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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. 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.

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

    Science.gov (United States)

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

    2012-03-01

    In the present work a nanocrystalline Ni-W metallic matrix was used to fabricate Ni-W/Al2O3 composite coatings. The MMC (metal matrix composite) coatings with inert α-Al2O3 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/Al2O3 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/Al2O3 composite coatings have been determined.

  4. Synthesis and mechanical behavior of carbon nanotube-magnesium composites hybridized with nanoparticles of alumina

    International Nuclear Information System (INIS)

    Carbon nanotubes reinforced magnesium based composites were prepared with diligence and care using the powder metallurgy route coupled with rapid microwave sintering. Nanometer-sized particles of alumina were used to hybridize the carbon nanotubes reinforcement in the magnesium matrix so as to establish the intrinsic influence of hybridization on mechanical behavior of the resultant composite material. The yield strength, tensile strength and strain-to-failure of the carbon nanotubes-magnesium composites were found to increase with the addition of nanometer-sized alumina particles to the composite matrix. Scanning electron microscopy observations of the fracture surfaces of the samples deformed and failed in uniaxial tension revealed the presence of cleavage-like features on the fracture surface indicative of the occurrence of locally brittle fracture mechanism in the composite microstructure

  5. Superhydrophobic Surface by Replication of Laser Micromachined Pattern in Epoxy/Alumina Nanoparticle Composite

    OpenAIRE

    2014-01-01

    Superhydrophobic surfaces were obtained by superposition of microstructure—defined by replication of laser micromachined masters, with nanostructure—created by durable epoxy/γ-Al2O3 nanoparticle composite, used for replication. Hierarchical surface topography thus obtained consisted of hexagonally spaced microcavities and nanoparticle agglomerates, exposed on the replica surface by radio frequency (RF) air plasma etching. Surface topography was further enhanced by rims around the microcavity ...

  6. Superhydrophobic Surface by Replication of Laser Micromachined Pattern in Epoxy/Alumina Nanoparticle Composite

    Directory of Open Access Journals (Sweden)

    Maciej Psarski

    2014-01-01

    Full Text Available Superhydrophobic surfaces were obtained by superposition of microstructure—defined by replication of laser micromachined masters, with nanostructure—created by durable epoxy/γ-Al2O3 nanoparticle composite, used for replication. Hierarchical surface topography thus obtained consisted of hexagonally spaced microcavities and nanoparticle agglomerates, exposed on the replica surface by radio frequency (RF air plasma etching. Surface topography was further enhanced by rims around the microcavity edges, resulting from nanosecond laser micromachining defects in aluminum masters. Subsequent wet chemical hydrophobization with 1H,1H,2H,2H-perfluorotetradecyltriethoxysilane (PFTDTES provided superhydrophobic behavior in replicas with a microcavity spacing of 30 μm, as indicated by a water contact angle of 160° and a sliding angle of 8°. The preparation method is relatively simple, inexpensive, and potentially scalable.

  7. 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.

  8. 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.

  9. Sintering behaviour of spinel–alumina composites

    Indian Academy of Sciences (India)

    Soumen Pal; A K Bandyopadhyay; P G Pal; S Mukherjee; B N Samaddar

    2009-04-01

    Study of alumina–magnesia binary phase diagram reveals that around 40–50 wt% 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 the exsolution of alumina makes some interlocking structures in between alumina and spinel phases. In the present investigation, refractory grade calcined alumina and spinel powder were used to make different batch compositions. Green pellets, formed at a pressure of 1550 kg cm-2 were fired at different temperatures of 1500°, 1550° and 1600°C for 2 h soaking time. Bulk density, percent apparent porosity, firing shrinkage etc were measured at each temperature. Sintering results were analysed to understand the mechanism of spinel–alumina interactions. SEM study of present samples does not reveal the distinct precipitation of needle shaped -alumina from spinel, but has some effect on densification process of spinel–alumina composites. Microstructural differences between present and previous work suggest an ample scope of further work in spinel–alumina composites.

  10. Processing and Performance of Alumina Fiber Reinforced Alumina Composites

    Institute of Scientific and Technical Information of China (English)

    P.Y.Lee; T.Uchijima; T.Yano

    2003-01-01

    Processing of alumina fiber-reinforced alumina matrix composites by hot-pressing was described. The mechanical properties of the composites fabricated by different sintering conditions including temperature and pressure have been investigated. The results indicated that the higher sintering temperature and pressure corresponded to the higher bulk density and higher maximum strength of the composite, whereas the pseudo-ductility of the composite was lower. The preliminary results of the composite with monazite-coated fibers showed that maximum strength could be improved up to 35% compared with the noncoated fiber composite in the same sintering condition. Moreover, the fracture behavior of the composite changed from completely brittle fracture to non-brittle fracture under the suitable sintering conditions. SEM observation of the fracture surface indicated that the coating worked as a protective barrier and avoided sintering of the fibers together even at high temperature and pressure during densification process.

  11. 40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Siloxane modified alumina... Specific Chemical Substances § 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this...

  12. Dynamic Tensile Response of Structured Alumina-Al Composites

    Science.gov (United States)

    Atisivan, Raj; Bandyopadhyay, Amit; Gupta, Yogendra

    2001-06-01

    Plate impact experiments were carried out to examine the high strain-rate tensile response of alumina-aluminum composites with tailored microstructures. A novel processing technique was used to fabricate interpenetrating phase alumina-aluminum composites with controlled and reproducible 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 will be discussed. Work supported by DOE.

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

    OpenAIRE

    Ben Hasan Somaya Ahmed; Dimitrijević Marija M.; Kojović Aleksandar; Stojanović Dušica B.; Obradović-Đuričić Kosovka; Jančić-Heinemann Radmila M.; Aleksić Radoslav

    2014-01-01

    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 m...

  14. MECHANICAL BEHAVIOUR OF ALUMINA-ZIRCONIA COMPOSITE BY SLURRY METHOD

    OpenAIRE

    JYOTI PRAKASH; DEVENDRA KUMAR; KALYANI MOHANTA

    2011-01-01

    Alumina has got some excellent properties like chemical inertness, thermal and mechanical strength against hazardous environment. Alumina is a good ceramic material which is being used for structuralapplications. To enhance the toughness and strength of the body some Zirconia is also used with it. The use of Zirconia in alumina is known as toughening of alumina. One difficulty arises, when alumina and alumina toughened composite are sintered , because the low sinterability of Alumina-Zirconia...

  15. 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.

  16. Superplastic properties of alumina-zirconia composites

    International Nuclear Information System (INIS)

    Superplastic deformation of two alumina-zirconia composites batches: the first with tetragonal ZrO2 stabilised with 3 mol.% Y2O3 and the second with ZrO2 stabilised with 2 mol.% Y2O3 (containing alumina volume fraction 10 - 86%) was studied. Grain sizes of two constituents were about 0.18-0.37 μm in the batch 1 and 0.36-0.14 μm in the batch 2. The composites were studied as a function of stress (20-130 MPa) and temperature (1451-1623 K) in compressive and bending tests. The strain rate was analysed in function of alumina volume fraction. It appeared that, the bigger than predicted by the rule of mixture strain rate decrease in function of alumina volume fraction is caused by improved creep resistance due to zirconium and yttrium ions doping of alumina grains. In zirconia grains modified interface-controlled Coble creep and simultaneously the intragranular dislocations motions contribute to the accommodation of grain boundary sliding (which is now thought to be main mechanism of superplastic behaviour). (author)

  17. Influence of Alumina Addition on the Optical Property of Zirconia/Alumina Composite Dental Ceramics

    Institute of Scientific and Technical Information of China (English)

    JIANG Li; LIAO Yunmao; LI Wei; WAN Qianbing; ZHAO Yongqi

    2011-01-01

    The influence of various alumina additions on the optical property of zirconia/alumina composite ceramics was investigated.The relative sintered densities,transmittances,color and the microstructure of the composite ceramics were studied.The experimental results showed that the relative sintered densities and transmittances decreased with alumina addition.The lightness increased obviously but the chroma change was small.Pure zirconia nanopowders sintered densely could obtain the relatively high transmittance,while the transmittance and the lightness of slight addition changed significantly.The zirconia/alumina composite ceramics with alumina addition less than 7.5wt% could achieve the relatively stable and reliable optical properties.

  18. Fracture toughness of advanced alumina ceramics and alumina matrix composites used for cutting tool edges

    OpenAIRE

    M. Szutkowska

    2012-01-01

    Purpose: Specific characteristics in fracture toughness measurements of advanced alumina ceramics and alumina matrix composites with particular reference to α-Al2O3, Al2O3-ZrO2, Al2O3-ZrO2-TiC and Al2O3-Ti(C,N) has been presented.Design/methodology/approach: The present study reports fracture toughness obtained by means of the conventional method and direct measurements of the Vickers crack length (DCM method) of selected tool ceramics based on alumina: pure alumina, alumina-zirconia composit...

  19. Alumina-based ceramic composite

    Science.gov (United States)

    Alexander, Kathleen B.; Tiegs, Terry N.; Becher, Paul F.; Waters, Shirley B.

    1996-01-01

    An improved ceramic composite comprising oxide ceramic particulates, nonoxide ceramic particulates selected from the group consisting of carbides, borides, nitrides of silicon and transition metals and mixtures thereof, and a ductile binder selected from the group consisting of metallic, intermetallic alloys and mixtures thereof is described. The ceramic composite is made by blending powders of the ceramic particulates and the ductile to form a mixture and consolidating the mixture of under conditions of temperature and pressure sufficient to produce a densified ceramic composite.

  20. 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

  1. Tribological properties of nanoscale alumina-zirconia composites

    NARCIS (Netherlands)

    Kerkwijk, B.; Winnubst, A.J.A.; Verweij, H.; Mulder, E.J.; Metselaar, H.S.C.; Schipper, D.J.

    1999-01-01

    The tribological properties of zirconia (Y-TZP), alumina and their composites, alumina dispersed in zirconia (ADZ) and zirconia-toughened alumina (ZTA), were investigated. These ceramics are made by colloidal processing methods such that well-defined, homogeneous microstructures with submicron grain

  2. MECHANICAL BEHAVIOUR OF ALUMINA-ZIRCONIA COMPOSITE BY SLURRY METHOD

    Directory of Open Access Journals (Sweden)

    JYOTI PRAKASH

    2011-02-01

    Full Text Available Alumina has got some excellent properties like chemical inertness, thermal and mechanical strength against hazardous environment. Alumina is a good ceramic material which is being used for structuralapplications. To enhance the toughness and strength of the body some Zirconia is also used with it. The use of Zirconia in alumina is known as toughening of alumina. One difficulty arises, when alumina and alumina toughened composite are sintered , because the low sinterability of Alumina-Zirconia forced the compact to give very low density body. To overcome this problem alumina and alumina composites are made from slurry method which gives nearly theoretical density. The combined effect of alumina and Zirconia on the phase transformation and microstructure development of heat-treated Alumina-Zirconia composites has been studied. Slurry is prepared by adding water, dispersant, binder and anti-foaming agent. In the present study, Sintering schedule is optimized and kept constant for all samples. After sintering, mechanical behaviour of the composite has been studied.

  3. A Novel Processing Route for Ni-doped Alumina Composites

    Institute of Scientific and Technical Information of China (English)

    JING Mao-xiang; SHEN Xiang-qian; ZHOU Jian-xin; LI Dong-hong; LI Wang-xing

    2006-01-01

    Alumina-based composites containing 0-15wt% Ni metallic phase were produced by hot press-sintering Ni-coated alumina powders. The Ni-coated alumina powders were prepared by the aqueous heterogeneous precipitation of alumina micro-powders and nickel sulfate salt followed by reduction process. The microstructural features and dispersion of Ni phase in Ni-coated alumina powders and the subsequent alumina-Ni cermets were investigated using scanning electron microscope (SEM), X-ray diffractometer (XRD), and transmission electron microscope (TEM). The relative density of the hot press-sintered composites was measured with the Archimedes' method while the fracture strength and the fracture toughness were defined with the three-point bending method and the micro-indentation fracture method. In the formation of alumina-Ni cermets from sintered Ni-coated alumina powders, Ni phase to some extent limits the densification rate and stifles the coarsening and growing process of alumina grains. The Ni phase is found to be located at the interfaces and the triple-joint junctions of alumina grains which results into alteration of the fracture mode of alumina and its increased fracture strength and fracture toughness if compared with monolithic alumina.

  4. Damping Behavior of Alumina Epoxy Nano-Composites

    Science.gov (United States)

    Katiyar, Priyanka; Kumar, Anand

    2016-05-01

    Polymer nano composites, consisting of a polymer matrix with nanoparticle filler, have been predicted to be one of the most beneficial applications of nanotechnology. Addition of nano particulates to a polymer matrix enhances its performance by capitalizing on the nature and properties of the nano-scale fillers. The damping behavior of composites with nano structured phases is significantly different from that of micro structured materials. Viscoelastic homopolymer exhibit a high material damping response over a relatively narrow range of temperature and frequencies. In many practical situations, a polymeric structure is required to possess better strength and stiffness properties together with a reasonable damping behavior. Viscoelastic polymers show higher loss factor beyond the glassy region which comes with a significant drop in the specific modulus. Addition of nano alumina particles to epoxy leads to improved strength and stiffness properties with an increase in glass transition temperature while retaining its damping capability. Experimental investigations are carried out on composite beam specimen fabricated with different compositions of alumina nano particles in epoxy to evaluate loss factor, tan δ. Impact damping method is used for time response analysis. A single point Laser is used to record the transverse displacement of a point on the composite beam specimen. The experimental results are compared with theoretical estimation of loss factor using Voigt estimation. The effect of inter phase is included in theoretical estimation of loss factor. The result reveals that the study of interface properties is very important in deriving the overall loss factor of the composite since interface occupies a significant volume fraction in the composite.

  5. Adsorptive removal of phenolic compounds using cellulose acetate phthalate–alumina nanoparticle mixed matrix membrane

    International Nuclear Information System (INIS)

    Highlights: • Composite membrane of cellulose–acetate–phthalate and alumina nanoparticle is cast. • Surface charge of the membrane changes with nanoparticle concentration and pH. • Separation of phenolic compounds occurs due to adsorption. • The removal efficiency is maximum for 20% nanoparticle with 91% removal of catechol. • Transmembrane pressure drop has negligible effect on solute separation. -- Abstract: Mixed matrix membranes (MMMs) were prepared using alumina nanoparticles and cellulose acetate phthalate (CAP) by varying concentration of nanoparticles in the range of 10 to 25 wt%. The membranes were characterized by scanning electron micrograph, porosity, permeability, molecular weight cut off, contact angle, surface zeta potential, mechanical strength. Addition of nanoparticles increased the porosity, permeability of the membrane up to 20 wt% of alumina. pH at point of zero charge of the membrane was 5.4. Zeta potential of the membrane became more negative up to 20 wt% of nanoparticles. Adsorption of phenolic derivatives, catechol, paranitrophenol, phenol, orthochloro phenol, metanitrophenol, by MMMs were investigated. Variation of rejection and permeate flux profiles were studied for different solutes as a function of various operating conditions, namely, solution pH, solute concentration in feed and transmembrane pressure drop. Difference in rejection of phenolic derivatives is consequence of interplay of surface charge and adsorption by alumina. Adsorption isotherm was fitted for different solutes and effects of pH were investigated. Catechol showed the maximum rejection 91% at solution pH 9. Addition of electrolyte reduced the rejection of solutes. Transmembrane pressure drop has insignificant effects on solute rejection. Competitive adsorption reduced the rejection of individual solute

  6. Adsorptive removal of phenolic compounds using cellulose acetate phthalate–alumina nanoparticle mixed matrix membrane

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Raka; De, Sirshendu, E-mail: sde@che.iitkgp.ernet.in

    2014-01-30

    Highlights: • Composite membrane of cellulose–acetate–phthalate and alumina nanoparticle is cast. • Surface charge of the membrane changes with nanoparticle concentration and pH. • Separation of phenolic compounds occurs due to adsorption. • The removal efficiency is maximum for 20% nanoparticle with 91% removal of catechol. • Transmembrane pressure drop has negligible effect on solute separation. -- Abstract: Mixed matrix membranes (MMMs) were prepared using alumina nanoparticles and cellulose acetate phthalate (CAP) by varying concentration of nanoparticles in the range of 10 to 25 wt%. The membranes were characterized by scanning electron micrograph, porosity, permeability, molecular weight cut off, contact angle, surface zeta potential, mechanical strength. Addition of nanoparticles increased the porosity, permeability of the membrane up to 20 wt% of alumina. pH at point of zero charge of the membrane was 5.4. Zeta potential of the membrane became more negative up to 20 wt% of nanoparticles. Adsorption of phenolic derivatives, catechol, paranitrophenol, phenol, orthochloro phenol, metanitrophenol, by MMMs were investigated. Variation of rejection and permeate flux profiles were studied for different solutes as a function of various operating conditions, namely, solution pH, solute concentration in feed and transmembrane pressure drop. Difference in rejection of phenolic derivatives is consequence of interplay of surface charge and adsorption by alumina. Adsorption isotherm was fitted for different solutes and effects of pH were investigated. Catechol showed the maximum rejection 91% at solution pH 9. Addition of electrolyte reduced the rejection of solutes. Transmembrane pressure drop has insignificant effects on solute rejection. Competitive adsorption reduced the rejection of individual solute.

  7. Textural stability of titania–alumina composite membranes

    NARCIS (Netherlands)

    Kumar, Krishnankutty-Nair P.; Keizer, Klaas; Burggraaf, Anthonie J.

    1993-01-01

    Textural evolution (porosity reduction, pore and crystallite growth) in titania–alumina composite membranes has been studied using thermal analysis, X-ray diffraction, field emission scanning electron microscopy and N2 physisorption techniques. The presence of alumina in the membranes improved the t

  8. Epitaxial growth of tungsten nanoparticles on alumina and spinel surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Suarez, T; Lopez-Esteban, S; Pecharroman, C; Esteban-Cubillo, A; Moya, J S [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), C/ Sor Juana Ines de la Cruz 3, 28049, Cantoblanco, Madrid (Spain); Diaz, L A; Torrecillas, R [Nanomaterials and Nanotechnology Research Center (CINN), Consejo Superior de Investigaciones CientIficas (CSIC), C/ Francisco Pintado Fe 26, 33011, Oviedo, Asturias (Spain); Gremillard, L [Universite de Lyon, INSA-Lyon, MATEIS, UMR CNRS 5510, 20 avenue Albert Einstein, Villeurbanne F-69621 (France)], E-mail: jsmoya@icmm.csic.es

    2008-05-28

    Isolated tungsten nanoparticles ({alpha}-W and {beta}-W phase) were synthesized and epitaxially grown on alumina and spinel particle surfaces with an average tungsten size of {<=}20 nm for a low tungsten content (of {<=}1.5 vol%). Using tungsten (VI) ethoxide alcoholic solutions, tungsten trioxide hydrated precursors were attached to a ceramic grains surface as a nanoparticle coating. High-resolution transmission electron microscopy (HRTEM) micrographs showed epitaxial interfaces between alumina, spinel and metallic tungsten. This epitaxial growth is assumed to be due to the effect of water vapour on the sublimation of ortho-tungstic acid during the reduction process in a hydrogen atmosphere. The planes involved in the epitaxy were found to be (22-bar 0){sub Al2O3} parallel (121){sub W} and (311){sub MgAl2O4} parallel (110){sub W}.

