Ghosh, Sunil K

    2017-09-01

    Super paramagnetic graphene oxide (GO) - Fe 3 O 4 nanoparticle composites were prepared and characterized by conventional techniques such as XRD, SEM, EDX, FT-IR, Raman, XPS, DLS and zeta potential, etc. TEM studies have confirmed nanoparticle nature of the composites. The GO-magnetic nanoparticle composites can be dispersed in mildly acidic aqueous solutions and get concentrated in a small volume under application of an external magnetic field. The composites were evaluated for the uptake of actinide ions such as Am 3+ , UO 2 2+ , Th 4+ and Pu 4+ from mildly acidic aqueous solutions. Am 3+ sorption sharply increased with pH as the K d values increased from about 10 at pH 1 to 10 5 at pH 3 beyond which a plateau in the K d values was seen. Eu 3+ displayed nearly comparable uptake behaviour to that of Am 3+ while the uptake of other metal ions followed the trend: Pu(IV)>Th(IV)>UO 2 2+ . The adsorption behaviour of Am 3+ onto the graphene oxide - Fe 3 O 4 nanoparticle composites fitted very well to the Langmuir as well as Temkin isotherm models. The desorption rate (using 1M HNO 3 ) was fast and reusability study results were highly encouraging. The very high uptake values suggest possible application of the magnetic nanoparticles in radioactive waste remediation in natural ground water. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Effect of mixing sequence on the curing of amine-hardened epoxy/ alumina nanocomposites as assessed by optical refractometry

    Directory of Open Access Journals (Sweden)

    2008-08-01

    Full Text Available High performance refractometry has been proven to be a useful tool to elucidate the isothermal curing process of nanocomposites. As a model system an amine-hardening epoxy filled with non-surface-treated alumina nanoparticles was selected. The tremendous resolution of this experimental technique is used to study morphological changes within nanocomposites via the refractive index. It is shown that these morphological changes are not simply due to the curing process but also depend on the sequence of mixing the nanoparticles either first into the resin or first into the hardener. Independent of the resin/hardener composition, the type of the mixing sequence discriminates systematically between two distinct refractive index curves produced by the curing process. The difference between the two refractive index curves increases monotonically with curing time, which underlines the importance of the initial molecular environment of the nanoparticles.

  20. Carbon nanotubes/laser ablation gold nanoparticles composites

    International Nuclear Information System (INIS)

    Lascialfari, Luisa; Marsili, Paolo; Caporali, Stefano; Muniz-Miranda, Maurizio; Margheri, Giancarlo; Serafini, Andrea; Brandi, Alberto; Giorgetti, Emilia; Cicchi, Stefano

    2014-01-01

    The production of nanohybrids formed by oxidized multiwalled carbon nanotubes (MWCNTs) and nanoparticles, produced by pulsed laser ablation in liquids process, is described. The use of linkers, obtained by transformation of pyrene-1-butanol, is mandatory to generate an efficient and stable interaction between the two components. Transmission electron microscopy and X-ray photoelectron spectroscopy analysis showed the obtainment of the efficient coverage of the MWCNTs by nanoparticles composed by metal gold and, partially, by oxides. - Highlights: • Laser ablation is a used for the production of gold nanoparticle colloids • An efficient decoration of carbon nanotubes with nanoparticles is obtained through the use of a linker • This method allows an efficient and tunable preparation of carbon nanotube hybrids

  1. Carbon nanotubes/laser ablation gold nanoparticles composites

    Energy Technology Data Exchange (ETDEWEB)

    Lascialfari, Luisa [Department of Chemistry, Università di Firenze, Via della Lastruccia 3-13, Sesto Fiorentino, Firenze 50019 (Italy); Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, via Madonna del Piano 10, Sesto Fiorentino, Firenze 50019 (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Via Giusti 9, Firenze 50123 (Italy); Marsili, Paolo [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, via Madonna del Piano 10, Sesto Fiorentino, Firenze 50019 (Italy); Caporali, Stefano [Department of Chemistry, Università di Firenze, Via della Lastruccia 3-13, Sesto Fiorentino, Firenze 50019 (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Via Giusti 9, Firenze 50123 (Italy); Muniz-Miranda, Maurizio [Department of Chemistry, Università di Firenze, Via della Lastruccia 3-13, Sesto Fiorentino, Firenze 50019 (Italy); Margheri, Giancarlo [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, via Madonna del Piano 10, Sesto Fiorentino, Firenze 50019 (Italy); Serafini, Andrea; Brandi, Alberto [Department of Chemistry, Università di Firenze, Via della Lastruccia 3-13, Sesto Fiorentino, Firenze 50019 (Italy); Giorgetti, Emilia, E-mail: emilia.giorgetti@fi.isc.cnr.it [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, via Madonna del Piano 10, Sesto Fiorentino, Firenze 50019 (Italy); Cicchi, Stefano, E-mail: stefano.cicchi@unifi.it [Department of Chemistry, Università di Firenze, Via della Lastruccia 3-13, Sesto Fiorentino, Firenze 50019 (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Via Giusti 9, Firenze 50123 (Italy)

    2014-10-31

    The production of nanohybrids formed by oxidized multiwalled carbon nanotubes (MWCNTs) and nanoparticles, produced by pulsed laser ablation in liquids process, is described. The use of linkers, obtained by transformation of pyrene-1-butanol, is mandatory to generate an efficient and stable interaction between the two components. Transmission electron microscopy and X-ray photoelectron spectroscopy analysis showed the obtainment of the efficient coverage of the MWCNTs by nanoparticles composed by metal gold and, partially, by oxides. - Highlights: • Laser ablation is a used for the production of gold nanoparticle colloids • An efficient decoration of carbon nanotubes with nanoparticles is obtained through the use of a linker • This method allows an efficient and tunable preparation of carbon nanotube hybrids.

  2. New combination of composite nanoparticles for improved electromagnetic interference shielding

    OpenAIRE

    Azadmanjiri, Jalal

    2017-01-01

    The scope of this research is to investigate generation and use of new “composite” nanoparticles, in particular conductive and magnetic nanoparticles, and study their potential to improve electromagnetic interference absorption for the high frequency range applications. EMI (electromagnetic interference) shielding is a method to prevent electromagnetic fields flowing between two locations by means of a barrier composed of functional materials. This dissertation presents research finding...

  3. Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials

    Science.gov (United States)

    2016-05-23

    decomposition method. Silica coating was done by reverse microemulsion. Silica layers on magnetite nanoparticles minimize the surface tension between the PDMS...be formed (Figure 8d). In addition hollow carbon layer could be formed by eliminating metal oxide nanoparticles using HNO3 solution. (Figure 9a...Figure 9. (a) Synthetic scheme of hollow carbon layer (b,c) TEM images of carbon nanofoams after removal of 16nm iron oxide nanocrystals from the

  4. Real-time measurement of size-resolved elemental composition ratio for flame synthesized composite nanoparticle aggregates using a tandem SMPS-ICP-OES.

    Science.gov (United States)

    Reed, Nathan; Fang, Jiaxi; Chavalmane, Sanmathi; Biswas, Pratim

    2017-01-01

    Composite nanoparticles find application in catalysis, drug delivery, and energy storage and require increasingly fine control of their physical properties and composition. While composite nanoparticles have been widely synthesized and characterized, little work has systematically correlated the initial concentration of precursors and the final composition of flame synthesized composite nanoparticles. This relationship is explored in a diffusion flame aerosol reactor by coupling a scanning mobility particle sizer (SMPS) with an inductively coupled plasma optical emission spectrometer (ICP-OES). A framework for studying the relationship between the initial precursor concentrations of different elements and the final nanoparticle composition is explored. The size-resolved elemental composition was measured by directly injecting size-selected fractions of aggregated magnetite and silicon dioxide composite nanoparticles into the ICP-OES plasma. This work showed a correlation between precursor molar ratio and the measured elemental ratio in the mobility size range of 50 to 140 nm. Building on previous work studying size resolved elemental composition of engineered nanoparticles, the analysis is extended to flame synthesized composite nanoparticle aggregates in this work.

  5. Antibacterial properties of composite resins incorporating silver and zinc oxide nanoparticles on Streptococcus mutans and Lactobacillus

    Directory of Open Access Journals (Sweden)

    Shahin Kasraei

    2014-05-01

    Full Text Available Objectives Recurrent caries was partly ascribed to lack of antibacterial properties in composite resin. Silver and zinc nanoparticles are considered to be broad-spectrum antibacterial agents. The aim of the present study was to evaluate the antibacterial properties of composite resins containing 1% silver and zinc-oxide nanoparticles on Streptococcus mutans and Lactobacillus. Materials and Methods Ninety discoid tablets containing 0%, 1% nano-silver and 1% nano zinc-oxide particles were prepared from flowable composite resin (n = 30. The antibacterial properties of composite resin discs were evaluated by direct contact test. Diluted solutions of Streptococcus mutans (PTCC 1683 and Lactobacillus (PTCC 1643 were prepared. 0.01 mL of each bacterial species was separately placed on the discs. The discs were transferred to liquid culture media and were incubated at 37℃ for 8 hr. 0.01 mL of each solution was cultured on blood agar and the colonies were counted. Data was analyzed with Kruskall-Wallis and Mann-Whitney U tests. Results Composites containing nano zinc-oxide particles or silver nanoparticles exhibited higher antibacterial activity against Streptococcus mutans and Lactobacillus compared to the control group (p < 0.05. The effect of zinc-oxide on Streptococcus mutans was significantly higher than that of silver (p < 0.05. There were no significant differences in the antibacterial activity against Lactobacillus between composites containing silver nanoparticles and those containing zinc-oxide nanoparticles. Conclusions Composite resins containing silver or zinc-oxide nanoparticles exhibited antibacterial activity against Streptococcus mutans and Lactobacillus.

  6. Friction and wear properties of ZrO2/SiO2 composite nanoparticles

    International Nuclear Information System (INIS)

    Li Wei; Zheng Shaohua; Cao Bingqiang; Ma Shiyu

    2011-01-01

    In this article, the lubrication properties of ZrO 2 /SiO 2 composite nanoparticles modified with aluminum zirconium coupling agent as additives in lubricating oil under variable applied load and concentration fraction were reported. It was demonstrated that the modified nanoparticles as additives in lubrication can effectively improve the lubricating properties. Under an optimized concentration of 0.1 wt%, the average friction coefficient was reduced by 16.24%. This was because the nanoparticles go into the friction zone with the flow of lubricant, and then the sliding friction changed to rolling friction with a result of the reduction of the friction coefficient.

  7. The effect of silver nanoparticles on composite shear bond strength to dentin with different adhesion protocols.

    Science.gov (United States)

    Fatemeh, Koohpeima; Mohammad Javad, Mokhtari; Samaneh, Khalafi

    2017-01-01

    The purpose of this study was to investigate the effect of silver nanoparticles on composite shear bond strength using one etch and rinse and one self-etch adhesive systems. Silver nanoparticles were prepared. Transmission electron microscope and X-ray diffraction were used to characterize the structure of the particles. Nanoparticles were applied on exposed dentin and then different adhesives and composites were applied. All samples were tested by universal testing machine and shear bond strength was assesed. Particles with average diameter of about 20 nm and spherical shape were found. Moreover, it was shown that pretreatment by silver nanoparticles enhanced shear bond strength in both etch and rinse, and in self-etch adhesive systems (p≤0.05). Considering the positive antibacterial effects of silver nanoparticles, using them is recommended in restorative dentistry. It seems that silver nanoparticles could have positive effects on bond strength of both etch-and-rinse and self-etch adhesive systems. The best results of silver nanoparticles have been achieved with Adper Single Bond and before acid etching.

  8. Gamma radiation effects on nano composites of Ag nanoparticles in Zn O matrices

    International Nuclear Information System (INIS)

    Villasenor C, L. S.

    2015-01-01

    The study of gamma radiation effects in nano composites of silver nanoparticles in a Zn O matrix has been performed in this work. First, silver nanoparticles (AgNPs) were synthesized by colloidal methods, with two different mean average sizes, 48 nm and 24 nm respectively. These nanoparticles were characterized by transmission electron microscopy (Tem) and UV-Vis spectroscopy (UV-Vis). Then, with the synthesized AgNPs, nano composites in a matrix of Zn O were prepared. The first nano composite was prepared with the 48 nm AgNPs at 9.5 weight % of silver (Ag) and the second nano composite with the 24 nm nanoparticles at 1.0 weight % of Ag. Both nano composites were analyzed by scanning electron microscopy (Sem). The formation of the Zn O phase in the nano composite was corroborated through X-ray diffraction analysis. It was observed that the presence of AgNPs during the formation of the AgNPs/Zn O nano composite modified the size and morphology of the structures obtained compared to those of the pure Zn O without nanoparticles, however both exhibit a radial structure. Then, the nano composite at 9.5 weight % of Ag was irradiated with gamma rays at doses of 1, 20 and 50 kGy. Samples were analyzed by Sem and the Bet technique, before and after being irradiated, in order to determine the effect of gamma radiation in the morphology, porosity and surface area of the studied material. Even when there are changes in porosity and Surface area, this difference is not very significant for some applications, however it will have to be considered during the design of a specific application of the nano composites. On the other hand, no morphology modifications were identified on the samples irradiated at the studied doses, with the electron microscopy techniques used. (Author)

  9. Alumina-base plasma-sprayed materials part I: Phase stability of alumina and alumina-chromia

    Science.gov (United States)

    Chráska, P.; Dubsky, J.; Neufuss, K.; Písacka, J.

    1997-09-01

    Aluminum oxide is a relatively cheap, abundant material that is widely used for plasma- spray applications. This material, however, exists in many crystallographic modifications with different properties. In addition, most of these modifications are metastable and cannot be used in applications employed at elevated temperatures. Usually γ, δ, or other phases form after spraying, while α phase (corundum) is often the most desirable phase due to high corrosion resistance and hardness. This paper first reviews the method of α stabilization in the as- sprayed materials offered in literature. Then, as an example, it summarizes the results of an extensive study of chromia additions to alumina. Chromia was chosen because of its complete solid solubility in alumina and its crystal lattice type, which is similar to that of alumina. It was demonstrated that the addition of approximately 20 wt% chromia results in the formation of one solid solution of (Al- Cr)2O3 in the α- modification. Finally, this paper discusses the thermal stability of various alumina phases. Phase change routes of heating for different starting alumina modifications are discussed, and a case study of alumina- chromia is presented. Both types of as-sprayed structures, a mixture of α, δ, and γ phases, and 100% (Al- Cr)2O3 were annealed up to 1300 °C and the phase composition checked. At lower temperatures and shorter holding times, the amount of α phase decreases while another metastable θ phase appears, and the fraction of γ + δ, if present, increases. At temperature above 1100 °C, the amount of α phase increases again.

  10. Study of microstructure and mechanical properties of ceramics composites alumina-zirconia reinforced with yttria for inert coating of metal matrices used in the petroleum industry; Estudo de microestrutura e propriedades mecanicas de compositos ceramicos alumina-zirconia reforcado com itria para revestimento inerte de matrizes metalicas usadas na industria petrolifera

    Energy Technology Data Exchange (ETDEWEB)

    Pontual, J.O.; Silva, N.D.G.; Ferreira, R.A.S.; Yadava, Y.P., E-mail: juliaopontual@hotmail.com, E-mail: yadava@ufpe.br [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Engenharia Mecanica

    2014-07-01

    The storage and transportation of crude oil is complicated due to the hostile environment provided by this. Under these conditions, it is imperative to search for alternative solutions, using an inert coating to protect from corrosion caused by crude oil. In this work, alumina-zirconia ceramic composites with 5-20%w zirconia and 1 - 2%w yttria were produced through thermomechanical process. The structural and microstructural characterization of the sintered material was carried out by X-ray diffraction and scanning electron microscopy. Mechanical properties were analyzed by Vickers hardness tests. Currently, the pads are submerged in crude oil and after 30-60 days will be removed and sent for stability test.(author)

  11. Silver nanoparticle protein corona composition in cell culture media.

    Directory of Open Access Journals (Sweden)

    Jonathan H Shannahan

    Full Text Available The potential applications of nanomaterials as drug delivery systems and in other products continue to expand. Upon introduction into physiological environments and driven by energetics, nanomaterials readily associate proteins forming a protein corona (PC on their surface. This PC influences the nanomaterial's surface characteristics and may impact their interaction with cells. To determine the biological impact of nanomaterial exposure as well as nanotherapeutic applications, it is necessary to understand PC formation. Utilizing a label-free mass spectrometry-based proteomics approach, we examined the composition of the PC for a set of four silver nanoparticles (AgNPs including citrate-stabilized and polyvinlypyrrolidone-stabilized (PVP colloidal silver (20 or 110 nm diameter. To simulate cell culture conditions, AgNPs were incubated for 1 h in Dulbecco's Modified Eagle Medium supplemented with 10% fetal bovine serum, washed, coronal proteins solubilized, and proteins identified and quantified by label-free LC-MS/MS. To determine which attributes influence PC formation, the AgNPs were characterized in both water and cell culture media with 10% FBS. All AgNPs associated a common subset of 11 proteins including albumin, apolipoproteins, keratins, and other serum proteins. 110 nm citrate- and PVP-stabilized AgNPs were found to bind the greatest number of proteins (79 and 85 respectively compared to 20 nm citrate- and PVP-stabilized AgNPs (45 and 48 respectively, suggesting a difference in PC formation based on surface curvature. While no relationships were found for other protein parameters (isoelectric point or aliphatic index, the PC on 20 nm AgNPs (PVP and citrate consisted of more hydrophobic proteins compared to 110 nm AgNPs implying that this class of proteins are more receptive to curvature-induced folding and crowding in exchange for an increased hydration in the aqueous environment. These observations demonstrate the significance of

  12. Incorporation of coconut shell based nanoparticles in kenaf/coconut fibres reinforced vinyl ester composites

    Science.gov (United States)

    S, Abdul Khalil H. P.; Masri, M.; Saurabh, Chaturbhuj K.; Fazita, M. R. N.; Azniwati, A. A.; Sri Aprilia, N. A.; Rosamah, E.; Dungani, Rudi

    2017-03-01

    In the present study, a successful attempt has been made on enhancing the properties of hybrid kenaf/coconut fibers reinforced vinyl ester composites by incorporating nanofillers obtained from coconut shell. Coconut shells were grinded followed by 30 h of high energy ball milling for the production of nanoparticles. Particle size analyzer demonstrated that the size of 90% of obtained nanoparticles ranged between 15-140 nm. Furthermore, it was observed that the incorporation of coconut shell nanofillers into hybrid composite increased water absorption capacity. Moreover, tensile, flexural, and impact strength increased with the filler loading up to 3 wt.% and thereafter decrease was observed at higher filler concentration. However, elongation at break decreased and thermal stability increased in nanoparticles concentration dependent manner. Morphological analysis of composite with 3% of filler loading showed minimum voids and fiber pull outs and this indicated that the stress was successfully absorbed by the fiber.

  13. Dataset for acrylate/silica nanoparticles formulations and photocured composites : Viscosity, filler dispersion and bulk Poisson׳s ratio

    NARCIS (Netherlands)

    Gojzewski, Hubert; Sadej, Mariola; Andrzejewska, Ewa; Kokowska, Martyna

    2017-01-01

    UV-curable polymer composites are of importance in industry, biomedical applications, scientific fields, and daily life. Outstanding physical properties of polymer composites were achieved with nanoparticles as filler, primarily in enhancing mechanical strength or barrier properties.

  14. Development and characterization of ceramic composites based on alumina-titania reinforced with rare earth oxide (holmium oxide) for the production of inert coatings in metal tanks of petroleum industry; Desenvolvimento e caracterizacao de compositos ceramicos baseados em alumina-titania reforcados com oxido de terra rara (oxido de holmio) para fabricacao de revestimentos inertes em tanques metalicos da industria petrolifera

    Energy Technology Data Exchange (ETDEWEB)

    Silva, N.D.G.; Pontual, J.O.; Ferreira, R.A.S.; Yadava, Y.P., E-mail: nokaa_demery@hotmail.com, E-mail: yadava@ufpe.br [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Engenharia Mecanica

    2014-07-01

    Due to the importance of petroleum and its derivatives for modern society, it is necessary to develop technologies that improve processes and transports of petroleum. The crude oil creates hostile environments and in the process of transport and storage of petroleum are used metallic materials, which corrode becoming a critical problem in this industry. One way of solving this problem is the use of ceramics based on alumina as inert coating on hostile environments. In this work was studied a structure, microstructure and mechanical properties of ceramic composite based on Al2O3 - TiO2 reinforced Ho2O3. The composites were produced by a thermomechanical process, sintered at 1350°C, were analyzed by x-ray diffraction, optical microscopy, scanning electron microscopy, and microhardness. Analyses were performed before and after immersion in earth and offshore crude petroleum to study stability of the developed composites and concluded that the ceramic composites immersed in petroleum show stable in hostile environments. (author)

  15. Nanoparticle/Metal–Organic Framework Composites for Catalytic Applications: Current Status and Perspective

    Directory of Open Access Journals (Sweden)

    Wenlong Xiang

    2017-11-01

    Full Text Available Nanoparticle/metal–organic frameworks (MOF based composites have recently attracted significant attention as a new class of catalysts. Such composites possess the unique features of MOFs (including clearly defined crystal structure, high surface area, single site catalyst, special confined nanopore, tunable, and uniform pore structure, but avoid some intrinsic weaknesses (like limited electrical conductivity and lack in the “conventional” catalytically active sites. This review summarizes the developed strategies for the fabrication of nanoparticle/MOF composites for catalyst uses, including the strategy using MOFs as host materials to hold and stabilize the guest nanoparticles, the strategy with subsequent MOF growth/assembly around pre-synthesized nanoparticles and the strategy mixing the precursors of NPs and MOFs together, followed by self-assembly process or post-treatment or post-modification. The applications of nanoparticle/MOF composites for CO oxidation, CO2 conversion, hydrogen production, organic transformations, and degradation of pollutants have been discussed. Superior catalytic performances in these reactions have been demonstrated. Challenges and future developments are finally addressed.

  16. Nanoparticles Decorated on Resin Particles and Their Flame Retardancy Behavior for Polymer Composites

    Directory of Open Access Journals (Sweden)

    Nour F. Attia

    2017-01-01

    Full Text Available New nanocomposites have been developed by doping of amberlite IR120 resin with spherical TiO2 nanoparticles in the presence of maleate diphosphate. Polystyrene composites of resin, maleate diphosphate, and resin-maleate diphosphate were prepared individually. This is in addition to preparation of polymer nanocomposites of polystyrene-resin doped TiO2 nanoparticles-maleate diphosphate. The flame retardancy and thermal stability properties of these developed polymer composites were evaluated. The inclusion of resin and resin doped nanoparticles improved the fire retardant behavior of polystyrene composites and enhanced their thermal stability. Synergistic behavior between flame retardant, resin, and nanoparticles was detected. The rate of burning of the polymer nanocomposites was recorded as 10.7 mm/min achieving 77% reduction compared to pure polystyrene (46.5 mm/min. The peak heat release rate (PHRR of the new polymer composites has reduced achieving 46% reduction compared to blank polymer. The morphology and dispersion of nanoparticles on resin and in polymer nanocomposites were characterized using transmission and scanning electron microscopy, respectively. The flame retardancy and thermal properties were evaluated using UL94 flame chamber, cone tests, and thermogravimetric analysis, respectively.

  17. Investigation of Structure and Physico-Mechanical Properties of Composite Materials Based on Copper - Carbon Nanoparticles Powder Systems

    Directory of Open Access Journals (Sweden)

    Kovtun V.

    2015-04-01

    Full Text Available Physico-mechanical and structural properties of electrocontact sintered copper matrix- carbon nanoparticles composite powder materials are presented. Scanning electron microscopy revealed the influence of preliminary mechanical activation of the powder system on distribution of carbon nanoparticles in the metal matrix. Mechanical activation ensures mechanical bonding of nanoparticles to the surface of metal particles, thus giving a possibility for manufacture of a composite with high physico-mechanical properties.

  18. Tribological behavior of in situ Ag nanoparticles/polyelectrolyte composite molecular deposition films

    International Nuclear Information System (INIS)

    Guo Yanbao; Wang Deguo; Liu Shuhai

    2010-01-01

    Multilayer polyelectrolyte films containing silver ions were obtained by molecular deposition method on a glass plate or a quartz substrate. The in situ Ag nanoparticles were synthesized in the multilayer polyelectrolyte films which were put into fresh NaBH 4 aqueous solution. The structure and surface morphology of composite molecular deposition films were observed by UV-vis spectrophotometer, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Tribological characteristic was investigated by AFM and micro-tribometer. It was found that the in situ Ag nanoparticles/polyelectrolyte composite molecular deposition films have lower coefficient of friction and higher anti-wear life than pure polyelectrolyte molecular deposition films.

  19. A Study on the Effect of Nano Alumina Particles on Fracture Behavior of PMMA

    Directory of Open Access Journals (Sweden)

    Arezou Sezavar

    2015-04-01

    Full Text Available In the current research, the role of nano-sized alumina on deformation and fracture mechanism of Poly Methyl Methacrylate (PMMA was investigated. For this purpose, PMMA matrix nanocomposite reinforced with different wt% of alumina (i.e., 5, 10 and 15 were fabricated using the compression molding technique. Tensile properties of produced nanocomposites were studied using Zwick Z250 apparatus at cross head speed of about 5 mm/min. In order to specify the role of alumina nanoparticles on deformation and fracture mechanism of PMMA, microscopic evaluation was performed using scanning electron microscope (SEM. The achieved results prove that tensile properties of PMMA depend on alumina wt%. For example, addition of 15 wt% alumina to PMMA causes an increase of about 25% modulus of elasticity. Micrographs taken from the fracture surface of PMMA and its nanocomposites show deformation and fracture mechanism of PMMA changes as alumina is added to it.

  20. Epoxy/α-alumina nanocomposite with high electrical insulation performance

    Directory of Open Access Journals (Sweden)

    Yun Chen

    2017-10-01

    Full Text Available An experimental study was conducted to improve the electrical insulation of epoxy resin. The effects of boehmite, γ-alumina and α-alumina nanoparticles on the volume resistivity, dielectric strength and glass transition temperature of epoxy nanocomposites were investigated. The results showed that α-alumina nanoparticles displayed obvious advantages in enhancing electrical insulation performance of epoxy nanocomposites, compared to boehmite and γ-alumina nanoparticles. The direct current volume resistivity and breakdown strength of epoxy nanocomposite with 2.0 wt% α-alumina nanoparticles was improved to 2.2 × 1018 Ω cm and 76.1 kV mm−1 respectively. And these improved values of electrical insulation properties are much higher than these of epoxy nanocomposites reported in previous studies. The main reason of these improvements may be that the epoxy/α-alumina interaction zone was enhanced by crosslink. Keywords: Nanocomposite, Epoxy resin, Insulation, α-alumina

  1. SERS of semiconducting nanoparticles (TiO{sub 2} hybrid composites).

    Energy Technology Data Exchange (ETDEWEB)

    Musumeci, A.; Gosztola, D.; Schiller, T.; Dimitrijevic, N.; Mujica, V.; Martin, D.; Rajh, T. (Center for Nanoscale Materials)

    2009-04-13

    Raman scattering of molecules adsorbed on the surface of TiO{sub 2} nanoparticles was investigated. We find strong enhancement of Raman scattering in hybrid composites that exhibit charge transfer absorption with TiO{sub 2} nanoparticles. An enhancement factor up to {approx}10{sup 3} was observed in the solutions containing TiO{sub 2} nanoparticles and biomolecules, including the important class of neurotransmitters such as dopamine and dopac (3,4-dihydroxy-phenylacetic acid). Only selected vibrations are enhanced, indicating molecular specificity due to distinct binding and orientation of the biomolecules coupled to the TiO{sub 2} surface. All enhanced modes are associated with the asymmetric vibrations of attached molecules that lower the symmetry of the charge transfer complex. The intensity and the energy of selected vibrations are dependent on the size and shape of nanoparticle support. Moreover, we show that localization of the charge in quantized nanoparticles (2 nm), demonstrated as the blue shift of particle absorption, diminishes SERS enhancement. Importantly, the smallest concentration of adsorbed molecules shows the largest Raman enhancements suggesting the possibility for high sensitivity of this system in the detection of biomolecules that form a charge transfer complex with metal oxide nanoparticles. The wavelength-dependent properties of a hybrid composite suggest a Raman resonant state. Adsorbed molecules that do not show a charge transfer complex show weak enhancements probably due to the dielectric cavity effect.

  2. Controllable synthesis and characterization of Fe3O4/Au composite nanoparticles

    International Nuclear Information System (INIS)

    Xing, Yan; Jin, Yan-Yan; Si, Jian-Chao; Peng, Ming-Li; Wang, Xiao-Fang; Chen, Chao; Cui, Ya-Li

    2015-01-01

    Fe 3 O 4 /Au composite nanoparticles (GoldMag NPs) have received considerable attention because of their advantageous properties arisen from both individual Au and Fe 3 O 4 nanoparticles. Many efforts have been devoted to the synthesis of these composite nanoparticles. Herein, GoldMag NPs were reported to be synthesized by two-step method. Fe 3 O 4 nanoparticles were prepared by co-precipitation and modified by the citric acid, and then citric acid-coated Fe 3 O 4 nanoparticles were used as seeds in sodium citrate solution to reduce the HAuCl 4 . The size of obtained nanoparticles was geared from 25 to 300 nm by controlling the concentration of reactants. The GoldMag NPs were characterized by UV–vis spectrometer, dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). The GoldMag NPs showed good superparamagnetism at room temperature and were well dispersed in water with surface plasmon resonance absorption peak varied from 538 nm to 570 nm. - Highlights: • A low cost, simple manipulation and nontoxic approach was designed for preparation of magnetic Fe 3 O 4 /Au (GoldMag NPs) nanocomposites. • The size of GoldMag NPs could be controlled from 25 to 300 nm by varying the concentration of reactants. • GoldMag NPs possessed good magnetic response, high dispersion, and good stability

  3. Optical properties of functional composite silver nanoparticles and their potential use in reproductive medicine

    Science.gov (United States)

    Syrvatka, Vasyl J.; Slyvchuk, Yurij I.; Rozgoni, Ivan I.; Gevkan, Ivan I.; Bilyy, Oleksandr I.

    2013-06-01

    Silver nanoparticles are promising product of nanotechnology with attractive physicochemical and biological properties. The main aim of the study was to investigate optical properties of functional silver nanoparticles with different composite agents: polyvinylpyrrolidone, bovine serum albumin, hyaluronan and to explore their potential using in reproductive medicine. The date obtained in the study showed that surface modification of nanoparticles leads to change of their optical, physicochemical and biological properties. The optical properties of silver nanoparticles display, that AgNPs with PVP and BSA is most stable in PBS than AgNPs with HA. However the absorption curves after 120 hours of storage show, that AgNPs-HA were the most stable in ethanol. Results show, that silver nanoparticles did not effect on sperm viability and motility, but cause a changes of some biochemical parameters of conditioned medium, particular increase the concentration of triglycerides, activity of alkaline phosphatase, lactate dehydrogenase and decrease the activity of aspartate aminotransferase and alanine aminotransferase after 3 h of in vitro cultivation at 37°C. According to our latest data AgNPs with HA have a less toxic effect on biological processes in rabbits sperm compared with AgNPs with PVP and BSA. Nevertheless all functional composites of silver nanoparticles at the concentration of 0.1 μg/mL have no toxic effect on spermatozoa and can be successfully applied in reproductive medicine at low concentrations as signal enhancers, optical sensors, and biomarkers.

  4. Alumina Technology Roadmap

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2002-02-01

    The Alumina Technology Roadmap outlines a comprehensive long-term research and development plan that defines the industry's collective future and establishes a clear pathway forward. It emphasizes twelve high-priority R&D areas deemed most significant in addressing the strategic goals.

  5. Bauxite and alumina

    Science.gov (United States)

    Bray, E.L.

    2010-01-01

    The article reports on the global market performance of bauxite and alumina in 2009 and presents an outlook for their 2010 performance. There were only several U.S. states that could produce bauxite and bauxitic clays including Georgia, Arkansas, and Alabama. The prices for imported refractory-grade calcined bauxite ranged between 426 U.S. dollars and 554 dollars per ton.

  6. alumina solid electrolyte

    Indian Academy of Sciences (India)

    -β/β -alumina; solid electrolyte; calcium impurity; specific resistance. 1. Introduction. Since its development in the 1980s, the Na/S battery has been one of the most promising candidates for energy storage applications. The Na/S battery functions based on the elec- trochemical reaction between sodium and sulphur to form.

  7. alumina solid electrolyte

    Indian Academy of Sciences (India)

    alumina was synthesized using a solid-state reaction. The changes in ... sive, because of its abundant lowcost raw materials and is suitable for high-volume mass production. The battery is composed of a sodium anode, a sulphur cathode, and. Na. +.

  8. Thermal Properties of Polymethyl Methacrylate Composite Containing Copper Nanoparticles.

    Science.gov (United States)

    Yu, Wei; Xie, Huaqing; Xin, Sha; Yin, Junshan; Jiang, Yitong; Wang, Mingzhu

    2015-04-01

    Thermal functional Materials have wide applications in thermal management fields, and inserting highly thermal conductive materials is effective in enhancing thermal conductivity of matrix. In this paper, copper nanoparticles were selected as the additive to prepare polymethyl methacrylate (PMMA) based nanocomposite with enhanced thermal properties. Uniform copper nanoparticles with pure face-centered lattice were prepared by liquid phase reduction method. Then, they were added into PMMA/N, N-Dimethylmethanamide (DMF) solution according to the different mass fraction for uniform dispersion. After DMF was evaporated, Cu-PMMA nanocomposites were gained. The thermal analysis measurement results showed that the decomposition temperature of nanocomposites decreased gradually with the increasing particle loadings. The thermal conductivity of the Cu-PMMA nanocomposites rose with the increasing contents of copper nanoparticles. With a 20 vol.% addition, the thermal conductivity was up to 1.2 W/m · K, a 380.5% increase compared to the pure PMMA. The results demonstrate that copper nanoparticles have great potential in enhancing thermal transport properties of polymer.

  9. Chitosan/bioactive glass nanoparticle composite membranes for periodontal regeneration

    NARCIS (Netherlands)

    Mota, J.; Yu, N.; Caridade, S.G.; Luz, G.M.; Gomes, M.E.R.; Reis, R.L.; Jansen, J.A.; Walboomers, X.F.; Mano, J.F.

    2012-01-01

    Barrier membranes are used in periodontal applications with the aim of supporting periodontal regeneration by physically blocking migration of epithelial cells. The present work proposes a combination of chitosan (CHT) with bioactive glass nanoparticles (BG-NPs) in order to produce a novel guided

  10. Lump Kinetic Analysis of Syngas Composition Effect on Fischer-Tropsch Synthesis over Cobalt and Cobalt-Rhenium Alumina Supported Catalyst

    OpenAIRE

    Dewi Tristantini; Ricky Kristanda Suwignjo

    2016-01-01

    This study investigated lump kinetic analysis of Fischer-Tropsch synthesis over Cobalt and Cobalt-Rhenium Alumina supported catalyst (Co/γ-Al2O3 and Co-Re/γ-Al2O3) at 20 bars and 483 K using feed gas with molar H2/CO ratios of 1.0 to 2.1. Syngas with H2/CO molar ratio of 1.0 represents syngas characteristic derived from biomass, while the 2.1 molar ratio syngas derived from coal. Rhenium was used as the promoter for the cobalt catalyst. Isothermal Langmuir adsorption mechanism was used to bui...

  11. Palladium nanoparticles/defective graphene composites as oxygen reduction electrocatalysts: A first-principles study

    KAUST Repository

    Liu, Xin

    2012-02-02

    The impact of graphene substrate-Pd nanoparticle interaction on the O, OH, and OOH adsorption that is directly related to the electrocatalytic performance of these composites in oxygen reduction reaction (ORR) has been investigated by first-principles-based calculations. The calculated binding energy of a Pd 13 nanoparticle on a single vacancy graphene is as high as -6.10 eV, owing to the hybridization between the dsp states of the Pd particles with the sp 2 dangling bonds at the defect sites. The strong interaction results in the averaged d-band center of the deposited Pd nanoparticles shifted away from the Fermi level from -1.02 to -1.45 eV. Doping the single vacancy graphene with B or N will further tune the average d-band center and also the activity of the composite toward O, OH, and OOH adsorption. The adsorption energies of O, OH, and OOH are reduced from -4.78, -4.38, and -1.56 eV on the freestanding Pd 13 nanoparticle to -4.57, -2.66, and -1.39 eV on Pd 13/single vacancy graphene composites, showing that the defective graphene substrate will not only stabilize the Pd nanoparticles but also reduce the adsorption energies of the O-containing species to the Pd particle, and so as the poisoning of the ORR active sites. © 2011 American Chemical Society.

  12. Magnetic and structural characterizations on nanoparticles of FePt, FeRh and their composites

    International Nuclear Information System (INIS)

    Ko, Hnin Yu Yu; Suzuki, Takao; Nam, Nguyen T.; Phuoc, Nguyen N.; Cao Jiangwei; Hirotsu, Yoshihiko

    2008-01-01

    The various compositions of FePt and FeRh nanoparticles, and their composite particles have been fabricated by the solution-phase chemical method and their magnetic properties characterized. High-resolution transmission electron microscopic observations indicate that mono-dispersed FeRh and FePt/FeRh nanoparticles are fabricated with the average size of 3-5 nm. However, larger size particles are distributed in the annealed state. From X-ray diffraction results, the as-deposited FeRh nanoparticles reveal a chemically disordered fcc structure which can be transformed into CsCl-type structure through thermal annealing. Similarly, the annealed FePt nanoparticles show the L1 0 -phase fct structure although the fcc structure is apparent in the as-deposited state. It is also found that the first time in the exchange bias effect in the composite of ferromagnetic (FePt) and anti-ferromagnetic (FeRh) nanoparticles; result in a shift of the hysteresis loop after field cooling process

  13. Study of Coating Geometries and Photoluminescence Properties of Metal Nanoparticles/Graphite Composites

    Directory of Open Access Journals (Sweden)

    Pasquale Barone

    2014-01-01

    Full Text Available In this work we present the results of a study of growth and characterization of metal nanoparticles (Ag, Au, and Co/carbon surfaces. The nanoparticles grew by laser ablation technique and their dimensions were controlled by light scattering study and AFM microscopy before their insertion on graphite surface. Nanoparticles appear randomly disposed on carbon surfaces aggregating to form big particles only in the case of silver. The different behavior of metal nanoparticles on carbon surface was explained in terms of different metal wetting of surface, in agreement with previous theoretical results of He et al. Chemical information, obtained by X-ray photoelectron spectroscopy, indicated that the doping process is a simple physisorption while the interfacial interaction between particles and carbon layers causes local defects in graphite structure and the appearance of a strong photoluminescence signal for all composites. Moreover, the visible optical absorption decreases about 10% indicating the progressive metallization of carbon surface.

  14. New compositions of cadmium selenium nanoparticles and dye molecules with cyclodextrin inclusion complexes

    International Nuclear Information System (INIS)

    Asimov, M.M.; Anufrik, S.S.; Tarkovsky, V.V.; Sazonko, H.H.

    2013-01-01

    Spectroscopic properties of new heterogeneous multicolor compositions based on cadmium selenium (CdSe/ZnS) nano crystal and inclusion complexes of dye molecule with cyclodextrin are presented. Spectral fluorescence of proposed compositions investigated in thin films. Signals from multicolor fluorescence of proposing compositions may be combined to definite spectral codes that could be used for tracking or verification of different objects. Calibration bar of signal within spectral codes guarantee high reliability in practical application of proposed multicolor compositions. Express analysis the size of nanoparticles during their synthesis and purification by spectroscopic methods is suggested. Application of Cyclodextrin molecules as target delivery systems is considered. (authors)

  15. Effect of correlation length between metallic nanoparticles in nonlinear properties of composition of oxide glass and metallic nanoparticles using SPFT

    Directory of Open Access Journals (Sweden)

    F. Naseri

    2014-03-01

    Full Text Available There is a kind of composite materials made up of noble metal nanoparticles (such as gold, silver, copper and a dielectric material (such as silica with unique properties. In this paper, using Strong Permittivity Fluctuation Theory (SPFT method, the coefficient of effective permittivity and the effective susceptibility coefficient are calculated for combining glass with metal nanoparticles, assuming that the nanoparticles are spherical. Coefficient of effective permittivity and the effective susceptibility index are estimated for the sample of homogeneous composite materials. And the results of this study are compared with experimental results and other models. It is observed that the data obtained for the zero-order estimate do not match the experimental results. By appropriate correlation length for the second- and third-order, specially for the second-order estimate of SPFT method, conformity between results can be established. Therefore, it can be concluded that SPFT method is betler than other models for calculating and improving the properties of the non-linear model.

  16. Influence of alumina oxide nanoparticles on the performance and emissions in a methyl ester of neem oil fuelled direct injection diesel engine

    Directory of Open Access Journals (Sweden)

    Balaji Gnanasikamani

    2017-01-01

    Full Text Available The experimental investigation of the influence of Al2O3 nanoadditive on performance and emissions in a methyl ester of neem oil fueled direct injection Diesel engine is reported in this paper. The Al2O3 nanoparticles are mixed in various proportions (100 to 300 ppm with methyl ester of neem oil. The performance and emissions are tested in a single cylinder computerized, 4-stroke, stationary, water-cooled Diesel engine of 3.5 kW rated power. Results show that the nanoadditive is effective in increasing the performance and controlling the NO emissions of methyl ester of neem oil fueled Diesel engines.

  17. Iron oxide nanoparticles: the Influence of synthesis method and size on composition and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, M.D., E-mail: mdcarvalho@fc.ul.pt [CCMM/Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, C8, 1749-016 Lisboa (Portugal); Henriques, F. [CCMM/Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, C8, 1749-016 Lisboa (Portugal); Ferreira, L.P. [CFMC/Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, 3004-516 Coimbra (Portugal); Godinho, M.; Cruz, M.M. [CFMC/Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal)

    2013-05-01

    Iron oxide nanoparticles with mean diameter ranging from 7 to 20 nm were synthesized using two routes: the precipitation method in controlled atmosphere and a reduction–precipitation method under air, in some cases followed by a hydrothermal treatment. The smallest nanoparticles were obtained by the reduction–precipitation method. In order to establish the composition of the iron oxide nanoparticles and its relation with size, the morphological, structural and magnetic properties of the prepared samples were investigated using X-ray diffraction, transmission electron microscopy, Mössbauer spectroscopy and SQUID magnetometry. The results allow to conclude that the nanoparticles can be essentially described as Fe3–xO₄, x decreasing with the particle size increase. The composition and magnetic behavior of the synthesized iron oxide nanoparticles are directly related with their size. The overall results are compatible with a core@shell structure model, where a magnetite core is surrounded by an oxidized magnetite layer (labeled as maghemite), the magnetite core dimension depending on the average particle size. - Graphical abstract: TEM images and Mössbauer spectroscopy spectra of Fe3–xO₄ samples with different sizes. Highlights: • Fe3–xO₄ nanoparticles with a mean size between 7 and 20 nm were synthesized. • The smallest nanoparticles were obtained by a reduction precipitation method, under air. • The increase of particles size was succeeded using a hydrothermal treatment at 150 °C. • The magnetic properties of the nanoparticles are directly related with their size.

  18. Orientation relationship in WC-Co composite nanoparticles synthesized by in situ reactions

    Science.gov (United States)

    Wang, Xilong; Song, Xiaoyan; Liu, Xuemei; Liu, Xingwei; Wang, Haibin; Zhou, Cheng

    2015-04-01

    Using the nanoscale violet tungsten oxide as the tungsten source, the WC-Co composite powder was synthesized by the in situ reactions. The particle size of the WC-Co composite powder has a narrow distribution with the mean particle size below 100 nm, and the single composite particle has a nanocrystalline structure with a mean grain size smaller than 10 nm. The detailed characterizations of the nanoparticle microstructure reveal that the orientation relationship and coherence at the interfaces can form during the in situ reactions and further inherit in the consolidated cemented carbide bulk material. The favorable crystallographic characteristics of the WC-Co composite nanoparticles play a significant role in the enhancement of the mechanical properties of the prepared cemented carbide bulk material.

  19. Superhydrophobic surfaces fabricated by surface modification of alumina particles

    Science.gov (United States)

    Richard, Edna; Aruna, S. T.; Basu, Bharathibai J.

    2012-10-01

    The fabrication of superhydrophobic surfaces has attracted intense interest because of their widespread potential applications in various industrial fields. Recently, some attempts have been carried out to prepare superhydrophobic surfaces using metal oxide nanoparticles. In the present work, superhydrophobic surfaces were fabricated with low surface energy material on alumina particles with different sizes. It was found that particle size of alumina is an important factor in achieving stable superhydrophobic surface. It was possible to obtain alumina surface with water contact angle (WCA) of 156° and a sliding angle of Superhydrophobicity of the modified alumina is attributed to the combined effect of the micro-nanostructure and low surface energy of fatty acid on the surface. The surface morphology of the alumina powder and coatings was determined by FESEM. The stability of the coatings was assessed by conducting water immersion test. Effect of heat treatment on WCA of the coating was also studied. The transition of alumina from hydrophilic to superhydrophobic state was explained using Wenzel and Cassie models. The method is shown to have potential application for creating superhydrophobic surface on cotton fabrics.

  20. Fabrication and characterization of nanofiber-nanoparticle-composites with phase change materials by electrospinning

    International Nuclear Information System (INIS)

    Babapoor, Aziz; Karimi, Gholamreza; Khorram, Mohammad

    2016-01-01

    Highlights: • Form-stable nanofibers with phase change material are produced by electrospinning. • PA6 and PEG are used as the supporting matrix and phase change material. • Various nanoparticles are used to enhance thermal properties of the fibers. • The nanofiber-nanoparticle composites exhibited desirable thermal stability. • Al 2 O 3 nanoparticles improved thermal conductivity of the composites considerably. - Graphical Abstract: Display Omitted - Abstract: Thermal energy storage has been recognized as one of the most important technologies for the utilization of renewable energy sources and conserving energy. In this investigation, through combination of polyethylene glycol (PEG) as a phase change material (PCM), polyamid6 (PA6) and various nanoparticles (SiO 2 , Al 2 O 3 , Fe 2 O 3 and ZnO) as supporting materials, novel form-stable PCMs-based composites were fabricated by single nozzle electrospinning. The structure, morphology and thermal properties of the prepared nanofiber-nanocomposite-enhanced phase change materials (NEPCMs) were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and differential scanning calorimeter, respectively. Based on the results, nanocomposites-nanofibers were successfully fabricated with high thermal stability and reliability. It is observed that in all composites, the fiber diameter is decreased by increasing the nanoparticles loading. The lowest average diameter obtained was for Fe 2 O 3 composite. Al 2 O 3 composite showed the maximum thermal conductivity enhancement. This study suggests that the fabricated nanocomposite-PCMs offer proper phase transition temperature range and high heat enthalpy values and hence, have potential for thermal energy storage applications.

  1. Poly (methyl methacrylate) Composites with Size-Selected Silver Nanoparticles Fabricated using Cluster Beam Technique

    DEFF Research Database (Denmark)

    Hanif, Muhammad; Juluri, Raghavendra Rao; Chirumamilla, Manohar

    2016-01-01

    An embedment of metal nanoparticles of well-defined sizes in thin polymer films is of significant interest for a number of practical applications, in particular, for preparing materials with tunable plasmonic properties. In this article, we present a fabrication route for metal–polymer composites...... tendency to flattening upon impact. By controlling the polymer hardness (from viscous to soft state) prior the cluster deposition and annealing conditions after the deposition the degree of immersion of the nanoparticles into polymer can be tuned, thus, making it possible to create composites with either...... particles partly or fully embedded into the film. Good size selection and rather homogeneous dispersion of nanoparticles in the thin polymer film lead to excellent plasmonic properties characterized by the narrow band and high quality factor of localized surface plasmon resonance....

  2. Gold Nanoparticles As A Modifying Agent of Ceramic-Polymer Composites

    Directory of Open Access Journals (Sweden)

    Sobczak-Kupiec A.

    2014-10-01

    Full Text Available Much effort has been invested in the development of biomaterials for the repair or replacement of hard tissue. The synthesis of composites based on mineral and organic constituents is nowadays extremely important for the development of materials for biomedical applications. In this paper we report the preparation and characterization of ceramic-polymer composites doped with gold nanoparticles. Properties and applications in medicine and dentistry of colloidal gold nanoparticles depends upon their size and shape. The influence of the presence of the metallic nanoparticles on the degradation process was investigated by pH and conductivity analyses of water filtrates. The nanocomposites were characterized with the use of X-ray Diffaction (XRD and Fourier Transformed Infrared Spectroscopy (FT-IR methods.

  3. The anti-microbial activity of titania-nickel ferrite composite nanoparticles

    Science.gov (United States)

    Rana, S.; Misra, R. D. K.

    2005-12-01

    A novel approach to synthesize a new generation of composite nanoparticles consisting of a photocatalytic shell of anatase-titania and a magnetic core of nickel ferrite has been adopted combining reverse micelle and chemical hydrolysis techniques. Titania is an effective anti-microbial agent that can be directly sprayed on infected areas of the human body or environment. Unfortunately, titania is an electrical insulator and is difficult to extract from the sprayed surface after treatment. The titania photocatalytic shell provides good antimicrobial capability that renders the bacteria inactive and removes the organic pollutants, while the nickel ferrite magnetic core enables controlled delivery of composite nanoparticles through the application of a small magnetic field, encouraging their application as removable anti-microbial photocatalyst nanoparticles.

  4. Influence of graphene nanoparticles on optical and dielectric properties of PVA-PEDOT:PSS blend composite

    Science.gov (United States)

    Hebbar, Vidyashree; Bhajantri, R. F.; Naik, Jagadish

    2017-05-01

    The composite films of PVA-PEDOT:PSS blend filled with synthesized Graphene oxide (GO) and reduced Graphene oxide (RGO) nanoparticles were prepared by solvent casting technique. The microstructural changes are confirmed in Fourier transform infrared (FTIR) spectroscopy. The UV-Visible absorption spectra exhibit peaks of GO along with a characteristic peak of PVA-PEDOT:PSS blend. The morphological effect is studied with Atomic Force Microscope (AFM). The dielectric parameters such as dielectric constant and dielectric loss increase with increase in wt.% of GO and RGO nanoparticles. The AC conductivities of the prepared nanocomposites measured with impedance analyzer shows maximum for 5 wt.% of GO nanoparticles doped PVA-PEDOT:PSS composites at high frequency.

  5. UV curing of nanoparticle reinforced acrylates

    Science.gov (United States)

    Bauer, F.; Flyunt, R.; Czihal, K.; Ernst, H.; Naumov, S.; Buchmeiser, M. R.

    2007-12-01

    To improve the surface hardness of radiation cured acrylate coatings, both silica nanoparticles and alumina particles with a few microns in size have been embedded into acrylate formulations. Regular mixing of nanoparticles into acrylate formulations, however, leads to highly viscous solutions inappropriate for coating procedures. The incompatibility of inorganic fillers and organic polymers can be avoided by surface modification of nanoparticles using trialkoxysilanes, which provide an interface between the two dissimilar materials. Nanoparticles modified by methacryloxypropyltrimethoxysilane (MEMO) and vinyltrimethoxysilane (VTMO), both having polymerisation-active groups, may be crosslinked with the acrylate resin. UV curing of the nanocomposites revealed an unexpected lower reactivity of the vinyl groups of VTMO modified silica compared to MEMO grafted on silica. For VTMO modification, DFT calculations showed a decrease of Mulliken atomic charge for the olefinic carbons pointing to a lower reactivity. For UV cured nano/microhybrid composites, a significant improvement of abrasion resistance was obtained.

  6. UV curing of nanoparticle reinforced acrylates

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, F. [Leibniz-Institut fuer Oberflaechenmodifizierung, Permoserstr. 15, Leipzig D-04318 (Germany)], E-mail: frank.bauer@iom-leipzig.de; Flyunt, R.; Czihal, K. [Leibniz-Institut fuer Oberflaechenmodifizierung, Permoserstr. 15, Leipzig D-04318 (Germany); Ernst, H. [University of Leipzig, Department of Experimental Physics I, Leipzig D-04103 (Germany); Naumov, S. [Leibniz-Institut fuer Oberflaechenmodifizierung, Permoserstr. 15, Leipzig D-04318 (Germany); Buchmeiser, M.R. [Leibniz-Institut fuer Oberflaechenmodifizierung, Permoserstr. 15, Leipzig D-04318 (Germany); University of Leipzig, Institute of Technical Chemistry, Leipzig D-04103 (Germany)

    2007-12-15

    To improve the surface hardness of radiation cured acrylate coatings, both silica nanoparticles and alumina particles with a few microns in size have been embedded into acrylate formulations. Regular mixing of nanoparticles into acrylate formulations, however, leads to highly viscous solutions inappropriate for coating procedures. The incompatibility of inorganic fillers and organic polymers can be avoided by surface modification of nanoparticles using trialkoxysilanes, which provide an interface between the two dissimilar materials. Nanoparticles modified by methacryloxypropyltrimethoxysilane (MEMO) and vinyltrimethoxysilane (VTMO), both having polymerisation-active groups, may be crosslinked with the acrylate resin. UV curing of the nanocomposites revealed an unexpected lower reactivity of the vinyl groups of VTMO modified silica compared to MEMO grafted on silica. For VTMO modification, DFT calculations showed a decrease of Mulliken atomic charge for the olefinic carbons pointing to a lower reactivity. For UV cured nano/microhybrid composites, a significant improvement of abrasion resistance was obtained.

  7. Magnetic proximity effects in nanoparticle composite systems and macrocrystals

    International Nuclear Information System (INIS)

    Wilbs, Genevieve

    2017-01-01

    Assemblies of magnetic nanoparticles are of major interest for future applications e.g. in spintronic devices, high density data storage systems or biomedical applications. The reason is not only the obvious miniaturization, but also their novel properties emerging only at the nanoscale. Hence, arranging nanoparticles like atoms in a crystal enables the fabrication of a new class of materials. To gain in-depth understanding of these systems, it is necessary to investigate them on all length scales. The present work provides a novel and extensive contribution to the understanding of the selfassembly of iron oxide nanoparticle superstructures and their influence on polarizable matrix materials. Through the investigation of the samples at all stages of preparation, a comprehensive picture of the unique phenomena observed at the end is derived. For this purpose, oleic acid coated iron oxide nanoparticles were deposited on silicon substrates by spincoating to manufacture two-dimensional arrangements. Hereby, the influence of several parameters has been investigated and optimized. Afterwards, the organic surfactant shell was removed by oxygen plasma treatment. This process has been studied in detail, because it initiates a phase transformation that significantly influences the magnetic properties of the system (e.g. by reducing the blocking temperature). Thin palladium or platinum films were then respectively deposited to create a matrix material. Aside from magnetometry measurements, first order reversal curves were obtained in cooperation with the Max-Planck-Institute for Intelligent Systems, both revealing that the matrix materials significantly influence the inter-particle interaction and vice versa. However, only by performing X-ray magnetic circular dichroism experiments at the Advanced Photon Source of the Argonne National Laboratory, it could be evidenced unambiguously that platinum can be polarized by an oxide. Additionally, these systems were investigated

  8. Inductive heat property of Fe3O4/polymer composite nanoparticles in an ac magnetic field for localized hyperthermia

    International Nuclear Information System (INIS)

    Zhao Donglin; Zhang Hailong; Zeng Xianwei; Xia Qisheng; Tang Jintian

    2006-01-01

    The magnetite (Fe 3 O 4 ) nanoparticles were prepared by coprecipitation of Fe 3+ and Fe 2+ with an aqueous NaOH solution. The Fe 3 O 4 /polyaniline (PANI) magnetic composite nanoparticles with a core-shell structure with a diameter of 30-50 nm were prepared via an in situ polymerization of aniline in an aqueous solution containing the Fe 3 O 4 magnetic fluid. The inductive heat property of Fe 3 O 4 /PANI composite nanoparticles in an alternating current (ac) magnetic field was investigated. The potential of Fe 3 O 4 /PANI nanoparticles was evaluated for localized hyperthermia treatment of cancers. The saturation magnetization, M s , and coercivity, H c , are 50.05 emu g -1 and 137 Oe for Fe 3 O 4 nanoparticles and 26.34 emu g -1 and 0 Oe for Fe 3 O 4 /PANI composite nanoparticles, respectively. Exposed in the ac magnetic field for 29 min, the temperatures of physiological saline suspensions containing Fe 3 O 4 nanoparticles or Fe 3 O 4 /PANI composite nanoparticles are 63.6 0 C and 52.4 0 C, respectively. The Fe 3 O 4 /PANI composite nanoparticles would be useful as good thermoseeds for localized hyperthermia treatment of cancers

  9. Surge-Resistant Nanocomposite Enameled Wire Using Silica Nanoparticles with Binary Chemical Compositions on the Surface

    OpenAIRE

    Jeseung Yoo; Yongbeom Kim; Suyong Kwon; Joohyun Lee; Young-Soo Seo

    2015-01-01

    We developed polyesterimide (PEI) nanocomposite enameled wires using surface-modified silica nanoparticles with binary chemical compositions on the surface. The modification was done using silanes assisted by ultrasound, which facilitated high density modification. Two different trimethoxysilanes were chosen for the modification on the basis of resemblance of chemical compositions on the silica surface to PEI varnish. The surface-modified silica was well dispersed in PEI varnish, which was co...

  10. Magnetoimpedance of thin film meander with composite coating layer containing Ni nanoparticles

    NARCIS (Netherlands)

    Lodewijk, K. J.; Fernandez, E.; Garcia-Arribas, A.; Kurlyandskaya, G. V.; Lepalovskij, V. N.; Safronov, A. P.; Kooi, B. J.

    2014-01-01

    Giant magnetoimpedance (GMI) [FeNi/Cu](4)/FeNi/Cu/[FeNi/Cu](4)/FeNi sensing meander elements were designed and tested aiming to develop a new instrumentation for characterization of polymer/magnetic nanoparticles composites. Acrylic copolymer of 95% of butyl methacrylate and 5% of methacrylic acid

  11. In Vitro Cytotoxicity Assessment of an Orthodontic Composite Containing Titanium-dioxide Nano-particles.

    Science.gov (United States)

    Heravi, Farzin; Ramezani, Mohammad; Poosti, Maryam; Hosseini, Mohsen; Shajiei, Arezoo; Ahrari, Farzaneh

    2013-01-01

    Background and aims. Incorporation of nano-particles to orthodontic bonding systems has been considered to prevent enamel demineralization around appliances. This study investigated cytotoxicity of Transbond XT adhesive containing 1 wt% titanium dioxide (TiO2) nano-particles. Materials and methods. Ten composite disks were prepared from each of the conventional and TiO2-containg composites and aged for 1, 3, 5, 7 and 14 days in Dulbecco's Modified Eagle's Medium (DMEM). The extracts were obtained and exposed to culture media of human gingival fibroblasts (HGF) and mouse L929 fibroblasts. Cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results. Both adhesives were moderately toxic for HGF cells on the first day of the experiment, but the TiO2-containing adhesive produced significantly lower toxicity than the pure adhesive (P0.05). There was a significant reduction in cell toxicity with increasing pre-incubation time (Pdetect cytotoxicity of dental composites. Conclusion. The orthodontic adhesive containing TiO2 nano-particles indicated comparable or even lower toxicity than its nano-particle-free counterpart, indicating that incorporation of 1 wt% TiO2 nano-particles to the composite structure does not result in additional health hazards compared to that occurring with the pure adhesive.

  12. Evaluation of carbon nanotube based copper nanoparticle composite for the efficient detection of agroviruses

    Science.gov (United States)

    Nanomaterials based sensors offer sensitivity and selectivity for the detection of a specific analyte-of-the-interest. Described here is a novel assay for the detection of a DNA sequence based on nanostructured carbon nanotubes/copper nanoparticles composite. This assay was modeled on strong electro...

  13. 1 composite mixture of TiO2 nanoparticles and nanotubes in dye

    Indian Academy of Sciences (India)

    Administrator

    90% of transmittance in visible region) was cleaned ultrasonically in deionized water, acetone and ethanol for 10 min. The TiO2 nanoparticles, composite mixture of (TNP + 50% TNT) and TiO2 nano- tubes were coated on ITO plate separately ...

  14. Dielectric properties of nanosilica/low-density polyethylene composites: The surface chemistry of nanoparticles and deep traps induced by nanoparticles

    Directory of Open Access Journals (Sweden)

    S. Ju

    2014-09-01

    Full Text Available Four kinds of nanosilica particles with different surface modification were employed to fabricate low-density polyethylene (LDPE composites using melt mixing and hot molding methods. The surface chemistry of modified nanosilica was analyzed by X-ray photoelectron spectroscopy. All silica nanoparticles were found to suppress the space charge injection and accumulation, increase the volume resistivity, decrease the permittivity and dielectric loss factor at low frequencies, and decrease the dielectric breakdown strength of the LDPE polymers. The modified nanoparticles, in general, showed better dielectric properties than the unmodified ones. It was found that the carrier mobility, calculated from J–V curves using the Mott-Gurney equation, was much lower for the nanocomposites than for the neat LDPE.

  15. The influence of metal nanoparticles on the mechanical properties of composite materials

    Directory of Open Access Journals (Sweden)

    KARIMOV Eduard Khasanovich

    2017-08-01

    Full Text Available The article presents the results of studies on changes in mechanical and physical properties of polymeric construction materials after the introduction of metal nanoparticles. As an example of metal nanoparticles the influence of nanoparticles of copper has been considered. The ways of formation of copper with dimensions of nanometers, a brief methodology and structure of the obtained filler are shown. Copper nanoparticles have unique anti-bacterial, thermal and conductive properties. These properties substantially remain in the polymer material. The resulting composite material has technological properties of polymers and unique physical properties of the filler. Polymer material was selected among the products of large-tonnage production: polyvinyl chloride, elastomers, polyethylene, polypropylene, polystyrene.The selection of copper ions from the nanoparticles depends on the type of stabilizing agent and on the chemical nature of the environment. The performance of antimicrobial properties in polymer materials is achieved by the dosage of copper in the amount of 1–2% by weight. To give a material the conductive properties of copper nanoparticles a higher concentration of metal is required. To use only plastic PVC as the carrier will limit the effectiveness of nanocrystals of copper and affect the mechanical parameters of the material. Therefore it is considered a more complex type of polymer material. Thermoplastic elastomers obtained from blends of rubber and plastic (or plastics, became of great interest in the industrial sector. The wax embedded in a polymeric matrix of polyethylene is used for heat storage of solar energy; thermal protection of electronic devices, nutritional products and medical products; a reduction in installed capacity and thermal comfort in vehicles. To improve the thermal conductivity copper nanoparticles are introduced in the mixture of polyethylene and wax. To obtain the polypropylene with copper nanoparticles

  16. Novel 'nano in nano' composites for sustained drug delivery: biodegradable nanoparticles encapsulated into nanofiber non-wovens.