  9. The effects of alumina nanoparticle on the properties of an epoxy resin system

    International Nuclear Information System (INIS)

    The aim of this investigation is to determine the reinforcing effects of alumina nanoparticle in a diglycidyl ether of bisphenol A (DGEBA) type epoxy resin using different approaches based on in situ Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical, mechanical and microstructure measurements. From the kinetic analysis using the Avrami equation, it has been seen that the kinetic parameters are influenced by the presence of nanoparticle and the used curing temperatures. Differential scanning calorimetry was used to probe the changes in reactivity by analyzing the reaction heat and the glass transition temperature values of the cured composites owing to the presence of nanoparticle and due to the diamine hardener. It was also found that a relatively low concentration of Al2O3 nanoparticle led to an impressive improvement of dynamic mechanical, mechanical, and thermal properties. The scanning electron microscopy (SEM) photographs showed that the surface roughness increased with the addition of nanoalumina

  10. The effects of alumina nanoparticle on the properties of an epoxy resin system

    Energy Technology Data Exchange (ETDEWEB)

    Omrani, Abdollah [Faculty of Chemistry, University of Mazandaran, P.O. Box 453, Babolsar, Mazandaran (Iran, Islamic Republic of)], E-mail: omrani@umz.ac.ir; Simon, Leonardo C. [Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Rostami, Abbas A. [Faculty of Chemistry, University of Mazandaran, P.O. Box 453, Babolsar, Mazandaran (Iran, Islamic Republic of)

    2009-03-15

    The aim of this investigation is to determine the reinforcing effects of alumina nanoparticle in a diglycidyl ether of bisphenol A (DGEBA) type epoxy resin using different approaches based on in situ Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical, mechanical and microstructure measurements. From the kinetic analysis using the Avrami equation, it has been seen that the kinetic parameters are influenced by the presence of nanoparticle and the used curing temperatures. Differential scanning calorimetry was used to probe the changes in reactivity by analyzing the reaction heat and the glass transition temperature values of the cured composites owing to the presence of nanoparticle and due to the diamine hardener. It was also found that a relatively low concentration of Al{sub 2}O{sub 3} nanoparticle led to an impressive improvement of dynamic mechanical, mechanical, and thermal properties. The scanning electron microscopy (SEM) photographs showed that the surface roughness increased with the addition of nanoalumina.

  11. 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.

  12. 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)

  13. Enriched fluoride sorption using alumina/chitosan composite

    International Nuclear Information System (INIS)

    Alumina possesses an appreciable defluoridation capacity (DC) of 1566 mg F-/kg. In order to improve its DC, it is aimed to prepare alumina polymeric composites using the chitosan. Alumina/chitosan (AlCs) composite was prepared by incorporating alumina particles in the chitosan polymeric matrix, which can be made into any desired form viz., beads, candles and membranes. AlCs composite displayed a maximum DC of 3809 mg F-/kg than the alumina and chitosan (52 mg F-/kg). The fluoride removal studies were carried out in batch mode to optimize the equilibrium parameters viz., contact time, pH, co-anions and temperature. The equilibrium data was fitted with Freundlich and Langmuir isotherms to find the best fit for the sorption process. The calculated values of thermodynamic parameters indicate the nature of sorption. The surface characterisation of the sorbent was performed by FTIR, AFM and SEM with EDAX analysis. A possible mechanism of fluoride sorption by AlCs composite has been proposed. Suitability of AlCs composite at field conditions was tested with a field sample taken from a nearby fluoride-endemic village. This work provides a potential platform for the development of defluoridation technology.

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

    International Nuclear Information System (INIS)

    Graphene was oxidized with H2O2 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 H2O2 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

  15. Solvent mediated assembly of nanoparticles confined in mesoporous alumina.

    Energy Technology Data Exchange (ETDEWEB)

    Alvine, K. J.; Pontoni, D.; Shpyrko, O. G.; Pershan, P. S.; Cookson, D. J.; Shin, K.; Russell, T. P.; Brunnbauer, M.; Stellacci, F.; Gang, O.; BNL; Massachusetts Inst. of Tech.; Univ. of Massachusetts; Harvard Univ.; Univ. Massachusetts

    2006-01-01

    The controlled self-assembly of thiol stabilized gold nanocrystals in a mediating solvent and confined within mesoporous alumina was probed in situ with small angle x-ray scattering. The evolution of the self-assembly process was controlled reversibly via regulated changes in the amount of solvent condensed from an undersaturated vapor. Analysis indicated that the nanoparticles self-assembled into cylindrical monolayers within the porous template. Nanoparticle nearest-neighbor separation within the monolayer increased and the ordering decreased with the controlled addition of solvent. The process was reversible with the removal of solvent. Isotropic clusters of nanoparticles were also observed to form temporarily during desorption of the liquid solvent and disappeared upon complete removal of liquid. Measurements of the absorption and desorption of the solvent showed strong hysteresis upon thermal cycling. In addition, the capillary filling transition for the solvent in the nanoparticle-doped pores was shifted to larger chemical potential, relative to the liquid/vapor coexistence, by a factor of 4 as compared to the expected value for the same system without nanoparticles.

  16. Synthesis and Photoluminescence Enhancement of Silver Nanoparticles Decorated Porous Anodic Alumina

    Institute of Scientific and Technical Information of China (English)

    Song Ye; Yidong Hou; Renyi Zhu; Shulong Gu; Jingquan Wang; Zhiyou Zhang; Sha Shi; Jinglei Du

    2011-01-01

    Silver nanoparticles (Ag NPs) were successfully assembled in porous anodic alumina (AAO) templates via a green silver mirror reaction. The Ag NPs/AAO composite templates then were characterized by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray microanalysis (EDX), and X-ray diffraction (XRD). Furthermore, the photoluminescence (PL) properties were also investigated. Compared with the blank AAO, the PL intensity of Ag NPs/AAO templates are enhanced and the maximum enhancement is 2.58 times. Based on the local electric field enhancement effect, the theoretical values were also deduced, which are basically coincident with the experimental.

  17. Impact loading of an aluminum/alumina composite

    OpenAIRE

    Johnson, J.; Hixson, R.; Gray, G

    1994-01-01

    The combined demands of increased strength and reduced weight in modern dynamic structural applications require improved understanding of composite materials subject to impact conditions. In order to isolate and identify individual contributions to composite material behavior under these conditions, an experimental and theoretical program was undertaken to examine dynamic behavior of an aluminum/alumina composite consisting of a 6061-T6 aluminum matrix containing elastic, spherical Al2O3 incl...

  18. Alumina composites for oxide/oxide fibrous monoliths

    International Nuclear Information System (INIS)

    Most work on ceramic fibrous monoliths (FMs) has focused on the Si3N4/BN system. In an effort to develop oxidation-resistant FMs, several oxide systems have recently been examined. Zirconia-toughened alumina and alumina/mullite appear to be good candidates for the cell phase of FMs. These composites offer higher strength and toughness than pure alumina and good high-temperature stability. By combining these oxides, possibly with a weaker high-temperature oxide as the cell-boundary phase, it should be possible to product a strong, resilient FM that exhibits graceful failure. Several material combinations have been examined. Results on FM fabrication and microstructural development are presented

  19. Characterization and optical theory of nanometal/porous alumina composite membranes

    Science.gov (United States)

    Hornyak, Gabor Lajos

    Physical and optical characterization of nanometal/porous alumina composite membranes fabricated by means of the template method of synthesis are presented. The optical absorption spectra of experimental composites were modeled by effective medium theories based on Maxwell-Garnett (MG), Bruggeman (BG) and the recently developed dynamical Maxwell-Garnett (DMG) approximations. Although the primary purpose of this work was to study the optical properties of template synthesized metal nanostructured composites, in a complementary sense, a straightforward means of probing the nature of effective medium theories in general via template synthesized material composites was also accomplished. The composite membranes were comprised of two components: an insulating template host material, which consisted of anodically formed porous alumina, and a metallic filling factor, which was formed electrochemically in situ within the pore channels of the host membrane. The size and orientation of the nanometals conformed to the dimensional constraints imposed by the diameter and orientation of the pore channels of the alumina. Because the pore channels of aluminas used in this study were parallel, traversed the thickness of the membrane and packed in a hexagonal array, the metal nanoparticles fabricated in those channels were also parallel to and insulated from one another. Particle aspect ratio was controlled by the duration of electrodeposition. The metallic particles thus formed are colloidal (nanophasic) forms of their respective bulk material counterparts. The optical characterization of gold, silver and aluminum nanoparticles were investigated experimentally and theoretically. Composites containing gold-silver alloy and copper particles were also investigated but only by simulations. The composites containing gold nanoparticles demonstrated strong absorption maxima (lambdamax) in the visible part of the electromagnetic (EM) spectrum due to the electronic resonance of the surface

  20. Defect-free nanostructured alumina coating doped with noble metal nanoparticles

    International Nuclear Information System (INIS)

    Nanostructured alumina coatings loaded with platinum or gold nanoparticles were prepared by two different methods. In the first method the alumina coatings were prepared in the presence of metal ions, which were reduced using UV irradiation once the film was deposited. In the second method, polyvinylpyrrolidone-stabilized nanoparticles were first synthesized and then incorporated in the coating. The texturation of the coating occurred in a last step by hot water treatment.

  1. Processing and Mechanical Properties of Various Zirconia/Alumina Composites for Fuel Cell Applications

    Science.gov (United States)

    Choi, Sung R.; Bansal, Narottam P.

    2002-01-01

    Various electrolyte materials for solid oxide fuel cells were fabricated by hot pressing 10 mol% yttria-stabilized zirconia (10-YSZ) reinforced with two different forms of alumina, particulates and platelets, each containing 0 to 30 mol% alumina. Flexure strength and fracture toughness of both particulate and platelet composites at ambient temperature increased with increasing alumina content, reaching a maximum at 30 mot% alumina. For a given alumina content, strength of particulate composites was greater than that of platelet composites, whereas, the difference in fracture toughness between the two composite systems was negligible. No virtual difference in elastic modulus and density was observed for a given alumina content between particulate and platelet composites. Thermal cycling up to 10 cycles between 200 to 1000 C did not show any effect on strength degradation of the 30 mol% platelet composites, indicative of negligible influence of CTE mismatches between YSZ matrix and alumina grains.

  2. Aggregation and settling in aqueous polydisperse alumina nanoparticle suspensions

    CERN Document Server

    Witharana, Sanjeeva; Xu, Dan; Lai, Xiaojun; Ding, Yulong

    2012-01-01

    Nanoparticle suspensions (also called nanofluids) are often polydisperse and tend to settle with time. Settling kinetics in these systems are known to be complex and hence challenging to understand. In this work, polydisperse spherical alumina (Al2O3) nanoparticles in the size range of ~10-100nm were dispersed in water and examined for aggregation and settling behaviour near its isoelectric point (IEP). A series of settling experiments were conducted and the results were analysed by photography and by Small Angle X-ray Scattering (SAXS). The settling curve obtained from standard bed height measurement experiments indicated two different types of behaviour, both of which were also seen in the SAXS data. But the SAXS data were remarkably able to pick out the rapid settling regime as a result of the high temporal resolution (10s) used. By monitoring the SAXS intensity, it was further possible to record the particle aggregation process for the first time. Optical microscopy images were produced on drying and drie...

  3. Preparation and characterization of alpha alumina nanoparticles by in-flight oxidation of flame synthesis

    International Nuclear Information System (INIS)

    Highlights: • Flame synthesis is a compact approach for the synthesis of metal oxide nanoparticles. • Single phase alumina nanoparticles have been synthesized from commercial aluminium powders. • Spherical particle is confirmed by TEM analysis. • Photoluminescence study is discussed elaborately. -- Abstract: Alpha alumina nanoparticles were synthesized from micron-sized commercial aluminium powders by in-flight oxidation of flame synthesis. The synthesized alumina nanoparticles were characterized using X-ray diffraction (XRD) and α phase alumina was confirmed. The average grain sizes were estimated to be 98 nm using Scherer’s formula. The formation of alumina nanoparticles was identified by scanning electron microscopy (SEM). Transmission electron microscopy (TEM) study shows the different sized spherical nanoparticles ranging from 70 nm to 150 nm. The energy dispersive X-ray analysis (EDAX) confirms the presence of aluminium and oxygen in the α-Al2O3 nanoparticles. The Photoluminescence spectrum of α-Al2O3 nanoparticles reveals the presence of a large amount of oxygen vacancies

  4. Graphene reinforced alumina nano-composites

    Czech Academy of Sciences Publication Activity Database

    Porwal, H.; Tatarko, Peter; Grasso, S.; Khaliq, J.; Dlouhý, Ivo; Reece, M.J.

    2013-01-01

    Roč. 64, NOV (2013), s. 359-369. ISSN 0008-6223 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 EU Projects: European Commission(XE) 264526 - GLACERCO Institutional support: RVO:68081723 Keywords : fracture toughness determination * ceramic-matrix composites * carbon nano tubes Subject RIV: JI - Composite Material s Impact factor: 6.160, year: 2013

  5. Macroporous silica–alumina composites with mesoporous walls

    Indian Academy of Sciences (India)

    Gautam Gundiah

    2001-04-01

    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 mesopores has been verified by X-ray diffraction. The surface areas of the samples vary between 676 and 1038 m2g–1, with the highest value in the sample with Si/Al = 48.

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

    International Nuclear Information System (INIS)

    Alumina-zirconia composites with ZrO2 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 ZrO2 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-ZrO2, t-ZrO2). 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 Al2O3, 14-21 for m-ZrO2 and 40-45 for t-ZrO2. 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-ZrO2; in addition, the marked increase in loss with frequency becomes sharper. The t-ZrO2, which is responsible for strengthening, does not show any significant influence on losses. It is therefore concluded, that ZrO2 strengthening of alumina is feasible without affecting mm-wave losses at room temperature as long as the presence of m-ZrO2 is avoided

  7. Mechanical Properties and Fracture Behaviour of Multilayer Alumina Composites

    Institute of Scientific and Technical Information of China (English)

    ZHENG Xinguo; ZHAO Fei; ZHANG Jinyong

    2015-01-01

    Adopting a ceramic/polymer multilayer structure design to simulate the structure of nacre is usually believed to be an effective way to increase the toughness of ceramic composites at the expense of the material's bending strength. However, in this study, we found that both the bending strength and the toughness could be improved simultaneously when using a certain Al2O3/Kevlar multilayer composite design compared to pure alumina samples with the same dimensions. The fracture behaviour of the Al2O3/Kevlar multilayer composite was studied to ifnd a reason for this improvement. The results showed that the complex and asymmetrical stresses occurring in the Kevlar-reinforced layers were the main reason for the differences in fracture behaviour. We expect our results to open up new ways for the design of future high performance ceramic composites.

  8. 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

    Science.gov (United States)

    Pisarek, Marcin; Nowakowski, Robert; Kudelski, Andrzej; Holdynski, Marcin; Roguska, Agata; Janik-Czachor, Maria; Kurowska-Tabor, Elżbieta; Sulka, Grzegorz D.

    2015-12-01

    Self-organized Al2O3 nanoporous/nanotubular (Al2O3-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/Al2O3-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/Al2O3-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/cm2 - 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 the top of the largest pores is responsible for the highest SERS activity of the resulting Ag-NPs/Al2O3-NP/Al composite layer, since it produces a variety of cavities and slits which function as resonators for the adsorbed molecules. The Ag-NPs/MeOx-NP/Me composite layers obtained ensure a good reproducibility of the SERS measurements.

  9. 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

    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 in the...... 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....

  10. Development of nanoparticles of alumina by sol-gel method using inorganic aluminum salts as precursors

    International Nuclear Information System (INIS)

    Alumina nanoparticles were synthesized by homogeneous precipitation method from inorganic aluminum salt solutions using urea followed by calcination. The nanoparticles so produced were spherical and acicular with uniform particle size distribution. The process describes synthesis of aluminum hydroxide Al(OH)/sub 3 /and boehmite AIOOH, and their thermal decomposition into alumina (Al/sub 2/O/sub 3)/. The structural and morphological properties of the prepared aluminum hydroxide and Nan crystalline powders were characterized by scanning electron microscopy, differential thermal analysis and thermo gravimetric analysis. (author)

  11. Fracture behavior of monazite-coated alumina fiber-reinforced alumina-matrix composites at elevated temperature

    International Nuclear Information System (INIS)

    High-temperature strength, fracture behavior and microstructure were observed for monazite-coated alumina fiber-reinforced alumina matrix composites hot-pressed at 1200-1300degC. The composites with 27-41 vol% alumina fiber showed no significant change in strength at 25-1100degC. However, the strength of the composites decreased markedly at a test temperature higher than 1100degC. The composites hot-pressed at a temperature lower than 1250degC fractured in a pseudoductile manner in the test temperature range from 25degC to 1100degC. Young's modulus of the elastic region decreased with increasing test temperature. These composites showed larger deformation at a test temperature above 1100degC. On the other hand, the composites hot-pressed at more than 1250degC fractured in a brittle manner at 25degC-1200degC of test temperature. The fracture energy of the composite increased with increasing test temperature and decreased with sintering temperature. (author)

  12. Coating hydroxyapatite/alpha alumina composites by mechanical alloying

    International Nuclear Information System (INIS)

    The biomaterials field has become a vital area, as these materials can enhance the quality and longevity of human life and science and technology associated with this field has now led to multi-million dollar business. Hydroxyapatite [Ca10(PO4)6(OH)2-HA] and alumina ceramics materials have been clinically applied in many areas of dentistry and orthopaedics. Their widespread use is based on a combination of good strength, modest fracture toughness, high wear resistance, good biocompatibility and excellent corrosion resistance. Alumina has also been used in jaw bone reconstruction. Other clinical applications include knee prostheses, bone segment replacements, bone screws, middle ear bone substitutes, and corneal replacements. Optimization of the surface structure of materials is of great concern at the present time since most failures occur on the surface (fatigue, fretting corrosion, corrosion, wear, etc.). As a result, improving the surface properties would greatly enhance the overall behaviour of materials. It is widely recognized that titanium displays poor wear resistance and that its fatigue performance depends to a large extent on its surface properties. The newly developed process, mechanical alloying MA, is therefore of considerable technological importance since it provides the possibility of dramatically improving the surface properties of titanium. Presented work describes the effect of MA treatment, as a non-conventional solid-state process, on the microstructure of IA/α-Al2O3 composites. Also, the necessary conditions for coating HA/α- Al2O3 composites on Ti-substrate were examined. To make HA and Al2O3 composites, α-Al2O3 powder was used because of its better sinterability than γ-AI2O3. HA/α-Al2O3 was successfully deposited on Ti-substrate by mechanical alloying (MA). From the X-Ray Diffraction (XRD) the as-synthesized and heat treated samples between 300C and 600C have not any phase transition or decomposition. From the scanning electron

  13. 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.

  14. 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.

  15. Effects of composition on the mechanical response of alumina-filled epoxy.

    Energy Technology Data Exchange (ETDEWEB)

    Montgomery, Stephen Tedford

    2009-10-01

    The effect of composition on the elastic responses of alumina particle-filled epoxy composites is examined using isotropic elastic response models relating the average stresses and strains in a discretely reinforced composite material consisting of perfectly bonded and uniformly distributed particles in a solid isotropic elastic matrix. Responses for small elastic deformations and large hydrostatic and plane-strain compressions are considered. The response model for small elastic deformations depends on known elastic properties of the matrix and particles, the volume fraction of the particles, and two additional material properties that reflect the composition and microstructure of the composite material. These two material properties, called strain concentration coefficients, are characterized for eleven alumina-filled epoxy composites. It is found that while the strain concentration coefficients depend strongly on the volume fraction of alumina particles, no significant dependence on particle morphology and size is observed for the compositions examined. Additionally, an analysis of the strain concentration coefficients reveals a remarkably simple dependency on the alumina volume fraction. Responses for large hydrostatic and plane-strain compressions are obtained by generalizing the equations developed for small deformation, and letting the alumina volume fraction in the composite increase with compression. The large compression plane-strain response model is shown to predict equilibrium Hugoniot states in alumina-filled epoxy compositions remarkably well.

  16. Mechanical Properties of a Graded Alumina-Zirconia Composite Prepared by Centrifugal Slip Casting

    International Nuclear Information System (INIS)

    Compositionally graded composite of alumina-20 vol%zirconia was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the centrifugal direction; zirconia tended to accumulate in the bottom section, while alumina in the top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thicknesss

  17. Mechanical Properties of a Graded Alumina-Zirconia Composite Prepared by Centrifugal Slip Casting

    Science.gov (United States)

    Hara, Yasuyuki; Onda, Tetsuhiko; Hayakawa, Motozo

    2008-02-01

    Compositionally graded composite of alumina-20 vol%zirconia was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the centrifugal direction; zirconia tended to accumulate in the bottom section, while alumina in the top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thicknesss

  18. 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.

  19. Research on toughening mechanisms of alumina matrix ceramic composite materials improved by rare earth additive

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xihua; LIU Changxia; LI Musen; ZHANG Jianhua

    2008-01-01

    Mixed rare earth elements were incorporated into alumina ceramic materials. Hot-pressing was used to fabricate alumina matrix composites in nitrogen atmosphere protection. Microstructures and mechanical properties of the composites were tested. It was indicated that the bending strength and fracture toughness of alumina matrix ceramic composites sintered at 1550℃ and 28 Mpa for 30 min were improved evidently. Besides mixed rare earth elements acting as a toughening phase, AlTiC master alloys were also added in as sintering assistants, which could prompt the formation of transient liquid phase, and thus nitrides of rare earth elements were produced. All of the above were beneficial for improving the mechanical properties of alumina matrix ceramic composites.

  20. [Research on bending strength and fracture toughness of alumina-glass composite].

    Science.gov (United States)

    Luo, X; Zhao, Y; Tian, J; Chao, Y; Zhang, S; Zhang, Y

    1998-12-01

    To develop a new ceramic material that can be machined and infiltrated with glass, a porous alumina blank sintered at 1350 degrees C was made of high purity, super fine alpha-alumina and then infiltrated with glass in this study. The density, bending strength and fracture toughness of the partially sintered alumina and alumina-glass composite were determined. The results indicated that the porous alumina density was 2.12 g/cm3, the three point bending strength 102 MPa, the fracture toughness 1.61 MPam1/2; that the alumina-glass composite density was 3.85 g/cm3, the three point bending strength 385 MPa, and the fracture toughness 4.05 MPam1/2. By SEM and EDXA analysis, lanthanum boroslicate glass was completely infiltrated into the 3 mm thick porous alumina blank for 6 h at 1150 degrees C. These suggest that the new developed alumina blank is suited for clinical use. PMID:10743233

  1. Charge-induced reversible bending in nanoporous alumina-aluminum composite

    Science.gov (United States)

    Cheng, Chuan; Ngan, A. H. W.

    2013-05-01

    Upon electrical charging, reversible bending was found in nanoporous anodic alumina-aluminum foil composites, as directly observed by an optical microscope and detected by in situ nanoindentation. The bending is thought to be the result of charge-induced surface stresses in the nanoporous alumina. The results suggest the possibility of a type of composite foil materials for applications as micro-scale actuators to transform electrical energy into mechanical energy.

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

    International Nuclear Information System (INIS)

    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).

  3. Reinforcing and toughening alumina/titania ceramic composites with nano-dopants from nanostructured composite powders

    International Nuclear Information System (INIS)

    Nanostructured alumina/titania composite powders were prepared using nanosized alumina and titania doped with nanosized zirconia and ceria through ball-milling, spray drying and heat treating. The nanostructured reconstituted powders were then cool isostatic pressed and pressureless sintered into bulk ceramic composites. The phase constitution and microstructures of as-prepared ceramic composites were characterized by using X-ray diffractometer and scanning electron microscope. The mechanical properties of the ceramic composites were evaluated by Vickers hardness test, flexural strength test and fracture toughness test. The effects of nano-dopants and sintering temperatures on the microstructures and mechanical properties of the composites were investigated. It was found that nano-dopants had the effects of lowering sintering temperature, accelerating densification, reinforcing and toughening the composites. The maximum flexural strength, fracture toughness and Vickers hardness of the composites with nano-dopants were 51, 20 and 56% higher than that of the composites without nano-dopants. The reinforcing and toughening mechanisms are discussed in detail.

  4. Glycine functionalized alumina nanoparticles stabilize collagen in ethanol medium

    Indian Academy of Sciences (India)

    S Prabhu; K Cheirmadurai; J Raghava Rao; P Thanikaivelan

    2016-02-01

    The synthesis of glycine functionalized Al$_2$O$_3$ nanoparticles (Gly@Al$_2$O$_3$) by a simple two-step process employing sucrose as a template was reported. The functionalization of Al$_2$O$_3$ nanoparticles with glycine was confirmed by Fourier transformed infrared (FT-IR) spectroscopy, X-ray diffraction, high-resolution scanning electron microscopy (HRSEM) and energy-dispersive X-ray (EDX) analysis. The interaction of Gly@Al$_2$O$_3$ nanoparticles 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@Al$_2$O$_3$ nanoparticles thereby suggesting applications in leather making, biomedicine and cosmetic fields.

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

    Energy Technology Data Exchange (ETDEWEB)

    Góral, Anna, E-mail: a.goral@imim.pl [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 Reymonta St., 30-059 Krakow (Poland); Nowak, Marek [Institute of Non-Ferrous Metals Gliwice, Light Metals Division Skawina, 19 Pilsudskiego St., 32-050 Skawina (Poland); Berent, Katarzyna; Kania, Bogusz [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 Reymonta St., 30-059 Krakow (Poland)

    2014-12-05

    Highlights: • Current density of the electrodeposition affects the incorporation of Al{sub 2}O{sub 3} in Ni matrix. • Ni/Al{sub 2}O{sub 3} composite coatings exhibit changes in crystallographic texture. • The pitting corrosion effects were observed in Ni/Al{sub 2}O{sub 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{sub 2}O{sub 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{sub 2}O{sub 3} particles show a distinct tendency to form agglomerates, approximately uniformly distributed into the nickel matrix.

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

    International Nuclear Information System (INIS)

    Highlights: • Current density of the electrodeposition affects the incorporation of Al2O3 in Ni matrix. • Ni/Al2O3 composite coatings exhibit changes in crystallographic texture. • The pitting corrosion effects were observed in Ni/Al2O3 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-Al2O3 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-Al2O3 particles show a distinct tendency to form agglomerates, approximately uniformly distributed into the nickel matrix

  7. Strengthening mechanisms and fracture surface characteristics of silicate glass matrix composites with inclusion of alumina particles of different particle sizes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Minghui, E-mail: mhchen@imr.ac.cn [State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Zhu, Shenglong; Wang, Fuhui [State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2013-03-15

    Strengthening mechanisms of silicate glass by the inclusion of alumina particles of different volume fractions and different particle sizes are reported. The formulas of three responsible strengthening mechanisms, based on inclusion/crack interactions and interfacial elemental diffusion, were deduced; these include crack deflection, crack bridging and interdiffusion. The strength of the glass/alumina composites increased with inclusion fraction, but followed strengthening mechanisms that varied with alumina particle size. Crack deflection and bridging mechanisms dominated in strengthening for the glass/alumina (at mean particle size of 6 μm) composites while interdiffusion mechanism played a major role in the glass/alumina (at mean particle size of 1 μm) composites. The theoretical deduction of strengthening mechanisms depending on the particle size of alumina inclusions was demonstrated by the experimental strength data and fracture surface characteristics of the glass/alumina composites.

  8. Strengthening mechanisms and fracture surface characteristics of silicate glass matrix composites with inclusion of alumina particles of different particle sizes

    International Nuclear Information System (INIS)

    Strengthening mechanisms of silicate glass by the inclusion of alumina particles of different volume fractions and different particle sizes are reported. The formulas of three responsible strengthening mechanisms, based on inclusion/crack interactions and interfacial elemental diffusion, were deduced; these include crack deflection, crack bridging and interdiffusion. The strength of the glass/alumina composites increased with inclusion fraction, but followed strengthening mechanisms that varied with alumina particle size. Crack deflection and bridging mechanisms dominated in strengthening for the glass/alumina (at mean particle size of 6 μm) composites while interdiffusion mechanism played a major role in the glass/alumina (at mean particle size of 1 μm) composites. The theoretical deduction of strengthening mechanisms depending on the particle size of alumina inclusions was demonstrated by the experimental strength data and fracture surface characteristics of the glass/alumina composites

  9. Manufacturing of high-strength aluminum/alumina composite by accumulative roll bonding

    International Nuclear Information System (INIS)

    The ARB process used as a technique in this study provides an effective alternative method for manufacturing high-strength aluminum/alumina composites. The microstructural evolution and mechanical properties of the aluminum/15 vol.% alumina composite are reported. The composite shows an excellent alumina particle distribution in the matrix. It is found that by increasing the number of ARB cycles, not only does elongation increase in the composites produced but also the tensile strength of the Al/15 vol.% Al2O3 composite improves by 4 times compared to that of the annealed aluminum used as the original raw material. Fracture surfaces after tensile tests are observed by scanning electron microscopy (SEM) to investigate the failure mode. Observations reveal that the failure mode in both ARB-processed composites and monolithic aluminum is of the shear ductile rupture type.

  10. Phase transformations in spray-dried alumina-zirconia composite powders

    International Nuclear Information System (INIS)

    Hydrated alumina-zirconia composite powders containing 7.5, 10.0, 12.5 wt % zirconia in the final oxidized state were prepared by spray-drying the inorganic salt derived gels. These gels were prepared by hydrolysing the metals salts with ammonia. The average particle size and surface area of this powder is found to be 6 microns and 6.92 m2/g respectively. Infrared spectra reveals the presence of adhesive water. In order to evaluate the phase transformation temperature, the powder samples were calcined at different temperatures ranging from 650 to 1500 degC for 30 minutes. X-ray diffraction patterns of the spay-dried as well as the calcined powders up to 850 degC revealed the powders are amorphous. Crystallized phases started forming after 900 degC and the first crystallized phase is tetragonal zirconia. Broad peaks of Θ-alumina were also found. This tetragonal phase is retained even after the treatment at 1500 degC. Some amount of Θ-alumina is transformed into α-alumina after 1000 degC, and this transformation is over by the formation of well crystallized α-alumina after 1300 degC. A comparison made with pure alumina shows that the presence of zirconia retards the formation of α-alumina, since pure alumina powder contains only α-alumina, after 950 degC treatment. The increasing amount of zirconia has no profound influence on this effect in the compositions studied. Differential thermal analysis (DTA) and thermal gravimetric analysis (TGA) were also used as a complement to the x-ray diffraction in determining the transformation temperature. (author). 12 refs., 7 figs

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

    International Nuclear Information System (INIS)

    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.

  12. Deposition of palladium nanoparticles on the pore walls of anodic alumina using sequential electroless deposition

    International Nuclear Information System (INIS)

    Palladium nanoparticles were deposited using a sequential electroless deposition technique on the pore walls of nanoporous anodic alumina. For the particle deposition a Pd(NH3)42+ solution was soaked in the alumina membrane and a heated air flow was applied in order to reduce the palladium complex to palladium metal nanoparticles. By repeating the deposition process the size of the nanoparticles could be tailored in this investigation between 6 and 11 nm. The size of the nanoparticles was also affected by the concentration of the Pd(NH3)42+ solution, i.e., higher concentration yielded larger particle mean diameters. The samples were investigated using high resolution scanning electron microscopy, x-ray diffraction (XRD), inductively coupled plasma with a mass spectrometer, high resolution transmission electron microscopy, and energy dispersive spectroscopy (EDS). Analysis revealed narrow size distributions of the particles as well as uniform particle coverage of the pore walls. No by-products were observed with EDS, and with the XRD analysis the metallic palladium crystallinity was confirmed

  13. Prediction of fracture characteristic of particle-reinforced alumina-based composites

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Residual microstresses in particle reinforced alumina/SiC and alumina/mullite composites were calcu- lated. The results indicated that there existed a linear relation between matrix microstresses and the particle contents in the composites. The influence of stress state on crack propagating and grain boundary strengthening was analyzed. Ratios of grain boundary toughness to grain toughness of these composites were calculated in view of microstress analysis, and percentage of transgranular fracture (PTF) that increases with the microstress in the alumina matrix was then deduced. The relationship between microstructure, component, matrix microstresses, and PTF was established. Therefore, the fracture characteristic was predicted on basis of the particle content and distribution in addition to the microstructure of the composites.

  14. 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

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

    DEFF Research Database (Denmark)

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

    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......, petroleum coke or biomass. The development of new catalysts is given a very high priority since they facilitate a much better utilization of our scarce energy reserves and it can drive the concept of waste-free ‘green’ chemistry and the development of a sustainable energy sector. Metal oxide surfaces like...... electrically 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...

  16. A new approach to copper ion removal from water by polymeric nanocomposite membrane embedded with γ-alumina nanoparticles

    Science.gov (United States)

    Ghaemi, Negin

    2016-02-01

    The ability of alumina (Al2O3) nanoparticles in adsorption of heavy metals was employed in improving the copper removal efficiency of PES membranes. Mixed matrix membranes were prepared using PES and different amounts of alumina nanoparticles by phase inversion method. The fabricated membranes were characterized in terms of morphology and performance using scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses, water contact angle and porosity measurements, determination of pure water flux, copper ion removal, and reusability test. Mixed matrix membranes revealed higher water permeation compared with the pristine PES membrane just by adding small amounts of nanoparticles (≤ 1.0 wt. %) as a result of increasing the membrane porosity and hydrophilicity after addition of alumina nanoparticles into the membrane matrix. Moreover, copper ion removal efficiency of alumina mixed membranes was improved. Membrane performance tests as well as adsorptive nature of alumina nanoparticles proposed that adsorption was the most possible separation mechanism by mixed matrix membranes. Reusability test of membrane confirmed the durability of removal efficiency even after four cycles of filtration.

  17. Influence of Surface Modification of Alumina on Improvement of Wetability in Aluminium Matrix Composite

    Directory of Open Access Journals (Sweden)

    Alireza Samiee

    2014-01-01

    Full Text Available In this research, aluminium powder (50 wt% and alumina (50 wt% were first milled at a specific ball-to-powder ratio in a high-energy planetary mill at different times to manufacture Al-Al2O3 composite. Then, the capsules of powdery composites (Al-Al2O3CP produced at the milling stage were added to aluminium melt and cast through ex situ. Scanning electron microscope SEM was used to study the morphology of the capsules and the microstructure of the produced composite. The percentage of powdery composite capsules and reinforcing particles present in the microstructure of Al-Al2O3 composite was measured by Image Tool software. The results of the tests showed that, by optimizing the milling time to 5 hours, the alumina particles are sufficiently placed in the matrix of the capsules; on the other hand, alumina particles are also properly coated with aluminium powder. When these capsules are added to aluminium melt, the rate of the wetting of alumina particles greatly increases and accordingly the percentage of the reinforcing particles in the cast composite matrix increases dramatically. By surface modification and accordingly increasing percentage of Al2O3, the tensile strength increases and the tensile strength of the composites is higher than that of the matrix alloy.

  18. Deformation of an alumina-zirconia-silicon carbide-whisker reinforced composite

    Energy Technology Data Exchange (ETDEWEB)

    Calderon-Moreno, J.M.; DeArellano-Lopez, A.R.; Dominguez-Rodriguez, A. [Seville Univ. (Spain). Dept. de Fisica de La Materia Condensada; Routbort, J.L. [Argonne National Lab., IL (United States); Leasky, T. [Materials and Electrochemical Research Corp., Tucson, AZ (United States)

    1993-04-01

    Alumina-zirconia composites (MERC) with the addition of 0 and 28 vol % of silicon carbide whiskers have been deformed under compression at constant rate at 1450C, in air. Mechanical results are compared with the behavior of a commercial alumina (ARCO) with analogous proportions of silicon carbide-whiskers (0 and 30 vol %), under the same testing conditions. Flow stresses are typically higher for ARCO materials than for MERC materials. The addition of SiC whiskers increases flow stresses in ARCO composites, and decreases them for MERC samples. Microstructural observations confirm that the change in flow stress is the result of the presence of a glass phase in the MERC samples.

  19. Shock-loading response of 6061-T6 aluminum-alumina metal-matrix composites

    OpenAIRE

    Vecchio, K.; Gray, G

    1994-01-01

    The purpose of this research is to systematically study the influence of peak-shock pressure and second-phase reinforcement on the structure/property response of shock-loaded 6061-T6 Al-alumina composites. The reload stress-strain response of monolithic 6061-T6 Al showed no increased shock hardening compared to the unshocked material deformed to an equivalent strain. The reload stress-strain response of the shock-loaded 6061-T6 Al-alumina composites exhibits a lower reload yield strength than...

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

    International Nuclear Information System (INIS)

    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

  1. Influence of the alumina microstructure and composition in thermoluminescence for using in dosimetry

    CERN Document Server

    Silva, M R

    2001-01-01

    Among its various applications alumina may be used in thermoluminescent dosimeters (TLD) to radiations. The TLD are commonly used to determine the absorbed doses of radiation received in many application fields as nuclear installations, radiodiagnostic and radiotherapy in medicine. In this work it was developed a study of the influence of the microstructure, grain size and composition on the thermoluminescent properties in alumina (pure and carbon doped). The alumina and carbon powders used as starting materials were characterized by x-ray diffraction (XRD), chemical analysis, particle size distribution and surface area were determined by and BET analysis, respectively. The Al sub 2 O sub 3 samples were sintered at 1650 deg C in air for one, three, five, seven and ten hours. The carbon doped samples were sintered using the same temperature for one hour, in a graphite resistance furnace in argon. Sintered materials were further characterised for phase composition and microstructure by XRD and scanning electron...

  2. Effect of chemical composition and alumina content on structure and properties of ceramic insulators

    Indian Academy of Sciences (India)

    Arman Sedghi; Nastaran Riahi-Noori; Naser Hamidnezhad; Mohammad Reza Salmani

    2014-04-01

    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 sample microstructures, samples were analyzed by scanning electron microscope (SEM) and x-ray diffraction (XRD) techniques. The results showed that, with chemical composition of 53.5 wt.% SiO2 and 37.5 wt.% alumina, highest electrical strength of 21.97 kV/mm was achieved in fabricated electrical porcelains. Increasing amount of alumina up to 30 wt.% decreases quartz and cristobalite phases, but increases corundum phase 3 to 5 times. SEM observation revealed that dense particles and uniform distribution of long and thin needle shaped mullite are predominant in sample microstructures with highest electrical strength.

  3. High Porosity Alumina as Matrix Material for Composites of Al-Mg Alloys

    International Nuclear Information System (INIS)

    The sophisticated industry and technologies require higher and higher assumptions against mechanical strength and surface hardness of ceramic reinforced metal alloys and metal matrix composites. Applying the well-known alumina powders by dry pressing technology and some special pore-forming additives and sintering technology the authors have successfully developed a new, high porosity alumina matrix material for composites of advenced Al-Mg alloys. The developed new matrix material have higher than 30% porosity, with homogenous porous structure and pore sizes from few nano up to 2–3 mm depending on the alloys containments. Thanks to the used materials and the sintering conditions the authors could decrease the wetting angles less than 90° between the high porosity alumina matrix and the Al-Mg alloys. Applied analytical methods in this research were laser granulometry, scanning electron microscopy, and X-ray diffraction. Digital image analysis was applied to microscopy results, to enhance the results of transformation

  4. Structural Characterization and Property Study on the Activated Alumina-activated Carbon Composite Material

    Institute of Scientific and Technical Information of China (English)

    CHEN Yan-Qing; WU Ren-Ping; YE Xian-Feng

    2012-01-01

    AlCl3,NH3·H2O,HNO3 and activated carbon were used as raw materials to prepare one new type of activated alumina-activated carbon composite material.The influence of heat treatment conditions on the structure and property of this material was discussed;The microstructures of the composite material were characterized by XRD,SEM,BET techniques;and its formaldehyde adsorption characteristic was also tested.The results showed that the optimal heat treatment temperature of the activated alumina-activated carbon composite material was 450 ℃,iodine adsorption value was 441.40 mg/g,compressive strength was 44 N,specific surface area was 360.07 m2/g,average pore size was 2.91 nm,and pore volume was 0.26 m3/g.According to the BET pore size distribution diagram,the composite material has dual-pore size distribution structure,the micro-pore distributes in the range of 0.6-1.7 nm,and the meso-pore in the range of 3.0-8.0 nm.The formaldehyde adsorption effect of the activated alumina-activated carbon composite material was excellent,much better than that of the pure activated carbon or activated alumina,and its saturated adsorption capacity was 284.19 mg/g.

  5. Preparation of white alumina spherical composite magnetic abrasive by gas atomization and rapid solidification

    International Nuclear Information System (INIS)

    White alumina (WA) spherical composite magnetic abrasive can be prepared directly by a process that combines gas atomization and rapid solidification. The structure and phase composition of this material were characterized by scanning electron microscopy and X-ray diffraction analysis. The results show that the composite magnetic abrasive has good sphericity, and the WA grains are tightly embedded uniformly and densely into the surface layer of matrix which consists of Fe-Si-Al-Ni soft magnetic alloy.