    Science.gov (United States)

    Beck-Broichsitter, Moritz; Thieme, Marcel; Nguyen, Juliane; Schmehl, Thomas; Gessler, Tobias; Seeger, Werner; Agarwal, Seema; Greiner, Andreas; Kissel, Thomas

    2010-12-08

    Novel 'nano in nano' composites consisting of biodegradable polymer nanoparticles incorporated into polymer nanofibers may efficiently modulate drug delivery. This is shown here using a combination of model compound-loaded biodegradable nanoparticles encapsulated in electrospun fibers. The dye coumarin 6 is used as model compound for a drug in order to simulate drug release from loaded poly(lactide-co-glycolide) nanoparticles. Dye release from the nanoparticles occurs immediately in aqueous solution. Dye-loaded nanoparticles which are encapsulated by electrospun polymer nanofibers display a significantly retarded release. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. In situ green synthesis and characterization of sericin-silver nanoparticle composite with effective antibacterial activity and good biocompatibility.

    Science.gov (United States)

    He, Huawei; Tao, Gang; Wang, Yejing; Cai, Rui; Guo, Pengchao; Chen, Liqun; Zuo, Hua; Zhao, Ping; Xia, Qingyou

    2017-11-01

    Silver nanoparticle has been widely applied to a variety of fields for its outstanding antimicrobial activity. However, the stability of silver nanoparticle limits its application under certain conditions. Thus, improving the stability of silver nanoparticle via biosynthesis is a promising shortcut to expand its application. Sericin from silkworm cocoon has good hydrophilicity, reaction activity, biocompatibility and biodegradability. In this study, we developed a novel, simple, one-step biosynthesis method to prepare sericin-silver nanoparticle composite in situ in solution. Sericin served as the reductant of silver ion, the dispersant and stabilizer of the prepared sericin-silver nanoparticle composite. Natural light was the only power source used to catalyze the synthesis of silver nanoparticle in situ in solution. The novel sericin-silver nanoparticle composite was characterized by ultraviolet-visible and fluorescence spectroscopy, X-ray diffraction, transmission electron microscopy and fourier transform infrared spectroscopy. The results showed silver nanoparticle could be synthesized through the reduction of AgNO 3 by the phenolic hydroxyl group of tyrosine residues of sericin under the catalysis of natural light. The synthesized silver nanoparticle had good crystalline, size distribution and long-term stability at room temperature. Light irradiation was essential for the preparation of sericin-silver nanoparticle composite. The antibacterial activity assay showed 25mg/L and 100mg/L were the minimum concentrations of sericin-silver nanoparticle composite required to inhibit the growth of Staphylococcus aureus and kill this bacterium, respectively. The cytotoxicity assay showed cell viability and cell growth were almost not affected by sericin-silver nanoparticle composite under the concentration of 25mg/L. Our study suggested the preparation of sericin-silver nanoparticle composite was environmentally friendly and energy conservation, and the prepared sericin

  18. Preparation of mixed matrix PES-based nanofiltration membrane filled with PANI-co-MWCNT composite nanoparticles

    International Nuclear Information System (INIS)

    Bagheripour, Ehsan; Moghadassi, Abdolreza; Hosseini, Sayed Mohsen

    2016-01-01

    Mixed matrix polyethersulfone/PANI-co-MWCNTs composite nanoparticle nanofiltration membrane was prepared by casting solution technique. Polyvinylpyrrolidone was also used as membrane pore former in membrane fabrication. The effect of polyaniline-co-multi walled carbon nanotubes composite nanoparticle concentration in the casting solution on membrane structure and performance was investigated. Scanning optical microscopy and scanning electron microscopy, FTIR analysis, porosity, mean pore size, contact angle, water content, NaCl/Na2SO4 rejection, water flux, tensile strength measurements and 3D surface image were also carried out in membrane characterization. SOM images showed nanoparticle agglomeration at high additive loading ratio. SEM images showed the membrane sub-layer porosity and thickness were changed by use of nanoparticles in membrane matrix. The membrane water content, porosity and pore size were increased by increase of nanoparticle concentration, except for 1%wt. Use of PANI-co- MWCNT nanoparticles in the membrane matrix caused a decrease of membrane contact angle from 63.43 to 46.76o. Salt rejection and water flux were improved initially by increase of nanoparticle concentration up to 0.1%wt and then decreased by more additive concentration. In addition, the membranes tensile strength was reduced by increase of PANI-co-MWCNTs composite nanoparticle concentration. 3D surface images showed a smoother surface for mixed matrix membrane filled with 0.1wt% PANI-co-MWCNTs. Modified membrane containing 0.1wt% composite nanoparticles showed better performance compared to others.

  19. Preparation of mixed matrix PES-based nanofiltration membrane filled with PANI-co-MWCNT composite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Bagheripour, Ehsan; Moghadassi, Abdolreza; Hosseini, Sayed Mohsen [Faculty of Engineering, Arak University, Arak (Iran, Islamic Republic of)

    2016-04-15

    Mixed matrix polyethersulfone/PANI-co-MWCNTs composite nanoparticle nanofiltration membrane was prepared by casting solution technique. Polyvinylpyrrolidone was also used as membrane pore former in membrane fabrication. The effect of polyaniline-co-multi walled carbon nanotubes composite nanoparticle concentration in the casting solution on membrane structure and performance was investigated. Scanning optical microscopy and scanning electron microscopy, FTIR analysis, porosity, mean pore size, contact angle, water content, NaCl/Na2SO4 rejection, water flux, tensile strength measurements and 3D surface image were also carried out in membrane characterization. SOM images showed nanoparticle agglomeration at high additive loading ratio. SEM images showed the membrane sub-layer porosity and thickness were changed by use of nanoparticles in membrane matrix. The membrane water content, porosity and pore size were increased by increase of nanoparticle concentration, except for 1%wt. Use of PANI-co- MWCNT nanoparticles in the membrane matrix caused a decrease of membrane contact angle from 63.43 to 46.76o. Salt rejection and water flux were improved initially by increase of nanoparticle concentration up to 0.1%wt and then decreased by more additive concentration. In addition, the membranes tensile strength was reduced by increase of PANI-co-MWCNTs composite nanoparticle concentration. 3D surface images showed a smoother surface for mixed matrix membrane filled with 0.1wt% PANI-co-MWCNTs. Modified membrane containing 0.1wt% composite nanoparticles showed better performance compared to others.

  20. Preparation of alumina microspheres

    International Nuclear Information System (INIS)

    Santos, W.R. dos; Abrao, A.

    1980-01-01

    Inorganic exchangers are widely used for adsorption and column partition chromatography. The main difficulty of using commercial alumina (in powder) for column chromatography is related to its packing, and the operations through the column become diffcult and time-consuming; also it turns to be virtually impossible to use large dimension columns. In order to eliminate these problems, a process for the preparation of alumina micro-spheres was developed as an adaptation of a similar process used to prepare nuclear fuel microspheres (UO 2 , ThO 2 ). The flowsheet of this process is presented together with the analytical results of sphericity after calcination, granulometry, density and characterization by X-ray diffractometry. Solubility tests showed that the so-prepared microspheres are well resistant to strong acids and bases; retention tests showed their efficiency, mainly to copper. (C.L.B.) [pt

  1. Compositional analysis of multi-element magnetic nanoparticles with a combined NMR and TEM approach

    Science.gov (United States)

    Gellesch, Markus; Hammerath, Franziska; Süß, Vicky; Haft, Marcel; Hampel, Silke; Wurmehl, Sabine; Büchner, Bernd

    2017-09-01

    The increasing interest in nanoscale materials goes hand in hand with the challenge to reliably characterize the chemical compositions and structural features of nanosized objects in order to relate those to their physical properties. Despite efforts, the analysis of the chemical composition of individual multi-element nanoparticles remains challenging—from the technical point of view as well as from the point of view of measurement statistics. Here, we demonstrate that zero-field solid-state nuclear magnetic resonance (NMR) complements local, single particle transmission electron microscopy (TEM) studies with information on a large assembly of chemically complex nanoparticles. The combination of both experimental techniques gives information on the local composition and structure and provides an excellent measurement statistic through the corresponding NMR ensemble measurement. This analytical approach is applicable to many kinds of magnetic materials and therefore may prove very versatile in the future research of particulate magnetic nanomaterials.

  2. Uranyl sorption onto alumina

    International Nuclear Information System (INIS)

    Jacobsson, A.M.M.

    1997-01-01

    The mechanism for the adsorption of uranyl onto alumina from aqueous solution was studied experimentally and the data were modeled using a triple layer surface complexation model. The experiments were carried out at low uranium concentrations (9 x 10 -11 --5 x 10 -8 M) in a CO 2 free environment at varying electrolyte concentrations (0.01--1 M) and pH (4.5--12). The first and second acid dissociation constants, pK a1 and pK a2 , of the alumina surface were determined from potentiometric titrations to be 7.2 ± 0.6 and 11.2 ± 0.4, respectively. The adsorption of uranium was found to be independent of the electrolyte concentration. The authors therefore conclude that the uranium binds as an inner sphere complex. The results were modeled using the code FITEQL. Two reactions of uranium with the surface were needed to fit the data, one forming a uranyl complex with a single surface hydroxyl and the other forming a bridged or bidentate complex reacting with two surface hydroxyls of the alumina. There was no evidence from these experiments of site heterogeneity. The constants used for the reactions were based in part on predictions made utilizing the Hard Soft Acid Base, HSAB, theory, relating the surface complexation constants to the hydrolysis of the sorbing metal ion and the acid dissociation constants of the mineral oxide surface

  3. Rheological Properties of Aqueous Nanometric Alumina Suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chuanping [Iowa State Univ., Ames, IA (United States)

    2004-01-01

    ' surfaces in the aqueous suspension. The viscosity of the suspension increases dramatically when the solid volume fraction exceeds 30 vol.%. The overlap of physically adsorbed water layers at this level causes the sharp increase in viscosity. Fructose molecules can weaken the interactions between the particle surfaces and water molecules, as a consequence, they release some bound water layers from the surfaces to the bulk medium. It is believed that fraction of the water that is bound by the solid surface is reduced hence becoming available for flow. The oxygen-17 relaxation time decreased with the increase of particle volume fractions in the suspension. Fructose addition increased the overall water mobility in the suspension. Only part of the alumina particle surfaces was covered with fructose molecules. This adsorption of fructose molecules on the particle surfaces increased the pH of the suspension with a concomitant decrease in ζ-potential of the alumina nanoparticles. The interactions between the nanometric alumina particles in water to a large extent can be explained by the DLVO theory. However, the interactions between particles in fructose solutions cannot be well described by the DLVO theory. The interaction forces (magnitude and range) as well as adhesive force and surface tension between nanometric alumina particles were decreased with the fructose concentration.

  4. Quantifying the composition of yttrium and oxygen rich nanoparticles in oxide dispersion strengthened steels.

    Science.gov (United States)

    Williams, C A; Smith, G D W; Marquis, E A

    2013-02-01

    Atom probe tomography (APT) is used to investigate the composition of oxygen rich nanoparticles within a ferritic matrix in Fe-14Cr-2W-0.1Ti oxide-dispersion-strengthened (ODS) steel. This study investigates whether artifacts associated with APT analysis are the cause of a sub-stoichiometric oxide composition measurement. Bulk Y₂O₃ is analyzed by APT, thus demonstrating the ability of the technique to measure near-stoichiometric composition measurements in insulating oxides. Through analysis of the sequence of ion hits on the detector during APT data acquisition, it is shown that a proportion of yttrium hits are spatially correlated but oxygen hits are not. Y-O based nanoparticles in a ferritic matrix are analyzed by APT using voltage pulsing and a laser pulsing with a range of laser energies from 0.3-0.8 nJ. When the material is analyzed using a high effective evaporation field, this influences the effect of trajectory aberrations, and the apparent size of the nanoparticles is reduced. Some reduction in Y:O ratio is observed, caused by high instances of multiple-ion evaporation events. From a detailed comparison between the results of APT analysis of the bulk Y₂O₃ the nanoparticles in the ODS material are concluded to have an approximate Y:O ratio of 1:1. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. Pyrene As a New Detector for Determining the Composition of Silver Nanoparticle Dispersions in Aqueous Solutions

    Science.gov (United States)

    Romanovskaya, G. I.; Kazakova, S. Yu.; Koroleva, M. V.; Zuev, B. K.

    2018-03-01

    It is proposed that the fluorescence of monomeric molecules of pyrene in solid matrices or in concentrated micellar solutions be used as a detector for determining the compositional homogeneity of silver nanoparticle (NP) dispersions in aqueous solutions synthesized in different ways. It is found that the morphology of silver NPs affects the change in the fluorescence intensity of monomeric molecules of pyrene in a certain (violet or blue) region of the pyrene optical spectrum. The observed phenomenon is attributed to the resonance of electronic transitions in the monomeric molecules of pyrene in regions with plasmon oscillations in silver nanoparticles. A new way of obtaining fluorescent silver NPs is found.

  6. Diffraction of slow neutrons by holographic SiO2 nanoparticle-polymer composite gratings

    Science.gov (United States)

    Klepp, J.; Pruner, C.; Tomita, Y.; Plonka-Spehr, C.; Geltenbort, P.; Ivanov, S.; Manzin, G.; Andersen, K. H.; Kohlbrecher, J.; Ellabban, M. A.; Fally, M.

    2011-07-01

    Diffraction experiments with holographic gratings recorded in SiO2 nanoparticle-polymer composites have been carried out with slow neutrons. The influence of parameters such as nanoparticle concentration, grating thickness, and grating spacing on the neutron-optical properties of such materials has been tested. Decay of the grating structure along the sample depth due to disturbance of the recording process becomes an issue at grating thicknesses of about 100 microns and larger. This limits the achievable diffraction efficiency for neutrons. As a solution to this problem, the Pendellösung interference effect in holographic gratings has been exploited to reach a diffraction efficiency of 83% for very cold neutrons.

  7. Synthesis and Characterization of Silver Nanoparticle-Multiwalled Carbon Nanotube Composites

    Directory of Open Access Journals (Sweden)

    Dunieskys G. Larrude

    2014-01-01

    Full Text Available Multiwalled carbon nanotubes (MWCNTs grown by spray pyrolysis have been decorated with silver nanoparticles prepared via the silver mirror reaction. Good dispersion of silver nanostructures was obtained on the surface of MWCNTs, resulting in an efficient and simple wet chemistry method for increasing the reactivity of the carbon nanotubes surfaces. High-resolution transmission electron microscopy showed the orientations of the crystallography planes of the anchored silver nanoparticles and revealed their size distribution. Raman spectroscopy results confirm that the composite material preserves the integrity of the MWCNTs. Scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were also employed for sample characterization.

  8. Fractal Aggregation in Silica Nanoparticle and Surfactant Composites

    Science.gov (United States)

    Kumar, Sugam; Aswal, V. K.

    2011-07-01

    The role of cationic surfactant on particle aggregation of anionic silica nanoparticles has been studied by small-angle neutron scattering (SANS). We show that the aggregation is characterized by the fractal structure. The fractal dimension is found to be same irrespective of varying the surfactant and its concentration. These results are explained on the basis of that the aggregation of particles mediated by the oppositely charged surfactant micelles between them and governed by the diffusion limited aggregation. Both adsorbed and free micelles coexists and the number of adsorbed micelles does not change with varying surfactant concentration however decreases with the increase in the size of the micelle.

  9. Neutron-optical gratings from nanoparticle-polymer composites

    Science.gov (United States)

    Klepp, J.; Pruner, C.; Ellabban, M. A.; Tomita, Y.; Lemmel, H.; Rauch, H.; Fally, M.

    2011-04-01

    The preparation of neutron-optical phase gratings with light-optical holography is reviewed. We compare the relevant concepts of: (i) Kogelnik's theory for Bragg diffraction of light by thick volume gratings, which can be used to analyze holographic gratings with both light and neutrons, and (ii) the dynamical theory of neutron diffraction. Without going into mathematical detail, we intend to illuminate their correspondence. The findings are illustrated by analyzing data obtained from reconstruction of nanoparticle holographic gratings with both light and neutrons.

  10. Obtenção de um revestimento compósito de poliéster-uretana reforçado com alumina pela técnica de deposição por imersão sobre fibras de poliamida 6 Preparation of a composite coating of alumina reinforced polyester urethane by dip coating on polyamide 6 fibers

    Directory of Open Access Journals (Sweden)

    F. A. L. Sánchez

    2009-12-01

    Full Text Available O uso de revestimentos compósitos de matriz polimérica e reforço cerâmico capazes de manter a flexibilidade e a elasticidade das fibras poliméricas, agregando propriedades típicas dos materiais cerâmicos (como ação bactericida ou fotocatalítica, resistência à chama, ao desgaste e à abrasão, tem atraído interesse da indústria têxtil. Baseado na técnica dip coating e usando fibras sintéticas de poliamida como substrato, foram produzidas suspensões de poliéster-uretana com partículas de alumina (tamanho médio de partícula 2,2 μm para obtenção de revestimentos uniformes e espessos sobre o material base, poliamida 6. A viscosidade das suspensões foi controlada pela adição de carboximetilcelulose e avaliada por reometria rotacional. A distribuição granulométrica das suspensões também foi determinada. Os parâmetros operacionais do dip coating, i.e., velocidade de bobinamento e temperatura dos fornos, foram mantidos constantes em todas as amostras. O processo mostrou viabilidade para deposição uniforme do recobrimento avaliado, com espessura adequada, indicando ser promissor para revestir fibras, agregando propriedades de interesse tecnológico.Ceramic reinforced polymer composite coatings that can retain the flexibility and elasticity of the polymeric fibers, being also able to incorporate the functionality of ceramic materials (e.g. fire, wear, or abrasion resistance, antibacterial performance, photocatalytic effect are interesting to the processing of textile materials. In this work, polyester-urethane slurries with alumina particles (mean particle size: 2.2 μm were developed based on the dip coating technique and using polyamide-6 synthetic fibers as the substrate, seeking to obtain an uniform and thick coating. The viscosity of the slurries was varied using carboxymethylcellulose as a rheological agent and evaluated by rotational rheometry. Particle size distribution of the slurries was also analyzed. The

  11. Decreased astroglial cell adhesion and proliferation on zinc oxide nanoparticle polyurethane composites

    Science.gov (United States)

    Seil, Justin T; Webster, Thomas J

    2008-01-01

    Nanomaterials offer a number of properties that are of interest to the field of neural tissue engineering. Specifically, materials that exhibit nanoscale surface dimensions have been shown to promote neuron function while simultaneously minimizing the activity of cells such as astrocytes that inhibit central nervous system regeneration. Studies demonstrating enhanced neural tissue regeneration in electrical fields through the use of conductive materials have led to interest in piezoelectric materials (or those materials which generate a transient electrical potential when mechanically deformed) such as zinc oxide (ZnO). It has been speculated that ZnO nanoparticles possess increased piezoelectric properties over ZnO micron particles. Due to this promise in neural applications, the objective of the present in vitro study was, for the first time, to assess the activity of astroglial cells on ZnO nanoparticle polymer composites. ZnO nanoparticles embedded in polyurethane were analyzed via scanning electron microscopy to evaluate nanoscale surface features of the composites. The surface chemistry was characterized via X-ray photoelectron spectroscopy. Astroglial cell response was evaluated based on cell adhesion and proliferation. Astrocyte adhesion was significantly reduced on ZnO nanoparticle/polyurethane (PU) composites with a weight ratio of 50:50 (PU:ZnO) wt.%, 75:25 (PU:ZnO) wt.%, and 90:10 (PU:ZnO) wt.% in comparison to pure PU. The successful production of ZnO nanoparticle composite scaffolds suitable for decreasing astroglial cell density demonstrates their potential as a nerve guidance channel material with greater efficiency than what may be available today. PMID:19337420

  12. Efficient anaerobic treatment of synthetic textile wastewater in a UASB reactor with granular sludge enriched with humic acids supported on alumina nanoparticles.

    Science.gov (United States)

    Cervantes, Francisco J; Gómez, Rafael; Alvarez, Luis H; Martinez, Claudia M; Hernandez-Montoya, Virginia

    2015-07-01

    A novel technique to co-immobilize humus-reducing microorganisms and humic substances (HS), supported on γ-Al2O3 nanoparticles (NP), by a granulation process in an upflow anaerobic sludge bed (UASB) reactor is reported in the present work. Larger granules (predominantly between 1 and 1.7 mm) were produced using NP coated with HS compared to those obtained with uncoated NP (mostly between 0.25 and 0.5 mm). The HS-enriched granular biomass was then tested for its capacity to achieve the reductive decolorization of the recalcitrant azo dye, reactive red 2 (RR2), in the same UASB reactor operated with a hydraulic residence time of 12 h and with glucose as electron donor. HS-enriched granules achieved higher decolorization and COD removal efficiencies, as compared to the control reactor operated in the absence of HS, in long term operation and applying high concentrations of RR2 (40-400 mg/L). This co-immobilizing technique could be attractive for its application in UASB reactors for the reductive biotransformation of several contaminants, such as nitroaromatics, poly-halogenated compounds, metalloids, among others.

  13. Effect of reinforcement nanoparticles addition on mechanical properties of SBS/curaua fiber composites

    Energy Technology Data Exchange (ETDEWEB)

    Borba, Patricia M. [Servico Nacional de Aprendizagem Industrial (CETEPO/SENAI/RS), Sao Leopoldo, RS (Brazil). Centro Tecnologico de Polimeros; Tedesco, Adriana [Braskem S. A., III Polo Petroquimico, Triunfo, RS (Brazil); Lenz, Denise M., E-mail: denise.lenz@gmail.com [Universidade Luterana do Brasil (ULBRA), Canoas, RS (Brazil). Programa de Pos-graduacao em Engenharia de Materiais e Processos Sustentaveis

    2014-03-15

    Composites of styrene-butadiene-styrene triblock copolymer (SBS) matrix with curauá fiber and/or a nanoparticulated mineral (montmorillonite clay - MMT) used as reinforcing agents were prepared by melt-mixing. The influence of clay addition on properties like tensile and tear strength, rebound resilience, flex fatigue life, abrasion loss, hardness and water absorption of composites with 5, 10 and 20 wt% of curauá fiber was evaluated in presence of maleic anhydride grafted styrene-(ethylene-co-butylene)-styrene triblock copolymer (MA-g-SEBS) coupling agent. Furthermore, the effect of mineral plasticizer loading on tensile strength of selected composites was investigated. The hybrid SBS composite that showed the best overall mechanical performance was composed by 2 wt% of MMT and 5 wt% of curauá fiber. Increasing fiber content up to 20 wt% resulted in a general decrease in all mechanical properties as well as incorporation of 5 wt% MMT caused a decrease in the tensile strength in all fiber contents. The hybrid composites showed clay agglomerates (tactoids) poorly dispersed that could explain the poor mechanical performance of composites at higher concentrations of curauá fiber and MMT nanoparticles. The addition of plasticizer further decreased the tensile strength while the addition of MMT nanoparticles decreased water absorption for all SBS composites. (author)

  14. Study of the effects of the interconnectivity of the metallic phase on the electrical and thermal behavior in alumina-ni and zirconia-ni interpenetrating phase composites (IPCs)

    International Nuclear Information System (INIS)

    Shahid, R.N.; Awais, H.B.; Mehmood, M.; Tariq, N.H.

    2007-01-01

    The addition of metallic inclusion in ceramic matrix can enhance the electrical and magnetic properties of the composite. Connectivity of conducting phase in an insulating matrix can be studied using electrical conductivity, thermal expansion, Hall Effect and by microscopic techniques. The wide range of application of such studies include, susceptor materials for induction heating, thin film resistors, gel formation permeability in porous structure and electromagnetic behavior of composites. The main phenomenon to be investigated is the insulating to conducting transition by the determination to of percolation range. This phenomenon depends on the concentration, shape, dimension and the crystallographic direction of the imbedded conducting particles. In this investigation variable concerning the percolation range of alumina- Ni and zirconia-Ni composites have been studied. The results provided the role of the size ratio of particles of matrix and the conducting phase, variation of resistance in terms of real part of impedance and thermal expansion on percolation effect. Scanning electron image have been used to study the percolation microscopically. (author)

  15. Classical Bahavior of Alumina (Al2O3) Nanofluids in Antifrogen N with Experimental Evidence

    NARCIS (Netherlands)

    Saleemi, M.; Vanapalli, Srinivas; Nikkam, N.; Toprak, M.S.; Muhammed, M.

    2015-01-01

    A nanofluid is a suspension containing nanoparticles in conventional heat transfer fluids. This paper reports on an investigation of alumina (Al2O3) nanoparticles in Antifrogen N, also called AFN, which is a popular antifreeze coolant consisting primarily of ethylene glycol and other additives to

  16. Electron microscopy localization and characterization of functionalized composite organic-inorganic SERS nanoparticles on leukemia cells

    International Nuclear Information System (INIS)

    Koh, Ai Leen; Shachaf, Catherine M.; Elchuri, Sailaja; Nolan, Garry P.; Sinclair, Robert

    2008-01-01

    We demonstrate the use of electron microscopy as a powerful characterization tool to identify and locate antibody-conjugated composite organic-inorganic nanoparticle (COINs) surface enhanced Raman scattering (SERS) nanoparticles on cells. U937 leukemia cells labeled with antibody CD54-conjugated COINs were characterized in their native, hydrated state using wet scanning electron microscopy (SEM) and in their dehydrated state using high-resolution SEM. In both cases, the backscattered electron (BSE) detector was used to detect and identify the silver constituents in COINs due to its high sensitivity to atomic number variations within a specimen. The imaging and analytical capabilities in the SEM were further complemented by higher resolution transmission electron microscopy (TEM) images and scanning Auger electron spectroscopy (AES) data to give reliable and high-resolution information about nanoparticles and their binding to cell surface antigens.

  17. Core/shell fluorescent magnetic silica-coated composite nanoparticles for bioconjugation

    Science.gov (United States)

    He, Rong; You, Xiaogang; Shao, Jun; Gao, Feng; Pan, Bifeng; Cui, Daxiang

    2007-08-01

    A new class of highly fluorescent, photostable, and magnetic core/shell nanoparticles has been synthesized from a reverse microemulsion method. The obtained bifunctional nanocomposites were characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) spectrometry, photoluminescence (PL) spectrometry, and fluorescence microscopy in a magnetic field. To further improve their biocompatibility, the silica-coated nanoparticles were functionalized with amino groups. The fluorescent magnetic composite nanoparticles (FMCNPs) had a typical diameter of 50 ± 5 nm and a saturation magnetization of 3.21 emu g-1 at room temperature, and exhibited strong excitonic photoluminescence. Through activation with glutaraldehyde, the FMCNPs were successfully conjugated with goat anti-mouse immunoglobin G (GM IgG), and the bioactivity and binding specificity of the as-prepared FMCNPs-GM IgG were confirmed via immunofluorescence assays, commonly used in bioanalysis. So they are potentially useful for many applications in biolabelling, imaging, drug targeting, bioseparation and bioassays.

  18. Core/shell fluorescent magnetic silica-coated composite nanoparticles for bioconjugation

    International Nuclear Information System (INIS)

    He Rong; You Xiaogang; Shao Jun; Gao Feng; Pan Bifeng; Cui Daxiang

    2007-01-01

    A new class of highly fluorescent, photostable, and magnetic core/shell nanoparticles has been synthesized from a reverse microemulsion method. The obtained bifunctional nanocomposites were characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) spectrometry, photoluminescence (PL) spectrometry, and fluorescence microscopy in a magnetic field. To further improve their biocompatibility, the silica-coated nanoparticles were functionalized with amino groups. The fluorescent magnetic composite nanoparticles (FMCNPs) had a typical diameter of 50 ± 5 nm and a saturation magnetization of 3.21 emu g -1 at room temperature, and exhibited strong excitonic photoluminescence. Through activation with glutaraldehyde, the FMCNPs were successfully conjugated with goat anti-mouse immunoglobin G (GM IgG), and the bioactivity and binding specificity of the as-prepared FMCNPs-GM IgG were confirmed via immunofluorescence assays, commonly used in bioanalysis. So they are potentially useful for many applications in biolabelling, imaging, drug targeting, bioseparation and bioassays

  19. Study of energy transfer between molecules placed in the vicinity of a bimetal composite nanoparticle

    Energy Technology Data Exchange (ETDEWEB)

    Daneshfar, Nader, E-mail: ndaneshfar@gmail.com, E-mail: ndaneshfar@razi.ac.ir [Department of Physics, Razi University, Kermanshah (Iran, Islamic Republic of)

    2015-10-15

    In this study, the problem of energy transfer between two molecules near a bimetallic composite nanoparticle is investigated. The influence of the interaction between metal particles on the intermolecular energy is studied, because when two metal nanoparticles are placed close to each other, their plasmons coupling giving rise to new features. On the other hand, we discuss the transfer of resonance energy between donor and acceptor molecules (a single donor and a single acceptor) in the presence of a nanocomposite containing gold and silver nanoparticles based on the Maxwell-Garnett effective medium theory and within the quasistatic limit. We show that the interaction energy strongly depends on the particle size, the filling factor of metal particles, the intermolecular distance (the distance between the donor and acceptor molecules), and the dielectric constant of host matrix.

  20. Gelatin-Chitosan composite capped gold nanoparticles: a matrix for the growth of hydroxyapatite

    Science.gov (United States)

    Sobhana, S. S. Liji; Sundaraseelan, J.; Sekar, S.; Sastry, T. P.; Mandal, A. B.

    2009-02-01

    Growth of hydroxyapatite (HA) on gelatin-chitosan composite capped gold nanoparticles is presented for the first time by employing wet precipitation methods and we obtained good yields of HA. Fourier transform infrared spectroscopy (FTIR) spectrum has shown the characteristic bands of phosphate groups in the HA. Scanning electron microscopy (SEM) pictures have shown spherical nanoparticles with the size in the range of 70-250 nm, whereas ≥2-50 nm sized particles were visualized in high resolution transmission electron microscopy (HR-TEM). X-ray diffraction (XRD) spectrum has shown Bragg reflections which are comparable with the HA. Energy dispersive X-ray (EDX) studies have confirmed calcium/phosphate stoichiometric ratio of HA. The thermogravimetric analysis (TGA) has shown about 74% of inorganic crystals in the nanocomposite formed. These results have revealed that gelatin-chitosan capped gold nanoparticles, acted as a matrix for the growth of HA.

  1. Influence of the synthesis conditions of gold nanoparticles on the structure and architectonics of dipeptide composites

    Energy Technology Data Exchange (ETDEWEB)

    Loskutov, Alexander I., E-mail: ailoskutov@yandex.ru [Moscow State Technological University STANKIN (Russian Federation); Guskova, Olga A. [Leibniz Institute of Polymer Research Dresden (Germany); Grigoriev, Sergey N.; Oshurko, Vadim B. [Moscow State Technological University STANKIN (Russian Federation); Tarasiuk, Aleksei V. [Russian Academy of Medical Sciences, FSBI “Zakusov Institute of Pharmacology” (Russian Federation); Uryupina, Olga Ya. [Russian Academy of Sciences, Frumkin Institute of Physical Chemistry and Electrochemistry (Russian Federation)

    2016-08-15

    A wide variety of peptides and their natural ability to self-assemble makes them very promising candidates for the fabrication of solid-state devices based on nano- and mesocrystals. In this work, we demonstrate an approach to form peptide composite layers with gold nanoparticles through in situ reduction of chloroauric acid trihydrate by dipeptide and/or dipeptide/formaldehyde mixture in the presence of potassium carbonate at different ratios of components. Appropriate composition of components for the synthesis of highly stable gold colloidal dispersion with particle size of 34–36 nm in dipeptide/formaldehyde solution is formulated. Infrared spectroscopy results indicate that dipeptide participates in the reduction process, conjugation with gold nanoparticles and the self-assembly in 2D, which accompanied by changing peptide chain conformations. The structure and morphology of the peptide composite solid layers with gold nanoparticles on gold, mica and silica surfaces are characterized by atomic force microscopy. In these experiments, the flat particles, dendrites, chains, mesocrystals and Janus particles are observed depending on the solution composition and the substrate/interface used. The latter aspect is studied on the molecular level using computer simulations of individual peptide chains on gold, mica and silica surfaces.

  2. Chemical composition dispersion in bi-metallic nanoparticles: semi-automated analysis using HAADF-STEM

    International Nuclear Information System (INIS)

    Epicier, T.; Sato, K.; Tournus, F.; Konno, T.

    2012-01-01

    We present a method using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) to determine the chemical composition of bi-metallic nanoparticles. This method, which can be applied in a semi-automated way, allows large scale analysis with a statistical number of particles (several hundreds) in a short time. Once a calibration curve has been obtained, e.g., using energy-dispersive X-ray spectroscopy (EDX) measurements on a few particles, the HAADF integrated intensity of each particle can indeed be directly related to its chemical composition. After a theoretical description, this approach is applied to the case of iron–palladium nanoparticles (expected to be nearly stoichiometric) with a mean size of 8.3 nm. It will be shown that an accurate chemical composition histogram is obtained, i.e., the Fe content has been determined to be 49.0 at.% with a dispersion of 10.4 %. HAADF-STEM analysis represents a powerful alternative to fastidious single particle EDX measurements, for the compositional dispersion in alloy nanoparticles.

  3. Natural polysaccharides promote chondrocyte adhesion and proliferation on magnetic nanoparticle/PVA composite hydrogels.

    Science.gov (United States)

    Hou, Ruixia; Nie, Lei; Du, Gaolai; Xiong, Xiaopeng; Fu, Jun

    2015-08-01

    This paper aims to investigate the synergistic effects of natural polysaccharides and inorganic nanoparticles on cell adhesion and growth on intrinsically cell non-adhesive polyvinyl alcohol (PVA) hydrogels. Previously, we have demonstrated that Fe2O3 and hydroxyapatite (nHAP) nanoparticles are effective in increasing osteoblast growth on PVA hydrogels. Herein, we blended hyaluronic acid (HA) and chondroitin sulfate (CS), two important components of cartilage extracellular matrix (ECM), with Fe2O3/nHAP/PVA hydrogels. The presence of these natural polyelectrolytes dramatically increased the pore size and the equilibrium swelling ratio (ESR) while maintaining excellent compressive strength of hydrogels. Chondrocytes were seeded and cultured on composite PVA hydrogels containing Fe2O3, nHAP and Fe2O3/nHAP hybrids and Fe2O3/nHAP with HA or CS. Confocal laser scanning microscopy (CLSM) and cell counting kit-8 (CCK-8) assay consistently confirmed that the addition of HA or CS promotes chondrocyte adhesion and growth on PVA and composite hydrogels. Particularly, the combination of HA and CS exhibited further promotion to cell adhesion and proliferation compared with any single polysaccharide. The results demonstrated that the magnetic composite nanoparticles and polysaccharides provided synergistic promotion to cell adhesion and growth. Such polysaccharide-augmented composite hydrogels may have potentials in biomedical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Interfacially Optimized, High Energy Density Nanoparticle-Polymer Composites for Capacitive Energy Storage

    Science.gov (United States)

    Shipman, Joshua; Riggs, Brian; Luo, Sijun; Adireddy, Shiva; Chrisey, Douglas

    Energy storage is a green energy technology, however it must be cost effective and scalable to meet future energy demands. Polymer-nanoparticle composites are low cost and potentially offer high energy storage. This is based on the high breakdown strength of polymers and the high dielectric constant of ceramic nanoparticles, but the incoherent nature of the interface between the two components prevents the realization of their combined full potential. We have created inkjet printable nanoparticle-polymer composites that have mitigated many of these interface effects, guided by first principle modelling of the interface. We detail density functional theory modelling of the interface and how it has guided our use in in specific surface functionalizations and other inorganic layers. We have validated our approach by using finite element analysis of the interface. By choosing the correct surface functionalization we are able to create dipole traps which further increase the breakdown strength of our composites. Our nano-scale understanding has allowed us to create the highest energy density composites currently available (>40 J/cm3).

  5. Rubber composite fibers containing silver nanoparticles prepared by electrospinning and in-situ chemical crosslinking

    Directory of Open Access Journals (Sweden)

    M. Tian

    2012-04-01

    Full Text Available Rubber composite fibers containing silver nanoparticles with high morphological stability were prepared through combination of electrospinning and in-situ chemical crosslinking. The composite fibers included those of Ag/polybutadiene rubber (BR, Ag/polyisobutylene-isoprene rubber (IIR, and Ag/silicon rubber (SiR. During the study, Ag nanoparticles (Ag NPs were first generated through reducing the Ag+ ions in rubber/N,N-dimethyformamide/tetrahydrofuran solutions upon ultraviolet-irradiation; subsequently, rubber composite fibers with uniform diameters from hundreds of nanometers to several micrometers were made by electrospinning the above solutions. The electrospinning was carried out with in-situ chemical crosslinking. The results indicated that chemical crosslinking during (and shortly after electrospinning was able to improve substantially the morphological stability of rubber fibers. As indicated by the results acquired from UV absorption spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscope, Ag nanoparticles with sizes of 10~20 nm were uniformly dispersed in rubber fibers. It was believed that, in addition to the protection of polyvinyl pyrrolidone, a rapid solvent evaporation and limited motion space for a very fine fiber during electrospinning could prevent/mitigate the aggregation of Ag NPs, resulting in a very uniform dispersion. The electrospun Ag NPs/BR composite fibers made of the solution containing very low loading amount (3 wt% of AgNO3 demonstrated strong antimicrobial activity.

  6. Soft landing of bare nanoparticles with controlled size, composition, and morphology

    Science.gov (United States)

    Johnson, Grant E.; Colby, Robert; Laskin, Julia

    2015-02-01

    Physical synthesis employing magnetron sputtering and gas aggregation in a modified commercial source has been coupled with size-selection and ion soft landing to prepare bare nanoparticles on surfaces with controlled coverage, size, composition, and morphology. Employing atomic force microscopy (AFM) and scanning electron microscopy (SEM), it is demonstrated that the size and coverage of nanoparticles on flat and stepped surfaces may be controlled using a quadrupole mass filter and the length of deposition, respectively. AFM shows that nanoparticles bind randomly to flat surfaces when soft landed at relatively low coverage (4 × 104 ions μm-2). On stepped surfaces at intermediate coverage (4 × 105 ions μm-2) nanoparticles bind along step edges forming extended linear chains. At the highest coverage (2 × 106 ions μm-2) nanoparticles form a continuous film on flat surfaces. On one surface with sizable defects, the presence of localized imperfections results in agglomeration of nanoparticles onto these features and formation of neighboring zones devoid of particles. Employing high resolution scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) the customized magnetron sputtering/gas aggregation source is demonstrated to produce bare single metal particles with controlled morphology as well as bimetallic alloy nanoparticles with defined core-shell structures of that are of interest to catalysis.Physical synthesis employing magnetron sputtering and gas aggregation in a modified commercial source has been coupled with size-selection and ion soft landing to prepare bare nanoparticles on surfaces with controlled coverage, size, composition, and morphology. Employing atomic force microscopy (AFM) and scanning electron microscopy (SEM), it is demonstrated that the size and coverage of nanoparticles on flat and stepped surfaces may be controlled using a quadrupole mass filter and the length of deposition, respectively. AFM shows

  7. Simulation of localized surface plasmon in metallic nanoparticles embedded in amorphous silicon

    Science.gov (United States)

    Fantoni, A.; Fernandes, M.; Vygranenko, Y.; Louro, P.; Vieira, M.; Texeira, D.; Ribeiro, A.; Alegria, E.

    2017-08-01

    We propose the development and realization of a plasmonic structure based on the LSP interaction of metal nanoparticles with an embedding matrix of amorphous silicon. This structure need to be usable as the basis for a sensor device applied in biomedical applications, after proper functionalization with selective antibodies. The final sensor structure needs to be low cost, compact and disposable. The study reported in this paper aims to analyze different materials for nanoparticles and embedding medium composition. Metals of interest for nanoparticles composition are Aluminum, Gold and Alumina. As a preliminary approach to this device, we study in this work the optical properties of metal nanoparticles embedded in an amorphous silicon matrix, as a function of size, aspect-ratio and metal type. Following an analysis based on the exact solution of the Mie theory, experimental measurements realized with arrays of metal nanoparticles are compared with the simulations.

  8. Core–shell composite particles composed of biodegradable polymer particles and magnetic iron oxide nanoparticles for targeted drug delivery

    Energy Technology Data Exchange (ETDEWEB)

    Oka, Chiemi; Ushimaru, Kazunori [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Horiishi, Nanao [Bengala Techno Laboratory, 9-5-1006, 1-1 Kodai, Miyamae-ku, Kawasaki 216-0007 (Japan); Tsuge, Takeharu [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Kitamoto, Yoshitaka, E-mail: kitamoto.y.aa@m.titech.ac.jp [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan)

    2015-05-01

    Core–shell composite particles with biodegradability and superparamagnetic behavior were prepared using a Pickering emulsion for targeted drug delivery based on magnetic guidance. The composite particles were composed of a core of biodegradable polymer and a shell of assembled magnetic iron oxide nanoparticles. It was found that the dispersibility of the nanoparticles is crucial for controlling the core–shell structure. The addition of a small amount of dispersant into the nanoparticle's suspension could improve the dispersibility and led to the formation of composite particles with a thin magnetic shell covering a polymeric core. The composite particles were also fabricated with a model drug loaded into the core, which was released via hydrolysis of the core under strong alkaline conditions. Because the core can also be biodegraded by lipase, this result suggests that the slow release of the drug from the composite particles should occur inside the body. - Highlights: • Core−shell composites with biodegradability and magnetism are prepared. • O/W emulsion stabilized by iron oxide nanoparticles is utilized for the preparation. • The nanoparticle's dispersibility is crucial for controlling the composite structure. • Composites loading a model drug are also prepared. • The model drug is released with decomposition of the composites.

  9. Core–shell composite particles composed of biodegradable polymer particles and magnetic iron oxide nanoparticles for targeted drug delivery

    International Nuclear Information System (INIS)

    Oka, Chiemi; Ushimaru, Kazunori; Horiishi, Nanao; Tsuge, Takeharu; Kitamoto, Yoshitaka

    2015-01-01

    Core–shell composite particles with biodegradability and superparamagnetic behavior were prepared using a Pickering emulsion for targeted drug delivery based on magnetic guidance. The composite particles were composed of a core of biodegradable polymer and a shell of assembled magnetic iron oxide nanoparticles. It was found that the dispersibility of the nanoparticles is crucial for controlling the core–shell structure. The addition of a small amount of dispersant into the nanoparticle's suspension could improve the dispersibility and led to the formation of composite particles with a thin magnetic shell covering a polymeric core. The composite particles were also fabricated with a model drug loaded into the core, which was released via hydrolysis of the core under strong alkaline conditions. Because the core can also be biodegraded by lipase, this result suggests that the slow release of the drug from the composite particles should occur inside the body. - Highlights: • Core−shell composites with biodegradability and magnetism are prepared. • O/W emulsion stabilized by iron oxide nanoparticles is utilized for the preparation. • The nanoparticle's dispersibility is crucial for controlling the composite structure. • Composites loading a model drug are also prepared. • The model drug is released with decomposition of the composites

  10. Electromagnetic properties of Fe-Co granular composite materials containing acicular nanoparticles

    Science.gov (United States)

    Kasagi, Teruhiro; Massango, Herieta; Tsutaoka, Takanori; Yamamoto, Shinichiro; Hatakeyama, Kenichi

    2018-03-01

    Electromagnetic properties of acicular (needle-like) Fe76Co24 nanoparticle composite materials have been studied in microwave frequency range up to 20 GHz. The Fe76Co24 particles are commercially available acicular Fe76Co24 nanoparticles with an approximate length and diameter of 100 and 25 nm, respectively. The Fe76Co24 nanocomposites were prepared by embedding the Fe76Co24 nanoparticle in an appropriate resin. Since the metallic Fe76Co24 nanoparticles have an oxidized surface, even high particle content composites at 78 vol.%, which is in the percolated state, does not show metallic conduction; a low frequency plasmonic state with the negative permittivity spectrum was not observed. Meanwhile, the negative permeability spectrum caused by the magnetic resonance in Fe76Co24 alloy was obtained in the high particle content composites. From the measurement of the complex permeability spectra under the external dc magnetic field, it was clarified that the gyromagnetic spin rotation mainly contributes to the permeability spectrum of nanocomposites due to extremely small quantity of domain walls in the acicular nanoparticles. This result suggests that the negative permeability spectrum was caused by the gyromagnetic spin resonance. By the comparison of the complex permeability spectrum between the acicular Fe76Co24 nanocomposite and the spherical Fe50Co50 microcomposite, the gyromagnetic spin resonance frequency of the acicular nanocomposite tends to locate higher than that of the spherical microcomposite owing to the demagnetizing field effect. Therefore, it can be concluded that the negative permeability frequency band of the acicular nanocomposite is higher than that of the spherical microcomposite at the same particle content.

  11. Optical bistability in nonlinear composites with coated ellipsoidal nanoparticles

    CERN Document Server

    Pinchuk, A

    2003-01-01

    Nonlinear composite structures show great promise for use in optical switching, signal processing, etc. We derive an effective nonlinear dielectric permittivity of composite structures where coated ellipsoidal nonlinear particles are imbedded in a linear host medium. The derived expression for the effective dielectric permittivity tensor follows the Clasius-Mossotti approximation. We observe conditions for the existence of the optical bistability effect in a coated ellipsoidal particle with a nonlinear core and a metallic shell. Our numerical results show stronger bistability effects in more dense suspensions of nonlinear heterogeneous ellipsoids.

  12. Highly Hydrophilic Thin-Film Composite Forward Osmosis Membranes Functionalized with Surface-Tailored Nanoparticles

    KAUST Repository

    Tiraferri, Alberto

    2012-09-26

    Thin-film composite polyamide membranes are state-of-the-art materials for membrane-based water purification and desalination processes, which require both high rejection of contaminants and high water permeabilities. However, these membranes are prone to fouling when processing natural waters and wastewaters, because of the inherent surface physicochemical properties of polyamides. The present work demonstrates the fabrication of forward osmosis polyamide membranes with optimized surface properties via facile and scalable functionalization with fine-tuned nanoparticles. Silica nanoparticles are coated with superhydrophilic ligands possessing functional groups that impart stability to the nanoparticles and bind irreversibly to the native carboxyl moieties on the membrane selective layer. The tightly tethered layer of nanoparticles tailors the surface chemistry of the novel composite membrane without altering the morphology or water/solute permeabilities of the membrane selective layer. Surface characterization and interfacial energy analysis confirm that highly hydrophilic and wettable membrane surfaces are successfully attained. Lower intermolecular adhesion forces are measured between the new membrane materials and model organic foulants, indicating the presence of a bound hydration layer at the polyamide membrane surface that creates a barrier for foulant adhesion. © 2012 American Chemical Society.

  13. [Preparation and property evaluation of graphene oxide based silver nanoparticles composite materials].

    Science.gov (United States)

    Shen, Yupu; He, Jiantai; Zhang, Yangde; Shen, Yukun; Zhang, Longjiao

    2014-04-01

    We prepared silver nanoparticles/polyethyleneimine-reduction graphene oxide (AgNP/rGO-PEI) composite materials, and evaluated their quality performance in our center. Firstly, we prepared AgNP/rGO-PEI, and then analysed its stability, antibacterial activity, and cellular toxicity by comparing the AgNP/rGO-PEI with the silver nanoparticles (PVP/AgNP) modified by polyvinylpyrrolidone. We found in the study that silver nanoparticles (AgNP) distributed relatively uniformly in AgNP/rGO-PEI surface, silver nanoparticles mass fraction was 4.5%, and particle size was 6-13 nm. In dark or in low illumination light intensity of 3 000 lx meter environment (lux) for 10 days, PVP/AgNP aggregation was more obvious, but the AgNP/rGO-PEI had good dispersibility and its aggregation was not obvious; AgNP/rGO-PEI had a more excellent antibacterial activity, biological compatibility and relatively low biological toxicity. It was concluded that AgNP/rGO-PEI composite materials had reliable quality and good performance, and would have broad application prospects in the future.

  14. Synthesis of Ca,Y-zirconia/hydroxyapatite nanoparticles and composites

    Czech Academy of Sciences Publication Activity Database

    Částková, K.; Hadraba, Hynek; Matoušek, A.; Roupcová, P.; Chlup, Zdeněk; Novotná, L.; Cihlář, J.

    2016-01-01

    Roč. 36, č. 12 (2016), s. 2903-2912 ISSN 0955-2219 R&D Projects: GA ČR GA14-11234S; GA MŠk(CZ) LQ1601 Institutional support: RVO:68081723 Keywords : Zirconia * Hydroxyapatite * Composite * Bioactivity * Mechanical properties Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 3.411, year: 2016

  15. Effects of Environment On Creep Behavior of Nextel720/Alumina-Mullite Ceramic Composite With 45 Deg. Fiber Orientation at 1200 Deg. C

    Science.gov (United States)

    2009-03-01

    appearance in commercial airplanes with the introduction of the Boeing 707 in the 1950s. Today, composites make up a large percentage of aircraft...structural components. Composites comprise 9% of the aircraft structural weight in the Boeing 777. Boeing is predicting that 50% of the material used on...the 787 Dreamliner , scheduled for delivery in 2010, will be composites [2]. Ceramic matrix composites (CMCs), capable of maintaining excellent

  16. Self-assembled thin films of Fe3O4-Ag composite nanoparticles for spintronic applications

    Science.gov (United States)

    Jiang, Chengpeng; Leung, Chi Wah; Pong, Philip W. T.

    2017-10-01

    Controlled self-assembly of multi-component magnetic nanoparticles could lead to nanomaterial-based magnetic devices with novel structures and intriguing properties. Herein, self-assembled thin films of Fe3O4-Ag composite nanoparticles (CNPs) with hetero-dimeric shapes were fabricated using interfacial assembly method. The CNP-assembled thin films were further transferred to patterned silicon substrates followed by vacuum annealing, producing CNP-based magnetoresistive (MR) devices. Due to the presence of intra-particle interfaces and inter-particle barriers, an enhanced MR ratio and a non-linear current-voltage relation were observed in the device. The results of this work can potentially pave the way to the future exploration and development of spintronic devices built from composite nanomaterials.

  17. Wear resistance analysis of the aluminum 7075 alloy and the nanostructured aluminum 7075 - silver nanoparticles composites

    Directory of Open Access Journals (Sweden)

    Estrada-Ruiz R.H.

    2016-01-01

    Full Text Available Nanostructured composites of the aluminum 7075 alloy and carbon-coated silver nanoparticles were synthetized by the mechanical milling technique using a high-energy mill SPEX 8000M; the powders generated were compacted, sintered and hot-extruded to produce 1 cm-diameter bars. The composites were then subjected to a wear test using a pin-on-disc device to validate the hypothesis that second phase-ductile nanometric particles homogenously distributed throughout the metalmatrix improve the wear resistance of the material. It was found that silver nanoparticles prevent the wear of the material by acting as an obstacle to dislocations movement during the plastic deformation of the contact surface, as well as a solid lubricant when these are separated from the metal-matrix.

  18. NiCrxFe2− xO4 ferrite nanoparticles and their composites with ...

    Indian Academy of Sciences (India)

    Half of the samples have been sintered at 620°C and the other at 1175°C. Then polypyrrole (PPy)–NiCrFe2-O4 composites have been synthesized by polymerization of pyrrole monomer in the presence of NiCrFe2-O4 nanoparticles. The structure, morphology and magnetic properties of the samples have been ...

  19. Titanium Dioxide Nanoparticles: Synthesis, X-Ray Line Analysis and Chemical Composition Study

    OpenAIRE

    Chenari,Hossein Mahmoudi; Seibel,Christoph; Hauschild,Dirk; Reinert,Friedrich; Abdollahian,Hossein

    2016-01-01

    TiO$_{2}$ nanoparticleshave been synthesized by the sol-gel method using titanium alkoxide and isopropanolas a precursor. The structural properties and chemical composition of the TiO$_{2}$ nanoparticles were studied usingX-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy.The X-ray powder diffraction pattern confirms that the particles are mainly composed of the anatase phase with the preferential orientation along [101] direction.The physical parameters suc...

  20. The thermodynamic properties of hydrated γ-Al2O3 nanoparticles

    Science.gov (United States)

    Spencer, Elinor C.; Huang, Baiyu; Parker, Stewart F.; Kolesnikov, Alexander I.; Ross, Nancy L.; Woodfield, Brian F.

    2013-12-01

    In this paper we report a combined calorimetric and inelastic neutron scattering (INS) study of hydrated γ-Al2O3 (γ-alumina) nanoparticles. These complementary techniques have enabled a comprehensive evaluation of the thermodynamic properties of this technological and industrially important metal oxide to be achieved. The isobaric heat capacity (Cp) data presented herein provide further critical insights into the much-debated chemical composition of γ-alumina nanoparticles. Furthermore, the isochoric heat capacity (Cv) of the surface water, which is so essential to the stability of all metal-oxides at the nanoscale, has been extracted from the high-resolution INS data and differs significantly from that of ice-Ih due to the dominating influence of strong surface-water interactions. This study also encompassed the analysis of four γ-alumina samples with differing pore diameters [4.5 (1), 13.8 (2), 17.9 (3), and 27.2 nm (4)], and the results obtained allow us to unambiguously conclude that the water content and pore size have no influence on the thermodynamic behaviour of hydrated γ-alumina nanoparticles.

  1. Mechanically-reinforced electrospun composite silk fibroin nanofibers containing hydroxyapatite nanoparticles

    International Nuclear Information System (INIS)

    Kim, Hyunryung; Che, Lihua; Ha, Yoon; Ryu, WonHyoung

    2014-01-01

    Electrospun silk fibroin (SF) scaffolds provide large surface area, high porosity, and interconnection for cell adhesion and proliferation and they may replace collagen for many tissue engineering applications. Despite such advantages, electrospun SF scaffolds are still limited as bone tissue replacement due to their low mechanical strengths. While enhancement of mechanical strengths by incorporating inorganic ceramics into polymers has been demonstrated, electrospinning of a mixture of SF and inorganic ceramics such as hydroxyapatite is challenging and less studied due to the aggregation of ceramic particles within SF. In this study, we aimed to enhance the mechanical properties of electrospun SF scaffolds by uniformly dispersing hydroxyapatite (HAp) nanoparticles within SF nanofibers. HAp nanoaprticles were modified by γ-glycidoxypropyltrimethoxysilane (GPTMS) for uniform dispersion and enhanced interfacial bonding between HAp and SF fibers. Optimal conditions for electrospinning of SF and GPTMS-modified HAp nanoparticles were identified to achieve beadless nanofibers without any aggregation of HAp nanoparticles. The MTT and SEM analysis of the osteoblasts-cultured scaffolds confirmed the biocompatibility of the composite scaffolds. The mechanical properties of the composite scaffolds were analyzed by tensile tests for the scaffolds with varying contents of HAp within SF fibers. The mechanical testing showed the peak strengths at the HAp content of 20 wt.%. The increase of HAp content up to 20 wt.% increased the mechanical properties of the composite scaffolds, while further increase above 20 wt.% disrupted the polymer chain networks within SF nanofibers and weakened the mechanical strengths. - Highlights: • Electrospun composite silk fibroin scaffolds were mechanically-reinforced. • GPTMS enhanced hydroxyapatite distribution in silk fibroin nanofibers. • Mechanical property of composite scaffolds increased up to 20% of hydroxyapatite. • Composite

  2. Asymmetric monometallic nanorod nanoparticle dimer and related compositions and methods

    KAUST Repository

    Han, Yu

    2016-03-31

    The fabrication of asymmetric monometallic nanocrystals with novel properties for plasmonics, nanophotonics and nanoelectronics. Asymmetric monometallic plasmonic nanocrystals are of both fundamental synthetic challenge and practical significance. In an example, a thiol-ligand mediated growth strategy that enables the synthesis of unprecedented Au Nanorod-Au Nanoparticle (AuNR-AuNP) dimers from pre-synthesized AuNR seeds. Using high-resolution electron microscopy and tomography, crystal structure and three-dimensional morphology of the dimer, as well as the growth pathway of the AuNP on the AuNR seed, was investigated for this example. The dimer exhibits an extraordinary broadband optical extinction spectrum spanning the UV, visible, and near infrared regions (300 - 1300 nm). This unexpected property makes the AuNR-AuNP dimer example useful for many nanophotonic applications. In two experiments, the dimer example was tested as a surface- enhanced Raman scattering (SERS) substrate and a solar light harvester for photothermal conversion, in comparison with the mixture of AuNR and AuNP. In the SERS experiment, the dimer example showed an enhancement factor about 10 times higher than that of the mixture, when the excitation wavelength (660 nm) was off the two surface plasmon resonance (SPR) bands of the mixture. In the photothermal conversion experiment under simulated sunlight illumination, the dimer example exhibited an energy conversion efficiency about 1.4 times as high as that of the mixture.

  3. Bauxite Mining and Alumina Refining

    Science.gov (United States)

    Frisch, Neale; Olney, David

    2014-01-01

    Objective: To describe bauxite mining and alumina refining processes and to outline the relevant physical, chemical, biological, ergonomic, and psychosocial health risks. Methods: Review article. Results: The most important risks relate to noise, ergonomics, trauma, and caustic soda splashes of the skin/eyes. Other risks of note relate to fatigue, heat, and solar ultraviolet and for some operations tropical diseases, venomous/dangerous animals, and remote locations. Exposures to bauxite dust, alumina dust, and caustic mist in contemporary best-practice bauxite mining and alumina refining operations have not been demonstrated to be associated with clinically significant decrements in lung function. Exposures to bauxite dust and alumina dust at such operations are also not associated with the incidence of cancer. Conclusions: A range of occupational health risks in bauxite mining and alumina refining require the maintenance of effective control measures. PMID:24806720

  4. Electric conductance of films prepared from polymeric composite nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Hain, J.; Pich, A.; Adler, H. J.; Rais, David; Nešpůrek, Stanislav

    2008-01-01

    Roč. 268, č. 1 (2008), s. 61-65 ISSN 1022-1360. [Microsymposium on Advanced Polymer Materials for Photonics and Electronics /47./. Prague, 15.07.2007-19.07.2007] R&D Projects: GA AV ČR KAN400720701; GA MŠk OC 138 Institutional research plan: CEZ:AV0Z40500505 Keywords : coatings * composites * conducting polymers Subject RIV: BM - Solid Matter Physics ; Magnetism

  5. Understanding the Enhanced Catalytic Performance of Ultrafine Transition Metal Nanoparticles-Graphene Composites

    Science.gov (United States)

    Liu, Xin; Meng, Changgong; Han, Yu

    2015-09-01

    Catalysis, as the key to minimize the energy requirement and environmental impact of today's chemical industry, plays a vital role in many fields directly related to our daily life and economy, including energy generation, environment control, manufacture of chemicals, medicine synthesis, etc. Rational design and fabrication of highly efficient catalysts have become the ultimate goal of today's catalysis research. For the purpose of handling and product separation, heterogeneous catalysts are highly preferred for industrial applications and a large part of which are the composites of transition metal nanoparticles (TMNPs). With the fast development of nanoscience and nanotechnology and assisted with theoretical investigations, basic understanding on tailoring the electronic structure of these nanocomposites has been gained, mainly by precise control of the composition, morphology, interfacial structure and electronic states. With the rise of graphene, chemical routes to prepare graphene were developed and various graphene-based composites were fabricated. Transition metal nanoparticles-reduced graphene oxide (TMNPs-rGO) composites have attracted considerable attention, because of their intriguing catalytic performance which have been extensively explored for energy- and environment-related applications to date. This review summarizes our recent experimental and theoretical efforts on understanding the superior catalytic performance of subnanosized TMNPs-rGO composites.

  6. Effective non-retarded method as a tool for the design of tunable nanoparticle composite absorbers

    International Nuclear Information System (INIS)

    Ortiz, Guillermo; Inchaussandague, Marina; Skigin, Diana; Depine, Ricardo; Mochán, W Luis

    2014-01-01

    We investigate the capabilities of an effective non-retarded formalism (ENR) for the exploration and design of nanoparticle composites with specific optical properties. We consider a composite material comprising periodically distributed metallic spheres in a dielectric host matrix. The effective macroscopic dielectric function of the composite medium is obtained by means of the ENR and is used to calculate the electromagnetic response of a slab made of an inhomogeneous material. This response is compared with that obtained by using the layer Korringa–Kohn–Rostoker wave calculation method (LKKR). We analyze the optical properties for different filling fractions, especially in the vicinity of the resonance frequencies of the macroscopic dielectric function. We notice that for dense systems within the long wavelength regime, the results of some analytical theories developed by other authors do not properly describe the multipolar excitations and interactions of orders higher than the dipole, in contrast with the results obtained by using an ENR. Therefore, those methods are not suitable for the design of compound films with novel properties. We show that by appropriately choosing the parameters of the composite, it is possible to achieve a tunable absorber film, and more generally, we show that ENR is a versatile tool for the design of nanoparticle composite materials with specific properties. (paper)

  7. Structural characterization, formation mechanism and stability of curcumin in zein-lecithin composite nanoparticles fabricated by antisolvent co-precipitation.

    Science.gov (United States)

    Dai, Lei; Sun, Cuixia; Li, Ruirui; Mao, Like; Liu, Fuguo; Gao, Yanxiang

    2017-12-15

    Curcumin (Cur) exhibits a range of bioactive properties, but its application is restrained due to its poor water solubility and sensitivity to environmental stresses. In this study, zein-lecithin composite nanoparticles were fabricated by antisolvent co-precipitation technique for delivery of Cur. The result showed that the encapsulation efficiency of Cur was significantly enhanced from 42.03% in zein nanoparticles to 99.83% in zein-lecithin composite nanoparticles. The Cur entrapped in the nanoparticles was in an amorphous state confirmed by differential scanning calorimetry and X-ray diffraction. Fourier transform infrared analysis revealed that hydrogen bonding, electrostatic interaction and hydrophobic attraction were the main interactions among zein, lecithin, and Cur. Compared with single zein and lecithin nanoparticles, zein-lecithin composite nanoparticles significantly improved the stability of Cur against thermal treatment, UV irradiation and high ionic strength. Therefore, zein-lecithin composite nanoparticles could be a potential delivery system for water-insoluble bioactive compounds with enhanced encapsulation efficiency and chemical stability. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Preparation of cellulose composites with in situ generated copper nanoparticles using leaf extract and their properties.