  6. Evaluation of Activation Energy (Ea) Profiles of Nanostructured Alumina Polycarbonate Composite Insulation Materials

    OpenAIRE

    Sudha L. K.; Sukumar Roy; K. Uma Rao

    2014-01-01

    This paper focuses enhancement of the electrical insulation properties of commercial polycarbonate using nanostructured alumina as an additive material. Various polycarbonate composites have been prepared by varying the level of additive material and DC conductivity in presence of oxygen of the derived composite materials has been measured in which activation energy (Ea) profiles of the composites have been evaluated. Results show that the incorporation of additive significantly reduces the E...

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

    OpenAIRE

    Justyna Zygmuntowicz; Aleksandra Miazga; Katarzyna Konopka; Katarzyna Jedrysiak; Waldemar Kaszuwara

    2015-01-01

    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 a...

  8. Preparation of alumina-zirconia composites containing microfibers

    Czech Academy of Sciences Publication Activity Database

    Hadraba, Hynek; Chlup, Zdeněk; Drdlík, D.

    Bratislava: Slovenská akademie věd, 2015 - (Lenčéš, Z.; Valúchová, J.). s. 73-73 ISBN 978-80-971648-3-6. [Engineering Ceramics 2015. 10.05.2015-14.05.2015, Smolenice castle] R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068; GA ČR(CZ) GA15-06390S Institutional support: RVO:68081723 Keywords : alumina * zirconia * fibres * laminates * electrophoretic deposition Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

  9. Mechanical properties of dense to porous alumina/lanthanum hexaaluminate composite ceramics

    International Nuclear Information System (INIS)

    For development of new composite materials based on lanthanum hexaaluminate and alumina ceramics, a better understanding of the microstructure-properties relationship is essential. In this paper, attention was focused on the evaluation of mechanical properties of lanthanum hexaaluminate/alumina particulate composite. It was found out that the lanthanum hexaaluminate content plays a critical role in determination of the microstructure and mechanical properties of the composite ceramics. In situ formation of plate-like lanthanum hexaaluminate in the ceramic matrix was accompanied with formation of pores so that the microstructure shifted from dense to porous. Increasing the lanthanum hexaaluminate content up to a certain value enhanced the fracture toughness, increased the hardness, and increased the elastic modulus of the composite materials. Further increase in the lanthanum hexaaluminate content degraded the hardness as well as the elastic modulus of composite ceramics. The influence of lanthanum hexaaluminate on mechanical properties was described by means of microstructure, porosity, and intrinsic characteristics of lanthanum hexaaluminate.

  10. Enhancement of stability of aqueous suspension of alumina nanoparticles by femtosecond laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Youngsang; Ha, Jeonghong; Kim, Dongsik, E-mail: dskim87@postech.ac.kr [Department of Mechanical Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Choi, Tae-Youl [Department of Mechanical and Energy Engineering, University of North Texas, 3940 N. Elm St. Denton, Texas 76207 (United States); Jeong, Dae-Yong [Department of Materials Science & Engineering, Inha University, Incheon 402-751 (Korea, Republic of); Lee, Seung Yong [Materials Architecturing Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of)

    2015-09-21

    In this work, we report substantially enhanced colloidal stability of aqueous nanoparticle suspensions by ultrashort laser pulse irradiation. A Ti:Sapphire femtosecond laser (wavelength: 800 nm; pulse duration: 50 fs at full width at half maximum) was used to modify the electrochemical properties of nanoparticle suspensions at laser fluences below the particle ablation threshold. The colloidal stability of the suspension was evaluated by zeta potential and dynamic light scattering (DLS). The DLS results along with the images from transmission electron microscopy revealed that the laser irradiation caused no distinct morphological change to the individual alumina particles, but a substantial portion of the clustered particles was fragmented by the laser pulses, decreasing the apparent size of the suspended particles. Also, X-ray photoelectron spectroscopy analysis indicates that the laser irradiation modified the surface chemistry of the alumina particles. The stabilizing capability of the proposed technique was turned out to be better than that of conventional ultrasonic treatments. The stability of the laser-treated sample with no added surfactant was maintained for up to 30 days, without requiring an additional homogenizing process such as magnetic stirring.

  11. Enhancement of stability of aqueous suspension of alumina nanoparticles by femtosecond laser irradiation

    International Nuclear Information System (INIS)

    In this work, we report substantially enhanced colloidal stability of aqueous nanoparticle suspensions by ultrashort laser pulse irradiation. A Ti:Sapphire femtosecond laser (wavelength: 800 nm; pulse duration: 50 fs at full width at half maximum) was used to modify the electrochemical properties of nanoparticle suspensions at laser fluences below the particle ablation threshold. The colloidal stability of the suspension was evaluated by zeta potential and dynamic light scattering (DLS). The DLS results along with the images from transmission electron microscopy revealed that the laser irradiation caused no distinct morphological change to the individual alumina particles, but a substantial portion of the clustered particles was fragmented by the laser pulses, decreasing the apparent size of the suspended particles. Also, X-ray photoelectron spectroscopy analysis indicates that the laser irradiation modified the surface chemistry of the alumina particles. The stabilizing capability of the proposed technique was turned out to be better than that of conventional ultrasonic treatments. The stability of the laser-treated sample with no added surfactant was maintained for up to 30 days, without requiring an additional homogenizing process such as magnetic stirring

  12. Thermophysical properties and elastic moduli of alumina-zirconia composite ceramics

    Czech Academy of Sciences Publication Activity Database

    Hostaša, J.; Pabst, W.; Matějíček, Jiří; Gregorová, E.; Malangré, D.

    Stockholm : City Conference Centre(CCC), 2011, s. 722-722. [Conference of the European Ceramic Society (ECerS XII)/12th./. Stockholm (SE), 19.06.2011-23.06.2011] Institutional research plan: CEZ:AV0Z20430508 Keywords : alumina * zirconia * composites * thermal diffusivity * elastic modulus Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

  13. Application of powder metallurgy and hot rolling processes for manufacturing aluminum/alumina composite strips

    International Nuclear Information System (INIS)

    In this study, aluminum matrix composites (AMC) with 2, 4, 6 and 10 wt% alumina were produced using powder metallurgy (PM), mechanical milling (MM) and vacuum hot pressing (VHP) techniques; then, this was followed by the hot-rolling process. During hot rolling, AMCs with 6 and 10 wt% Al2O3 were fractured whereas strip composites with 2 and 4 wt% Al2O3 were produced successfully. Microstructure and mechanical properties of the samples were investigated by optical and scanning electron microscopes and tensile and hardness tests, respectively. Microscopic evaluations of the hot-rolled composites showed a uniform distribution of alumina particles in the aluminum matrix. It was found that with increasing alumina content in the matrix, tensile strength (TS) and hardness increased and the percentage of elongation also decreased. Scanning electron microscope (SEM) was used to investigate aluminum/alumina interfaces and fracture surfaces of the hot rolled specimens after tensile test. SEM observations demonstrated that the failure mode in the hot-rolled Al-2 wt% Al2O3 composite strips is a typical ductile fracture, while the failure mode was shear ductile fracture with more flat surfaces in Al-4 wt% Al2O3 strips.

  14. Alumina reinforced tetragonal zirconia (TZP) composites. Final technical report, July 1, 1993--December 31, 1996

    International Nuclear Information System (INIS)

    This final technical report summarizes the significant research results obtained during the period July 1, 1993 through December 31, 1996 in the DOE-supported research project entitled, open-quotes Alumina Reinforced Tetragonal Zirconia (TZP) Compositesclose quotes. The objective of the research was to develop high-strength and high-toughness ceramic composites by combining mechanisms of platelet, whisker or fiber reinforcement with transformation toughening. The approach used included reinforcement of Celia- or yttria-partially-stabilized zirconia (Ce-TZP or Y-TZP) with particulates, platelets, or continuous filaments of alumina

  15. Fabrication and Structure Characterization of Alumina-Aluminum Interpenetrating Phase Composites

    Science.gov (United States)

    Dolata, Anna J.

    2016-01-01

    Alumina-Aluminum composites with interpenetrating networks structure belong to advanced materials with potentially better properties when compared with composites reinforced by particles or fibers. The paper presents the experimental results of fabrication and structure characterization of Al matrix composites locally reinforced via Al2O3 ceramic foam. The composites were obtained using centrifugal infiltration of porous ceramics by liquid aluminum alloy. Both scanning electron microscopy (SEM + EDS) and x-ray tomography were used to determine the structure of foams and composites especially in reinforced areas. The quality of castings, degree of pore filling in ceramic foams by Al alloy, and microstructure in area of interface were assessed.

  16. 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.

  17. Synthesis and characterization of Fe3P composite nanorods produced by phosphate reduction in anodized alumina templates

    International Nuclear Information System (INIS)

    A synthetic method for nanoscale iron phosphide rod production based on reductive annealing of iron phosphate deposited in porous alumina membranes has been explored. Two methods of pore filling, incipient wetness and drip-drying of precursor phosphate particles, were investigated. Reduction was carried out in a flowing H2/Ar atmosphere at 650-800 deg. C for 2 h and the template was removed by dissolution in NaOH. Particle morphology, composition and phase were examined by scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy and energy-dispersive spectroscopy. The data suggest that rods are formed as heterogeneous structures comprising Fe3P nanoparticles within an amorphous matrix

  18. 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

  19. Alumina-Activated Carbon Composite as Adsorbent of Procion Red Dye from Wastewater Songket Industry

    OpenAIRE

    Poedji Loekitowati Hariani; Fatma Fatma; Zulfikar Zulfikar

    2015-01-01

    Alumina-activated carbon composite has been synthesized and studied for adsorption procion red dye. Composite was prepared by precipitation method aluminium hydroxide on the surface of activated carbon followed by calcinations. The Fourier transform Infra Red (FTIR), Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS) and Brunaeur Emmet Teller (BET) surface are being used to characterize the adsorbent. Batch adsorption experiments were carried out for the adsorption of...

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

    International Nuclear Information System (INIS)

    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

  1. Hydrogen Selective Thin Palladium-Copper Composite Membranes on Alumina Supports

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Hankwon; Oyama, S. Ted

    2011-08-15

    Thin and defect-free Pd–Cu composite membranes with high hydrogen permeances and selectivities were prepared by electroless plating of palladium and copper on porous alumina supports with pore sizes of 5 and 100 nm coated with intermediate layers. The intermediate layers on the 100 nm supports were prepared by the deposition of boehmite sols of different particle sizes, and provided a graded, uniform substrate for the formation of defect-free, ultra-thin palladium composite layers. The dependence of hydrogen flux on pressure difference was studied to understand the dominant mechanism of hydrogen transport through a Pd–Cu composite membrane plated on an alumina support with a pore size of 5 nm. The order in hydrogen pressure was 0.98, and indicated that bulk diffusion through the Pd–Cu layer was fast and the overall process was limited by external mass-transfer or a surface process. Scanning electron microscopy (SEM) images of the Pd–Cu composite membrane showed a uniform substrate created after depositing one intermediate layer on top of the alumina support and a dense Pd–Cu composite layer with no visible defects. Cross-sectional views of the membrane showed that the Pd–Cu composite layer had a top layer thickness of 160 nm (0.16 μm), which is much thinner than previously reported.

  2. Alumina-Activated Carbon Composite as Adsorbent of Procion Red Dye from Wastewater Songket Industry

    Directory of Open Access Journals (Sweden)

    Poedji Loekitowati Hariani

    2015-03-01

    Full Text Available Alumina-activated carbon composite has been synthesized and studied for adsorption procion red dye. Composite was prepared by precipitation method aluminium hydroxide on the surface of activated carbon followed by calcinations. The Fourier transform Infra Red (FTIR, Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS and Brunaeur Emmet Teller (BET surface are being used to characterize the adsorbent. Batch adsorption experiments were carried out for the adsorption of procion red dye. Effect of the mass of composite, stirrer speed, contact times and pH of the solution on the adsorption capacity were studied. The obtained optimum conditions applied to adsorp of procion red dye from wastewater songket industry. The result showed that the adsorption optimum at mass of alumina-activated carbon composite 0.1 g, stirrer speed 150 rpm, contact times 2 hours at pH of the solution 9. The adsorption isotherm data according to Langmuir isotherm. The alumina-activated carbon composite can be removal of procion red dye from wastewater songket industry with effectiveness adsorption of 88.21 %.

  3. Fracture Behavior of Alumina-based Prismatic Ceramic Composites

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The fracture toughness and fracture work of Al2O3/SiC prismatic ceramic composites was evaluated in this paper, which showed the fracture energy was improved greatly. Based on the observation for crack propagation and fracture morphology, the fracture behavior of the prismatic composites was analyzed. In the bending test, the composites displayed a non-catastrophic behavior and a graceful failure with reasonable load-carrying capability.

  4. 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.

  5. 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

  6. Study on Microstructure of Alumina Based Rare Earth Ceramic Composite

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Analysis techniques such as SEM, TEM and EDAX were used to investigate the microstructure of rare earth reinforced Al2O3/(W, Ti)C ceramic composite. Chemical and physical compatibility of the composite was analyzed and interfacial microstructure was studied in detail. It is found that both Al2O3 and (W, Ti)C phases are interlaced with each other to form the skeleton structure in the composite. A small amount of pores and glass phases are observed inside the material which will inevitably influence the physical and mechanical property of the composite. Thermal residual stresses resulted from thermal expansion mismatch can then lead to the emergence of dislocations and microcracks. Interfaces and boundaries of different types are found to exist inside the Al2O3/(W, Ti)C rare earth ceramic composite, which is concerned with the addition of rare earth element and the extent of solid solution of ceramic phases.

  7. Mechanical Properties of Alumina Trihydrate Filled Polypropylene/Ethylene Propylene Diene Monomer Composites for Cable Applications

    International Nuclear Information System (INIS)

    Polymeric materials such as polypropylene (PP), polyethylene (PE) and ethylene propylene diene monomer (EPDM) are widely used as insulators for cable applications. We investigated the effect of alumina trihydrate (ATH) loading on the mechanical properties of PP/ EPDM blend. Preliminary study showed that PP/ EPDM (60:40) was the optimum composition. ATH filled PP/ EPDM composites was prepared by using twin screw extruder. In this study, the tensile properties and hardness of the composites were evaluated. The tensile modulus and hardness increased while elongation at break and tensile strength decreased with increasing ATH content. Scanning electron microscope was used to study the morphology of ATH in PP/ EPDM blend. (author)

  8. Alumina-Mo cermet composite compacts obtained by SPS from mechanical activated powders

    OpenAIRE

    Boyero Molina, Carlos

    2013-01-01

    In this work, the main purpose is to develop different composites of Al2O3-Mo varying the volume percentage of materials to see their variation of properties and to find the best composition of metal and ceramic in order to get the best results. As a short way to explain the process to develop the composite, we could say that these were the main stages of the production: 1. For obtaining a homogeneous ceramic-metallic mixture of powders we milled alumina and molybdenum powde...

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

    International Nuclear Information System (INIS)

    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)

  10. 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...

  11. Microstructural stability of zirconia-alumina composite coatings during hot corrosion test at 1050 oC

    International Nuclear Information System (INIS)

    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 oC 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.

  12. Laminated alumina/zirconia ceramic composites prepared by electrophoretic deposition

    Czech Academy of Sciences Publication Activity Database

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

    Bratislava : VEDA, 2011 - (Pavol Šajgalík, Zoltán Lenčéš). s. 70 ISBN 978-80-970657-4-4. [Advanced Research Workshop Engineering Ceramics 2011 from Materials to Components. 08.05.2011-12.05.2011, Smolenice Castle] R&D Projects: GA ČR(CZ) GAP108/11/1644 Institutional research plan: CEZ:AV0Z20410507 Keywords : Ceramic laminates * Electrophoretic deposition * Hardness Subject RIV: JI - Composite Materials

  13. Fracture behaviour of alumina-zirconia composites containing microfibers

    Czech Academy of Sciences Publication Activity Database

    Chlup, Zdeněk; Hadraba, Hynek; Drdlík, D.

    Bratislava: Slovenská akademie věd, 2015 - (Lenčéš, Z.; Valúchová, J.). s. 65-65 ISBN 978-80-971648-3-6. [Engineering Ceramics 2015. 10.05.2015-14.05.2015, Smolenice castle] R&D Projects: GA ČR(CZ) GA14-24252S Institutional support: RVO:68081723 Keywords : EPD * mechanical properties * composite * micro-fibres Subject RIV: JL - Materials Fatigue, Friction Mechanics

  14. Tribocorrosion Behavior of Aluminum/Alumina Composite Manufactured by Anodizing and ARB Processes

    Science.gov (United States)

    Jamaati, Roohollah; Toroghinejad, Mohammad Reza; Szpunar, Jerzy A.; Li, Duanjie

    2011-12-01

    In the present work, tribocorrosion behavior of Al/Al2O3 composite strips manufactured by anodizing and accumulative roll bonding (ARB) processes was investigated. The alumina quantity was 0.48, 1.13, and 3.55 vol.% in the aluminum matrix. Tribocorrosion experiments were conducted using a ball-on-plate tribometer, where the sliding contact was fully immersed in 1 wt.% NaCl solution. The composite sample served as a working electrode and its open circuit potential (OCP) was monitored before, during, and after sliding. In order to characterize the electrochemical behavior of the surface before and after sliding electrochemical impedance spectroscopy (EIS) was used and wear was also measured. Furthermore, the influence of quantity and distribution of reinforcement particles in the matrix on OCP and EIS was evaluated. It was found that the quantity, shape, size, and dispersion of alumina particles in the aluminum matrix strongly affected the measured tribocorrosion characteristics. The results showed that inhomogeneous, lower quantity, fine, and acicular-shape alumina particles cause serious materials loss in tribocorrosion process.

  15. Microstructure-property relationships in alumina trihydrate filled poly (methyl methacrylate) composite materials

    Science.gov (United States)

    Zhang, Ruoyu

    2015-07-01

    The mechanical properties (Young's modulus and fracture toughness) of composite made from a poly (methyl methacrylate) (PMMA) matrix filled with alumina trihydrate(ATH) are reported. The experiments were performed using flexural tests and single edge notched bend (SENB) tests. The composites samples were tested at a range of filler volume fractions (34.7%, 39.4% and 44.4%) and mean filler diameters (8 pm, 15 pm and 25 pm). The data of Young's modulus agreed well with the results of Lielens model and finite element analysis (FEA) model.

  16. Effect of silica sol on the properties of alumina-based ceramic core composites

    International Nuclear Information System (INIS)

    A series of alumina-based ceramic cores sintered at 1300 deg. C, 1400 deg. C, and 1500 deg. C for 5 h were prepared, and the phases and microstructures were characterized by X-ray diffraction and scanning electron microscopy. The effect of colloidal silica sols on the properties of ceramic core was discussed. The properties of these materials were determined. The microstructure of the core formed on the substantially un-reacted coarse Al2O3 particles was predominantly a polycrystalline composition consisting essentially of in situ synthesized 3Al2O3.2SiO2. The colloidal silica sol contents do not have an appreciable effect on the densification and shrinkage of alumina ceramic core. The ceramic cores of 5 wt% colloidal silica sol contents sintered at 1500 deg. C for 5 h showed the smallest creep deformation in the present research.

  17. 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

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

    Indian Academy of Sciences (India)

    Mustafa Übeylı; R Orhan Yildirim; Bılgehan Ögel

    2005-10-01

    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 behaviour of materials. This testing gives significant ideas and information about failure mechanisms and behaviour of materials under low velocity impact. 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 with ceramic front layer and aged-aluminum alloy as backing layer was the most effective among different investigated specimens against low velocity impact loads.

  19. 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.

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

    International Nuclear Information System (INIS)

    This research used the low cost, open atmosphere combustion chemical vapor deposition (CCVDSM) method to efficiently deposit protective coatings onto alumina fibers (3M NextelTM610) for use in ceramic matrix composites (CMCs). La-monazite (LaPO4) 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 NextelTM610 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.)