    Science.gov (United States)

    Sadanand, V; Rajini, N; Varada Rajulu, A; Satyanarayana, B

    2016-10-05

    In the present work, copper nanoparticles (CuNPs) were in situ generated in cellulose matrix using Ocimum sanctum leaf extract as a reducing agent and aq. CuSO4 solution by diffusion process. Some CuNPs were also formed outside the film in the solution which were separated and viewed by Transmission electron microscope and Scanning electron microscope (SEM). The composite films showed good antibacterial activity against Escherichia coli bacteria when the CuNPs were generated using higher concentrated aq. CuSO4 solutions. The cellulose, matrix and the composite films were characterized by Fourier transform infrared spectroscopic, X-ray diffraction, thermogravimetric analysis and SEM techniques. The tensile strength of the composite films was lower than that of the matrix but still higher than the conventional polymers like polyethylene and polypropylene used for packaging applications. These biodegradable composite films can be considered for packaging and medical applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. High-performance flexible hydrogen sensor made of WS2 nanosheet–Pd nanoparticle composite film

    International Nuclear Information System (INIS)

    Kuru, Cihan; Choi, Duyoung; Liu, Chin Hung; Yavuz, Serdar; Jin, Sungho; Kargar, Alireza; Choi, Chulmin; Bandaru, Prabhakar R

    2016-01-01

    We report a flexible hydrogen sensor, composed of WS 2 nanosheet–Pd nanoparticle composite film, fabricated on a flexible polyimide substrate. The sensor offers the advantages of light-weight, mechanical durability, room temperature operation, and high sensitivity. The WS 2 –Pd composite film exhibits sensitivity (R 1 /R 2, the ratio of the initial resistance to final resistance of the sensor) of 7.8 to 50 000 ppm hydrogen. Moreover, the WS 2 –Pd composite film distinctly outperforms the graphene–Pd composite, whose sensitivity is only 1.14. Furthermore, the ease of fabrication holds great potential for scalable and low-cost manufacturing of hydrogen sensors. (paper)

  10. Surface modification by metal ion implantation forming metallic nanoparticles in an insulating matrix

    International Nuclear Information System (INIS)

    Salvadori, M.C.; Teixeira, F.S.; Sgubin, L.G.; Cattani, M.; Brown, I.G.

    2014-01-01

    Highlights: • Metal nanoparticles can be produced through metallic ion implantation in insulating substrate, where the implanted metal self-assembles into nanoparticles. • The nanoparticles nucleate near the maximum of the implantation depth profile, that can be estimated by computer simulation using the TRIDYN. • Nanocomposites, obtained by this way, can be produced in different insulator materials. More specifically we have studied Au/PMMA (polymethylmethacrylate), Pt/PMMA, Ti/alumina and Au/alumina systems. • The nanocomposites were characterized by measuring the resistivity of the composite layer as function of the dose implanted, reaching the percolation threshold. • Excellent agreement was found between the experimental results and the predictions of the theory. - Abstract: There is special interest in the incorporation of metallic nanoparticles in a surrounding dielectric matrix for obtaining composites with desirable characteristics such as for surface plasmon resonance, which can be used in photonics and sensing, and controlled surface electrical conductivity. We have investigated nanocomposites produced by metal ion implantation into insulating substrates, where the implanted metal self-assembles into nanoparticles. The nanoparticles nucleate near the maximum of the implantation depth profile (projected range), which can be estimated by computer simulation using the TRIDYN code. TRIDYN is a Monte Carlo simulation program based on the TRIM (Transport and Range of Ions in Matter) code that takes into account compositional changes in the substrate due to two factors: previously implanted dopant atoms, and sputtering of the substrate surface. Our study show that the nanoparticles form a bidimentional array buried a few nanometers below the substrate surface. We have studied Au/PMMA (polymethylmethacrylate), Pt/PMMA, Ti/alumina and Au/alumina systems. Transmission electron microscopy of the implanted samples show that metallic nanoparticles form in

  11. Theoretical characterization of the surface composition of ruthenium nanoparticles in equilibrium with syngas

    Science.gov (United States)

    Cusinato, Lucy; Martínez-Prieto, Luis M.; Chaudret, Bruno; Del Rosal, Iker; Poteau, Romuald

    2016-05-01

    A deeper understanding of the relationship between experimental reaction conditions and the surface composition of nanoparticles is crucial in order to elucidate mechanisms involved in nanocatalysis. In the framework of the Fischer-Tropsch synthesis, a resolution of this complex puzzle requires a detailed understanding of the interaction of CO and H with the surface of the catalyst. In this context, the single- and co-adsorption of CO and H to the surface of a 1 nm ruthenium nanoparticle has been investigated with density functional theory. Using several indexes (d-band center, crystal overlap Hamilton population, density of states), a systematic analysis of the bond properties and of the electronic states has also been done, in order to bring an understanding of structure/property relationships at the nanoscale. The H : CO surface composition of this ruthenium nanoparticle exposed to syngas has been evaluated according to a thermodynamic model fed with DFT energies. Such ab initio thermodynamic calculations give access to the optimal H : CO coverage values under a wide range of experimental conditions, through the construction of free energy phase diagrams. Surprisingly, under the Fischer-Tropsch synthesis experimental conditions, and in agreement with new experiments, only CO species are adsorbed at the surface of the nanoparticle. These findings shed new light on the possible reaction pathways underlying the Fischer-Tropsch synthesis, and specifically the initiation of the reaction. It is finally shown that the joint knowledge of the surface composition and energy descriptors can help to identify possible reaction intermediates.A deeper understanding of the relationship between experimental reaction conditions and the surface composition of nanoparticles is crucial in order to elucidate mechanisms involved in nanocatalysis. In the framework of the Fischer-Tropsch synthesis, a resolution of this complex puzzle requires a detailed understanding of the interaction

  12. Preparation of asymmetrically nanoparticle-supported, monodisperse composite dumbbells by protruding a smooth polymer bulge from rugged spheres.

    Science.gov (United States)

    Nagao, Daisuke; Goto, Kanako; Ishii, Haruyuki; Konno, Mikio

    2011-11-01

    A novel method is proposed to create asymmetrically nanoparticle-supported, monodisperse composite dumbbells. The method consists of the three steps of double soap-free emulsion polymerizations before and after a heterocoagulation. In the first step, soap-free emulsion polymerization was conducted to cover silica cores with cross-linked poly(methyl methacrylate) (PMMA) shells. Then, positively or negatively charged silica nanoparticles were heterocoagulated with the silica-PMMA core-shell particles. In the heterocoagulations, the nanoparticles surface-modified with a cationic silane coupling agent, 3-aminopropyltriethoxysilane, were used as the positively charged ones, and silica nanoparticles without any treatment were used as the negatively charged ones. In the third step, soap-free polymerizations at different pH values were performed to protrude a polystyrene (PSt) bulge from the core-shell particles supporting the charged silica nanoparticles. In the polymerization, the core-shell particles heterocoagulated with the positively charged silica nanoparticles were aggregated in an acidic condition whereas the silica nanoparticles supported on the core-shell particles were dissolved in a basic condition. For the negatively charged silica nanoparticle, a PSt bulge was successfully protruded from the core-shell particle in acidic and neutral conditions without aggregation of the core-shell particles. The protrusion of the PSt bulge became distinctive when the number of heterocoagulated silica nanoparticles per core-shell particle was increased. Additional heterocoagulation experiments, in which positively or negatively charged magnetite nanoparticles were mixed with the asymmetrically nanoparticle-supported composite dumbbells, confirmed direct exposure of silica nanoparticles to the outer solvent phase.

  13. Reduced Graphene Oxide-Based Silver Nanoparticle-Containing Composite Hydrogel as Highly Efficient Dye Catalysts for Wastewater Treatment

    Science.gov (United States)

    Jiao, Tifeng; Guo, Haiying; Zhang, Qingrui; Peng, Qiuming; Tang, Yongfu; Yan, Xuehai; Li, Bingbing

    2015-01-01

    New reduced graphene oxide-based silver nanoparticle-containing composite hydrogels were successfully prepared in situ through the simultaneous reduction of GO and noble metal precursors within the GO gel matrix. The as-formed hydrogels are composed of a network structure of cross-linked nanosheets. The reported method is based on the in situ co-reduction of GO and silver acetate within the hydrogel matrix to form RGO-based composite gel. The stabilization of silver nanoparticles was also achieved simultaneously within the gel composite system. The as-formed silver nanoparticles were found to be homogeneously and uniformly dispersed on the surface of the RGO nanosheets within the composite gel. More importantly, this RGO-based silver nanoparticle-containing composite hydrogel matrix acts as a potential catalyst for removing organic dye pollutants from an aqueous environment. Interestingly, the as-prepared catalytic composite matrix structure can be conveniently separated from an aqueous environment after the reaction, suggesting the potentially large-scale applications of the reduced graphene oxide-based nanoparticle-containing composite hydrogels for organic dye removal and wastewater treatment. PMID:26183266

  14. Synthesis and heating effect of iron/iron oxide composite and iron oxide nanoparticles.

    Science.gov (United States)

    Zeng, Q; Baker, I; Loudis, J A; Liao, Y F; Hoopes, P J

    2007-02-09

    Fe/Fe oxide nanoparticles, in which the core consists of metallic Fe and the shell is composed of Fe oxides, were obtained by reduction of an aqueous solution of FeCl 3 within a NaBH 4 solution, or, using a water-in-oil micro-emulsion with CTAB as the surfactant. The reduction was performed either in an inert atmosphere or in air, and passivation with air was performed to produce the Fe/Fe 3 O 4 core/shell composite. Phase identification and particle size were determined by X-ray diffraction and TEM. Thermal analysis was performed using a differential scanning calorimeter. The quasistatic magnetic properties were measured using a VSM, and the specific absorption rates (SARs) of both Fe oxide and Fe/Fe 3 O 4 composite nanoparticles either dispersed in methanol or in an epoxy resin were measured by Luxtron fiber temperature sensors in an alternating magnetic field of 150 Oe at 250 kHz. It was found that the preparation conditions, including the concentrations of solutions, the mixing procedure and the heat treatment, influence the particle size, the crystal structure and consequently the magnetic properties of the particles. Compared with Fe oxides, the saturation magnetization ( M S ) of Fe/Fe 3 O 4 particles (100-190 emu/g) can be twice as high, and the coercivity ( H C ) can be tunable from several Oe to several hundred Oe. Hence, the SAR of Fe/Fe 3 O 4 composite nanoparticles can be much higher than that of Fe oxides, with a maximum SAR of 345 W/g. The heating behavior is related to the magnetic behavior of the nanoparticles.

  15. Developing a predictive model for the chemical composition of soot nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Violi, Angela [Univ. of Michigan, Ann Arbor, MI (United States); Michelsen, Hope [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Hansen, Nils [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Wilson, Kevin [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2017-04-07

    In order to provide the scientific foundation to enable technology breakthroughs in transportation fuel, it is important to develop a combustion modeling capability to optimize the operation and design of evolving fuels in advanced engines for transportation applications. The goal of this proposal is to develop a validated predictive model to describe the chemical composition of soot nanoparticles in premixed and diffusion flames. Atomistic studies in conjunction with state-of-the-art experiments are the distinguishing characteristics of this unique interdisciplinary effort. The modeling effort has been conducted at the University of Michigan by Prof. A. Violi. The experimental work has entailed a series of studies using different techniques to analyze gas-phase soot precursor chemistry and soot particle production in premixed and diffusion flames. Measurements have provided spatial distributions of polycyclic aromatic hydrocarbons and other gas-phase species and size and composition of incipient soot nanoparticles for comparison with model results. The experimental team includes Dr. N. Hansen and H. Michelsen at Sandia National Labs' Combustion Research Facility, and Dr. K. Wilson as collaborator at Lawrence Berkeley National Lab's Advanced Light Source. Our results show that the chemical and physical properties of nanoparticles affect the coagulation behavior in soot formation, and our results on an experimentally validated, predictive model for the chemical composition of soot nanoparticles will not only enhance our understanding of soot formation since but will also allow the prediction of particle size distributions under combustion conditions. These results provide a novel description of soot formation based on physical and chemical properties of the particles for use in the next generation of soot models and an enhanced capability for facilitating the design of alternative fuels and the engines they will power.

  16. NETWORKS OF NANOPARTICLES IN ORGANIC – INORGANIC COMPOSITES: ALGORITHMIC EXTRACTION AND STATISTICAL ANALYSIS

    Directory of Open Access Journals (Sweden)

    Ralf Thiedmann

    2012-03-01

    Full Text Available The rising global demand in energy and the limited resources in fossil fuels require new technologies in renewable energies like solar cells. Silicon solar cells offer a good efficiency but suffer from high production costs. A promising alternative are polymer solar cells, due to potentially low production costs and high flexibility of the panels. In this paper, the nanostructure of organic–inorganic composites is investigated, which can be used as photoactive layers in hybrid–polymer solar cells. These materials consist of a polymeric (OC1C10-PPV phase with CdSe nanoparticles embedded therein. On the basis of 3D image data with high spatial resolution, gained by electron tomography, an algorithm is developed to automatically extract the CdSe nanoparticles from grayscale images, where we assume them as spheres. The algorithm is based on a modified version of the Hough transform, where a watershed algorithm is used to separate the image data into basins such that each basin contains exactly one nanoparticle. After their extraction, neighboring nanoparticles are connected to form a 3D network that is related to the transport of electrons in polymer solar cells. A detailed statistical analysis of the CdSe network morphology is accomplished, which allows deeper insight into the hopping percolation pathways of electrons.

  17. Titanium dioxide nanoparticles: synthesis, X-Ray line analysis and chemical composition study

    Energy Technology Data Exchange (ETDEWEB)

    Chenari, Hossein Mahmoudi, E-mail: mahmoudi_hossein@guilan.ac.ir, E-mail: h.mahmoudiph@gmail.com [University of Guilan, Rasht (Iran, Islamic Republic of); Seibel, Christoph; Hauschild, Dirk; Reinert, Friedrich [Karlsruhe Institute of Technology - KIT, Gemeinschaftslabor für Nanoanalytik, Karlsruhe (Germany); Abdollahian, Hossein [Nanotechnology Research Center of Urmia University, Urmia, (Iran, Islamic Republic of)

    2016-11-15

    TiO{sub 2} nanoparticles have been synthesized by the sol-gel method using titanium alkoxide and isopropanol as a precursor. The structural properties and chemical composition of the TiO{sub 2} nanoparticles were studied using X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy.The X-ray powder diffraction pattern confirms that the particles are mainly composed of the anatase phase with the preferential orientation along [101] direction. The physical parameters such as strain, stress and energy density were investigated from the Williamson- Hall (W-H) plot assuming a uniform deformation model (UDM), and uniform deformation energy density model (UDEDM). The W-H analysis shows an anisotropic nature of the strain in nano powders. The scanning electron microscopy image shows clear TiO{sub 2} nanoparticles with particle sizes varying from 60 to 80nm. The results of mean particle size of TiO{sub 2} nanoparticles show an inter correlation with the W-H analysis and SEM results. Our X-ray photoelectron spectroscopy spectra show that nearly a complete amount of titanium has reacted to TiO{sub 2}. (author)

  18. Deciphering the Surface Composition and the Internal Structure of Alloyed Silver-Gold Nanoparticles.

    Science.gov (United States)

    Grasmik, Viktoria; Rurainsky, Christian; Loza, Kateryna; Evers, Mathies V; Prymak, Oleg; Heggen, Marc; Tschulik, Kristina; Epple, Matthias

    2018-03-09

    Spherical bimetallic AgAu nanoparticles in the molar ratios 30:70, 50:50, and 70:30 with a diameter of 30 to 40 nm were analyzed together with pure silver and gold nanoparticles of the same size. Dynamic light scattering (DLS) and differential centrifugal sedimentation (DCS) were used for size determination. Cyclic voltammetry (CV) was used to determine the nanoalloy composition, together with atomic absorption spectroscopy (AAS), energy-dispersive X-ray spectroscopy (EDX) and Ultraviolet-visible (UV/vis) spectroscopy. Underpotential deposition (UPD) of lead (Pb) on the particle surface gave information about its spatial elemental distribution and surface area. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) were applied to study the shape and the size of the nanoparticles. X-ray powder diffraction gave the crystallite size and the microstrain. The particles form a solid solution (alloy) with an enrichment of silver on the nanoparticle surface, including some silver-rich patches. UPD indicated that the surface only consists of silver atoms. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Cyanate ester-nanoparticle composites as multifunctional structural capacitors

    Science.gov (United States)

    De Leon, J. Eliseo

    An important goal of engineering is to increase the energy density of electrical energy storage devices used to deliver power onboard mobile platforms. Equally important is the goal to reduce the overall mass of the vehicles transporting these devices to achieve increased fuel and cost efficiency. One approach to meeting both these objectives is to develop multifunctional systems that serve as both energy storage and load bearing structural devices. Multifunctional devices consist of constituents that individually perform a subset of the overall desired functions. However, the synergy achieved by the combination of each constituent's characteristics allows for system-level benefits that cannot be achieved by simply optimizing the separate subsystems. We investigated multifunctional systems consisting of light weight polymer matrix and high dielectric constant fillers to achieve these objectives. The monomer of bisphenol E cyanate ester exhibited excellent processing ability because of its low room temperature viscosity. Additionally, the fully cured thermoset demonstrated excellent thermal stability, specific strength and stiffness. Fillers, including multi-walled carbon nanotubes, nanometer scale barium titanate and nanometer scale calcium copper titanate, offer high dielectric constants that raised the effective dielectric constant of the polymer matrix composite. The combination of high epsilon'and high dielectric strength produce high energy density components exhibiting increased electrical energy storage. Mechanical (load bearing) improvements of the PMCs were attributed to covalently bonded nanometer and micrometer sized filler particles, as well as the continuous glass fiber, integrated into the resin systems which increased the structural characteristics of the cured composites. Breakdown voltage tests and dynamic mechanical analysis were employed to demonstrate that precise combinations of these constituents, under the proper processing conditions, can

  20. NIR-responsive upconversion nanoparticles/anatase TiO2 composite aerogel

    Science.gov (United States)

    Li, Fu-Chih; Wada, Hiroyuki; Kitamoto, Yoshitaka

    2018-02-01

    NIR-responsive upconversion nanoparticles (UCNPs)/TiO2 composite aerogel is successfully fabricated by a sol–gel process and a supercritical drying process. The UCNPs of the cubic and hexagonal phases of NaYF4:Yb,Ho are synthesized by a solvothermal process, and the UCNPs are doped into the anatase phase of the TiO2 aerogel via a sol–gel process. To find the optimum parameters for the synthesis of this new type of photocatalytic composite, the synthesis conditions of NaYF4:Yb,Ho/TiO2 aerogel are investigated, such as the optimum amount of doped UCNPs and the temperature of the sol–gel process. The photoluminescences of NaYF4:Yb,Ho/TiO2 composite aerogels are investigated under 980 nm excitation. The NaYF4:Yb,Ho nanoparticles (NPs), which exist in the TiO2 matrix, absorbed the NIR light and transferred it to the visible region. The realization of an NIR-responsive mechanism in the UCNPs/TiO2 composite aerogel helps improve the synthesis process and in the design of the structure of this new type of photocatalytic material.

  1. Healing of Early Stage Fatigue Damage in Ionomer/Fe3O4 Nanoparticle Composites

    Directory of Open Access Journals (Sweden)

    Wouter Post

    2016-12-01

    Full Text Available This work reports on the healing of early stage fatigue damage in ionomer/nano-particulate composites. A series of poly(ethylene-co-methacrylic acid zinc ionomer/Fe3O4 nanoparticle composites with varying amounts of ionic clusters were developed and subjected to different levels of fatigue loading. The initiated damage was healed upon localized inductive heating of the embedded nanoparticles by exposure of the particulate composite to an alternating magnetic field. It is here demonstrated that healing of this early stage damage in ionomer particulate composites occurs in two different steps. First, the deformation is restored by the free-shrinkage of the polymer at temperatures below the melt temperature. At these temperatures, the polymer network is recovered thereby resetting the fatigue induced strain hardening. Then, at temperatures above the melting point of the polymer phase, fatigue-induced microcracks are sealed, hereby preventing crack propagation upon further loading. It is shown that the thermally induced free-shrinkage of these polymers does not depend on the presence of ionic clusters, but that the ability to heal cracks by localized melting while maintaining sufficient mechanical integrity is reserved for ionomers that contain a sufficient amount of ionic clusters guaranteeing an acceptable level of mechanical stability during healing.

  2. Electromagnetic interference shielding performance of waterborne polyurethane composites filled with silver nanoparticles deposited on functionalized graphene

    Science.gov (United States)

    Lin, Sheng-Chi; Ma, Chen-Chi M.; Hsiao, Sheng-Tsung; Wang, Yu-Sheng; Yang, Chih-Yu; Liao, Wei-Hao; Li, Shin-Ming; Wang, Jeng-An; Cheng, Tzu-Yu; Lin, Chih-Wen; Yang, Ruey-Bin

    2016-11-01

    The objective of this study was to prepare an electromagnetic interference shielding material, waterborne polyurethane (WPU) filled with silver-nanoparticle-decorated functional reduced graphene oxide (Ag@FRGO). Functional reduced graphene oxide (FRGO) was functionalized through free-radical polymerization before chemical reduction, to prevent restacking and aggregation during the reduction. After the functionalization, the homogeneous dispersion of FRGO promoted the formation of conductive networks throughout the WPU matrix. To enhance the electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) of the composites, silver nanoparticles (Ag NPs) were deposited on the FRGO surface. Subsequently, WPU composites were synthesized through the solution-mixing method. Their microstructure, morphology, electrical conductivity, and EMI SE were investigated, and the results showed that, among Ag@FRGO/WPU composites with different values for the weight ratio of Ag NPs to FRGO, the Ag@FRGO/WPU composite with 5 wt% FRGO and a weight ratio of Ag to NPs of 10:1 (10Ag@FRGO/WPU) exhibited the highest electrical conductivity (25.52 S/m) and an EMI SE of 35 dB in the frequency range of 8.2-12.4 GHz (X-band).

  3. Shaping Nanoparticles with Hydrophilic Compositions and Hydrophobic Properties as Nanocarriers for Antibiotic Delivery.

    Science.gov (United States)

    Ahmad Nor, Yusilawati; Niu, Yuting; Karmakar, Surajit; Zhou, Liang; Xu, Chun; Zhang, Jun; Zhang, Hongwei; Yu, Meihua; Mahony, Donna; Mitter, Neena; Cooper, Matthew A; Yu, Chengzhong

    2015-09-23

    Inspired by the lotus effect in nature, surface roughness engineering has led to novel materials and applications in many fields. Despite the rapid progress in superhydrophobic and superoleophobic materials, this concept of Mother Nature's choice is yet to be applied in the design of advanced nanocarriers for drug delivery. Pioneering work has emerged in the development of nanoparticles with rough surfaces for gene delivery; however, the preparation of nanoparticles with hydrophilic compositions but with enhanced hydrophobic property at the nanoscale level employing surface topology engineering remains a challenge. Herein we report for the first time the unique properties of mesoporous hollow silica (MHS) nanospheres with controlled surface roughness. Compared to MHS with a smooth surface, rough mesoporous hollow silica (RMHS) nanoparticles with the same hydrophilic composition show unusual hydrophobicity, leading to higher adsorption of a range of hydrophobic molecules and controlled release of hydrophilic molecules. RMHS loaded with vancomycin exhibits an enhanced antibacterial effect. Our strategy provides a new pathway in the design of novel nanocarriers for diverse bioapplications.

  4. Metal matrix-metal nanoparticle composites with tunable melting temperature and high thermal conductivity for phase-change thermal storage.

    Science.gov (United States)

    Liu, Minglu; Ma, Yuanyu; Wu, Hsinwei; Wang, Robert Y

    2015-02-24

    Phase-change materials (PCMs) are of broad interest for thermal storage and management applications. For energy-dense storage with fast thermal charging/discharging rates, a PCM should have a suitable melting temperature, large enthalpy of fusion, and high thermal conductivity. To simultaneously accomplish these traits, we custom design nanocomposites consisting of phase-change Bi nanoparticles embedded in an Ag matrix. We precisely control nanoparticle size, shape, and volume fraction in the composite by separating the nanoparticle synthesis and nanocomposite formation steps. We demonstrate a 50-100% thermal energy density improvement relative to common organic PCMs with equivalent volume fraction. We also tune the melting temperature from 236-252 °C by varying nanoparticle diameter from 8.1-14.9 nm. Importantly, the silver matrix successfully prevents nanoparticle coalescence, and no melting changes are observed during 100 melt-freeze cycles. The nanocomposite's Ag matrix also leads to very high thermal conductivities. For example, the thermal conductivity of a composite with a 10% volume fraction of 13 nm Bi nanoparticles is 128 ± 23 W/m-K, which is several orders of magnitude higher than typical thermal storage materials. We complement these measurements with calculations using a modified effective medium approximation for nanoscale thermal transport. These calculations predict that the thermal conductivity of composites with 13 nm Bi nanoparticles varies from 142 to 47 W/m-K as the nanoparticle volume fraction changes from 10 to 35%. Larger nanoparticle diameters and/or smaller nanoparticle volume fractions lead to larger thermal conductivities.

  5. Preparation of Pt–GO composites with high-number-density Pt nanoparticles dispersed uniformly on GO nanosheets

    Directory of Open Access Journals (Sweden)

    Nanting Li

    2016-04-01

    Full Text Available Pt–GO composites with high-number-density Pt nanoparticles dispersed uniformly on GO nanosheets were prepared using ethylene glycol as reducer at 180 °C. The nanoparticles had an average size of 12 nm with corners and edges on their surfaces. The composites had electrochemically active surface area of 31.7 m2 g−1 with a ratio (If/Ir=0.96 of the forward anodic peak current (If to the reverse anodic peak current (Ir in cyclic voltammetry curves, which is much higher than those of the reported Pt nanodendrites/reduced graphene oxide composites.

  6. Fabrication and characterization of silver/titanium dioxide composite nanoparticles in ethylene glycol with alkaline solution through sonochemical process.

    Science.gov (United States)

    Jhuang, Ya-Yi; Cheng, Wen-Tung

    2016-01-01

    This paper aims to study fabrication and characterization of silver/titanium oxide composite nanoparticle through sonochemical process in the presence of ethylene glycol with alkaline solution. By using ultrasonic irradiation of a mixture of silver nitrate, the dispersed TiO2 nanoparticle in ethylene glycol associated with aqueous solution of sodium oxide yields Ag/TiO2 composite nanoparticle with shell/core-type geometry. The powder X-ray diffraction (XRD) of the Ag/TiO2 composites showed additional diffraction peaks corresponding to the face-centered cubic (fcc) structure of silver crystallization phase, apart from the signals from the cores of TiO2. Transmission electron microscopy (TEM) images of Ag/TiO2 composites, which average particle size is roughly 80 nm, reveal that the titanium oxide coated by Ag nanoparticle with a grain size of about 2-5 nm. Additionally, the formation of silver nanoparticles on TiO2 was monitored by ultraviolet visible light spectrophotometer (UV-Vis). As measured the optical absorption spectra of as-synthesized Ag nanoparticle varying with time, the mechanism of surface formatting silver shell on the cores of TiO2 could be explored by autocatalytic reaction; the conversion of Ag particle from silver ion is 98% for the reaction time of 1000 s; and the activity energy of synthesizing Ag nanoparticles on TiO2 is 40 kJ/mol at temperature ranging from 5 to 25°C. Hopefully, this preliminary investigation could be used for mass production of composite nanoparticles assisted by ultrasonic chemistry in the future. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Electrospun Polyaniline-Based Composite Nanofibers: Tuning the Electrical Conductivity by Tailoring the Structure of Thiol-Protected Metal Nanoparticles

    Directory of Open Access Journals (Sweden)

    Filippo Pierini

    2017-01-01

    Full Text Available Composite nanofibers made of a polyaniline-based polymer blend and different thiol-capped metal nanoparticles were prepared using ex situ synthesis and electrospinning technique. The effects of the nanoparticle composition and chemical structure on the electrical properties of the nanocomposites were investigated. This study confirmed that Brust’s procedure is an effective method for the synthesis of sub-10 nm silver, gold, and silver-gold alloy nanoparticles protected with different types of thiols. Electron microscopy results demonstrated that electrospinning is a valuable technique for the production of composite nanofibers with similar morphology and revealed that nanofillers are well-dispersed into the polymer matrix. X-ray diffraction tests proved the lack of a significant influence of the nanoparticle chemical structure on the polyaniline chain arrangement. However, the introduction of conductive nanofillers in the polymer matrix influences the charge transport noticeably improving electrical conductivity. The enhancement of electrical properties is mediated by the nanoparticle capping layer structure. The metal nanoparticle core composition is a key parameter, which exerted a significant influence on the conductivity of the nanocomposites. These results prove that the proposed method can be used to tune the electrical properties of nanocomposites.

  8. Plasma Methods of Obtainment of Multifunctional Composite Materials, Dispersion-Hardened by Nanoparticles

    Science.gov (United States)

    Sizonenko, O. N.; Grigoryev, E. G.; Pristash, N. S.; Zaichenko, A. D.; Torpakov, A. S.; Ye, V. Lypian; Tregub, V. A.; Zholnin, A. G.; Yudin, A. V.; Kovalenko, A. A.

    2017-09-01

    High voltage electric discharge (HVED) in disperse system "hydrocarbon liquid - powder" due to impact of plasma discharge channel, electromagnetic fields, shock waves mechanical impact, hydro flows and volume microcavitation leads to synthesis of nanocarbon, metal powders dispersion and synthesis of micro- (from 10-6 to 10-7 m) and nanosized (from 10-7 to 10-9 m) composite powders of hardening phases. Spark plasma sintering (SPS) of powder mixtures allows targeted control of grain growth rate and thus allows obtainment of multifunctional composite materials dispersion hardened by nanoparticles. Processes of HVED synthesis of micro- and nanosized powders of new compositions from elemental metal powders and their mixtures with the subsequent application of high-speed SPS of obtained powders create conditions for increase of strength (by 10-20 %), hardness and wear-resistance (by 30-60 %) of obtained materials.

  9. Silica-based composite and mixed-oxide nanoparticles from atmospheric pressure flame synthesis

    Science.gov (United States)

    Akurati, Kranthi K.; Dittmann, Rainer; Vital, Andri; Klotz, Ulrich; Hug, Paul; Graule, Thomas; Winterer, Markus

    2006-08-01

    Binary TiO2/SiO2 and SnO2/SiO2 nanoparticles have been synthesized by feeding evaporated precursor mixtures into an atmospheric pressure diffusion flame. Particles with controlled Si:Ti and Si:Sn ratios were produced at various flow rates of oxygen and the resulting powders were characterized by BET (Brunauer-Emmett-Teller) surface area analysis, XRD, TEM and Raman spectroscopy. In the Si-O-Ti system, mixed oxide composite particles exhibiting anatase segregation formed when the Si:Ti ratio exceeded 9.8:1, while at lower concentrations only mixed oxide single phase particles were found. Arrangement of the species and phases within the particles correspond to an intermediate equilibrium state at elevated temperature. This can be explained by rapid quenching of the particles in the flame and is in accordance with liquid phase solubility data of Ti in SiO2. In contrast, only composite particles formed in the Sn-O-Si system, with SnO2 nanoparticles predominantly found adhering to the surface of SiO2 substrate nanoparticles. Differences in the arrangement of phases and constituents within the particles were observed at constant precursor mixture concentration and the size of the resultant segregated phase was influenced by varying the flow rate of the oxidant. The above effect is due to the variation of the residence time and quenching rate experienced by the binary oxide nanoparticles when varying the oxygen flow rate and shows the flexibility of diffusion flame aerosol reactors.

  10. Surface-enrichment with hydroxyapatite nanoparticles in stereolithography-fabricated composite polymer scaffolds promotes bone repair.

    Science.gov (United States)

    Guillaume, O; Geven, M A; Sprecher, C M; Stadelmann, V A; Grijpma, D W; Tang, T T; Qin, L; Lai, Y; Alini, M; de Bruijn, J D; Yuan, H; Richards, R G; Eglin, D

    2017-05-01

    Fabrication of composite scaffolds using stereolithography (SLA) for bone tissue engineering has shown great promises. However, in order to trigger effective bone formation and implant integration, exogenous growth factors are commonly combined to scaffold materials. In this study, we fabricated biodegradable composite scaffolds using SLA and endowed them with osteopromotive properties in the absence of biologics. First we prepared photo-crosslinkable poly(trimethylene carbonate) (PTMC) resins containing 20 and 40wt% of hydroxyapatite (HA) nanoparticles and fabricated scaffolds with controlled macro-architecture. Then, we conducted experiments to investigate how the incorporation of HA in photo-crosslinked PTMC matrices improved human bone marrow stem cells osteogenic differentiation in vitro and kinetic of bone healing in vivo. We observed that bone regeneration was significantly improved using composite scaffolds containing as low as 20wt% of HA, along with difference in terms of osteogenesis and degree of implant osseointegration. Further investigations revealed that SLA process was responsible for the formation of a rich microscale layer of HA corralling scaffolds. To summarize, this work is of substantial importance as it shows how the fabrication of hierarchical biomaterials via surface-enrichment of functional HA nanoparticles in composite polymer stereolithographic structures could impact in vitro and in vivo osteogenesis. This study reports for the first time the enhance osteopromotion of composite biomaterials, with controlled macro-architecture and microscale distribution of hydroxyapatite particles, manufactured by stereolithography. In this process, the hydroxyapatite particles are not only embedded into an erodible polymer matrix, as reported so far in the literature, but concentrated at the surface of the structures. This leads to robust in vivo bone formation at low concentration of hydroxyapatite. The reported 3D self-corralling composite

  11. Effect of alumina coating and extrusion deformation on ...

    Indian Academy of Sciences (India)

    2018-02-05

    Feb 5, 2018 ... (a) TGA–DSC curves of as-received SCF, SCF preform and alumina-coated SCF preforms and (b) XRD .... In order to determine the presence of the reaction product, the composites were fur- ther examined by XRD with a much lower scan speed of. 0.25. ◦ min .... than being parallel to the observing plane.

  12. Development of novel self-healing and antibacterial dental composite containing calcium phosphate nanoparticles.

    Science.gov (United States)

    Wu, Junling; Weir, Michael D; Melo, Mary Anne S; Xu, Hockin H K

    2015-03-01

    Fracture and secondary caries are the primary reasons for dental restoration failure. The objective of this study was to develop a self-healing composite to heal cracks, while containing dimethylaminohexadecyl methacrylate (DMAHDM) for antibacterial function and nanoparticles of amorphous calcium phosphate (NACP) for remineralization. Microcapsules were synthesized with poly(urea-formaldehyde) (PUF) shells containing triethylene glycol dimethacrylate (TEGDMA) and N,N-dihydroxyethyl-p-toluidine (DHEPT) as healing liquid. Composite contained 20 mass% of NACP and 35% glass fillers. In addition, composite contained 0%, 2.5%, 5%, 7.5%, or 10% of microcapsules. A single edge V-notched beam method measured fracture toughness (KIC) and self-healing efficiency. A dental plaque microcosm biofilm model was used to test the antibacterial properties. Incorporation of microcapsules up to 7.5% into the composite did not adversely affect the mechanical properties (p > 0.1). Successful self-healing was achieved, with KIC recovery of 65-81% (mean ± sd; n = 6) to regain the load-bearing capability after composite fracture. The self-healing DMAHDM-NACP composite displayed a strong antibacterial potency, inhibiting biofilm viability and lactic acid production, and reducing colony-forming units by 3-4 orders of magnitude, compared to control composite without DMAHDM. A dental composite was developed with triple benefits of self-healing after fracture, antibacterial activity, and remineralization capability for the first time. The self-healing, antibacterial and remineralizing composite may be promising for tooth cavity restorations to combat bulk fracture and secondary caries. The method of using triple agents (self-healing microcapsules, DMAHDM, and NACP) may have wide applicability to other dental composites, adhesives, sealants and cements. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Glycine functionalized alumina nanoparticles stabilize collagen in ...

    Indian Academy of Sciences (India)

    Research Initiatives for Waterless Tanning' (RIWT-. CSC0202) is greatly acknowledged. CSIR-CLRI Communi- cation no. 1156. References. [1] Ramachandran G N and Kartha G 1955 Nature 176 593. [2] Usha R and Ramasami T 1999 Thermochim.

  14. Reaction products between Bi-Sr-Ca-Cu-oxide thick films and alumina substrates

    International Nuclear Information System (INIS)

    Alarco, J.A.; Ilushechkin, A.; Yamashita, T.; Bhargava, A.; Barry, J.; Mackinnon, I.D.R.

    1997-01-01

    The structure and composition of reaction products between Bi-Sr-Ca-Cu-oxide (BSCCO) thick films and alumina substrates have been characterized using a combination of electron diffraction, scanning electron microscopy and energy dispersive X-ray spectrometry (EDX). Sr and Ca are found to be the most reactive cations with alumina. Sr 4 Al 6 O 12 SO 4 is formed between the alumina substrates and BSCCO thick films prepared from paste with composition close to Bi-2212 (and Bi-2212+10 wt.% Ag). For paste with composition close to Bi(Pb)-2223 +20 wt.% Ag, a new phase with f.c.c. structure, lattice parameter about a=24.5 A and approximate composition Al 3 Sr 2 CaBi 2 CuO x has been identified in the interface region. Understanding and control of these reactions is essential for growth of high quality BSCCO thick films on alumina. (orig.)

  15. Fischer-Tropsch synthesis on hierarchically structured cobalt nanoparticle/carbon nanofiber/carbon felt composites.

    Science.gov (United States)

    Zarubova, Sarka; Rane, Shreyas; Yang, Jia; Yu, Yingda; Zhu, Ye; Chen, De; Holmen, Anders

    2011-07-18

    The hierarchically structured carbon nanofibers (CNFs)/carbon felt composites, in which CNFs were directly grown on the surface of microfibers in carbon felt, forming a CNF layer on a micrometer range that completely covers the microfiber surfaces, were tested as a novel support material for cobalt nanoparticles in the highly exothermic Fischer-Tropsch (F-T) synthesis. A compact, fixed-bed reactor, made of disks of such composite materials, offered the advantages of improved heat and mass transfer, relatively low pressure drop, and safe handling of immobilized CNFs. An efficient 3-D thermal conductive network in the composite provided a relatively uniform temperature profile, whereas the open structure of the CNF layer afforded an almost 100 % effectiveness of Co nanoparticles in the F-T synthesis in the fixed bed. The greatly improved mass and heat transport makes the compact reactor attractive for applications in the conversion of biomass, coal, and natural gas to liquids. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Preparation of new composite ceramics based on gadolinium-doped ceria and magnesia nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Jingying; Schelter, Matthias; Zosel, Jens; Oelssner, Wolfram [Kurt-Schwabe-Institut fuer Mess- und Sensortechnik e.V. Meinsberg, Waldheim (Germany); Mertig, Michael [Kurt-Schwabe-Institut fuer Mess- und Sensortechnik e.V. Meinsberg, Waldheim (Germany); Physikalische Chemie, Mess- und Sensortechnik, Technische Universitaet Dresden (Germany)

    2017-09-15

    To achieve solid electrolyte materials for electrochemical energy storage devices with very high oxygen ion conductivity, composites of gadolinium-doped ceria (GDC) and magnesia (MgO) are developed in this study. Three different preparation methods are used to prepare nanoparticles from these two components. According to the characterization results, the self-propagating high-temperature synthesis is best suited for the preparation of both nanometer-sized GDC powder as solid electrolyte and MgO powder as insulator. The structures of the prepared nanometer-sized powders have been characterized by X-ray diffraction and transmission electron microscopy. They show narrow size distributions in the lower nanometer range. Then, dense composite ceramics are prepared from a MgO-GDC mixture by sintering. The size of the crystallite domains in the sintered ceramic is in the upper nanometer range. TEM and TEM-EDX images of a new composite ceramic based on gadolinium-doped ceria and magnesia nanoparticles. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Magnetic Composite Thin Films of Fe{sub x}O{sub y} Nanoparticles and Photocrosslinked Dextran Hydrogels

    Energy Technology Data Exchange (ETDEWEB)

    Brunsen, Annette, E-mail: brunsen@mpip-mainz.mpg.de [Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz (Germany); Department of Chemistry, Technical University Darmstadt, Petersenstr. 22, 64287 Darmstadt (Germany); Utech, Stefanie, E-mail: utech@uni-mainz.de [Johannes Gutenberg University Mainz, Institute of Physical Chemistry, Jakob-Welder-Weg 11, 55099 Mainz (Germany); Institut fuer Mikrotechnik Mainz GmbH (IMM), Carl-Zeiss-Str. 18-20, 55129 Mainz, German (Germany); Maskos, Michael, E-mail: maskos@uni-mainz.de [Institut fuer Mikrotechnik Mainz GmbH (IMM), Carl-Zeiss-Str. 18-20, 55129 Mainz, German (Germany); Knoll, Wolfgang, E-mail: Wolfgang.Knoll@ait.ac.at [Austrian Institute of Technology, Tech Gate Vienna, Donau-City-Str. 1, 1220 Wien (Austria); Jonas, Ulrich, E-mail: jonas@mpip-mainz.mpg.de [Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz (Germany) and Macromolecular Chemistry, Department Chemistry - Biology, University of Siegen, Adolf-Reichwein-Str. 2, 57076 Siegen (Germany) and Foundation for Research and Technology - Hellas - FORTH, Institute of Electronic Structure and Laser (IESL), Bio-Organic Materials Chemistry Laboratory - BOMCLab, Nikolaou Plastira 100, Vassilika Vouton, 71110 Heraklion, Crete (Greece)

    2012-04-15

    Magnetic hydrogel composites are promising candidates for a broad field of applications from medicine to mechanical engineering. Here, surface-attached composite films of magnetic nanoparticles (MNP) and a polymeric hydrogel (HG) were prepared from magnetic iron oxide nanoparticles and a carboxymethylated dextran with photoreactive benzophenone substituents. A blend of the MNP and the dextran polymer was prepared by mixing in solution, and after spin-coating and drying the blend film was converted into a stable MNP-HG composite by photocrosslinking through irradiation with UV light. The bulk composite material shows strong mobility in a magnetic field, imparted by the MNPs. By utilizing a surface layer of a photoreactive adhesion promoter on the substrates, the MNP-HG films were covalently immobilized during photocrosslinking. The high stability of the composite was documented by rinsing experiments with UV-Vis spectroscopy, while surface plasmon resonance and optical waveguide mode spectroscopy was employed to investigate the swelling behavior in dependence of the nanoparticle concentration, the particle type, and salt concentration. - Highlights: Black-Right-Pointing-Pointer blending of iron oxide nanoparticles with photocrosslinkable carboxymethyldextran. Black-Right-Pointing-Pointer UV irradiation of blend yields surface-attached, magnetic hydrogel films. Black-Right-Pointing-Pointer film characterization by surface plasmon resonance/optical waveguide spectroscopy. Black-Right-Pointing-Pointer swelling decreases with increasing nanoparticle content. Black-Right-Pointing-Pointer swelling decreases with increasing NaCl salt concentration in the aqueous medium.

  18. Nanoparticle and gelation stabilized functional composites of an ionic salt in a hydrophobic polymer matrix.

    Directory of Open Access Journals (Sweden)

    Selin Kanyas

    Full Text Available Polymer composites consisted of small hydrophilic pockets homogeneously dispersed in a hydrophobic polymer matrix are important in many applications where controlled release of the functional agent from the hydrophilic phase is needed. As an example, a release of biomolecules or drugs from therapeutic formulations or release of salt in anti-icing application can be mentioned. Here, we report a method for preparation of such a composite material consisted of small KCOOH salt pockets distributed in the styrene-butadiene-styrene (SBS polymer matrix and demonstrate its effectiveness in anti-icing coatings. The mixtures of the aqueous KCOOH and SBS-cyclohexane solutions were firstly stabilized by adding silica nanoparticles to the emulsions and, even more, by gelation of the aqueous phase by agarose. The emulsions were observed in optical microscope to check its stability in time and characterized by rheological measurements. The dry composite materials were obtained via casting the emulsions onto the glass substrates and evaporations of the organic solvent. Composite polymer films were characterized by water contact angle (WCA measurements. The release of KCOOH salt into water and the freezing delay experiments of water droplets on dry composite films demonstrated their anti-icing properties. It has been concluded that hydrophobic and thermoplastic SBS polymer allows incorporation of the hydrophilic pockets/phases through our technique that opens the possibility for controlled delivering of anti-icing agents from the composite.

  19. Nanoparticle and Gelation Stabilized Functional Composites of an Ionic Salt in a Hydrophobic Polymer Matrix

    Science.gov (United States)

    Kanyas, Selin; Aydın, Derya; Kizilel, Riza; Demirel, A. Levent; Kizilel, Seda

    2014-01-01

    Polymer composites consisted of small hydrophilic pockets homogeneously dispersed in a hydrophobic polymer matrix are important in many applications where controlled release of the functional agent from the hydrophilic phase is needed. As an example, a release of biomolecules or drugs from therapeutic formulations or release of salt in anti-icing application can be mentioned. Here, we report a method for preparation of such a composite material consisted of small KCOOH salt pockets distributed in the styrene-butadiene-styrene (SBS) polymer matrix and demonstrate its effectiveness in anti-icing coatings. The mixtures of the aqueous KCOOH and SBS-cyclohexane solutions were firstly stabilized by adding silica nanoparticles to the emulsions and, even more, by gelation of the aqueous phase by agarose. The emulsions were observed in optical microscope to check its stability in time and characterized by rheological measurements. The dry composite materials were obtained via casting the emulsions onto the glass substrates and evaporations of the organic solvent. Composite polymer films were characterized by water contact angle (WCA) measurements. The release of KCOOH salt into water and the freezing delay experiments of water droplets on dry composite films demonstrated their anti-icing properties. It has been concluded that hydrophobic and thermoplastic SBS polymer allows incorporation of the hydrophilic pockets/phases through our technique that opens the possibility for controlled delivering of anti-icing agents from the composite. PMID:24516593

  20. Antiviral activity of silver nanoparticle/chitosan composites against H1N1 influenza A virus

    Science.gov (United States)

    Mori, Yasutaka; Ono, Takeshi; Miyahira, Yasushi; Nguyen, Vinh Quang; Matsui, Takemi; Ishihara, Masayuki

    2013-02-01

    Silver nanoparticle (Ag NP)/chitosan (Ch) composites with antiviral activity against H1N1 influenza A virus were prepared. The Ag NP/Ch composites were obtained as yellow or brown floc-like powders following reaction at room temperature in aqueous medium. Ag NPs (3.5, 6.5, and 12.9 nm average diameters) were embedded into the chitosan matrix without aggregation or size alternation. The antiviral activity of the Ag NP/Ch composites was evaluated by comparing the TCID50 ratio of viral suspensions treated with the composites to untreated suspensions. For all sizes of Ag NPs tested, antiviral activity against H1N1 influenza A virus increased as the concentration of Ag NPs increased; chitosan alone exhibited no antiviral activity. Size dependence of the Ag NPs on antiviral activity was also observed: antiviral activity was generally stronger with smaller Ag NPs in the composites. These results indicate that Ag NP/Ch composites interacting with viruses exhibit antiviral activity.

  1. Chemical composition analysis and product consistency tests to support enhanced Hanford waste glass models. Results for the third set of high alumina outer layer matrix glasses

    Energy Technology Data Exchange (ETDEWEB)

    Fox, K. M. [Savannah River Site (SRS), Aiken, SC (United States); Edwards, T. B. [Savannah River Site (SRS), Aiken, SC (United States)

    2015-12-01

    In this report, the Savannah River National Laboratory provides chemical analyses and Product Consistency Test (PCT) results for 14 simulated high level waste glasses fabricated by the Pacific Northwest National Laboratory. The results of these analyses will be used as part of efforts to revise or extend the validation regions of the current Hanford Waste Treatment and Immobilization Plant glass property models to cover a broader span of waste compositions. The measured chemical composition data are reported and compared with the targeted values for each component for each glass. All of the measured sums of oxides for the study glasses fell within the interval of 96.9 to 100.8 wt %, indicating recovery of all components. Comparisons of the targeted and measured chemical compositions showed that the measured values for the glasses met the targeted concentrations within 10% for those components present at more than 5 wt %. The PCT results were normalized to both the targeted and measured compositions of the study glasses. Several of the glasses exhibited increases in normalized concentrations (NCi) after the canister centerline cooled (CCC) heat treatment. Five of the glasses, after the CCC heat treatment, had NCB values that exceeded that of the Environmental Assessment (EA) benchmark glass. These results can be combined with additional characterization, including X-ray diffraction, to determine the cause of the higher release rates.

  2. Manipulating fluorescence color and intensity with regular metal nanoparticle-based composite materials

    Energy Technology Data Exchange (ETDEWEB)

    Nikitin, Andrey G., E-mail: nikitin@cinam.univ-mrs.fr [Centre Interdisciplinaire de Nanoscience de Marseille (CINaM, UPR 3118 CNRS), Aix-Marseille University, Campus de Luminy, Case 913, 13288 Marseille, France and Faculty of Physics and Technology, Al-Farabi Kazakh National University, 71 Al-Farabi Ave., 050040 Almaty (Kazakhstan)

    2016-02-01

    This paper first studies the role of structural parameters of ordered metal nanoparticle-based composites in the modification of the spectra and intensity of directional emission from organic molecules. It then investigates the possibilities of white light generation via color conversion using two materials, one emitting in the green and the other one in the red spectral region. The structures under study exhibit enhanced emission within small solid angle in the forward direction due to excitation of the quasiguided modes. These modes modify the angle-dependent local photon density of states and, thus, result in efficient directional outcoupling of radiation.

  3. Hemicyanine LB film—Silver nanoparticle composite: contrasting fluorescence responses sensitive to the ultrathin film assembly sequence

    Science.gov (United States)

    Maganti, Lasya; Dwivedi, Itisha; Jose, Anju; Radhakrishnan, T. P.

    2017-07-01

    Fluorescence emission of molecules is strongly influenced by the plasmonic field of metal nanoparticles, with significant enhancement induced under optimal conditions. Nanocomposite ultrathin films fabricated with citrate-stabilized Ag nanoparticles and LB film of a cationic hemicyanine amphiphile, are shown to produce opposing fluorescence emission trends upon subtle variation in the assembly sequence. Monolayer LB films of the pure amphiphile show aggregation-induced quenching with increasing deposition pressure. Composite films formed by adsorption of Ag nanoparticles on the Langmuir film (self-assembly together with steered assembly) followed by LB transfer, show further quenching. However, adsorption of Ag nanoparticles on the pre-formed amphiphile LB film (self-assembly following steered assembly), causes the fluorescence to increase with the extent of adsorption. Spectroscopy and microscopy provide insight into the contrasting, tunable emission. Formation of Ag nanoparticle chains on the Langmuir film and their direct contact with the monolayer cause the fluorescence quenching; adsorption of isolated Ag nanoparticles on the LB film along with multilayer formation leads to the enhancement. The study illustrates the versatility of LB film—metal nanoparticle composites in producing distinct materials responses through subtle changes in the mode of assembly.

  4. Thermal probes of nanoparticle interfaces: Thermodiffusion and thermal conductivity of nanoparticle suspensions

    Science.gov (United States)

    Putnam, Shawn Arthur

    This dissertation presents an experimental study of heat transport and mass transport in nanoparticle composites. The 3o-method was used for high precision thermal conductivity measurements of PMMA polymers filled with alumina nanoparticles. A microfluidic beam deflection technique, developed in this thesis, was used to measure both the thermal conductivity (Λ) and the thermodiffusion coefficient (DT) of nanoparticle suspensions. Thermal conductivity studies of polymer nanocomposites used effective medium theory and data for the changes in thermal conductivity to estimate the thermal conductance of PMMA/alumina interfaces in the temperature range of 40 30 nm. Thermal conductivity studies of nanoparticle suspensions measured the thermal diffusivity to a precision better than 1%. Solutions of G60--C 70 fullerenes and alkanethiolate-protected Au nanoparticles were measured to maximum volume fractions of 0.6% and 0.35 vol%, respectively. Anomalous enhancements in Λ were not observed. The largest enhancement in Λ was 1.3 +/- 0.8% for 4 nm diameter Au particles suspended in ethanol. Thermodiffusion studies investigated aqueous suspensions of charged polystyrene nanoparticles, proteins of T4 lysozyme, and mutant variants of T4 lysozyme at small particle concentrations (cp ≈ 1-2 vol%). DT was measured as a function of temperature, particle size, particle charge, ionic strength, and ionic species. At room temperature and high salt concentrations (>100 mM), DT for 26 nm polystyrene nanoparticles varied systematically within the range --0.9x10-7 cm2 K -1 50°C, the thermodiffusion coefficients were positive with a value consistent with the predictions of a theoretical model originally proposed by B. Derjaguin that is based on the enthalpy changes due to polarization of water molecules in the double-layer. At high temperatures, DT was also independent of particle size.

  5. DC bias effect on alternating current electrical conductivity of poly(ethylene terephthalate)/alumina nanocomposites

    International Nuclear Information System (INIS)

    Nikam, Pravin N.; Deshpande, Vineeta D.

    2016-01-01

    Polymer nanocomposites based on metal oxide (ceramic) nanoparticles are a new class of materials with unique properties and designed for various applications such as electronic device packaging, insulation, fabrication and automotive industries. Poly(ethylene terephthalate) (PET)/alumina (Al 2 O 3 ) nanocomposites with filler content between 1 wt% and 5 wt% were prepared by melt compounding method using co-rotating twin screw extruder and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and precision LCR meter techniques. The results revealed that proper uniform dispersion at lower content up to 2 wt% of nano-alumina observed by using TEM. Aggregation of nanoparticles was observed at higher content of alumina examined by using SEM and TEM. The frequency dependences of the alternating current (AC) conductivity (σ AC ) of PET/alumina nanocomposites on the filler content and DC bias were investigated in the frequency range of 20Hz - 1MHz. The results showed that the AC and direct current (DC) conductivity increases with increasing DC bias and nano-alumina content upto 3 wt%. It follows the Jonscher’s universal power law of solids. It revealed that σ AC of PET/alumina nanocomposites can be well characterized by the DC conductivity (σ DC ), critical frequency (ω c ), critical exponent of the power law (s). Roll of DC bias potential led to an increase of DC conductivity (σ DC ) due to the creation of additional conducting paths with the polymer nanocomposites and percolation behavior achieved through co-continuous morphology.

  6. A general strategy to achieve ultra-high gene transfection efficiency using lipid-nanoparticle composites.

    Science.gov (United States)

    Vankayala, Raviraj; Chiang, Chi-Shiun; Chao, Jui-I; Yuan, Chiun-Jye; Lin, Shyr-Yeu; Hwang, Kuo Chu

    2014-09-01

    Gene therapy provides a new hope for previously "incurable" diseases. Low gene transfection efficiency, however, is the bottle-neck to the success of gene therapy. It is very challenging to develop non-viral nanocarriers to achieve ultra-high gene transfection efficiencies. Herein, we report a novel design of "tight binding-but-detachable" lipid-nanoparticle composite to achieve ultrahigh gene transfection efficiencies of 60∼82%, approaching the best value (∼90%) obtained using viral vectors. We show that Fe@CNPs nanoparticles coated with LP-2000 lipid molecules can be used as gene carriers to achieve ultra-high (60-80%) gene transfection efficiencies in HeLa, U-87MG, and TRAMP-C1 cells. In contrast, Fe@CNPs having surface-covalently bound N,N,N-trimethyl-N-2-methacryloxyethyl ammonium chloride (TMAEA) oligomers can only achieve low (23-28%) gene transfection efficiencies. Similarly ultrahigh gene transfection/expression was also observed in zebrafish model using lipid-coated Fe@CNPs as gene carriers. Evidences for tight binding and detachability of DNA from lipid-nanoparticle nanocarriers will be presented. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. G-CSF loaded nanofiber/nanoparticle composite coated with collagen promotes wound healing in vivo.

    Science.gov (United States)

    Tanha, Shima; Rafiee-Tehrani, Morteza; Abdollahi, Mohamad; Vakilian, Saeid; Esmaili, Zahra; Naraghi, Zahra Safaei; Seyedjafari, Ehsan; Javar, Hamid Akbari

    2017-10-01

    Sustained release of functional growth factors can be considered as a beneficial methodology for wound healing. In this study, recombinant human granulocyte colony-stimulating factor (G-CSF)-loaded chitosan nanoparticles were incorporated in Poly(ε-caprolactone) (PCL) nanofibers, followed by surface coating with collagen type I. Physical and mechanical properties of the PCL nanofibers containing G-CSF loaded chitosan nanoparticles PCL/NP(G-CSF) and in vivo performance for wound healing were investigated. G-CSF structural stability was evaluated through SDS_PAGE, reversed phase (RP) HPLC and size-exclusion chromatography, as well as circular dichroism. Nanofiber/nanoparticle composite scaffold was demonstrated to have appropriate mechanical properties as a wound dresser and a sustained release of functional G-CSF. The PCL/NP(G-CSF) scaffold showed a suitable proliferation and well-adherent morphology of stem cells. In vivo study and histopathological evaluation outcome revealed that skin regeneration was dramatically accelerated under PCL/NP(G-CSF) as compared with control groups. Superior fibroblast maturation, enhanced collagen deposition and minimum inflammatory cells were also the beneficial properties of PCL/NP(G-CSF) over the commercial dressing. The synergistic effect of extracellular matrix-mimicking nanofibrous membrane and G-CSF could develop a suitable supportive substrate in order to extensive utilization for the healing of skin wounds. © 2017 Wiley Periodicals Inc. J Biomed Mater Res Part A: 105A: 2830-2842, 2017. © 2017 Wiley Periodicals, Inc.

  8. Thermal conductivity and phase-change properties of aqueous alumina nanofluid

    International Nuclear Information System (INIS)

    Teng, Tun-Ping

    2013-01-01

    Highlights: ► The alumina nanofluid with chitosan was produced by two-step synthesis method. ► The k and phase-change properties of alumina nanofluid were examined. ► Adding Al 2 O 3 nanoparticles into water indeed improves the k. ► Adding the chitosan decreases the thermal conductivity of alumina nanofluid. ► The T cp and h c are 53.4% and 97.8% of those in DW with the optimal combination. - Abstract: This study uses thermal conductivity and differential scanning calorimeter experiments to explore the thermal conductivity and phase-change properties of alumina (Al 2 O 3 )–water nanofluid produced using a two-step synthesis method. Deionized water (DW) is used as a control group, and the Al 2 O 3 –water nanofluid uses chitosan as a dispersant. Nanoparticle morphology and materials were confirmed using transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. The results show that adding Al 2 O 3 nanoparticles to DW improves DW thermal conductivity, but adding chitosan reduces the thermal conductivity of Al 2 O 3 –water nanofluid. Adding the nanoparticles to DW affects the phase-change peak temperature and phase change heat. The optimal combination is 0.1 wt.% chitosan and 0.5 wt.% Al 2 O 3 nanoparticles; the charging phase-change peak temperature and latent heat are 53.4% and 97.8% of those in DW, respectively

  9. Effects of ball milling and sintering on alumina and alumina-boron compounds

    Science.gov (United States)

    Cross, Thomas

    Alumina has a wide variety of applications, but the processing of alumina based materials can be costly. Mechanically milling alumina has been shown to enhance the sintering properties while decreasing the sintering temperature. Additions of boron have also proven to increase sintering properties of alumina. These two processes, mechanical milling and boron additions, will be combined to test the sintering properties and determine if they are improved upon even further compared to the individual processes. Multiple samples of pure alumina, 0.2 weight percent boron, and 1.0 weight percent boron are batched and processed in a ball mill for different time intervals. These samples are then characterized to observe the structure and properties of the samples after milling but before sintering. Pellets are dry pressed from the milled powders, sintered at 1200°C for one to 10 hours, and characterized to determine the impact of processing. X-ray diffractometry (XRD) was used on each sample to determine crystallite size and lattice parameters at different stages throughout the experiment. XRD was also used to identify any samples with an aluminum borate phase. Scanning electron microscopy (SEM) was used to observe the powder and pellet morphology and to measure bulk chemical composition. Samples were sputter coated with an Au-Pd coating observed in the SEM to characterize the topography as a function of variables such as milling time, boron composition, and sintering time. Additionally, porosity and change in diameter were measured to track the sintering process. Milling sample for longer periods of time would be unnecessary due to the crystallite size leveling off between 10 and 12 hours of milling time. Samples of alumina with 0.2 weight percent boron prove to have very little effect on the sintering properties. At 1.0 weight percent boron, there are changes in diffraction patterns and topography after being sintered for one hour. The porosities of all of the sintered

  10. Preparation and application of conducting polymer/Ag/clay composite nanoparticles formed by in situ UV-induced dispersion polymerization

    Science.gov (United States)

    Zang, Limin; Qiu, Jianhui; Yang, Chao; Sakai, Eiichi

    2016-02-01

    In this work, composite nanoparticles containing polypyrrole, silver and attapulgite (PPy/Ag/ATP) were prepared via UV-induced dispersion polymerization of pyrrole using ATP clay as a templet and silver nitrate as photoinitiator. The effects of ATP concentration on morphology, structure and electrical conductivity were studied. The obtained composite nanoparticles with an interesting beads-on-a-string morphology can be obtained in a short time (10 min), which indicates the preparation method is facile and feasible. To explore the potential applications of the prepared PPy/Ag/ATP composite nanoparticles, they were served as multifunctional filler and blended with poly(butylene succinate) (PBS) matrix to prepare biodegradable composite material. The distribution of fillers in polymer matrix and the interfacial interaction between fillers and PBS were confirmed by scanning electron microscope, elemental mapping and dynamic mechanical analysis. The well dispersed fillers in PBS matrix impart outstanding antibacterial property to the biodegradable composite material as well as enhanced storage modulus due to Ag nanoparticles and ATP clay. The biodegradable composite material also possesses modest surface resistivity (106 ~ 109 Ω/◻).

  11. Preparation and application of conducting polymer/Ag/clay composite nanoparticles formed by in situ UV-induced dispersion polymerization.

    Science.gov (United States)

    Zang, Limin; Qiu, Jianhui; Yang, Chao; Sakai, Eiichi

    2016-02-03

    In this work, composite nanoparticles containing polypyrrole, silver and attapulgite (PPy/Ag/ATP) were prepared via UV-induced dispersion polymerization of pyrrole using ATP clay as a templet and silver nitrate as photoinitiator. The effects of ATP concentration on morphology, structure and electrical conductivity were studied. The obtained composite nanoparticles with an interesting beads-on-a-string morphology can be obtained in a short time (10 min), which indicates the preparation method is facile and feasible. To explore the potential applications of the prepared PPy/Ag/ATP composite nanoparticles, they were served as multifunctional filler and blended with poly(butylene succinate) (PBS) matrix to prepare biodegradable composite material. The distribution of fillers in polymer matrix and the interfacial interaction between fillers and PBS were confirmed by scanning electron microscope, elemental mapping and dynamic mechanical analysis. The well dispersed fillers in PBS matrix impart outstanding antibacterial property to the biodegradable composite material as well as enhanced storage modulus due to Ag nanoparticles and ATP clay. The biodegradable composite material also possesses modest surface resistivity (10(6)~ 10(9) Ω/◻).