  1. Porous hydroxyapatite composite with alumina for bone repair

    International Nuclear Information System (INIS)

    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+Al2O3 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 Al2O3 powder from supplier (MERK). The fine HA powder, measuring 2O3. 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+Al2O3 gives higher maximum compression strength compared to the porous hydroxyapatite itself. Observation from this studied the increasing of temperature will increase the strength. (author)

  2. Effect of liquid level and laser power on the formation of spherical alumina nanoparticles by nanosecond laser ablation of alumina target

    Energy Technology Data Exchange (ETDEWEB)

    Al-Mamun, Sharif Abdullah [Research Center for Micro-Nano Technology, Hosei University, 3-11-15 Midori-cho, Koganei, Tokyo 184-0003 (Japan); Nakajima, Reiko [Department of Materials Chemistry, Hosei University, 3-7-2 Kajino-cho, Koganei, Tokyo 184-8584 (Japan); Ishigaki, Takamasa, E-mail: ishigaki@hosei.ac.jp [Research Center for Micro-Nano Technology, Hosei University, 3-11-15 Midori-cho, Koganei, Tokyo 184-0003 (Japan); Department of Materials Chemistry, Hosei University, 3-7-2 Kajino-cho, Koganei, Tokyo 184-8584 (Japan); Department of Chemical Science and Technology, 3-7-2 Kajino-cho, Koganei, Tokyo 184-8584 (Japan); Nano Ceramics Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

    2012-11-15

    Alumina nanoparticles (NPs) were synthesized by laser ablation of a bulk {alpha}-alumina (corundum) target immersed in distilled water using nanosecond laser pulses of 1064-nm wavelength. We investigated the effect of laser power and water column above the target. Synthesized particles were analyzed regarding particle shape and size distributions with scanning electron and transmission electron microscopy. Ablated NPs were spherical in shape and the average particle size ranged from 12 to 18 nm at varied laser power and water levels, although a very small number of melted droplets of submicron spheroids and irregular-shaped cracked particles were observed. X-ray diffraction analysis was conducted, which shows mainly the peaks of {alpha}-Al{sub 2}O{sub 3} and minor peaks of {gamma}-Al{sub 2}O{sub 3}. Phase identification of NPs, using high-resolution transmission electron micrograph lattice images and fast Fourier transform exhibits both metastable {gamma}-Al{sub 2}O{sub 3} and stable {alpha}-Al{sub 2}O{sub 3} phases.

  3. Influence of Nano Fillers in the Development of Glass Epoxy –Nano Alumina Hybrid Nano Composite

    OpenAIRE

    K. Kalyani Radha

    2014-01-01

    The research is carried out to develop a new polymer matrix hybrid Nano composite. The effect of alumina Nano particles between the glass fibre and epoxy resin was investigated. Well-dispersed Nano particles enhanced significantly the mechanical strength between fibre and matrix. The experimental analysis demonstrated that the quality of fibre/matrix interface was improved after the addition of alumina Nano particles to glass fiber.

  4. Compaction study of particulate iron-chromium matrix composite reinforced with alumina

    International Nuclear Information System (INIS)

    Recently, a sharper focus on cost reduction in producing advanced composites systems has increased and leads to an interest in ferrous matrix composite which is cheaper compared to Cobalt, Nickel and their alloys that are scarce, expensive and their dust is especially harmful. In the present investigation, Fe-Cr-Al2O3 composite was prepared using conventional powder metallurgy technique; mixing, compaction and sintering. Consolidation of particulate materials is dependent on the compaction process. As load is increased, the number of contacting asperities increases and they flatten and grow to form a planar contact surface. These asperities eventually merge to form bonding surfaces between particles. This paper focused on finding the optimum compaction parameter in a uniaxial pressing. Six different pressure were studied; (250, 375, 500, 625, 750 and 875)MPa. experimental results show that the optimum compaction parameter is 750 MPa that produced highest linear shrinkage, highest bulk density, lowest porosity and highest hardness value. Every sample has formed binary alloy of Fe-Cr alloy, confirmed by XRD and alumina are homogeneously distributed in the Fe-Cr matrix revealed by optical micrograph and SEM. from EDX, the composites consist of iron, chromium and alumina. (author)

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

    International Nuclear Information System (INIS)

    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–Al2O3 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 2O3 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–Al2O3 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 2O3 nancomposites respectively. Spark plasma sintering imparts enhanced densification and matrix-reinforcement proximity which have been corroborated with the experimental results

  6. Weibull Probability Model for Fracture Strength of Aluminium (1101)-Alumina Particle Reinforced Metal Matrix Composite

    Institute of Scientific and Technical Information of China (English)

    A.Suresh Babu; V.Jayabalan

    2009-01-01

    In recent times, conventional materials are replaced by metal matrix composites (MMCs) due to their high specific strength and modulus.Strength reliability, one of the key factors restricting wider use of composite materials in various applications, is commonly characterized by Weibull strength distribution function.In the present work, statistical analysis of the strength data of 15% volume alumina particle (mean size 15 μm)reinforced in aluminum alloy (1101 grade alloy) fabricated by stir casting method was carried out using Weibull probability model.Twelve tension tests were performed according to ASTM B577 standards and the test data, the corresponding Weibull distribution was obtained.Finally the reliability of the composite behavior in terms of its fracture strength was presented to ensure the reliability of composites for suitable applications.An important implication of the present study is that the Weibull distribution describes the experimentally measured strength data more appropriately.

  7. Tantalum Clusters Supported on Silica-Alumina: Influence of Support Composition and Chemistry on Cluster Structure

    International Nuclear Information System (INIS)

    Small cationic tantalum clusters were prepared on the surfaces of SiO2, silica-aluminas, and ?-Al2O3 supports by treating physisorbed pentabenzyltantalum at 523 K for 24 h in flowing H2. The rate of decomposition and the products formed in the decomposition of pentabenzyltantalum are dependent on the support composition. When the support was SiO2, the evolved products were mainly biphenyl and a small amount of toluene, indicating that the Ta-C bond in pentabenzyltantalum was activated. As the alumina content of the support increased, diphenylmethane, benzene, and ethylene were increasingly formed, and these products show that the activation of the C-C bonds linking the C atoms of methyl groups to the aromatic rings of the benzyl ligands was facilitated. Infrared spectra of the surface species and mass spectra of the effluents formed during the treatment show that the composition of the support had significant influence on the decomposition of pentabenzyltantalum, and the chemistry is inferred to be related to the electron-donor properties of the supports. Extended X-ray absorption fine structure (EXAFS) spectra recorded at the Ta LIII edge indicate the formation of clusters with a Ta-Ta first-shell coordination number of 3, and images obtained by scanning transmission electron microscopy (STEM) confirm the presence of such small clusters. X-ray absorption near edge structure (XANES) data indicate that the formal oxidation state of the tantalum in the clusters decreased from 3.0 to 2.6 as the support was changed from SiO2 to silica-aluminas to ?-Al2O3. The data suggest that the tantalum clusters were anchored to the supports via bridging O atoms. The EXAFS data show that the support composition had little influence on the cluster structure.

  8. Composite fluorocarbon membranes by surface-initiated polymerization from nanoporous gold-coated alumina.

    Science.gov (United States)

    Escobar, Carlos A; Zulkifli, Ahmad R; Faulkner, Christopher J; Trzeciak, Alex; Jennings, G Kane

    2012-02-01

    This manuscript describes the versatile fabrication and characterization of a novel composite membrane that consists of a porous alumina support, a 100 nm thick nanoporous gold coating, and a selective poly(5-(perfluorohexyl)norbornene) (pNBF6) polymer that can be grown exclusively from the nanoporous gold or throughout the membrane. Integration of the three materials is achieved by means of silane and thiol chemistry, and the use of surface-initiated ring-opening metathesis polymerization (SI-ROMP) to grow the pNBF6. The use of SI-ROMP allows tailoring of the extent of polymerization of pNBF6 throughout the structure by varying polymerization time. Scanning electron microscopy (SEM) images indicate that the thin polymer films cover the structure entirely. Cross-sectional SEM images of the membrane not only corroborate growth of the pNBF6 polymer within both the porous alumina and the nanoporous gold coating but also show the growth of a pNBF6 layer between these porous substrates that lifts the nanoporous gold coating away from the alumina. Advancing contact angle (θ(A)) measurements show that the surfaces of these composite membranes exhibit both hydrophobic (θ(A) = 121-129)° and oleophobic (θ(A) = 69-74)° behavior due to the fluorocarbon side chains of the pNBF6 polymer that dominate the surface. Results from electrochemical impedance spectroscopy (EIS) confirm that the membranes provide effective barriers to aqueous ions, as evidenced by a resistive impedance on the order of 1 × 10(7) Ω cm(2). Sulfonation of the polymer backbone substantially enhances ion transport through the composite membrane, as indicated by a 40-60 fold reduction in resistive impedance. Ion transport and selectivity of the membrane change by regulating the polymerization time. The fluorinated nature of the sulfonated polymer renders the membrane selective toward molecules with similar chemical characteristics. PMID:22195729

  9. The Use of alumina or Mullite in Fabricating Silicon Carbide Composite Materials

    International Nuclear Information System (INIS)

    The effect of additions of Al2 O3 powder or Al2 O3 produced by Al(NO3)3. 9 H2 O Hydrolysis to fine and coarse Si C powder on the green density of CIP bodies was investigated. It was found that the green density increases by addition of Al2 O3 to Si C and decreases by precipitating Al(OH)3 on Si C due to the coating of the latter by Al2 O3 after calcination. Pressureless sintering of Si C-Al2 O3 composites is accompanied by a weight loss which increases by increasing the firing temperature or the mole % alumina up to 30% and decreases above this ratio. The weight loss was attributed to the formation of the gaseous products Si O, CO, and Al2 O which are volatile at the sintering temperature used. Aluminum oxycarbides and aluminum carbide were identified in the sintered compacts while in some samples Si C disappears or residual traces are found. Mixtures containing Si C and mullite showed a weight loss after pressureless sintering higher than the corresponding mixtures containing Si C and alumina under the same conditions. Hipping retarded the weight loss due to the inhibition of the reactions causing the weight loss. It was found that hipping was more effective in reducing weight loss in the case of Si C- mullite composites than in the case of Si C-alumina composites. The compatible phases were used to construct the tie tetrahedra in the Si - C - Al - O system and hence in obtaining the Al2 O3 - Al4 C3 - Si C-Si O2 quaternary diagram. 11 figs., 2 tabs

  10. Mechanically Processed Alumina Reinforced Ultra-high Molecular Weight Polyethylene (UHMWPE) Matrix Composites

    OpenAIRE

    Elmkharram, Hesham Moh. A.

    2013-01-01

    Alumina particles filled Ultra-high Molecular Weight Polyethylene (UHMWPE), with Al2O3 contents 0, 1, and 2.5 wt% were milled for up to 10 hours by the mechanical alloying (MA) process performed at room temperature to produce composite powders. Compression molding was utilized to produce sheets out of the milled powders. A partial phase transformation from orthorhombic and amorphous phases to monoclinic phase was observed to occur for both the un-reinforced and reinforced UHMWPE in the soli...

  11. Forming of tubes and bars of alumina/LY12 composites by liquid extrusion process

    Institute of Scientific and Technical Information of China (English)

    齐乐华; 李贺军; 崔培玲; 史忠科

    2003-01-01

    Tube and bar products of aluminum alloy composites reinforced by alumina short-fiber were formed in a single process with liquid extrusion technology. The microstructure verifies that the reinforcing effect is obvious in the deformation direction since fibers are distributed along this direction, which is resulted from the flow and crystallization under pressure of liquid metal and large plastic deformation of solidified metal in the process. The interface between fiber and matrix belongs to mechanical bonding. The fractograph demonstrates ductile mode. Liquid extrusion process opens up a new way for fabricating tube, bar and shaped products.

  12. 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*.

  13. Investigation of the Thermal, Mechanical, and Fracture Properties of Alumina-Epoxy Composites

    Energy Technology Data Exchange (ETDEWEB)

    McGrath,L.; Parnas, R.; King, S.; Schroeder, J.; Fischer, D.; Lenhart, J.

    2008-01-01

    A combination of dynamic shear rheology, thermomechanical analysis (TMA), scanning electron microscopy (SEM), Near-Edge X-ray Absorption Fine Structure (NEXAFS), and fracture toughness testing was utilized to characterize the thermal, mechanical, chemical, and fracture properties of alumina (a-Al2O3)-filled epoxy resins as a function of average filler size, size distribution, particle shape, loading, and epoxy crosslink density. In general the cured properties of the filled composites were robust. Small changes in particle size, shape, and size distribution had little impact on the final properties. Resin crosslink density and filler loading were the most critical variables, causing changes in all properties. However, most applications could likely tolerate small changes in these variables also. SEM and NEXAFS characterization of the fracture surfaces revealed that the fracture occurs at the filler interface and the interfacial epoxy composition is similar to the bulk resin, indicating a weak epoxy-alumina interaction. These results are critical for implementation of particulate-filled polymer composites in practical applications because relaxed material specifications and handling procedures can be incorporated in production environments to improve efficiency.

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

    Directory of Open Access Journals (Sweden)

    J.W. Kaczmar

    2013-04-01

    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.

  15. 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.

  16. Mechanical behavior of porous magnesium/alumina composites with high strength and low density

    International Nuclear Information System (INIS)

    Porous alumina-reinforced magnesium composites were synthesized through a powder metallurgical method and characterized using optical microscope, scanning electron microscope, and compression testing. The microstructural study exhibited that the average pore sizes increased with the increase of porosity and were about 25 μm, 70 μm, and 100 μm for the samples with 10%, 28%, and 38% porosities respectively. The mechanical characterization indicated that (i) the stress–strain curves were composed of three regimes: an initial regime that deformed elastically along an approximately linear line, a long and intermediate regime, and a densification regime with a steep increase of stress; (ii) the synthesized porous magnesium composites possessed lower density and higher yield strength than those of cast dense magnesium; (iii) the average yield strength and Young's modulus were anisotropic for the porous magnesium composites synthesized in this work

  17. Research on removal of fluoride in aqueous solution by alumina-modified expanded graphite composite

    International Nuclear Information System (INIS)

    Graphical abstract: Amorphous Alumina-modified Expanded Graphite (Al2O3/EG) were prepared through mass appropriate Al(NO3)3 solution and EG, then calcinating at 450 °C for 2 h and used for F− adsorption. Al2O3/EG can remove trace amounts of F− in solution effectively and the final F− concentrate can be decreased to less than 0.28 ppm. The isotherms and thermodynamics parameters indicate that the adsorption is a multi-molecular layer adsorption between the adsorbed molecules, and the process is spontaneous endothermic. - Highlights: • We have grafted amorphous alumina nano-peas with a diameter of 10–30 nm. • The Al2O3/EG adsorbent showed a considerably high adsorption efficiency over a relatively wide pH range of 3.0–7.0. • Al2O3/EG can remove trace amounts of F− in solution effectively. • The final F− concentrate can be decreased to less than 0.28 ppm. - Abstract: Amorphous Alumina-modified Expanded Graphite (Al2O3/EG) composite was prepared via a facile solution method followed by thermal treatment at 450 °C for 2 h, which was used to remove trace F− in aqueous solution. Alumina nano-peas (with a diameter of 10–30 nm) were observed on the surface of EG by Field Scanning Electron Microscope (FSEM). The X-ray powder diffraction (XRD) results dominated the Alumina was amorphous. FTIR spectra analysis indicated that Al-F bends appeared after adsorption. The effect of pH and adsorbent dose were studied in a series of batch adsorption experiments. The Effect of pH results showed that the solution pH had no significant effect on F− removal between pH = 3.0–7.0. The superior adsorbent properties of Al2O3/EG proved highly effective in absorbing F−, where the removal rate reached 94.4% and the adsorption capacity reached 1.18 mg/g. The results showed that Al2O3/EG could removed trace amounts of F− in solution effectively and the residual F− concentrate could decreased to less than 0.28 ppm. The isotherms and thermodynamics parameters

  18. Al/Al2O3 Composite Coating Deposited by Flame Spraying for Marine Applications: Alumina Skeleton Enhances Anti-Corrosion and Wear Performances

    Science.gov (United States)

    Huang, Jing; Liu, Yi; Yuan, Jianhui; Li, Hua

    2014-04-01

    Here we report aluminum-alumina composite coatings fabricated by flame spraying for potential marine applications against both corrosion and wear. Microstructure examination suggested dense coating structures and the evenly distributed alumina splats formed hard skeleton connecting individual Al splats. The anti-corrosion and wear performance of the coatings were enhanced significantly by the addition of alumina. Failure analyses of the coatings after accelerated corrosion testing disclosed the intact alumina skeleton, which prevented further advancement of the corrosion. The results suggest that there is great potential for the cost-effective Al-Al2O3 coatings with tailorable alumina contents for application in the marine environment.

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

    International Nuclear Information System (INIS)

    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

  20. 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.

  1. 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.

  2. 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.

  3. Biocompatibility Study of A Hydroxyapatite-Alumina and Silicon Carbide Composite Scaffold for Bone Tissue Engineering

    Directory of Open Access Journals (Sweden)

    Mohammad Saki

    2009-01-01

    Full Text Available Objective: To date, several scaffolds have been fabricated for application in bone tissuerepair. However, there remains a need for synthesis of scaffolds with better mechanicalproperties, which can be applied to defects in weight-bearing bones. We constructed acomposite ceramic bioscaffold of hydroxyapatite-alumina and silicon carbide (HA-Al2O3-SiC to take advantage of the mechanical properties of this combination and show that itsupports osteoblast-like cell attachment and growth.Materials and Methods: Ceramic composite microporous scaffolds were synthesizedusing an organic template (commercial polyurethane sponge with an open, interconnectedmicroporosity. Osteoblast-like cells (Saos-2 were then cultured on the scaffold andtheir growth pattern and viability were compared with those cultured in cell culture-treatedflasks. Scanning electron microscopy (SEM was used to assess cell attachment andmigration.Results: The fabricated scaffold shows fairly uniform pore morphologies. Cell growthand viability studies show that the scaffold is able to support osteoblast attachment andgrowth. However, SEM images indicated that the cells do not spread optimally on thescaffold surfaces.Conclusion: Our data suggest that that a ceramic hydroxyapatite-alumina and siliconcarbide composite scaffold is a viable option for bone tissue repair. However, its surfaceproperties should be optimized to maximise the attachment of osteoblasts.

  4. Chemical Mechanical Polishing of Glass Substrate with α-Alumina-g-Polystyrene Sulfonic Acid Composite Abrasive

    Institute of Scientific and Technical Information of China (English)

    LEI Hong; BU Naijing; ZHANG Zefang; CHEN Ruling

    2010-01-01

    Abrasive is the one of key influencing factors during chemical mechanical polishing(CMP) process. Currently, α-Alumina (α-Al2O3) particle, as a kind of abrasive, has been widely used in CMP slurries, but their high hardness and poor dispersion stability often lead to more surface defects. After being polished with composite particles, the surface defects of work pieces decrease obviously. So the composite particles as abrasives in slurry have been paid more attention. In order to reduce defect caused by pure α-Al2O3 abrasive, α-alumina-g-polystyrene sulfonic acid (α-Al2O3-g-PSS) composite abrasive was prepared by surface graft polymerization. The composition, structure and morphology of the product were characterized by Fourier transform infrared spectroscopy(FTIR), X-ray photoelectron spectroscopy(XPS), time-of-flight secondary ion mass spectroscopy(TOF-SIMS), and scanning electron microscopy(SEM), respectively. The results show that polystyrene sulfonic acid grafts onto α-Al2O3, and has well dispersibility. Then, the chemical mechanical polishing performances of the composite abrasive on glass substrate were investigated with a SPEEDFAM-16B-4M CMP machine. Atomic force microscopy(AFM) images indicate that the average roughness of the polished glass substrate surface can be decreased from 0.835 nm for pure α-Al2O3 abrasive to 0.583 nm for prepared α-Al2O3-g-PSS core-shell abrasive. The research provides a new and effect way to improve the surface qualities during CMP.

  5. Wear behaviour of composite materials based on 2024 Al-alloy reinforced with δ alumina fibres

    Directory of Open Access Journals (Sweden)

    J.W. Kaczmar

    2010-11-01

    Full Text Available Purpose: Wear improvement of aluminum matrix composite materials reinforced with alumina fibres, was investigated. The effects of the applied pressure and T6 heat treatment on wear resistance were determined.Design/methodology/approach: Wear tests were carried out on pin-on disc device at constant sliding velocity and under three pressures, which in relation to diameter of specimens corresponds to pressures of 0.8 MPa, 1.2 MPa and 1.5 MPa. To produce composite materials porous performs were prepared. They are characterized by the suitable permeability and good strength required to resist stresses arising during squeeze casting process. Performs exhibited semi-oriented arrangement of fibres and open porosity enabled producing of composite materials 10% (in vol.% of Al2O3 fibres (Saffil.Findings: In comparison with T6 heat treated monolithic 2024 aluminium alloy composites revealed slightly better resistance under lower pressure. Probably, during wear process produced hard debris containing fragments of alumina fibres are transferred between surfaces and strongly abrade specimens. Under smaller pressures wear process proceeded slowly and mechanically mixed layer MML was formed.Research limitations/implications: Reinforcing of 2024 aluminium alloy could be inefficient for wear purposes. Remelting and casting of wrought alloy could deteriorate its properties. Interdendrite porosities and coarsening of grains even after squeeze casting process were observed.Practical implications: Aluminum casting alloys can be locally reinforced to improve hardness and wear resistance under small pressures.Originality/value: Investigations are valuable for persons, what are interested in aluminum cast composite materials reinforced with ceramic fibre performs.

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

    International Nuclear Information System (INIS)

    Research highlights: → In-situ SHS processing method plus vacuum hot-pressing process were applied. → Mechanical and electronic properties and microscopic structures were studied. → 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 A12O3 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, A12O3 and a small amount of Ti3Al phases in the composites and the reaction mechanisms of the process were proposed. SEM observation revealed that a two-phase (γ + α2) TiAl-Ti3Al 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 Al2O3. Therefore, interface combination of the composite was improved, making the composite tougher (a toughness as high as 7.9 MPa m1/2) than monophase Al2O3 ceramic.

  7. Modeling the dependence of alumina solubility on temperature and melt composition in cryolite-based melts

    Science.gov (United States)

    Zhang, Yunshu; Rapp, Robert A.

    2004-06-01

    The solubility of alumina in NaF-AlF3 melts was calculated and modeled thermodynamically for the temperature range of 1240 to 1300 K (967 °C to 1027 °C). The solute complexes of alumina in the cryolite melts were identified to be Na2Al2OF6 (acidic solute), Na2Al2O2F4 (neutral solute), and Na4Al2O2F6 (basic solute). The assumption that the oxygen-free solute species in solution were Na3AlF6 and NaAlF4 was supported by the modeling results. The equilibrium constants for the formation reactions of the solutes were calculated and the corresponding Δ G {/f 0} values were evaluated as a function of temperature. The interaction derivatives (∂ ln a NaF/∂ x add, ∂ ln a NaF/∂ x add, and ∂ ln a AlF3/∂ x add) for small additions of LiF, CaF2, and MgF2 to the NaF-AlF3-Al2O3 ternary system were also estimated as a function of temperature and melt composition.

  8. X-Ray-, Cathodo-, and Photoluminescence of Yttrium-Aluminum Composites on Porous Anodic Alumina Films

    Science.gov (United States)

    Khoroshko, L. S.; Kortov, V. S.; Gaponenko, N. V.; Raichyonok, T. F.; Tikhomirov, S. A.; Pustovarov, V. A.

    2016-07-01

    Yttrium-aluminum composites doped with terbium were synthesized by precipitation on porous anodic alumina fi lms grown on silicon substrates. The fabricated structures demonstrated x-ray-, cathodo-, and photoluminescence with characteristic bands of trivalent terbium upon excitation by Cu Kα x-rays of energy 8.86 keV, a 180-keV electron beam, and optical UV radiation, respectively. The terbium luminescence bands increased in intensity as the terbium concentration increased from 0.01 to 0.25 mol%. The intensity of a broad band in the blue spectral region with a maximum at 410 nm that was due to photoluminescence of the porous anodic alumina fi lm increased as the excitation wavelength increased from 260 to 340 nm. Simultaneously, the intensities of luminescence bands in the range 480-650 nm associated with Tb 3 + 5 D 4 - 7 F j ( j = 3, 4, 5, 6) transitions decreased. The possibility of practical application of the synthesized luminescent structures was discussed.

  9. Evaluating the mechanical behavior of hot rolled Al/alumina composite strips using shear punch test

    International Nuclear Information System (INIS)

    The evaluation of mechanical properties, like yield and ultimate shear strengths from shear punch tests, is important when availability of material, is limited. A shear punch test setup was built, and the mechanical properties of different strips of hot rolled pure aluminum, post-rolling annealed pure aluminum, as-milled pure aluminum, and 4 wt% Al2O3 were investigated. The materials were first manufactured using powder metallurgy and then processed by hot rolling procedure. Microstructures of the samples were investigated by optical and scanning electron microscopes. It was found that by increasing alumina content in the matrix, shear strength and hardness were increased; also, the percentage of shear elongation was decreased. The results, also, indicated that by applying mechanical milling on pure aluminum powders before the hot rolling process, shear strength and hardness increased more than other samples. Moreover, shear strength was increased by increasing the amount of alumina particles in composite strips. SEM observations demonstrated that the amount of flat surface in shear failure micrographs increased by increasing the amount of shear strength and hardness

  10. 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.

  11. An alumina toughened zirconia composite for dental implant application: in vivo animal results.

    Science.gov (United States)

    Schierano, Gianmario; Mussano, Federico; Faga, Maria Giulia; Menicucci, Giulio; Manzella, Carlo; 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

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

    Science.gov (United States)

    Oberste Berghaus, Jörg; Legoux, Jean-Gabriel; Moreau, Christian; Tarasi, Fariba; Chráska, Tomas

    2008-03-01

    Micro-laminates and nanocomposites of Al2O3 and ZrO2 can potentially exhibit higher hardness and fracture toughness and lower thermal conductivity than alumina or zirconia alone. The potential of these improvements for abrasion protection and thermal barrier coatings is generating considerable interest in developing techniques for producing these functional coatings with optimized microstructures. Al2O3-ZrO2 composite coatings were deposited by suspension thermal spraying (APS and HVOF) of submicron feedstock powders. The liquid carrier employed in this approach allows for controlled injection of much finer particles than in conventional thermal spraying, leading to unique and novel fine-scaled microstructures. The suspensions were injected internally using a Mettech Axial III plasma torch and a Sulzer-Metco DJ-2700 HVOF gun. The different spray processes induced a variety of structures ranging from finely segregated ceramic laminates to highly alloyed amorphous composites. Mechanisms leading to these structures are related to the feedstock size and in-flight particle states upon their impact. Mechanical and thermal transport properties of the coatings were compared. Compositionally segregated crystalline coatings, obtained by plasma spraying, showed the highest hardness of up to 1125 VHN3 N, as well as the highest abrasion wear resistance (following ASTM G65). The HVOF coating exhibited the highest erosion wear resistance (following ASTM G75), which was related to the toughening effect of small dispersed zirconia particles in the alumina-zirconia-alloyed matrix. This microstructure also exhibited the lowest thermal diffusivity, which is explained by the amorphous phase content and limited particle bonding, generating local thermal resistances within the structure.

  13. Reactive processing and characterization of nickel aluminide-alumina functionally gradient composites

    Science.gov (United States)

    Zhu, Hexiang

    The reactive hot compaction (RHC) technique was successfully utilized to produce bulk in-situ nickel aluminide (NiAl)-alumina (Al 2O3) functionally gradient composites (FGCs) as well as thin FGC coating. The FGCs consisted of four or five layers with alumina content increasing from less than 3vol.% to about 35vol.%. The composites were fabricated via reactive processing of the powder mixtures of nickel, aluminum, partially oxidized aluminum (Al*) and/or nickel oxide (NiO). The technique resulted in a gradual transition of the microstructure and properties along the thickness of the FGC, and led to reduced residual stresses and a strong bonding between the NiAl substrate and the FGC coating. The FGC also had higher fracture toughness than the corresponding composites. The phase and microstructural development for the three powder mixture systems (Ni-Al, Ni-Al*, and NiO-Al), which occurred during reactive processing of the composites, were systematically studied. The reaction process of Ni + Al powder mixtures was found to be strongly affected by pressure, heating rates, heat loss and diffusion barrier. It was found that the formation of NiAl occurred rapidly via combustion reaction at high heating rates and with small heat loss. At slow heating rates, however, the reaction process was slow and controlled by solid-state diffusion. The phase formation sequence for the slow solid-state reaction was determined to be: NiAl3 → Ni2Al3 → NiAl (Ni3Al) → NiAl. An Al2O3 particle network was produced during RHC of Ni + Al* powders, while an interpenetrating Al2O3 skeleton formed for NiO + Al powders. The formation of Al2O 3 phases during RHC of NiO + Al powders was a three-stage process, with the Al2O3 phases coming from both the liquid and the solid state reactions. The solid state displacement reaction between NiO and nickel-aluminides (NiAl3, Ni2Al3, NiAl) is believed to lead to the formation of an interpenetrating Al2O 3 network in the final product. The in

  14. Dry sliding wear behaviour of Cu based composite materials reinforced with alumina fibers

    Directory of Open Access Journals (Sweden)

    K. Naplocha

    2013-01-01

    Full Text Available Purpose: Parameters for new manufacturing route of Cu casting reinforced with alumina fibers were elaborated. There was observed improvement of hardness and wear properties of composite materials comparing to the unreinforced copper and this indicates for the proper applied process parameters.Design/methodology/approach: Manufacturing of composite materials involves two stages, preparation of porous preforms and next their infiltration with molten Cu. Preforms exhibits semioriented arrangement of fibers and their open porosity makes possible the production of composite materials with 10 and 20% by volume of Al2O3 fibers (Saffil. Wear tests were carried out applying the pin-on-disc concept at constant sliding velocity and under two different pressures. Specimens were pressed against the cast iron counterpart prepared from standard brake disc material.Findings: Reinforcing of pure Cu with ceramic fibers results in the significant increase of hardness both by reducing the grain size and creating high level of residual stresses due to thermal mismatch of composite components. Fibers improves effectively wear resistance and under lower pressure of 0.2 MPa, in relation to unreinforced Cu, composite with 20% of fibers exhibits 6 times lower volume lost. Under smaller pressure wear process proceeded with plastic deformation of subsurface, cracking of reinforcement and transferring such segments to friction surface. Wear products containing hard fragments of alumina fibers as well as iron and copper oxides are transferred between surfaces and abrade weared parts. Thus only after friction against composite with 10% of fiber wear of iron counterpart was relatively small.Research limitations/implications: Reinforcing of Cu by squeeze casting method requires application of the die from high temperature resistant steel tool. Preform preheated to high temperature before infiltration, should be transferred to the mold very quickly in order to keep temperature

  15. 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- composite s * Mechanical properties * Machinability Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.605, year: 2014

  16. Characterization of silane coated hollow sphere alumina-reinforced ultra high molecular weight polyethylene composite as a possible bone substitute material

    Indian Academy of Sciences (India)

    S Roy; S Pal

    2002-12-01

    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 were characterized for mechanical properties using destructive and non-destructive ultrasonic testing methods. The physical properties of the composite were determined and compared with those of cortical bone.

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

    International Nuclear Information System (INIS)

    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

  18. A novel structure for carbon nanotube reinforced alumina composites with improved mechanical properties

    International Nuclear Information System (INIS)

    Engineering ceramics have high stiffness, excellent thermostability, and relatively low density, but their brittleness impedes their use as structural materials. Incorporating carbon nanotubes (CNTs) into a brittle ceramic might be expected to provide CNT/ceramic composites with both high toughness and high temperature stability. Until now, however, materials fabrication difficulties have limited research on CNT/ceramic composites. The mechanical failure of CNT/ceramic composites reported previously is primarily attributed to poor CNT-matrix connectivity and severe phase segregation. Here we show that a novel processing approach based on the precursor method can diminish the phase segregation of multi-walled carbon nanotubes (MWCNTs), and render MWCNT/alumina composites highly homogeneous. The MWCNTs used in this study are modified with an acid treatment. Combined with a mechanical interlock induced by the chemically modified MWCNTs, this approach leads to improved mechanical properties. Mechanical measurements reveal that only 0.9 vol% acid-treated MWCNT addition results in 27% and 25% simultaneous increases in bending strength (689.6 ± 29.1 MPa) and fracture toughness (5.90 ± 0.27 MPa m1/2), respectively

  19. Alumina-tantalum composite for femoral head applications in total hip arthroplasty

    International Nuclear Information System (INIS)

    Dense composite laminates of alumina (Al2O3) and tantalum (Ta) were fabricated by hot pressing and tested in vitro for potential use as a femoral head material in total hip arthroplasty (THA). Al2O3-Ta composite laminates hot pressed at 1450 deg. C and 1650 deg. C had flexural strengths of 940 ± 180 MPa and 1090 ± 340 MPa, respectively, which were far larger than the values of 420 ± 140 MPa and 400 ± 130 MPa for Al2O3 hot pressed at 1450 deg. C and 1650 deg. C, respectively. The interfacial shear strength, determined by a double-notched specimen test, was 310 ± 80 MPa for the composite laminate hot pressed at 1650 deg. C, indicating strong interfacial bonding between Al2O3 and Ta. Scanning electron microscopy (SEM), energy dispersive X-ray (EDS) analysis, and X-ray mapping of polished sections of the hot-pressed laminates showed the presence of an interfacial region formed presumably by diffusion of O (at 1450 deg. C) or O and Al (1650 deg. C) from Al2O3 into Ta. Composite femoral heads of Al2O3 and Ta could combine the low wear of an Al2O3 articulating surface with the safety of a ductile metal femoral head.

  20. Chemical mechanical polishing of hard disk substrate with {alpha}-alumina-g-polystyrene sulfonic acid composite abrasive

    Energy Technology Data Exchange (ETDEWEB)

    Lei Hong, E-mail: hong_lei2005@yahoo.com.c [Research Center of Nano-science and Nano-technology, Shanghai University, Shanghai 200444 (China); Bu Naijing; Chen Ruling; Hao Ping [Research Center of Nano-science and Nano-technology, Shanghai University, Shanghai 200444 (China); Neng Sima; Tu Xifu; Yuen Kwok [Shenzhen Kaifa Magnetic Recording Co., LTD, Shenzhen, 518035 (China)

    2010-05-03

    {alpha}-Alumina-g-polystyrene sulfonic acid ({alpha}-Al{sub 2}O{sub 3}-g-PSS) composite abrasive was prepared by surface activation, graft polymerization and sulfonation, successively. The composition, dispersibility and morphology of the product were characterized by Fourier transformed infrared spectroscopy, laser particle size analysis and scanning electron microscopy, respectively. The chemical mechanical polishing (CMP) performances of the composite abrasive on hard disk substrate with nickel-phosphorous plating were investigated. The microscopy images of the polished surfaces show that {alpha}-Al{sub 2}O{sub 3}-g-PSS composite abrasive results in improved CMP and post-CMP cleaning performances than pure {alpha}-alumina abrasive under the same testing conditions.

  1. Asymmetric Composite Nanoparticles with Anisotropic Surface Functionalities

    Directory of Open Access Journals (Sweden)

    Donglu Shi

    2009-01-01

    Full Text Available Asymmetric inorganic/organic composite nanoparticles with anisotropic surface functionalities represent a new approach for creating smart materials, requiring the selective introduction of chemical groups to dual components of composite, respectively. Here, we report the synthesis of snowman-like asymmetric silica/polystyrene heterostructure with anisotropic functionalities via a chemical method, creating nanostructure possibly offering two-sided biologic accessibility through the chemical groups. Carboxyl group was introduced to polystyrene component of the snowman-like composites by miniemulsion polymerization of monomer on local surface of silica particles. Moreover, amino group was then grafted to remained silica surface through facile surface modification of the composite nanoparticles. The asymmetric shape of these composites was confirmed by TEM characterization. Moreover, characteristics of anisotropic surface functionalities were indicated by Zeta potential measurement and confocal laser microscopy after being labeled with fluorescent dyes. This structure could find potential use as carriers for biological applications.

  2. 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 material is relatively high, carbon nanoparticle doped SU-8 is a valid candidate for the piezoresistive readout in polymer based cantilever sensors, with potentially higher sensitivity than silicon based cantilevers....

  3. Urea-formaldehyde as a precursor for the preparation of alumina-zirconia composites by sol-gel polymeric route

    International Nuclear Information System (INIS)

    Homogeneous ultra fine pure alumina zirconia powders were prepared through the polymerization reaction taking place between urea and formaldehyde. Composites with varying concentration of zirconia namely 10, 20, 30, 40 and 50% were prepared. The concentration of both cations Al3+ and Zr4+ substituted in the hosting resin structure was kept constant equivalent to one mol oxide utilizing AlCl3 and ZrCl4 as precursors. Conditions of preparation comprising temperature, time and pH were optimized. DTA and IR were performed for the obtained resins. The respective crystalline phases developed and the distribution of pores in powders calcined at 1000 C were determined by XRD and Hg porosimeter, respectively. XRD showed that the main phases present were minor amounts of γ-alumina and θ-alumina together with cubic zirconia. Maximum densification of green compacts was achieved by composites containing 20 and 30 mol% zirconia. SEM of bodies fired at 1550 c from composites containing 20 and 50 mol% ZrO2 showed equigranular zirconia and alumina particles that cannot be differentiated morphologically. Map analysis showed well distribution of both elements Al and Zr. (orig.)

  4. Following the evolution of morphology, composition and crystallography of alumina based catalysts after laser ablation: Implications for analysis by LA-ICP-AES

    International Nuclear Information System (INIS)

    Fundamental understanding of aerosol formation during laser ablation is important for the development of LA-ICP analysis of complex samples. Using a Lina Spark AtomizerTM, the application of this technique to the field of heterogeneous catalysis gave an accuracy of 5-15% while extreme values of +100% could be obtained in some cases. To improve understanding of laser ablation processes, particles generated during ablation of alumina based catalysts were collected and analysed using different microscopy and surface analysis techniques. Morphological study by scanning electron microscopy showed that most of the particles leaving the ablation cell were nanoparticle aggregates generated from vapor condensation. An XRD study of these aerosols revealed that the condensation converge on the formation of a spinel structure with large coherence domains. Elemental composition of the aerosol was also followed and exhibited differences between a catalyst containing large Mo concentration or low Pt concentration.

  5. Nanoparticle composites for printed electronics

    International Nuclear Information System (INIS)

    Printed Electronics is a rapidly developing sector in the electronics industry, in which nanostructured materials are playing an increasingly important role. In particular, inks containing dispersions of semiconducting nanoparticles, can form nanocomposite materials with unique electronic properties when cured. In this study we have extended on our previous studies of functional nanoparticle electronic inks, with the development of a solvent-based silicon ink for printed electronics which is compatible with existing silver inks, and with the investigation of other metal nanoparticle based inks. It is shown that both solvent-based and water-based inks can be used for both silver conductors and semiconducting silicon, and that qualitatively there is no difference in the electronic properties of the materials printed with a soluble polymer binder to when an acrylic binder is used. (paper)

  6. Nanoparticle composites for printed electronics

    Science.gov (United States)

    Männl, U.; van den Berg, C.; Magunje, B.; Härting, M.; Britton, D. T.; Jones, S.; van Staden, M. J.; Scriba, M. R.

    2014-03-01

    Printed Electronics is a rapidly developing sector in the electronics industry, in which nanostructured materials are playing an increasingly important role. In particular, inks containing dispersions of semiconducting nanoparticles, can form nanocomposite materials with unique electronic properties when cured. In this study we have extended on our previous studies of functional nanoparticle electronic inks, with the development of a solvent-based silicon ink for printed electronics which is compatible with existing silver inks, and with the investigation of other metal nanoparticle based inks. It is shown that both solvent-based and water-based inks can be used for both silver conductors and semiconducting silicon, and that qualitatively there is no difference in the electronic properties of the materials printed with a soluble polymer binder to when an acrylic binder is used.

  7. The effect of α-alumina particles on the properties of EN AC-44200 Al alloy based composite materials

    OpenAIRE

    J.W. Kaczmar; A. Kurzawa

    2012-01-01

    Purpose: The unreinforced EN AC-44200 aluminium alloy is characterized by the medium mechanical properties and the purpose of performed investigations was improvement of mechanical properties of this alloy by introducing stable ceramic α-alumina particles.Design/methodology/approach: The composite materials were manufactured by squeeze casting of porous ceramic preforms characterized by the open porosities of 90%, 80%, 70% and 60% with the liquid EN AC- 44200 aluminum alloy. The composite mat...