  12. Preparation and antibacterial activities of Ag/Ag+/Ag3+ nanoparticle composites made by pomegranate (Punica granatum) rind extract

    Science.gov (United States)

    Yang, Hui; Ren, Yan-yu; Wang, Tao; Wang, Chuang

    Nano-silver and its composite materials are widely used in medicine, food and other industries due to their strong conductivity, size effect and other special performances. So far, more microbial researches have been applied, but a plant method is rarely reported. In order to open up a new way to prepare AgNP composites, pomegranate peel extract was used in this work to reduce Ag+ to prepare Ag/Ag+/Ag3+ nanoparticle composites. UV-Vis was employed to detect and track the reduction of Ag+ and the forming process of AgNPs. The composition, structure and size of the crystal were analyzed by XRD and TEM. Results showed that, under mild conditions, pomegranate peel extract reacted with dilute AgNO3 solution to produce Ag/Ag+/Ag3+ nanoparticle composites. At pH = 8 and 10 mmol/L of AgNO3 concentration, the size of the achieved composites ranged between 15 and 35 nm with spherical shapes and good crystallinity. The bactericidal experiment indicated that the prepared Ag/Ag+/Ag3+ nanoparticles had strong antibacterial activity against gram positive bacteria and gram negative bacteria. FTIR analysis revealed that biological macromolecules with groups of sbnd NH2, sbnd OH, and others were distributed on the surface of the newly synthesized Ag/Ag+/Ag3+ nanoparticles. This provided a useful clue to further study the AgNP biosynthesis mechanism.

  13. In vitro bioactivity and mechanical properties of bioactive glass nanoparticles/polycaprolactone composites.

    Science.gov (United States)

    Ji, Lijun; Wang, Wenjun; Jin, Duo; Zhou, Songtao; Song, Xiaoli

    2015-01-01

    Nanoparticles of bioactive glass (NBG) with a diameter of 50-90 nm were synthesized using the Stöber method. NBG/PCL composites with different NBG contents (0 wt.%, 10 wt.%, 20 wt.%, 30 wt.% and 40 wt.%) were prepared by a melt blending and thermal injection moulding technique, and characterized with XRD, FTIR, and SEM to study the effect of NBG on the mechanical properties and in vitro bioactivity of the NBG/PCL composites. In spite of the high addition up to 40 wt.%, the NBG could be dispersed homogeneously in the PCL matrix. The elastic modulus of the NBG/PCL composites was improved remarkably from 198±13 MPa to 851±43 MPa, meanwhile the tensile strength was retained in the range of 19-21.5 MPa. The hydrophilic property and degradation behavior of the NBG/PCL composites were also improved with the addition of the NBG. Moreover, the composites with high NBG content showed outstanding in vitro bioactivity after being immersed in simulated body fluid, which could be attributed to the excellent bioactivity of the synthesized NBG. Copyright © 2014. Published by Elsevier B.V.

  14. Surfactant Incorporated Co Nanoparticles Polymer Composites with Uniform Dispersion and Double Percolation

    Directory of Open Access Journals (Sweden)

    Tajamal Hussain

    2017-01-01

    Full Text Available Series of Cobalt nanoparticles incorporated polymethylmethacrylate composites in the presence and absence of dodecyl-benzene-sulphonic acid (DBSA-CoNPs/PMMA and CoNPs/PMMA, resp. were synthesized by solution mixing methodology. UV-visible and FTIR techniques were used to confirm the formation of nanocomposite. UV-visible spectra of the composites showed the incorporation of filler particles in the polymer matrix. On the other hand, FTIR spectra indicated the physical interaction between the two phases of the composite. Moreover, the electrical nature of the composites was studied by plotting graphs between electrical conductivity (measured using LCR meter at 100 kHz and contents of the filler particles as introduced in the polymer matrix. An increase in electrical conductivity was first observed with increasing filler concentration up to the critical percolation threshold value (0.5% for DBSA-CoNPs/PMMA and 1% for CoNPs/PMMA, which then dropped upon further increments in the filler content. However, at higher concentrations, a second jump in the conductivity was observed in case of DBSA-CoNPs/PMMA composites.

  15. Magnetic graphene oxide inlaid with silver nanoparticles as antibacterial and drug delivery composite.

    Science.gov (United States)

    Kooti, Mohammad; Sedeh, Azar Naghdi; Motamedi, Hossein; Rezatofighi, Seyedeh Elham

    2018-04-01

    A three-component composite consisted of graphene oxide, cobalt ferrite, and silver nanoparticles has been prepared by a facile method and fully characterized. The antibacterial activity of this composite has been greatly enhanced after being combined with ciprofloxacin drug. This clearly showed the occurrence of a strong synergistic effect between ciprofloxacin and the Ag NPs in the composite. The ciprofloxacin-conjugated composite was found to be a potent antimicrobial agent while having rather low cytotoxicity and high stability. The studies based on field emission scanning electron microscopy (FESEM) analysis and zeta potential measurement have revealed that the composite sticks to the bacterial cell wall causing irreversible cell damage. This multifunctional magnetic nanocomposite was also examined as drug delivery system for ciprofloxacin in solutions with different pH. It was observed that the release of ciprofloxacin in this system is pH-sensitive with gradual and controlled manner. Mechanisms for the synergistic effect and drug release behavior, as well as explanation for the antibacterial action, of the nanocomposite were also demonstrated.

  16. Promoting effect of tin oxides on alumina-supported gold catalysts used in CO oxidation

    Science.gov (United States)

    Somodi, Ferenc; Borbáth, Irina; Hegedűs, Mihály; Lázár, Károly; Sajó, István E.; Geszti, Olga; Rojas, Sergio; Fierro, Jose Luis Garcia; Margitfalvi, József L.

    2009-11-01

    In this study the influence of SnO x nanoparticles on the catalytic performance of alumina-supported gold catalysts was investigated in CO oxidation. The tin modified supports were prepared by grafting of tetraethyltin onto the surface of alumina via its hydroxyl groups. The decomposition of organometallic surface species in oxygen yielded highly dispersed tin oxide on the surface of alumina. Gold was introduced onto the tin modified alumina support by both deposition-precipitation with urea and direct anionic exchange techniques using HAuCl 4 solution. Based on catalytic and different spectroscopic measurements it is suggested that the presence of "Sn n+ -Au ensemble sites" is responsible for the increased activity of these catalysts.

  17. Structure change of alumina castable by adding magnesia or spinel; Maguneshia matawa supineru no tenka ni yoru arumina kei kyasutaburu no soshiki henka

    Energy Technology Data Exchange (ETDEWEB)

    Mori, J.; Onoue, M.; Toritani, Y.; Tanaka, S. [Kawasaki Refractories Co. Ltd., Hyogo (Japan)

    1995-01-10

    Alumina-spinel castable is developed as the refractory for lining ladles, and compared with the existing refractory its durability is greatly raised. This material is obtained by adding spinel to alumina base, and besides improvement of the slag penetration resistance it is likely to reduce the structure spoiling. To solve this problem, alumina castable added by magnesia draws much attention recently. Although alumina-spinel and alumina-magnesia are both castables with Al2O3, MgO as their main compositions, and their whole chemical compositions are almost the same, the durability of alumina-magnesia is sometimes much better according to the applying conditions. In this study, the structure change of alumina castable by adding magnesia or spinel was investigated, and the reason of the influence on the durability was studied. 6 refs., 6 figs., 1 tab.

  18. Surge-Resistant Nanocomposite Enameled Wire Using Silica Nanoparticles with Binary Chemical Compositions on the Surface

    Directory of Open Access Journals (Sweden)

    Jeseung Yoo

    2015-01-01

    Full Text Available We developed polyesterimide (PEI nanocomposite enameled wires using surface-modified silica nanoparticles with binary chemical compositions on the surface. The modification was done using silanes assisted by ultrasound, which facilitated high density modification. Two different trimethoxysilanes were chosen for the modification on the basis of resemblance of chemical compositions on the silica surface to PEI varnish. The surface-modified silica was well dispersed in PEI varnish, which was confirmed by optical observation and viscosity measurement. The glass transition temperature of the silica-PEI nanocomposite increased with the silica content. The silica-dispersed PEI varnish was then used for enameled wire fabrication. The silica-PEI nanocomposite enameled wire exhibited a much longer lifetime compared to that of neat PEI enameled wire in partial discharge conditions.

  19. Sr-hexaferrite/maghemite composite nanoparticles-possible new mediators for magnetic hyperthermia

    Energy Technology Data Exchange (ETDEWEB)

    Veverka, P; Pollert, E [Institute of Physics, ASCR, Cukrovarnicka 10, 162 53 Praha 6 (Czech Republic); Zaveta, K [Faculty of Mathematics and Physics, Charles University in Prague, V Holesovickach 2, 180 00 Praha 8 (Czech Republic); Vasseur, S; Duguet, E [Institut de Chimie de la Matiere Condensee de Bordeaux-ICMCB CNRS/Universite Bordeaux 1, 87 avenue du Dr Schweitzer, 33608 Pessac (France)], E-mail: pollert@fzu.cz

    2008-05-28

    Composite nanoparticles with variable ratios of M-type Sr-hexaferrite and maghemite phases were prepared via the sol-gel method employing polyvinylalcohol as the stabilizing agent, followed by thermal treatment at 600 deg. C for 32-190 min. The measurements in static magnetic field revealed considerable variation of the coercivity and remanence depending on the relative content of the highly magnetically anisotropic Sr-hexaferrite phase. Calorimetric heating experiments were carried out on aqueous gel suspensions under an alternating magnetic field of maximum amplitude H{sub max} = 15.1-68.4 kA m{sup -1} and frequency {nu} = 108 kHz. They showed a strong dependence of the heating efficiency on the coercivity and remanence of the composites, with a specific absorption rate (SAR) value ranging from units to tens of W/g(Fe{sub ferrimagnetic})

  20. Promising psyllium-based composite containing TiO2 nanoparticles as aspirin-carrier matrix

    Directory of Open Access Journals (Sweden)

    Marcela-Corina Rosu

    2014-06-01

    Full Text Available Composite nanomaterials represent a new trend in the biomedical field. Coupling inorganic/organic constituents with non-toxicity/biocompatibility properties leads to develop the new systems having special characteristics that can be used in various bio-applications. This paper describes the preparation and characterization of psyllium-based composites containing TiO2 nanoparticles in order to develop new therapeutic strategies for aspirin drug delivery. The structural characteristics of obtained materials were investigated by FTIR spectroscopy. The UV–vis spectrophotometric analysis was performed to evaluate the aspirin release behavior under different pH conditions at 37 °C. Combining psyllium (as an excellent source of fiber with TiO2 inorganic unit (as vehicle of aspirin it was found that polymeric-TiO2 networks have promising potential for controlled aspirin release as therapeutic agent.

  1. DESIGN OF A NOVEL CONDUCTING COMPOSITE SUPPORTED BY PLATINUM NANOPARTICLES FOR HYDROGEN PRODUCTION FROM WATER

    Directory of Open Access Journals (Sweden)

    Didem BALUN KAYAN

    2016-09-01

    Full Text Available Because of the decrease in fossil fuel resources and the continuous increase in energy demands, clean energy requirements become extremely important for future energy generation systems. Hydrogen is well known as an efficient and environmentally friendly energy carrier. Highly catalytic active and low-cost electrocatalysts for hydrogen production are key issues for sustainable energy technologies. Here we report an aluminium electrode modified with polypyrrole (PPy-chitosan (Chi composite film decorated with Pt nanoparticles for hydrogen production from water. Hydrogen evolution reaction (HER is examined by cyclic voltammetry (CV, Tafel polarization curves and electrochemical impedance spectroscopy (EIS in 0.5M H2SO4. The structural properties of the modified surfaces analyses were investigated by scanning electron microscopy (SEM. The stability tests also performed for aluminium electrode coted with PPy-Chi/Pt composite film.

  2. POLYMER COMPOSITE FILMS WITH SIZE-SELECTED METAL NANOPARTICLES FABRICATED BY CLUSTER BEAM TECHNIQUE

    DEFF Research Database (Denmark)

    Ceynowa, F. A.; Chirumamilla, Manohar; Popok, Vladimir

    2017-01-01

    Formation of polymer films with size-selected silver and copper nanoparticles (NPs) is studied. Polymers are prepared by spin coating while NPs are fabricated and deposited utilizing a magnetron sputtering cluster apparatus. The particle embedding into the films is provided by thermal annealing...... after the deposition. The degree of immersion can be controlled by the annealing temperature and time. Together with control of cluster coverage the described approach represents an efficient method for the synthesis of thin polymer composite layers with either partially or fully embedded metal NPs....... Combining electron beam lithography, cluster beam deposition and thermal annealing allows to form ordered arrays of metal NPs on polymer films. Plasticity and flexibility of polymer host and specific properties added by coinage metal NPs open a way for different applications of such composite materials...

  3. Molten-droplet synthesis of composite CdSe hollow nanoparticles

    KAUST Repository

    Gullapalli, Sravani

    2012-11-16

    Many colloidal synthesis routes are not scalable to high production rates, especially for nanoparticles of complex shape or composition, due to precursor expense and hazards, low yields, and the large number of processing steps. The present work describes a strategy to synthesize hollow nanoparticles (HNPs) out of metal chalcogenides, based on the slow heating of a low-melting-point metal salt, an elemental chalcogen, and an alkylammonium surfactant in octadecene solvent. The synthesis and characterization of CdSe HNPs with an outer diameter of 15.6 ± 3.5 nm and a shell thickness of 5.4 ± 0.9 nm are specifically detailed here. The HNP synthesis is proposed to proceed with the formation of alkylammonium-stabilized nano-sized droplets of molten cadmium salt, which then come into contact with dissolved selenium species to form a CdSe shell at the droplet surface. In a reaction-diffusion mechanism similar to the nanoscale Kirkendall effect it is speculated that the cadmium migrates outwardly through this shell to react with more selenium, causing the CdSe shell to thicken. The proposed CdSe HNP structure comprises a polycrystalline CdSe shell coated with a thin layer of amorphous selenium. Photovoltaic device characterization indicates that HNPs have improved electron transport characteristics compared to standard CdSe quantum dots, possibly due to this selenium layer. The HNPs are colloidally stable in organic solvents even though carboxylate, phosphine, and amine ligands are absent; stability is attributed to octadecene-selenide species bound to the particle surface. This scalable synthesis method presents opportunities to generate hollow nanoparticles with increased structural and compositional variety. © 2012 IOP Publishing Ltd.

  4. Effect of carrier gas composition on transferred arc metal nanoparticle synthesis

    International Nuclear Information System (INIS)

    Stein, Matthias; Kiesler, Dennis; Kruis, Frank Einar

    2013-01-01

    Metal nanoparticles are used in a great number of applications; an effective and economical production scaling-up is hence desirable. A simple and cost-effective transferred arc process is developed, which produces pure metal (Zn, Cu, and Ag) nanoparticles with high production rates, while allowing fast optimization based on energy efficiency. Different carrier gas compositions, as well as the electrode arrangements and the power input are investigated to improve the production and its efficiency and to understand the arc production behavior. The production rates are determined by a novel process monitoring method, which combines an online microbalance method with a scanning mobility particle sizer for fast production rate and size distribution measurement. Particle characterization is performed via scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction measurements. It is found that the carrier gas composition has the largest impact on the particle production rate and can increase it with orders of magnitude. This appears to be not only a result of the increased heat flux and melt temperature but also of the formation of tiny nitrogen (hydrogen) bubbles in the molten feedstock, which impacts feedstock evaporation significantly in bi-atomic gases. A production rate of sub 200 nm particles from 20 up to 2,500 mg/h has been realized for the different metals. In this production range, specific power consumptions as low as 0.08 kWh/g have been reached.

  5. Charge transport in conjugated polymer-semiconductor nanoparticle composite near the percolation threshold

    Science.gov (United States)

    Cardoso, L. S.; Gonçalves, G. E.; Kanda, D. H. F.; Bianchi, R. F.; Nagashima, H. N.

    2017-12-01

    This paper describes a new statistical model to predict the frequency dependence of the conductivity of conjugated polymer-semiconductor nanoparticle composites. The model considers AC conduction in an inhomogeneous medium represented by a two-dimensional model of resistor network. The conductivity between two neighboring sites in the polymer matrix and the semiconductor particles is assumed to obey the random free energy barrier model and the Drude model, respectively. The real and imaginary parts of the AC conductivity were determined using the transfer-matrix technique, and the statistical model was applied to experimental data of thin films composed of polyaniline (PANI) and indium-tin-oxide (ITO) nanoparticles. The conductivity critical exponent ( s) obtained in two dimensions for PANI/ITO films below the percolation threshold was found to be 2.7, which is greater than the universal value of s described by the classical percolation theory ( s = 1.3). This non-universality is explained by the existence of a local electric field distribution in the bulk of the nanocomposite. Finally, these results are discussed in terms of the distribution of potential barriers that vary according to the concentration of ITO amount in the composite.

  6. Morphological and compositional characteristics of bimetallic core@shell nanoparticles revealed by MEIS

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, Dario F., E-mail: dario.f.sanchez@gmail.com [Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre (Brazil); Moiraghi, Raquel; Cometto, Fernando P.; Pérez, Manuel A. [INFIQC, Departamento de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba (Argentina); Fichtner, Paulo F.P. [Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre (Brazil); Department of Metallurgy, Engineering School UFRGS, Porto Alegre (Brazil); Grande, Pedro L. [Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre (Brazil)

    2015-03-01

    Highlights: • Characterization of the morphology, structure and composition of Au@Ag core@shell nanoparticles, high polydispersity in the shell thickness. • Subnanometer resolution with a representative sampling achieved through the combination of Medium Energy Ion Scattering with Transmission Electron Microscopy. • For samples synthesized with baths of different AgNO{sub 3} concentrations, determination of the nanoparticles’ Ag shell thicknesses distribution of about a few nanometers around the Au core. - Abstract: In this paper we report the application of a suitable methodology to study the morphology, structure and composition of core@shell nanoparticles (NPs) systems with polydispersity in the shell thickness, with subnanometer resolution and good sampling. Through the combination of Medium Energy Ion Scattering with Transmission Electron Microscopy, we perform a systematic investigation on core@shell Au@Ag NPs synthesized by an original wet chemical method. For samples synthesized with baths of different AgNO{sub 3} concentrations, the present approach allowed us to determine the NP's Ag shell thicknesses distribution of about a few nanometers around the Au core.

  7. Space-oriented immobilization of fully active laccase on PPy–ferromagnetic nanoparticles composite layer

    International Nuclear Information System (INIS)

    Matysiak, Edyta; Nowicka, Anna M.; Wagner, Barbara; Donten, Mikolaj

    2016-01-01

    Immobilization of paramagnetic molecule of laccase (Lac) under influence of external magnetic field was performed to enhance catalytic activity of the enzyme. A thin layer of composite containing ferromagnetic nanoparticles: carbon-encapsulated iron nanoparticles (Fe@CNps) embedded in electrochemically polymerised PPy film was used for focusing external magnetic field in a space close to the electrode. It was found that magnetic interactions between paramagnetic centres of macromolecules and Fe@C Nps enhance catalytic performance probably by decreasing the gap between the surface of the electrode and active sides of the enzyme. Catalytic efficiency of immobilized enzyme (laccase separated from the fungus Trametes versicolor) was evaluated by the investigation of its ability to bioelectrocatalytic oxygen reduction. For characterization of the composite layers electrochemical gravimetric techniques, inductively coupled plasma mass spectrometry with laser ablation and scanning electron microscopy have been used. Electrochemical experiments performed in the absence and presence of magnetic field indicated significantly higher activity of enzyme and strong enhancement of oxygen reduction current in presence of external magnetic field. It is clear that proposed method helps to maintain enzyme in its highly electroactive form allowing direct electron transfer (DET) between the electrode and the enzyme.

  8. Magnetic field aligned assembly of nonmagnetic composite dumbbells in nanoparticle-based aqueous ferrofluid.

    Science.gov (United States)

    Takahashi, Hayato; Nagao, Daisuke; Watanabe, Kanako; Ishii, Haruyuki; Konno, Mikio

    2015-05-26

    Monodisperse, nonmagnetic, asymmetrical composite dumbbells in a suspension of magnetic nanoparticles (ferrofluid) were aligned by application of an external magnetic field to the ferrofluid. The asymmetrical composite dumbbells were prepared by two-step soap-free emulsion polymerization consisting of the first polymerization to coat spherical silica cores with cross-linked poly(methyl methacrylate) (PMMA) shell and the second polymerization to protrude a polystyrene (PSt) lobe from the core-shell particles. A chain structure of nonmagnetic dumbbells oriented to the applied magnetic field was observed at nanoparticle content of 2.0 vol % and field strengths higher than 1.0 mT. A similar chain structure of the dumbbells was observed under application of alternating electric field at strengths higher than 50 V/mm. Parallel and orthogonally combined applications of the electric and magnetic fields were also conducted to examine independence of the electric and magnetic applications as operational factors in the dumbbell assembling. Dumbbell chains stiffer than those in a single application of external field were formed in the parallel combined application of electric and magnetic fields. The orthogonal combination of the different applied fields could form a magnetically aligned chain structure of the nonmagnetic dumbbells oriented to the electric field. The present work experimentally indicated that the employment of inverse magnetorheological effect for nonmagnetic, anisotropic particles can be a useful method for the simultaneous controls over the orientation and the positon of anisotropic particles in their assembling.

  9. Fabrication and Application of Iron(III-Oxide Nanoparticle/Polydimethylsiloxane Composite Cone in Microfluidic Channels

    Directory of Open Access Journals (Sweden)

    Cheng-Chun Huang

    2012-01-01

    Full Text Available This paper presented the fabrication and applications of an iron(III-oxide nanoparticle/polydimethylsiloxane (PDMS cone as a component integrated in lab on a chip. The two main functions of this component were to capture magnetic microbeads in the microfluid and to mix two laminar fluids by generating disturbance. The iron(III-oxide nanoparticle/PDMS cone was fabricated by automatic dispensing and magnetic shaping. Three consecutive cones of 300 μm in height were asymmetrically placed along a microchannel of 2 mm in width and 1.1 mm in height. Flow passing the cones was effectively redistributed for Renolds number lower than . Streptavidin-coated magnetic microbeads which were bound with biotin were successfully captured by the composite cones as inspected under fluorescence microscope. The process parameters for fabricating the composite cones were investigated. The fabricated cone in the microchannel could be applied in lab on a chip for bioassay in the future.

  10. Preliminary study on nano- and micro-composite sol-gel based alumina coatings on structural components of lead-bismuth eutectic cooled fast breeder reactors

    International Nuclear Information System (INIS)

    Dou, Peng; Kasada, Ryuta

    2011-01-01

    In order to protect the structural components of lead-bismuth eutectic cooled fast breeder reactors from liquid metal corrosion, Al 2 O 3 nano- and micro-composite coatings were developed using an improved sol-gel process, which includes dipping specimens in a sol-gel solution dispersed with fine α-Al 2 O 3 powders prepared by mechanical milling. Accelerated corrosion tests were conducted on coated specimens in liquid lead-bismuth eutectic at 500 o C under dynamic conditions. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed that the coatings are composed of α-Al 2 O 3 and they are about 10 μm thick. After the corrosion tests, no spallation occurred on the coatings, and neither Pb nor Bi penetrated into the coatings, which indicates that the coatings possess an enhanced dynamic LBE corrosion resistance to lead-bismuth eutectic corrosion. The nano-structured composite particles integrated into the coatings play an important role in achieving such superior lead-bismuth eutectic corrosion resistance.

  11. Fabrication, characterization, and mechanical properties of spark plasma sintered Al–BN nanoparticle composites

    Energy Technology Data Exchange (ETDEWEB)

    Firestein, Konstantin L., E-mail: kosty@firestein.ru [National University of Science and Technology “MISIS”, Leninsky prospect 4, Moscow 119049 (Russian Federation); Steinman, Alexander E.; Golovin, Igor S. [National University of Science and Technology “MISIS”, Leninsky prospect 4, Moscow 119049 (Russian Federation); Cifre, Joan [Universitat de les Illes Balears, Ctra. de Valldemossa, km. 7.5, E-07122 Palma de Mallorca (Spain); Obraztsova, Ekaterina A.; Matveev, Andrei T.; Kovalskii, Andrey M. [National University of Science and Technology “MISIS”, Leninsky prospect 4, Moscow 119049 (Russian Federation); Lebedev, Oleg I. [CRISMAT, UMR 6508, CNRS-ENSICAEN, 6Bd Marechal Juin, 14050 Caen (France); Shtansky, Dmitry V., E-mail: shtansky@shs.misis.ru [National University of Science and Technology “MISIS”, Leninsky prospect 4, Moscow 119049 (Russian Federation); Golberg, Dmitri, E-mail: golberg.dmitri@nims.go.jp [World Premier International Center for Materials Nanoarchitectonics (WPI-MANA) National Institute for Materials Science (NIMS), Namiki 1, Tsukuba, Ibaraki 3050044 (Japan)

    2015-08-26

    Fabrication of high strength yet light and low cost composite materials with good mechanical properties at room and elevated temperatures is a challenge that metallurgy and materials science communities are facing for many years, and no “dream material” has been developed so far. The primary goal of this study was to fabricate, characterize, and to carry out tensile tests on Al-based composite materials strengthened with commercially-available BN nanoparticles (BNNPs). The composites were fabricated by spark plasma sintering (SPS) technique. The structures of powder mixtures and composite materials, as well as their fracture surfaces, were studied by scanning and transmission electron microscopy. The influence of BNNPs content (0.5, 1.5, 3, 4.5, 6, and 7.5 wt%) and holding times (5, 60, and 300 min) at 600 °C during SPS on the tensile strength was investigated. A maximum increase in strength was observed for Al-based composites with 4.5 wt% of BNNPs. The sample demonstrated a 50% increase in tensile strength compared with pristine Al. Although the tensile tests performed at 300 °C revealed that the tensile strength became 20% lower than the strength at room temperature, it was, however, still 75% higher compared with that of the pure Al at 300 °C. In addition, at 300 °C the Al–BNNPs composites demonstrated a much higher value of yield stress, about 115 MPa, which is 190% higher than that of pure Al at the same temperature. The damping properties of Al–BNNPs composites were evaluated by temperature dependent internal friction (TDIF) measurements. The obtained results are discussed based on structural analysis and the TDIF data.

  12. Preparation and photocatalytic activity of immobilized composite photocatalyst (titania nanoparticle/activated carbon)

    International Nuclear Information System (INIS)

    Mahmoodi, Niyaz Mohammad; Arami, Mokhtar; Zhang, Jason

    2011-01-01

    Research highlights: → Dyes were decolorized and degraded using novel immobilized composite photocatalyst. → Formate, acetate and oxalate anions were detected as dominant aliphatic intermediates where, they were further oxidized slowly to CO 2 . → Nitrate, chloride and sulfate anions were detected as the photocatalytic mineralization products of dyes. → Novel immobilized composite photocatalyst is the most effective novel immobilized composite photocatalyst to degrade of textile dyes. - Abstract: An immobilized composite photocatalyst, titania (TiO 2 ) nanoparticle/activated carbon (AC), was prepared and its photocatalytic activity on the degradation of textile dyes was tested. AC was prepared using Canola hull. Basic Red 18 (BR18) and Basic Red 46 (BR46) were used as model dyes. Fourier transform infrared (FTIR), wavelength dispersive X-ray spectroscopy (WDX), scanning electron microscopy (SEM), UV-vis spectrophotometry, chemical oxygen demand (COD) and ion chromatography (IC) analyses were employed. The effects of reaction parameters such as weight percent (wt.%) of activated carbon, pH, dye concentration and anions (NO 3 - , Cl - , SO 4 2- , HCO 3 - and CO 3 2- ) were investigated on dye degradation. Data showed that dyes were decolorized and degraded using novel immobilized composite photocatalyst. Formate, acetate and oxalate anions were detected as dominant aliphatic intermediates where, they were further oxidized slowly to CO 2 . Nitrate, chloride and sulfate anions were detected as the photocatalytic mineralization products of dyes. Results show that novel immobilized composite photocatalyst with 2 wt.% of AC is the most effective novel immobilized composite photocatalyst to degrade of textile dyes.

  13. Facile Synthesis of Pt Nanoparticle and Graphene Composite Materials: Comparison of Electrocatalytic Activity with Analogous CNT Composite

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jihye; Jang, Ho Young; Jung, Insub; Yoon, Yeoheung; Jang, Heejeong; Lee, Hyoyoung; Park, Sungho [Sungkyunkwan Univ., Suwon (Korea, Republic of)

    2014-07-15

    Here, we present a facile method to synthesize Pt nanoparticles (NPs) and graphene composite materials (Pt/G) via vacuum filtration. Anodic aluminum oxide (AAO) templates were used to separate Pt/G composite and liquid phase. This method can be used to easily tune the mass ratio of Pt NPs and graphene. Pt NPs, graphene, and carbon nanotubes (CNTs) as building blocks were characterized by a variety of techniques such as scanning electron microscopy, UV-Vis spectroscopy, and Raman spectroscopy. We compared the electrocatalytic activities of Pt/G with Pt NP and CNT films (Pt/CNT) by cyclic voltammetry (CV), CO oxidation, and methanol oxidation. Pt/G was much more stable than pure Pt films. Also, Pt/G had better electrochemical activity, CO tolerance and methanol oxidation than Pt/CNT loaded with the same amount of Pt NPs due to the better dispersion of Pt NPs on graphene flakes without aggregation. We further synthesized Au Pt disk/G and Pt nanorods/G to determine if our synthetic method can be applied to other NP shapes such as nanodisks and nanorods, for further electrocatalysis studies.

  14. Nanoalloying and phase transformations during thermal treatment of physical mixtures of Pd and Cu nanoparticles

    Directory of Open Access Journals (Sweden)

    Vineetha Mukundan

    2014-03-01

    Full Text Available Nanoscale alloying and phase transformations in physical mixtures of Pd and Cu ultrafine nanoparticles are investigated in real time with in situ synchrotron-based x-ray diffraction complemented by ex situ high-resolution transmission electron microscopy. The combination of metal–support interaction and reactive/non-reactive environment was found to determine the thermal evolution and ultimate structure of this binary system. At 300 °C, the nanoparticles supported on silica and carbon black intermix to form a chemically ordered CsCl-type (B2 alloy phase. The B2 phase transforms into a disordered fcc alloy at higher temperature (> 450 °C. The alloy nanoparticles supported on silica and carbon black are homogeneous in volume, but evidence was found of Pd surface enrichment. In sharp contrast, when supported on alumina, the two metals segregated at 300 °C to produce almost pure fcc Cu and Pd phases. Upon further annealing of the mixture on alumina above 600 °C, the two metals interdiffused, forming two distinct disordered alloys of compositions 30% and 90% Pd. The annealing atmosphere also plays a major role in the structural evolution of these bimetallic nanoparticles. The nanoparticles annealed in forming gas are larger than the nanoparticles annealing in helium due to reduction of the surface oxides that promotes coalescence and sintering.

  15. Investigating mechanical properties of polymethylmethacrylate/silver nanoparticle composites by molecular dynamics simulation

    Science.gov (United States)

    Ju, Shin-Pon; Chen, Hsing-Yin; Shih, Che-Wei

    2018-01-01

    The molecular dynamics simulation (MD) was carried out to investigate the mechanical properties of pristine polymethylmethacrylate (PMMA) and the composites of PMMA mixed with the silver nanoparticles (PMMA/AgNPs) at two AgNP weight fractions at 0.60 and 1.77 wt%. From the stress-strain profiles by the tensile process, it can be seen that the improvement on Young's modulus is insignificant at these lower AgNP fractions. The tensile strength of pristine PMMA can be slightly improved by the embedded AgNPs at 1.77 wt%, because the local density and strength of PMMA in the vicinity of AgNP surface within about 8.2 Å are improved. For the temperature effect on the mechanical properties of pristine PMMA and PMMA/AgNP composite, the Young's moduli and strength of pristine PMMA and PMMA/AgNP composite significantly decrease at temperatures of 450 and 550 K, which are close to the predicted melting temperature of pristine PMMA about 460 K. At these temperatures, the PMMA materials become more ductile and the AgNPs within the PMMA matrix display higher mobility than those at 300 K. When the tensile strain increases, the AgNPs tend to get closer and the fracture appears at the PMMA part, leading to the close values of Young's modulus and ultimate strength for pristine PMMA and PMMA/AgNP composite at 450 and 550 K.