  8. Tunnel magnetoresistance in alumina, magnesia and composite tunnel barrier magnetic tunnel junctions

    OpenAIRE

    Schebaum, Oliver; Drewello, Volker; Auge, Alexander; Reiss, Günter; Münzenberg, Markus; Schuhmann, Henning; Seibt, Michael; Thomas, Andy

    2010-01-01

    Using magnetron sputtering, we have prepared Co-Fe-B/tunnel barrier/Co-Fe-B magnetic tunnel junctions with tunnel barriers consisting of alumina, magnesia, and magnesia-alumina bilayer systems. The highest tunnel magnetoresistance ratios we found were 73% for alumina and 323% for magnesia-based tunnel junctions. Additionally, tunnel junctions with a unified layer stack were prepared for the three different barriers. In these systems, the tunnel magnetoresistance ratios at optimum annealing te...

  9. 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.

  10. An investigation of the thermal cycling damage of 25 vol. pct SiCw/alumina ceramic matrix composite

    Science.gov (United States)

    Armstrong, William D.; Taya, Minoru

    1989-01-01

    An investigation was made of the thermal cycling damage of a 25 vol pct SiC whisker/alumina (SiCw/Al2O3) composite. Thermal cycling tests were conducted by subjecting a composite specimen to two different fluidized beds. After thermal cycling the composite specimens were subjected to elastic modulus and effective fracture toughness measurements. The thermal cycled specimens were investigated with SEM and TEM studies. It was found that this composite has a relatively high resistance to thermal cycling.

  11. Nanoscale calcium aluminate coated graphite for improved performance of alumina based monolithic refractory composite

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Sol–gel Ca-doped γ-Al2O3 accomplished graphite retention. • Nanocoating considerably improved matrix-aggregate bonding. • Less porous simulated matrix upgraded slag resistance. - Abstract: The synthesis and properties of high alumina castable containing nanostructured calcium aluminate coated graphite were studied in terms of slag resistance and overall physical characteristics. Raman spectroscopy, BET surface area and field emission scanning electron microscopy (FESEM) were performed to exclusively understand the coating characteristics and its compatibility in refractory composite. The coating not only secured graphite in castable for prolonged period but also noticeably improved matrix to aggregate contact. The microstructural aspects of castables were investigated, with special emphasis on a representative matrix prepared and infiltrated with slag at elevated temperature. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) of fired composite containing surface-treated graphite was quite prospective. It circumvented the problems of incorporating as-received graphite in castables and should be in the attention of refractory researchers and producers

  12. Nanoscale calcium aluminate coated graphite for improved performance of alumina based monolithic refractory composite

    Energy Technology Data Exchange (ETDEWEB)

    Mukhopadhyay, S., E-mail: msunanda_cct@yahoo.co.in

    2013-07-15

    Graphical abstract: - Highlights: • Sol–gel Ca-doped γ-Al{sub 2}O{sub 3} accomplished graphite retention. • Nanocoating considerably improved matrix-aggregate bonding. • Less porous simulated matrix upgraded slag resistance. - Abstract: The synthesis and properties of high alumina castable containing nanostructured calcium aluminate coated graphite were studied in terms of slag resistance and overall physical characteristics. Raman spectroscopy, BET surface area and field emission scanning electron microscopy (FESEM) were performed to exclusively understand the coating characteristics and its compatibility in refractory composite. The coating not only secured graphite in castable for prolonged period but also noticeably improved matrix to aggregate contact. The microstructural aspects of castables were investigated, with special emphasis on a representative matrix prepared and infiltrated with slag at elevated temperature. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) of fired composite containing surface-treated graphite was quite prospective. It circumvented the problems of incorporating as-received graphite in castables and should be in the attention of refractory researchers and producers.

  13. Joint properties of friction welded 6061 aluminum alloy/YSZ–alumina composite at low rotational speed

    International Nuclear Information System (INIS)

    Highlights: • Joint properties of FW for 6061 Al alloy/alumina–YSZ composite were clarified. • Different technique analyses with varying speeds were used in the experiment. • The microstructure, microhardness and bending strength of the joint were evaluated. • The results showed that joint was able to be friction welded in the low speed. • The low speed gave maximum bending strength and lower microhardness values. - Abstract: In this study, a ceramic composite of alumina–yttria stabilized zirconia (YSZ) was friction welded to 6061 aluminum alloy. Alumina rods containing 25 wt.% YSZ were formed using slip casting and subsequently sintered at 1600 °C to form a solid body. The 6061 aluminum alloy sample was cut and polished, and then subjected to friction welding experiments. Both rods were 16 mm in diameter. The results of this study showed that the alumina–25 wt.% YSZ composite was able to be friction welded to 6061 aluminum alloy at a lower rotational speed of 630 rpm compared with high rotational speeds. The friction force was maintained at 5 KN for a frictional time of 30 s. Optical Microscopy (OM) and Field Emission Scanning Electron Microscope (FESEM) were used to analyze the microstructure of the products, particularly at the interface of the joints. The joints were also examined with EDX line and area (energy dispersive X-ray) in order to determine the phases formed during the low speed welding. The mechanical properties including bending strength and Vickers microhardness were measured. The experimental results indicated that the mechanical strength of friction welded alumina–25 wt.% YSZ composite/6061 aluminum alloy components were obviously affected by joining in the low rotational speed (630 rpm), having higher strength as compared to higher rotational speed

  14. 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 μg 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

  15. Electrochemical Corrosion Behaviour of Alumina-Al 6061 and Silicon Carbide-Al 6061 Metal-Matrix Composites

    International Nuclear Information System (INIS)

    The electrochemical corrosion behaviour of powder metallurgy-processed metal-matrix composites (MMCs)based on Al alloy 6061 reinforced with particulate Al2O3 or Sic has been studied in chloride-containing environment. Also, the corrosion behaviour of the unrein forced Al 6061 produced by the same route investigated. Electrochemical tests were conducted on composites containing 10 and 20 vo l% of both reinforced particulates. Potentiodynamic polarization tests have been carried out in neutral as well as acidic and alkaline de-aerated 10-3M Na CI solution. In the neutral environment, the addition of Al2O3 particulates was found to shift both the corrosion potential (Ecorr) and the break down potential (Eb) slightly into the positive direction irrespective of the volume fraction added (10 and 20 vo l%). On the other hand , Sic caused a shift of Ecorr into the active site while the Eb value was slightly ennobled. For both composites, the corrosion current values at the break down potentials were almost the same as the unrein forced alloy. In an attempt to further clarify the role of both particulate addition, cathodic polarization runs were conducted in both acidic (ph 3) and alkaline (ph 9)solutions for 20 vo l% of Al2O3 and 20 vo l% Sic composite specimens. This indicated that cathodic current values for Sic composites were higher than those corresponding to the unrein forced alloy 6061, and those for the Al2O3 composites were lower

  16. 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.

  17. Age-hardening characteristics of δ-alumina fibre reinforced aluminium-silicon LM-13 alloy metal matrix composites

    OpenAIRE

    Akbulut, H; Durman, M.; F. Yilmaz

    1993-01-01

    Metal Matrix Composites (MMCs) with an aluminium-silicon based LM-13 alloy and short-staple Saffil (δ-alumina) fibres with volume fractions of 0.10, 0.15, 0.20, 0.25 and 0.30 have been produced using a pressure liquid infiltration process. The standard T6 heat treatment procedure was applied to both the unreinforced matrix alloy and the composites, and the effect of the fibres on the age-hardening characteristics of the composites has been investigated by means of hardness measurements.

  18. A comparison of the aging kinetics of a cast alumina-6061 aluminum composite and a monolithic 6061 aluminum alloy.

    OpenAIRE

    Hafley, Johanna L.

    1989-01-01

    Electrical resistivity and hardness measurements were conducted during isothermal aging treatments of an alumina particulate reinforced 6061 aluminum metal matrix composite and a monolithic 6061 aluminum control material. Transmission electron microscopy was utilized to examine the microstructural changes accompanying the changes in the resistivity of the monolithic during aging. In addition, differential scanning calorimetry was used to investigate the growth kinetics and thermal stability o...

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

    OpenAIRE

    Thomas Hanemann; Dorothée Vinga Szabó

    2010-01-01

    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 thermomechani...

  20. Unifying the templating effects of porous anodic alumina on metallic nanoparticles for carbon nanotube synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Haase, Mark R., E-mail: Mark.R.Haase@gmail.com, E-mail: haasemr@mail.uc.edu; Alvarez, Noe T.; Malik, Rachit; Schulz, Mark; Shanov, Vesselin [580 Engineering Research Center, Department of Biomedical, Chemical and Environmental Engineering (United States)

    2015-09-15

    Carbon nanotubes (CNTs) are a promising material for many applications, due to their extraordinary properties. Some of these properties vary in relation to the diameter of the nanotubes; thus, precise control of CNT diameter can be critical. Porous anodic alumina (PAA) membranes have been successfully used to template electrodeposited catalyst. However, the catalysts used in CNT synthesis are frequently deposited with more precise techniques, such as electron beam deposition. We test the efficacy of PAA as a template for electron beam-deposited catalyst by studying the diameter distribution of CNTs grown catalyst of various thicknesses supported by PAA. These are then compared by ANOVA to the diameter distributions of CNTs grown on metal catalyst supported by a conventional alumina film. These results also allow a unified description of two templating effects, the more common particles-in-pores model, and the recently described particles-between-pores.

  1. γ-Alumina Nanoparticle Catalyzed Efficient Synthesis of Highly Substituted Imidazoles

    Directory of Open Access Journals (Sweden)

    Bandapalli Palakshi Reddy

    2015-10-01

    Full Text Available γ-Alumina nano particle catalyzed multi component reaction of benzil, arylaldehyde and aryl amines afforded the highly substituted 1,2,4,5-tetraaryl imidazoles with good to excellent yield in less reaction time under the sonication as well as the conventional methods. Convenient operational simplicity, mild conditions and the reusability of catalyst were the other advantages of this developed protocol.

  2. Residual stresses generated during joining of dissimilar alumina-zirconia composites by plastic deformation and its implications on mechanical properties

    International Nuclear Information System (INIS)

    Ceramic bars of zirconia toughened-alumina composites were fabricated by pressureless sintering in air at 1450 deg. C for 4 h. Composite samples were fabricated with two different compositions: zirconia with 60 vol.% alumina (ZT60A) and zirconia with 40 vol.% alumina (ZT40A). Average four-point-bend strengths for the ZT40A and ZT60A were 480 ± 45 MPa and 410 ± 120 MPa, respectively. Three-layered sandwich structures were fabricated by joining two bars of sintered ZT60A with a sintered ZT40A bar. High-temperature plastic joining was accomplished at 1350 deg. C at a strain rate of 5 x 10-6 s-1 and a compressive stress ranging from 30-40 MPa. Bend tests conducted on the layered structure exhibited average strengths of 707 ± 81 MPa. Strength enhancements for the multilayered structure were higher than those predicted by stress analysis. Stress enhancements were compared with the residual stresses measured in the layered sample using X-ray micro-diffraction at the Advance Photon Source (APS). Scanning electron microscopy (SEM) was also conducted to identify the location of failure causing flaws.

  3. Piezoelectric Nanoparticle-Polymer Composite Materials

    Science.gov (United States)

    McCall, William Ray

    Herein we demonstrate that efficient piezoelectric nanoparticle-polymer composite materials can be synthesized and fabricated into complex microstructures using sugar-templating methods or optical printing techniques. Stretchable foams with excellent tunable piezoelectric properties are created by incorporating sugar grains directly into polydimethylsiloxane (PDMS) mixtures containing barium titanate (BaTiO3 -- BTO) nanoparticles and carbon nanotubes (CNTs), followed by removal of the sugar after polymer curing. Porosities and elasticity are tuned by simply adjusting the sugar/polymer mass ratio and the electrical performance of the foams showed a direct relationship between porosity and the piezoelectric outputs. User defined 2D and 3D optically printed piezoelectric microstructures are also fabricated by incorporating BTO nanoparticles into photoliable polymer solutions such as polyethylene glycol diacrylate (PEGDA) and exposing to digital optical masks that can be dynamically altered. Mechanical-to-electrical conversion efficiency of the optically printed composite is enhanced by chemically altering the surface of the BTO nanoparticles with acrylate groups which form direct covalent linkages with the polymer matrix under light exposure. Both of these novel materials should find exciting uses in a variety of applications including energy scavenging platforms, nano- and microelectromechanical systems (NEMS/MEMS), sensors, and acoustic actuators.

  4. Preparation and properties of buckypaper-gold nanoparticle composites

    OpenAIRE

    GOUNKO, IOURI; BYRNE, MICHELE THERESE; HANLEY, CORMAC

    2010-01-01

    PUBLISHED Highly conductive buckypaper-gold nanoparticles composites have been prepared by the in situ electroless deposition of gold nanoparticles during the filtration that resulted in increases in conductivities of up to 684% at very low gold content.

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

    OpenAIRE

    Radosław Lach; Krzysztof Haberko; Mirosław Bućko

    2011-01-01

    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-...

  6. A Study of Parameters Affecting Wear Resistance of Alumina and Yttria Stabilized Zirconia Composite Coatings on Al-6061 Substrate

    OpenAIRE

    N Krishnamurthy; Prashanthareddy, M. S.; H. P. Raju; H. S. Manohar

    2012-01-01

    In this investigation, a composite coating of alumina and yttria stabilized zirconia in equal proportion was developed on Al-6061 substrate using Atmospheric Plasma Spraying technique. Two commercially available powders of chemical composition Al 25Fe7Cr5Ni and Al2O330(Ni 20Al) were used as bond coats. The coating samples were subjected to abrasive wear test as per ASTM G99. From the results it was found that wear rate and coefficient of friction depend on various parameters such as microstru...

  7. Composition, structure and electrical properties of alumina barrier layers grown in fluoride-containing oxalic acid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Jagminas, A. [Institute of Chemistry, A. Gostauto 9, LT-01108 Vilnius (Lithuania)], E-mail: jagmin@ktl.mii.lt; Vrublevsky, I. [Department of Microelectricals, Belarusian State University of Informatics and Radioelectricals, 6 Brovka Street, Minsk 220013 (Belarus); Kuzmarskyte, J.; Jasulaitiene, V. [Institute of Chemistry, A. Gostauto 9, LT-01108 Vilnius (Lithuania)

    2008-04-15

    The composition, structure and electrical properties of alumina barrier layers grown by anodic oxidation in F{sup -}-containing (FC) and F{sup -}-free (FF) oxalic acid solutions were studied using the re-anodizing/dissolution technique, Fourier-transformed infrared and X-ray photoelectron spectroscopy. These results confirmed formation in FC anodizing solutions of films structurally different from ones grown in FF oxalic acid baths. It was found that the barrier layer of FC alumina films is composed of two layers differing in the dissolution rate. These differences are related to the formation in the FC electrolyte of a barrier layer composed of a more microporous outer part and a thin, non-porous and non-scalloped inner part consisting of aluminum oxide and aluminum fluoride.

  8. Evaluation of interfacial bonding in dissimilar materials of YSZ-alumina composites to 6061 aluminium alloy using friction welding

    International Nuclear Information System (INIS)

    Research highlights: → Friction-welding process. → Joining between ceramic composite and metal alloy. → Slip casting of the yttria stabilized zirconia/alumina composite samples. - Abstract: The interfacial microstructures characteristics of alumina ceramic body reinforced with yttria stabilized zirconia (YSZ) was evaluated after friction welding to 6061 aluminum alloy using optical and electron microscopy. Alumina rods containing 25 and 50 wt% yttria stabilized zirconia were fabricated by slip casting in plaster of Paris (POP) molds and subsequently sintered at 1600 deg. C. On the other hand, aluminum rods were machine down to the required dimension using a lathe machine. The diameter of the ceramic and the metal rods was 16 mm. Rotational speeds for the friction welding were varied between 900 and 1800 rpm. The friction pressure was maintained at 7 MPa for a friction time of 30 s. Optical and scanning electron microscopy was used to analyze the microstructure of the resultant joints, particularly at the interface. The joints were also examined with EDX line (energy dispersive X-ray) in order to determine the phases formed during the welding. The mechanical properties of the friction welded YSZ-Al2O3 composite to 6061 alloy were determined with a four-point bend test and Vickers microhardness. The experimental results showed the degree of deformation varied significantly for the 6061 Al alloy than the ceramic composite part. The mechanical strength of friction-welded ceramic composite/6061 Al alloy components were obviously affected by joining rotational speed selected which decreases in strength with increasing rotational speed.

  9. Microstructural characterization by secondary ion mass spectrometry of (alumina + zirconia) fiber/glass composites with and without a tin dioxide interphase

    International Nuclear Information System (INIS)

    Alumina + zirconia fiber (PRD-166)/glass (N51A) matrix composites were fabricated with and without a tin dioxide barrier layer. A qualitative comparison of the elemental distribution was made between the two composite systems by secondary ion microscopy. Secondary ion mass spectrometry would appear to be especially useful to obtain the distribution of light elements such as B, Na, Cl, etc. in ceramic and glass composites. The authors study of PRD-166/glass and PRD-166/SnO2/glass composites shows that tin dioxide serves as an effective barrier between this (alumina + zirconia) fiber and the silica-based glass

  10. Alpha-alumina nanoparticles induce efficient autophagy-dependent cross-presentation and potent antitumour response

    Science.gov (United States)

    Li, Haiyan; Li, Yuhuan; Jiao, Jun; Hu, Hong-Ming

    2011-10-01

    Therapeutic cancer vaccination is an attractive strategy because it induces T cells of the immune system to recognize and kill tumour cells in cancer patients. However, it remains difficult to generate large numbers of T cells that can recognize the antigens on cancer cells using conventional vaccine carrier systems. Here we show that α-Al2O3 nanoparticles can act as an antigen carrier to reduce the amount of antigen required to activate T cells in vitro and in vivo. We found that α-Al2O3 nanoparticles delivered antigens to autophagosomes in dendritic cells, which then presented the antigens to T cells through autophagy. Immunization of mice with α-Al2O3 nanoparticles that are conjugated to either a model tumour antigen or autophagosomes derived from tumour cells resulted in tumour regression. These results suggest that α-Al2O3 nanoparticles may be a promising adjuvant in the development of therapeutic cancer vaccines.

  11. 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...

  12. 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

  13. Tension-Compression Fatigue of a Nextel™720/alumina Composite at 1200 °C in Air and in Steam

    Science.gov (United States)

    Lanser, R. L.; Ruggles-Wrenn, M. B.

    2016-02-01

    Tension-compression fatigue behavior of an oxide-oxide ceramic-matrix composite was investigated at 1200 °C in air and in steam. The composite is comprised of an alumina matrix reinforced with Nextel™720 alumina-mullite fibers woven in an eight harness satin weave (8HSW). The composite has no interface between the fiber and matrix, and relies on the porous matrix for flaw tolerance. Tension-compression fatigue behavior was studied for cyclical stresses ranging from 60 to 120 MPa at a frequency of 1.0 Hz. The R ratio (minimum stress to maximum stress) was -1.0. Fatigue run-out was defined as 105 cycles and was achieved at 80 MPa in air and at 70 MPa in steam. Steam reduced cyclic lives by an order of magnitude. Specimens that achieved fatigue run-out were subjected to tensile tests to failure to characterize the retained tensile properties. Specimens subjected to prior cyclic loading in air retained 100 % of their tensile strength. The steam environment severely degraded tensile properties. Tension-compression cyclic loading was considerably more damaging than tension-tension cyclic loading. Composite microstructure, as well as damage and failure mechanisms were investigated.

  14. Tension-Compression Fatigue of a Nextel™720/alumina Composite at 1200 °C in Air and in Steam

    Science.gov (United States)

    Lanser, R. L.; Ruggles-Wrenn, M. B.