  16. Effect of Acid Hydrolysis Conditions on the Properties of Cellulose Nanoparticle-Reinforced Polymethylmethacrylate Composites

    Directory of Open Access Journals (Sweden)

    Guangping Han

    2013-12-01

    Full Text Available Cellulose nanoparticles (CNPs were prepared from microcrystalline cellulose using two concentration levels of sulfuric acid (i.e., 48 wt% and 64 wt% with produced CNPs designated as CNPs-48 and CNPs-64, respectively followed by high-pressure homogenization. CNP-reinforced polymethylmethacrylate (PMMA composite films at various CNP loadings were made using solvent exchange and solution casting methods. The ultraviolet-visible (UV-vis transmittance spectra between 400 and 800 nm showed that CNPs-64/PMMA composites had a significantly higher optical transmittance than that of CNPs-48/PMMA. Their transmittance decreased with increased CNP loadings. The addition of CNPs to the PMMA matrix reduced composite’s coefficient of thermal expansion (CTE, and CNPs-64/PMMA had a lower CTE than CNPs-48/PMMA at the same CNP level. Reinforcement effect was achieved with the addition of CNPs to the PMMA matrix, especially at higher temperature levels. CNPs-64/PMMA exhibited a higher storage modulus compared with CNPs-48/PMMA material. All CNP-reinforced composites showed higher Young’s modulus and tensile strengths than pure PMMA. The effect increased with increased CNP loadings in the PMMA matrix for both CNPs-64/PMMA and CNPs-48/PMMA composites. CNPs affected the Young’s modulus more than they affected the tensile strength.

  17. Assessment of nanoparticle release and associated health effect of polymer-silicon composites

    International Nuclear Information System (INIS)

    Zhu, H; Irfan, A; Sachse, S; Njuguna, J

    2012-01-01

    Little information is currently available on possible release of nanomaterials or/and nanoparticles (NP) from conventional and novel products and associated health effect. This study aimed to assess the possible release of NP during the application stage of conventional and nanoproducts. NP release was monitored during physical processing of polymer-silicon composites, and the toxicity of both the released NP and the raw silica nanomaterials that were used as fillers in the nanocomposites was assessed in vitro using human lung epithelial A549 cells. This study suggests that 1) NP can be released from the conventional and novel polymer-silicon composites under certain application scenario; 2) the level of NP release from polymer composites could be altered by different reinforcement materials; e.g. nanostructured MMT could reduce the release while SiO2 NP could increase the release; 3) working with polymer composites under certain conditions could risk inhalation of high level of polymer NP; 4) raw nanomaterials appeared to be toxic in the chosen in vitro system. Further study of the effect of novel filler materials on NP release from final polymer products and the effect of released NP on environment and human health will inform design of safe materials and minimization of negative impact on the environment and human health.

  18. Preparation of Size-Controlled Silver Nanoparticles and Chitin-Based Composites and Their Antimicrobial Activities

    Directory of Open Access Journals (Sweden)

    Vinh Quang Nguyen

    2013-01-01

    Full Text Available A simple method for the preparation of size-controlled spherical silver nanoparticles (Ag NPs was reported for their generation by autoclaving a mixture of silver-containing glass powder and glucose. The particle size is regulated by the glucose concentration, with concentrations of 0.25, 1.0, and 4.0 wt% glucose providing small (3.48±1.83 nm in diameter, medium (6.53±1.78 nm, and large (12.9±2.5 nm particles, respectively. In this study, Ag NP/chitin composites were synthesized by mixing each of these three Ag NP suspensions with a <5% deacetylated (DAc chitin powder (pH 7.0 at room temperature. The Ag NPs were homogenously dispersed and stably adsorbed onto the chitin. The Ag NP/chitin composites were obtained as yellow or brown powders. Approximately 5, 15, and 20 μg of the small, medium, and large Ag NPs, respectively, were estimated to maximally adsorb onto 1 mg of chitin. The bactericidal and antifungal activities of the Ag NP/chitin composites increased as the amount of Ag NPs in the chitin increased. Furthermore, smaller Ag NPs (per weight in the chitin composites provided higher bactericidal and anti-fungal activities.

  19. Alumina Yield in the Bayer Process

    Science.gov (United States)

    Den Hond, R.

    The alumina industry has historically been able to reduce alumina production costs, by increasing the liquor alumina yield. To know the potential for further yield increases, the phase diagram of the ternary system Na2O-Al2O -H2O at various temperature levels was analysed. It was found that the maximum theorical precipitation alumina yield is 160 g/l, while that for digestion was calculated to be 675 g/l.

  20. Synthesis of titanium oxide nanoparticles using DNA-complex as template for solution-processable hybrid dielectric composites

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, J.C. [Center for Sustainable Materials Chemistry, 153 Gilbert Hall, Oregon State University, Corvallis, OR (United States); Mejia, I.; Murphy, J.; Quevedo, M. [Department of Materials Science and Engineering, University of Texas at Dallas, Dallas, TX (United States); Garcia, P.; Martinez, C.A. [Engineering and Technology Institute, Autonomous University of Ciudad Juarez, Ciudad Juarez, Chihuahua (Mexico)

    2015-09-15

    Highlights: • We developed a synthesis method to produce TiO{sub 2} nanoparticles using a DNA complex. • The nanoparticles were anatase phase (~6 nm diameter), and stable in alcohols. • Composites showed a k of 13.4, 4.6 times larger than the k of polycarbonate. • Maximum processing temperature was 90 °C. • Low temperature enables their use in low-voltage, low-cost, flexible electronics. - Abstract: We report the synthesis of TiO{sub 2} nanoparticles prepared by the hydrolysis of titanium isopropoxide (TTIP) in the presence of a DNA complex for solution processable dielectric composites. The nanoparticles were incorporated as fillers in polycarbonate at low concentrations (1.5, 5 and 7 wt%) to produce hybrid dielectric films with dielectric constant higher than thermally grown silicon oxide. It was found that the DNA complex plays an important role as capping agent in the formation and suspension stability of nanocrystalline anatase phase TiO{sub 2} at room temperature with uniform size (∼6 nm) and narrow distribution. The effective dielectric constant of spin-cast polycarbonate thin-films increased from 2.84 to 13.43 with the incorporation of TiO{sub 2} nanoparticles into the polymer host. These composites can be solution processed with a maximum temperature of 90 °C and could be potential candidates for its application in low-cost macro-electronics.

  1. Manufacturing and Morphological Analysis of Composite Material of Polystyrene Nanospheres/Cadmium Metal Nanoparticles

    Directory of Open Access Journals (Sweden)

    Pratama Jujur Wibawa

    2013-03-01

    drawn and proposed © 2013 BCREC UNDIP. All rights reserved. (Selected Paper from International Conference on Chemical and Material Engineering (ICCME 2012Received: 26th September 2012; Revised: 17th December 2012; Accepted: 18th December 2012[How to Cite: P. J. Wibawa, H. Saim, M. A. Agam, H. Nur, (2013. Manufacturing and Morphological Analysis of Composite Material of Polystyrene Nanospheres/ Cadmium metal nanoparticles. Bulletin of Chemical Reaction Engineering & Catalysis, 7 (3: 224-232. (doi:10.9767/bcrec.7.3.4043.224-232][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.7.3.4043.224-232 ] View in  |

  2. Stability, rheology and thermal analysis of functionalized alumina- thermal oil-based nanofluids for advanced cooling systems

    International Nuclear Information System (INIS)

    Ilyas, Suhaib Umer; Pendyala, Rajashekhar; Narahari, Marneni; Susin, Lim

    2017-01-01

    Highlights: • Alumina nanoparticles are functionalized with oleic acid. • Functionalization of alumina nanoparticles gives better dispersion in thermal oil. • Thermophysical properties of nanofluids are experimentally measured. • TGA confirms the improvement in life of nanofluids. - Abstract: Thermal oils are widely used as cooling media in heat transfer processes. However, their potential has not been utilised exquisitely in many applications due to low thermal properties. Thermal oil-based nanofluids are prepared by dispersing functionalized alumina with varying concentrations of 0.5–3 wt.% to enhance thermal properties of oil for advanced cooling systems. The oleic acid coated alumina is prepared and then dispersed in the oil to overcome the aggregation of nanoparticles in base fluid. The surface characterizations of functionalized nanoparticles are performed using different analysis such as XRD, EDS, SEM, TEM and FTIR. Dispersion behaviour and agglomeration studies are conducted at natural and functionalized conditions using different analysis to ensure long-term stability of nanofluids. In addition, rheological behaviour of non-Newtonian nanofluids is studied at high shear rates (100–2000 s −1 ). Effective densities and enhancement in thermal conductivities are measured for different nanofluids concentrations. Specific heat capacity is measured using Differential Scanning Calorimetry. The correlations are developed for thermophysical properties of nanofluids. Thermogravimetric analysis is performed with respect to temperature and time to exploit the effect of the addition of nanoparticles on the degradation of nanofluids. Significant improvement in the thermal properties of oil is observed using highly stable functionalized alumina nano-additives.

  3. Plasmonic properties of silver nanoparticles embedded in diamond like carbon films: Influence of structure and composition

    Energy Technology Data Exchange (ETDEWEB)

    Meškinis, Š., E-mail: sarunas.meskinis@fei.lt [Kaunas University of Technology, Institute of Materials Science, Savanoriu Ave. 271, Kaunas LT-50131 (Lithuania); Čiegis, A.; Vasiliauskas, A.; Tamulevičienė, A.; Šlapikas, K. [Kaunas University of Technology, Institute of Materials Science, Savanoriu Ave. 271, Kaunas LT-50131 (Lithuania); Juškėnas, R.; Niaura, G. [Institute of Chemistry, Center for Physical Sciences and Technology, Goštauto Str. 9, Vilnius LT-01108 (Lithuania); Tamulevičius, S. [Kaunas University of Technology, Institute of Materials Science, Savanoriu Ave. 271, Kaunas LT-50131 (Lithuania)

    2014-10-30

    Highlights: • Optical properties of DLC films containing silver (DLC:Ag) depends on substrate bias. • Position of the plasmonic peak depends on composition of DLC:Ag films. • Position of the plasmonic peak depends on structure of Ag nanoclusters. • Influence of composition prevails influence of the structure of DLC matrix. - Abstract: In the present study optical properties of hydrogenated diamond like carbon nanocomposite films containing silver nanoparticles (DLC:Ag) deposited by direct current (DC) unbalanced reactive magnetron sputtering were studied in 180–1100 nm range. Different substrate bias was used during deposition of the films. Structure of the films was investigated by multiwavelength Raman scattering spectroscopy and X-ray diffractometry (XRD). Chemical composition of the samples was studied by X-ray photoelectron spectroscopy (XPS), surface morphology was investigated by atomic force microscopy (AFM). Red shift of the surface plasmon resonance peak of DLC:Ag films with the increase of Ag atomic concentration was observed. It was found that high atomic concentration of oxygen in DLC:Ag films results in some redshift of the plasmonic peak, too. Such a behavior is explained by increase of the refractive index of the dielectric medium surrounding silver nanoparticle due to possible presence of the silver oxide interlayer at the Ag nanocluster and diamond like carbon matrix interface. It was demonstrated that influence of the increased Ag atomic concentration on position of the surface plasmon resonance peak of DLC:Ag films clearly prevails influence of the increased sp{sup 3}/sp{sup 2} ratio of the diamond like carbon matrix. Correlation between the structure of Ag nanocrystallites studied by XRD and position of the surface plasmon resonance peak position was observed.

  4. Attrition resistant gamma-alumina catalyst support

    Science.gov (United States)

    Singleton, Alan H.; Oukaci, Rachid; Goodwin, James G.

    2006-03-14

    A .gamma.-alumina catalyst support having improved attrition resistance produced by a method comprising the steps of treating a particulate .gamma.-alumina material with an acidic aqueous solution comprising water and nitric acid and then, prior to adding any catalytic material thereto, calcining the treated .gamma.-alumina.

  5. [Characterization of alumina adobe and sintered body of GI-infiltrated ceramic].

    Science.gov (United States)

    Wang, H; Chao, Y; Liao, Y; Liang, X; Zhu, Z; Gao, W

    2001-06-01

    This study was conducted to elucidate the mechanism of formation of porous structure by investigating the porosity of the alumina adobe and sintered body of GI-II Infiltrate Ceramic, and its role in strengthening and toughening this kind of ceramic composite. The alumina powder size-mass distribution was obtained by BI-XDC powder size analysis device; the open pore parameters of alumina adobe and sintered body were analyzed using the mercury pressure method. Their fracture surfaces were observed under scanning electronic microscope. Fine powder had two main size groups of 0.09-0.1 micron and 0.2-0.5 micron, respectively, and coarse powder, with size between 1.5 to 4.5 microns, occupied the majority of powder mass. Alumina adobe's pores became larger after sintering. The median pore radii of adobe and sintered body were 0.2531 micron and 0.3081 micron, respectively; the average pore radii changed from 0.0956 micron to 0.1102 micron. Under scanning electronic microscope, fine alumina powders were fused partially together and their surfaces were blunted, but coarse powders did not show such phenomena. The alumina size distribution contributes to the formation of porous structure of alumina sintered body. This porous structure is not only the shape skeleton but also the mechanical skeleton of GI-II Infiltrated Ceramic. It plays an important role in raising the mechanical properties of this kind of ceramic composite.

  6. Preparation and electrochemical performance of sulfur-alumina cathode material for lithium-sulfur batteries

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Kang [Faculty of Material Science and Chemistry, China University of Geosciences, 388 Lumo Road, 430074 Wuhan (China); Wang, Shengping, E-mail: spwang@cug.edu.cn [Faculty of Material Science and Chemistry, China University of Geosciences, 388 Lumo Road, 430074 Wuhan (China); Zhang, Hanyu; Wu, Jinping [Faculty of Material Science and Chemistry, China University of Geosciences, 388 Lumo Road, 430074 Wuhan (China)

    2013-06-01

    Highlights: ► Micron-sized alumina was synthesized as adsorbent for lithium-sulfur batteries. ► Sulfur-alumina material was synthesized via crystallizing nucleation. ► The Al{sub 2}O{sub 3} can provide surface area for the deposition of Li{sub 2}S and Li{sub 2}S{sub 2}. ► The discharge capacity of the battery is improved during the first several cycles. - Abstract: Nano-sized sulfur particles exhibiting good adhesion with conducting acetylene black and alumina composite materials were synthesized by means of an evaporated solvent and a concentrated crystallization method for use as the cathodes of lithium-sulfur batteries. The composites were characterized and examined by X-ray diffraction, environmental scanning electron microscopy and electrochemical methods, such as cyclic voltammetry, electrical impedance spectroscopy and charge–discharge tests. Micron-sized flaky alumina was employed as an adsorbent for the cathode material. The initial discharge capacity of the cathode with the added alumina was 1171 mAh g{sup −1}, and the remaining capacity was 585 mAh g{sup −1} after 50 cycles at 0.25 mA cm{sup −2}. Compared with bare sulfur electrodes, the electrodes containing alumina showed an obviously superior cycle performance, confirming that alumina can contribute to reducing the dissolution of polysulfides into electrolytes during the sulfur charge–discharge process.

  7. Silicon carbide whisker-zirconia reinforced mullite and alumina ceramics

    Science.gov (United States)

    Becher, Paul F.; Tiegs, Terry N.

    1987-01-01

    The flexural strength and/or fracture toughness of SiC whisker-reinforced composites utilizing mullite or alumina as the matrix material for the composite are increased by the addition of zirconia in a monoclinic or tetragonal phase to the matrix. The zirconia addition also provides for a lower hot-pressing temperature and increases the flexural strength and/or fracture toughness of the SiC whisker-reinforced composites over SiC whisker-reinforced composites of the similar matrix materials reinforced with similar concentrations of SiC whiskers.

  8. New Method for the Development of Plasmonic Metal-Semiconductor Interface Layer: Polymer Composites with Reduced Energy Band Gap

    Directory of Open Access Journals (Sweden)

    Shujahadeen B. Aziz

    2017-01-01

    Full Text Available Silver nanoparticles within a host polymer of chitosan were synthesized by using in situ method. Ultraviolet-visible spectroscopy was then carried out for the prepared chitosan : silver triflate (CS : AgTf samples, showing a surface plasmonic resonance (SPR peak at 420 nm. To prepare polymer composites with reduced energy band gap, different amounts of alumina nanoparticles were incorporated into the CS : AgTf solution. In the present work, the results showed that the reduced silver nanoparticles and their adsorption on wide band gap alumina (Al2O3 particles are an excellent approach for the preparation of polymer composites with small optical band gaps. The optical dielectric loss parameter has been used to determine the band gap experimentally. The physics behind the optical dielectric loss were interpreted from the viewpoint of quantum mechanics. From the quantum-mechanics viewpoint, optical dielectric loss was also found to be a complex equation and required lengthy numerical computation. From the TEM investigation, the adsorption of silver nanoparticles on alumina has been observed. The optical micrograph images showed white spots (silver specks with different sizes on the surface of the films. The second semicircle in impedance Cole-Cole plots was found and attributed to the silver particles.

  9. Fabrication of aluminum-alumina metal matrix composites via cold gas dynamic spraying at low pressure followed by friction stir processing

    Energy Technology Data Exchange (ETDEWEB)

    Hodder, K.J.; Izadi, H. [Department of Chemical and Materials Engineering, University of Alberta, 7th Floor, Electrical and Computer Engineering Research Facility, Edmonton, Alberta, Canada T6G 2V4 (Canada); McDonald, A.G. [Department of Mechanical Engineering, University of Alberta, 4-9 Mechanical Engineering Building, Edmonton, Alberta, Canada T6G 2G8 (Canada); Gerlich, A.P., E-mail: agerlich@uwaterloo.ca [Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1 (Canada)

    2012-10-30

    Cold gas dynamic spraying at low pressure (1 MPa gage or 150 psig) was used to fabricate Al-Al{sub 2}O{sub 3} metal matrix composite (MMC) coatings onto 6061 Al alloy. The powder contained Al powder admixed with -10 {mu}m Al{sub 2}O{sub 3} in fractions up to 90 wt.%. Scanning electron microscopy (SEM), Vickers microhardness testing, and image analysis were conducted to determine the microstructure, properties, and volume fraction of reinforcing particles in the coatings. The coatings were then friction-stir processed (FSP) at tool rotation speeds of 894 or 1723 RPM using a flat cylindrical tool. The Al{sub 2}O{sub 3} content and hardness of the final MMC coatings increased with increasing fractions of Al{sub 2}O{sub 3} particles in the feedstock powder, resulting in a maximum Al{sub 2}O{sub 3} content of 48 wt.% and a hardness of 85 HV of the as-sprayed coating when 90 wt.% Al{sub 2}O{sub 3} was used in the feed powder blend. After FSP, the hardness of the MMC increased to a maximum of 137 HV. The as-sprayed coatings contained Al{sub 2}O{sub 3} particles that were segregated between the Al particles, and FSP was effective in dispersing these Al{sub 2}O{sub 3} particles and decreasing their mean free path. It was suggested that this re-distribution and Al{sub 2}O{sub 3} particle size refinement during FSP improved the hardness of the MMC coatings.

  10. Characterization of Potential Exposures to Nanoparticles and Fibers during Manufacturing and Recycling of Carbon Nanotube Reinforced Polypropylene Composites.

    Science.gov (United States)

    Boonruksa, Pongsit; Bello, Dhimiter; Zhang, Jinde; Isaacs, Jacqueline A; Mead, Joey L; Woskie, Susan R

    2016-01-01

    Carbon nanotube (CNT) polymer composites are widely used as raw materials in multiple industries because of their excellent properties. This expansion, however, is accompanied by realistic concerns over potential release of CNTs and associated nanoparticles during the manufacturing, recycling, use, and disposal of CNT composite products. Such data continue to be limited, especially with regards to post-processing of CNT-enabled products, recycling and handling of nanowaste, and end-of-life disposal. This study investigated for the first time airborne nanoparticle and fibers exposures during injection molding and recycling of CNT polypropylene composites (CNT-PP) relative to that of PP. Exposure characterization focused on source emissions during loading, melting, molding, grinding, and recycling of scrap material over 20 cycles and included real-time characterization of total particle number concentration and size distribution, nanoparticle and fiber morphology, and fiber concentrations near the operator. Total airborne nanoparticle concentration emitted during loading, melting, molding, and grinding of CNT-PP had geometric mean ranging from 1.2 × 10(3) to 4.3 × 10(5) particles cm(-3), with the highest exposures being up to 2.9 and 300.7 times above the background for injection molding and grinding, respectively. Most of these emissions were similar to PP synthesis. Melting and molding of CNT-PP and PP produced exclusively nanoparticles. Grinding of CNT-PP but not PP generated larger particles with encapsulated CNTs, particles with CNT extrusions, and respirable fiber (up to 0.2 fibers cm(-3)). No free CNTs were found in any of the processes. The number of recycling runs had no significant impact on exposures. Further research into the chemical composition of the emitted nanoparticles is warranted. In the meanwhile, exposure controls should be instituted during processing and recycling of CNT-PP. © The Author 2015. Published by Oxford University Press on behalf

  11. Composition tunable cobalt–nickel and cobalt–iron alloy nanoparticles below 10 nm synthesized using acetonated cobalt carbonyl

    NARCIS (Netherlands)

    van Schooneveld, Matti M.; Campos-Cuerva, Carlos; Pet, Jeroen; Meeldijk, Johannes D.; van Rijssel, Jos; Meijerink, Andries; Erne, Ben H.; de Groot, Frank M. F.

    A general organometallic route has been developed to synthesize CoxNi1-x and CoxFe1-x alloy nanoparticles with a fully tunable composition and a size of 4–10 nm with high yield. In contrast to previously reported synthesis methods using dicobalt octacarbonyl (Co2(CO)8), here the cobalt–cobalt bond

  12. Characterisation and thermal properties of titanium dioxide nanoparticles-containing biodegradable polylactide composites synthesized by sol–gel method

    CSIR Research Space (South Africa)

    Mhlanga, N

    2014-01-01

    Full Text Available This study reports the synthesis, characterisation and thermal properties of polylactide (PLA)/titanium dioxide nanoparticles (TiO(sub2) NPs) composites using the sol–gel method. The percentage weight of TiO(sub2) NP sol was varied from 3, 8, 11...

  13. Nanoparticle dispersion effect of laser-surface melting in ZrB{sub 2p}/6061Al composites

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Yida; Chao, Yuhjin; Luo, Zhen, E-mail: lz-tju@163.com [Tianjin University, School of Material Science and Engineering (China); Huang, Yongxian [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology (China)

    2017-04-15

    Zirconium diboride (ZrB{sub 2p}, 15 vol%)/6061 aluminum (Al) composites were fabricated via in situ reaction. The existence, morphologies, and dispersion degree of the in situ ZrB{sub 2} particles with size from tens to hundreds of nanometers were studied by X-ray diffractometry, energy-dispersive X-ray spectroscopy, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. As the particle-settlement effect becomes dominant during the composite fabrication process, ZrB{sub 2} nanoparticles agglomerate to a certain extent in some areas of the as-cast composites. A laser-surface melting (LSM) strategy was applied to disperse agglomerated ZrB{sub 2} nanoparticles in as-cast composites, and the ZrB{sub 2} nanoparticle dispersion is affected visibly by LSM. After LSM, nanoparticles tend to distribute along the grain boundary. Particle clusters were dispersed in an explosive orientation and the particle diffusion distance varied in terms of its radius and melt-viscosity vicinity. High-resolution transmission electron microscopy showed the existence of a subgrain structure near the ZrB{sub 2}–Al interface after LSM. This may increase the yield strength when a dislocation tangle forms.

  14. Nanoparticle dispersion effect of laser-surface melting in ZrB2p/6061Al composites

    International Nuclear Information System (INIS)

    Zeng, Yida; Chao, Yuhjin; Luo, Zhen; Huang, Yongxian

    2017-01-01

    Zirconium diboride (ZrB 2p , 15 vol%)/6061 aluminum (Al) composites were fabricated via in situ reaction. The existence, morphologies, and dispersion degree of the in situ ZrB 2 particles with size from tens to hundreds of nanometers were studied by X-ray diffractometry, energy-dispersive X-ray spectroscopy, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. As the particle-settlement effect becomes dominant during the composite fabrication process, ZrB 2 nanoparticles agglomerate to a certain extent in some areas of the as-cast composites. A laser-surface melting (LSM) strategy was applied to disperse agglomerated ZrB 2 nanoparticles in as-cast composites, and the ZrB 2 nanoparticle dispersion is affected visibly by LSM. After LSM, nanoparticles tend to distribute along the grain boundary. Particle clusters were dispersed in an explosive orientation and the particle diffusion distance varied in terms of its radius and melt-viscosity vicinity. High-resolution transmission electron microscopy showed the existence of a subgrain structure near the ZrB 2 –Al interface after LSM. This may increase the yield strength when a dislocation tangle forms.

  15. Gas chromatographic separation of hydrogen isotopes on columns packed with alumina, modified alumina and sol-gel alumina.

    Science.gov (United States)

    Naik, Y P; Gupta, N K; Pillai, K T; Rao, G A Rama; Venugopal, V

    2012-01-06

    The stationary phase of alumina adsorbents, prepared by different chemical processes, was used to study the separation behaviour of hydrogen isotopes. Three types of alumina, obtained by conventional hydroxide route alumina coated with silicon oxide and alumina prepared by internal gelation process (IGP), were used as packing material to study the separation of HT and T(2) in a mixture at various temperatures. The conventional alumina and silicon oxide coated alumina resolved HT and T(2) at 77K temperature with different retention times. The retention times on SiO(2) coated columns were found to be higher than those of other adsorbents. However, the column filled with IGP alumina was found to be ideal for the separation of HT and T(2) at 240 K. The peaks were well resolved in less than 5 min on this column. Copyright © 2011 Elsevier B.V. All rights reserved.

  16. Effective reduction of p-nitrophenol by silver nanoparticle loaded on magnetic Fe3O4/ATO nano-composite

    Science.gov (United States)

    Karki, Hem Prakash; Ojha, Devi Prashad; Joshi, Mahesh Kumar; Kim, Han Joo

    2018-03-01

    A silver loaded hematite (Fe3O4) and antimony doped tin oxide (ATO) magnetic nano-composite (Ag-Fe3O4/ATO) was successfully synthesized by in situ one pot green and facile hydrothermal process. The formation of nano-composite, its structure, morphology, and stability were characterized by field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), electron diffraction spectroscopy (EDS), elemental mapping by high resolution scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infra-red spectroscopy (FTIR). UV-vis spectroscopy was used to monitor the catalytic reduction of p-nitrophenol (PNP) into p-aminophenol (PAP) in presence of Ag-Fe3O4/ATO nano-composite with excess of sodium borohydride (NaBH4). The pseudo-first order kinetic equation could describe the reduction of p-nitrophenol with excess of NaBH4. For the first time, ATO surface was used for hydrothermal growth of silver and iron oxide magnetic nanoparticles. The in situ growth of these nanoparticles provided an effective bonding of components of the nano-composite over the surface of ATO nanoparticles. This nano-composite exhibited easy synthesis, high stability, cost effective and rapid separation using external magnet. The excellent catalytic and anti-bacterial activity of as-synthesized silver nano-composite makes it potential nano-catalyst for waste water treatment as well as biomedical application.

  17. Thermo-chemical characterization of a Al nanoparticle and NiO nanowire composite modified by Cu powder

    International Nuclear Information System (INIS)

    Bohlouli-Zanjani, Golnaz; Wen, John Z.; Hu, Anming; Persic, John; Ringuette, Sophie; Zhou, Y. Norman

    2013-01-01

    Highlights: • First study on the copper modified powder-type Al nanoparticle and NiO nanowire composites. • Experimental findings were unique in identifying the AlNi formation and comparing with the Al/CuO thermite. • Potential applications in material joining and bonding. - Abstract: Thermo-chemical properties of the Al nanoparticle and NiO nanowire composites modified by the micro-sized copper additive were investigated experimentally. Their onset temperatures of ignition and energy release data per mass were characterized using differential thermal analysis measurements. These microstructures and chemical compositions of reaction products were analyzed using scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The fuel-rich Al/NiO/Cu composites produced two types of metallic spheres. Copper spheres were formed from melting and solidification of the copper additive, while AlNi composite spheres were identified by the energy dispersive X-ray spectroscopy and X-ray diffraction analyses. It was found that the amount of the copper additive did not significantly influence the onset temperature of thermite peaks, but caused a dramatic change in energy release. The aforementioned ignition and energetic properties were compared with these from the Al nanoparticle and CuO nanowire composites

  18. Preparation of composite PMMA microbeads hybridized with fluorescent YVO{sub 4}:Bi{sup 3+},Eu{sup 3+} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Akisada, K; Noguchi, Y; Isobe, T, E-mail: isobe@applc.keio.ac.jp [Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)

    2011-10-29

    Poly(methyl methacrylate) (PMMA) microbeads are hybridized with fluorescent YVO{sub 4}:Bi{sup 3+},Eu{sup 3+} nanoparticles using the layer-by-layer adsorption technique. The composite beads A are prepared by adsorbing negatively-charged YVO{sub 4}:Bi{sup 3+},Eu{sup 3+} nanoparticles onto positively-charged PMMA beads modified with poly(allylamine hydrochloride) (PAH). The composite beads B are prepared by adsorbing nanoparticles onto PMMA beads with multiple alternate layers of PAH and poly(sodium 4-styrenesulfonate) (PSS), i.e., with (PAH/PSS){sub 4}/PAH layers. The composite beads C are prepared by adsorbing 300 deg. C heated nanoparticles with negative charge onto PMMA beads with single PAH layer. These three kinds of composite beads are compared in terms of the amount of adsorbed nanoparticles and the fluorescent intensity.

  19. Effect of Bi{sub 4}Ti{sub 3}O{sub 12} nanoparticles on the electroactive phase content of poly (vinylidene-difluoride) composite films

    Energy Technology Data Exchange (ETDEWEB)

    Bhardwaj, Sumit, E-mail: sumit.bhardwaj4@gmail.com [Centre for Materials Science and Engineering, National Institute of Technology, Hamirpur, H.P. 177005 India (India); Department of Materials and Metallurgical Engineering, PEC University of Technology, Chandigarh – 160012 (India); Chand, Subhash [Department of Physics, National Institute of Technology, Hamirpur, H.P. 177005 (India); Raina, K. K. [School of Physics and Materials Science, Thapar University, Patiala, Punjab -147004 (India); Kumar, Ravi [Centre for Materials Science and Engineering, National Institute of Technology, Hamirpur, H.P. 177005 India (India)

    2015-08-28

    Poly (vinylidene-difluoride) (PVDF) composite films with homogeneously dispersed Bi{sub 4}Ti{sub 3}O{sub 12} nanoparticles were synthesized by spin coating method from mixed solvent solutions. The effects of ferroelectric nanoparticles loading on the formation of α, β and γ phases of PVDF were studied using X-ray diffraction, infrared and Raman spectroscopy. The amount of the ferroelectric β and γ phases present in the composite films was found to increase with increased nanoparticles loading. We have shown that the formation of electroactive phases of PVDF with extended chain conformations can be enhanced by the addition of a well-dispersed nanoparticles loading.