    2016-08-01

    Tension-compression fatigue behavior of an oxide-oxide ceramic-matrix composite was investigated at 1200 °C in air and in steam. The composite is comprised of an alumina matrix reinforced with Nextel™720 alumina-mullite fibers woven in an eight harness satin weave (8HSW). The composite has no interface between the fiber and matrix, and relies on the porous matrix for flaw tolerance. Tension-compression fatigue behavior was studied for cyclical stresses ranging from 60 to 120 MPa at a frequency of 1.0 Hz. The R ratio (minimum stress to maximum stress) was -1.0. Fatigue run-out was defined as 105 cycles and was achieved at 80 MPa in air and at 70 MPa in steam. Steam reduced cyclic lives by an order of magnitude. Specimens that achieved fatigue run-out were subjected to tensile tests to failure to characterize the retained tensile properties. Specimens subjected to prior cyclic loading in air retained 100 % of their tensile strength. The steam environment severely degraded tensile properties. Tension-compression cyclic loading was considerably more damaging than tension-tension cyclic loading. Composite microstructure, as well as damage and failure mechanisms were investigated.

  15. Effect of change in cation composition of cryolite-alumina melts on anodic overwork

    International Nuclear Information System (INIS)

    Stationary polarization of platinum and glass carbon anodes in minor KF and LiF doped cryolite-alumina melt at different concentrations of alumina is searched in laboratory cell. Individual additive of LiF results in the raise of anode overvoltage by 50-80 mV at glass carbon and ∼25 mV at platinum anodes. Substitution of part of Na+ ions for Li+ in the amount to ∼3.7 mol.% of LiF (∼1.8 mas.%) results in the low polarization

  16. 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

  17. 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.

  18. Aluminium AA6061 Matrix Composite Reinforced with Spherical Alumina Particles Produced by Infiltration: Perspective on Aerospace Applications

    OpenAIRE

    Claudio Bacciarini; Vincent Mathier

    2014-01-01

    Metal matrix composites, based on AA6061 reinforced with 60 vol% Al2O3 spherical particles, were produced by gas pressure infiltration and characterized for hardness, impulse excitation modulus, tensile properties (at room temperature and at 250°C), and machining. It was experimentally demonstrated that the novel alumina powder used in the present work does not react with the liquid Mg-containing matrix during the infiltration process. The AA6061 matrix therefore retains its ability to be str...

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

    DEFF Research Database (Denmark)

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

    2014-01-01

    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...

  20. Highly conductive alumina/NCN composites electrodes fabricated by gelcasting and reduction-sintering-An electrochemical behavior study in aggressive environments

    International Nuclear Information System (INIS)

    A novel highly conductive alumina/nano-carbon network composites (alumina/NCN composites) was fabricated by gelcasting and reduction-sintering method under argon atmosphere. The electrochemical behaviors of the alumina/NCN composites were studied systematically in some aggressive solutions (HCl, H2SO4, HNO3, NaOH, and KOH), using potentiodynamic polarization and chronoamperometry and X-ray diffraction and SEM observations. The results showed that the electrochemical stability and reproducibility of the composite electrodes in these diluted acids and alkalis were very good and had, in some extent, an electro-catalytic activity toward formation of hydrogen evolution and reduction of dissolved oxygen in aqueous solutions in comparison with a commercial graphite electrode. In addition, the pyrolyzed nano-carbon contents, size, and shape in the alumina matrix, have greatly effects on the electrochemical performances and electrode reactions in these solutions. It is found that the minimal residual carbon content of 0.62 wt.% in the matrix is enough to improve electrochemical performances and avoid to loss the ceramics physical properties at the same time. When the additional potential in all the tested electrolytes was at +1700 mV (vs. SCE), alumina particles at the electrode surface were not observed to dissolve into solution in this case, indicating the material being suitable for electrodes in aggressive solutions

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

    International Nuclear Information System (INIS)

    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.

  2. Fabrication and characterization of ultra-water-repellent alumina-silica composite films

    International Nuclear Information System (INIS)

    Ultra-water-repellent (UWR) films were prepared by microwave plasma-enhanced chemical vapour deposition using trimethylmethoxysilane and aluminium (III) diisopropoxide ethylacetoacetate (ADE) as raw materials. The film was mainly composed of silica and alumina and was apparently transparent. The film thickness was approximately 500 nm. The sample surface was treated with an organosilane in order to introduce hydrophobic groups. The hydrophobic modification led to a water contact angle of more than 1500, whose value corresponds to the UWR surface. The hardness of film with an optimized Al content was significantly improved compared with that without Al. The maximum hardness was 1.71 GPa. In consequence, we successfully prepared an UWR film in the silica-alumina system

  3. 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.

  4. 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.

  5. Effects of Slurry Chemistry on the Rate of Agglomeration of Alumina Nanoparticles for Chemical Mechanical Planarization

    Science.gov (United States)

    Brahma, Neil Anjan

    Chemical mechanical planarization (CMP) is a polishing process used during the manufacture of microelectronic integrated circuits. During fabrication of multilevel circuitry, excess deposited material must be removed and the wafer surface globally planarized for proper function of devices. This is especially necessary with copper interconnects, thus, copper CMP was the focus of this study. CMP requires the use of a slurry containing nanometer-sized abrasive particles along with a variety of chemical additives. The particles and chemicals act synergistically to mechanically and chemically remove material and provide a near globally planar surface. For optimal CMP performance, the effective abrasive particle size must be controlled. If particles aggregate, CMP performance may diminish and possibly even cause defective devices. The chemistry of the slurry (pH, ions present, etc) can not only affect the mean aggregate size of the abrasive particles, but also growth of aggregate over time. This research investigated the aggregation behavior of suspensions of 150 nm alumina particles in 1mM KNO3 with various additives (glycine, H2O2, benzotriazole, and sodium dodecyl sulfate) used in CMP of copper through effective particle (agglomerate) size versus time and zeta potential measurements. Aggregate size rate data were analyzed to elucidate the mechanism of aggregation, as well its effect on the structure of the resultant aggregate. The effects of temperature of the slurry were also explored. Finally, particle size distribution data collected at various stages of aggregation were incorporated into the Luo and Dornfeld model of CMP to investigate the dynamic nature of the CMP process.

  6. Influence of chemical composition on volume resistivity of alumina and zirconia plasma deposits

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Sedláček, J.

    Bratislava: FCHPT STU Bratislava, 2001 - (Koman, M.; Mikloš, D.). s. 23-24 ISBN 80-85330-90-3. [Development of Materials Science in Research and Education /11./. 09.09.2001-13.09.2001, Kežmarské Žlaby] Institutional research plan: CEZ:AV0Z2043910 Keywords : alumina, plasma Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

  7. 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.

  8. 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

    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...... production of H-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...

  9. Hydrogen gas evolution from water-dispersed titania and alumina nanoparticles by γ-ray irradiation

    International Nuclear Information System (INIS)

    Hydrogen gas evolution induced by 60Co gamma-ray irradiation of nanoparticles dispersed in water was investigated. Nanoparticles of TiO2 and Al2O3, whose average sizes were within the range of 14-33 nm, were employed. Hydrogen-gas yield from a sample dispersion in a closed vial was measured by gas chromatography after the irradiation. The sample exhibited much larger hydrogen yields than that in the pure water radiolysis. The hydrogen yield increased with the absorbed dose and the amount of particles dispersed in water. These results support the fact that the reaction is activated by both the γ-ray irradiation and the dispersed particles. In conjunction with results of TEM observation, it was implied that these enhancement effects should depend on the size and/or shape of the particles rather than their chemical species. We calculated the G-values for the hydrogen-gas evolution. They will be useful for the discussion about the reaction. (author)

  10. Nanocomposite formed by titanium ion implantation into alumina

    International Nuclear Information System (INIS)

    Composites of titanium nanoparticles in alumina were formed by ion implantation of titanium into alumina, and the surface electrical conductivity measured in situ as the implantation proceeded, thus generating curves of sheet conductivity as a function of dose. The implanted titanium self-conglomerates into nanoparticles, and the spatial dimensions of the buried nanocomposite layer can thus be estimated from the implantation depth profile. Rutherford backscattering spectrometry was performed to measure the implantation depth profile, and was in good agreement with the calculated profile. Transmission electron microscopy of the titanium-implanted alumina was used for direct visualization of the nanoparticles formed. The measured conductivity of the buried layer is explained by percolation theory. We determine that the saturation dose, φ0, the maximum implantation dose for which the nanocomposite material still remains a composite, is φ0 = 2.2 × 1016 cm−2, and the corresponding saturation conductivity is σ0 = 480 S/m. The percolation dose φc, below which the nanocomposite still has basically the conductivity of the alumina matrix, was found to be φc = 0.84 × 1016 cm−2. The experimental results are discussed and compared with a percolation theory model

  11. Development of ceramic composites from mixture of alumina and ceramic precursor polymer poly (silsesquioxane)); Desenvolvimento de compositos ceramicos a partir de mistura de alumina e polimero precursor ceramico polissilsesquioxano

    Energy Technology Data Exchange (ETDEWEB)

    Machado, Glauson Aparecido Ferreira

    2009-07-01

    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)

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

    International Nuclear Information System (INIS)

    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

  13. Effect of short milling time and microwave heating on phase evolution, microstructure and mechanical properties of alumina-mullite-zirconia composites

    Energy Technology Data Exchange (ETDEWEB)

    Majidian, Hudsa; Nikzad, Leila; Eslami-Shahed, Hossein; Ebadzadeh, Touradj [Materials and Energy Research Center, Alborz (Iran, Islamic Republic of). Ceramic Dept.

    2015-12-15

    Alumina-mullite-zirconia composites were prepared using alumina and zircon powders pressed uniaxially at 250 MPa and sintered in a microwave furnace held at 1 550 C for 90 min. The effects of short milling and sintering time on the density, phase evaluation and mechanical strength of the sintered composites were analyzed and compared with composites sintered in a conventional furnace. The goal was to decrease sintering time and temperature over that for conventional heating. The results showed that, although the densities were similar for both methods, the hardness, mechanical strength and fraction of the tetragonal zirconia phase of the microwave-sintered composites were much higher. The milling time yielded better densification and higher mechanical properties. It was found that the shorter sintering time in a microwave furnace requires longer milling time of the powders to obtain the same composite properties.

  14. Antimicrobial Bacterial Cellulose-Silver Nanoparticles Composite Membranes

    OpenAIRE

    Barud, Hernane S.; Thaís Regiani; Rodrigo F. C. Marques; Wilton R. Lustri; Younes Messaddeq; Ribeiro, Sidney J.L.

    2011-01-01

    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 toge...

  15. Investigation on the atomic oxygen erosion resistance of sol-gel alumina-silica composite films on Kapton

    International Nuclear Information System (INIS)

    Alumina-silica composite films with various Al/Si molar ratios were deposited on Kapton substrate by sol-gel method and their atomic oxygen (AO) erosion resistance was tested in a ground-based AO simulator. The surface morphologies and structures of the composite films were analyzed by scanning electronic microscopy, atomic force microscopy, Fourier transformed infrared spectroscopy and X-ray photoelectron spectroscopy. The results indicate that with increasing the Si content, the film surfaces tend to become smooth from a particle-like morphology of the AlOOH film. The composite films are a diphase structure composed of crystal AlOOH and amorphous SiO2, where Al-O-Si bonds were detected between the two phases. The AO exposure results suggest that the composite films with Al/Si = 1/1 and 1/2 have the best AO erosion resistance. The erosion yield of the coated Kapton decreases to 2.4 x 10-26 cm3|atom-1, two orders of magnitude less than the value of 3.0 x 10-24 cm3|atom-1 of pristine Kapton. Unlike the silica film, no crack was observed in the composite films during AO exposure. However, the micro-pores in the composite films with lower Si content become the path of AO eroding Kapton substrate. As the Si content increases, the composite films provide excellent AO protection for Kapton substrate. This is due to the good toughness and densification of the composite films

  16. PREDICTION OF TOOL CONDITION DURING TURNING OF ALUMINIUM/ALUMINA/GRAPHITE HYBRID METAL MATRIX COMPOSITES USING MACHINE LEARNING APPROACH

    Directory of Open Access Journals (Sweden)

    N. RADHIKA

    2015-10-01

    Full Text Available Aluminium/alumina/graphite hybrid metal matrix composites manufactured using stir casting technique was subjected to machining studies to predict tool condition during machining. Fresh tool as well as tools with specific amount of wear deliberately created prior to machining experiments was used. Vibration signals were acquired using an accelerometer for each tool condition. These signals were then processed to extract statistical and histogram features to predict the tool condition during machining. Two classifiers namely, Random Forest and Classification and Regression Tree (CART were used to classify the tool condition. Results showed that histogram features with Random Forest classifier yielded maximum efficiency in predicting the tool condition. This machine learning approach enables the prediction of tool failure in advance, thereby minimizing the unexpected breakdown of tool and machine.

  17. Composite comprising nanoparticles and method of making nanoparticles

    OpenAIRE

    Bozukova, Dimitriya; Jérôme, Christine

    2011-01-01

    The invention relates to a method for the production of nanoparticles comprising a conjugated polymer. The method comprises (i) providing a reaction mixture with a monomer, a photosensitising agent and a solvent, and (ii) exposing the reaction mixture to photo-irradiation to form nanoparticles of a conjugated polymer wherein the photosensitising agent is immiscible with the solvent.

  18. 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.

  19. Glucose microbiosensor based on alumina sol-gel matrix/electropolymerized composite membrane.

    Science.gov (United States)

    Chen, Xiaohong; Hu, Yibai; Wilson, George S

    2002-12-01

    A procedure is described that provides co-immobilization of enzyme and bovine serum albumin (BSA) within an alumina sol-gel matrix and a polyphenol layer permselective for endogenous electroactive species. BSA has first been employed for the immobilization of glucose oxidase (GOx) on a Pt electrode in a sol-gel to produce a uniform, thin and compact film with enhanced enzyme activity. Electropolymerization of phenol was then employed to form an anti-interference and protective polyphenol film within the enzyme layer. In addition, a stability-reinforcing membrane derived from (3-aminopropyl)-trimethoxysilane was constructed by electrochemically-assisted crosslinking. This hybrid film outside the enzyme layer contributed both to the improved stability and to permselectivity. The resulting glucose sensor was characterized by a short response time (<10 s), high sensitivity (10.4 nA/mM mm(2)), low interference from endogenous electroactive species, and a working lifetime of at least 60 days. PMID:12392950

  20. 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.

  1. Thresholds in creep behaviour of magnesium alloy matrix composites with short alumina fibres

    Czech Academy of Sciences Publication Activity Database

    Milička, Karel; Dobeš, Ferdinand

    Naples : University of Naples, 2005 - (Crivelli-Visconti, I.), s. 223-224 [Advancing with composites 2005. Naples (IT), 11.10.2005-14.10.2005] R&D Projects: GA ČR(CZ) GA106/03/0843 Institutional research plan: CEZ:AV0Z20410507 Keywords : metal matrix composite * creep * threshold stress Subject RIV: JI - Composite Materials

  2. Alumina/Phenolphthalein Polyetherketone Ceramic Composite Polypropylene Separator Film for Lithium Ion Power Batteries

    International Nuclear Information System (INIS)

    Highlights: • PEK-C (Tg: ∼230 °C) was used as binder to prepare ceramic coated composite PP separator. • The composite PP separator was stable and showed low thermal shrinkage in the electrolyte solvent. • The composite PP separator was helpful for high current density discharge. • The composite PP separator improved the safety performance of the coin cells. - Abstract: One way to obtain the lithium ion power battery with better safety performance was to increase the thermal shrinkage resistance of the separator at higher temperature. Phenolphthalein polyetherketone (PEK-C) is a polymer that can withstand high temperature to about 230 °C. Here, we developed a new Al2O3 coated composite polypropylene (PP) separator with PEK-C as binder. The coating layer was formed on the surface of the PP separator and both ceramic particles and binder did not infiltrated into the separator along the thickness direction. The composite separator with 4 μm coating layer provided balanced permeability and thermal shrinkage properties. The composite separator was stable at the electrochemical window for lithium ion battery. The coin cells with composite separator showed better charge/discharge performance than that of the cells with the PP separator. It seemed that the composite separator was helpful for high current density discharge. Also, the battery safety performance test had verified that the Al2O3 coated composite separator with PEK-C as binder had truly improved the safety performance of the coin cells. So, the newly developed Al2O3 coated composite PP separator was a promising safety product for lithium ion power batteries with high energy density

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

    International Nuclear Information System (INIS)

    Composites of the CaO-Al2O3-ZrO2 system are widely used in many industrial applications. In this study, porous Ca stabilized ZrO2 composites were developed from a starting mixture of m-ZrO2 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-ZrO2 formed with the composition of Ca0.15Zr0.85O1.85. The sintering of the mixtures lead to porous composites materials. Textural properties were analyzed considering the initial composition and the present crystalline phases. (author)

  4. 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)

  5. Laser synthesis and modification of composite nanoparticles in liquids

    International Nuclear Information System (INIS)

    The works devoted to the formation and modification of nanoparticles using laser ablation of solid targets in liquids are reviewed. Several approaches to implement laser ablation in liquids, aimed at synthesising nanoparticles of complex composition, are considered: direct laser ablation of a target of corresponding composition, laser ablation of a combined target composed of two different metals, laser irradiation of a mixture of two or more colloidal solutions, and laser ablation in reactive liquids. The properties of two-component bimetallic systems (Ag - Cu, Ag - Au), semiconductor nanocrystals (ZnO, CdSe), chalcopyrite nanoparticles, and doped oxide nanoparticles (ZnO:Ag, Gd2O2:Tb3+) formed as a result of single- and double-pulse laser ablation in different liquids (water, ethanol, acetone, solutions of polysaccharides) are discussed. (photonics and nanotechnology)

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

    International Nuclear Information System (INIS)

    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)

  7. 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.

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

    International Nuclear Information System (INIS)

    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

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

    Directory of Open Access Journals (Sweden)

    Sonia C. Ferreira

    2014-12-01

    Full Text Available Specimens of aluminum-based composites reinforced by silicon carbide nanoparticles (Al/SiCnp produced by powder metallurgy (PM were anodized under voltage control in tartaric-sulfuric acid (TSA. In this work, the influence of the amount of SiCnp 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 SiCnp. The current peaks and the steady-state current density recorded at each voltage step increases with the SiCnp volume fraction due to the oxidation of the SiCnp. The formation mechanism of the anodic film on Al/SiCnp 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 SiCnp in the anodic film.

  10. The structure of compositionally constrained zinc-ferrite spinel nanoparticles

    International Nuclear Information System (INIS)

    ZnFe2O4 bulk material shows a normal-spinel structure and a closely defined composition at Zn2+/Fe3+ ≅ 0.5. However, the composition of zinc ferrite, prepared as nanoparticles, can be varied in a broad range without losing the single-phase spinel structure. In this article, structural mechanisms enabling this non-stoichiometry were studied using the X-ray absorption fine structure (EXAFS) in combination with X-ray diffractometry (XRD), transmission electron microscopy (TEM), and magnetic measurements. Nanoparticles with a narrow size distribution were synthesized using co-precipitation in water-in-oil microemulsions. First, the structure of the stoichiometric zinc-ferrite nanoparticles was studied in dependence of their size and the annealing temperature. EXAFS analysis showed that the degree of inversion x (as defined in the compound formula (Zn1−xFex)[Fe2−xZnx]O4, with round and square brackets representing the tetrahedral and octahedral sites, respectively) increased with decreasing nanoparticles size. The structure of the stoichiometric nanoparticles and the nanoparticles of comparable size displaying Zn/Fe ratio of 0.2 (Fe-rich) and 0.7 (Zn-rich) were then compared. Analysis showed that the non-stoichiometry is structurally compensated predominantly in the core of the nanoparticle by the adjusted distribution of Zn and Fe ions over the two sublattices of the spinel structure.

  11. 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...

  12. Shear bond strength between alumina substrate and prosthodontic resin composites with various adhesive resin systems

    OpenAIRE

    AlJehani, Yousef A.; Baskaradoss, Jagan K; Geevarghese, Amrita; AlShehry, Marey A; Pekka K. Vallittu

    2015-01-01

    Background With the increase in demand for cosmetics and esthetics, resin composite restorations and all-ceramic restorations have become an important treatment alternative. Taking into consideration the large number of prosthodontic and adhesive resins currently available, the strength and durability of these materials needs to be evaluated. This laboratory study presents the shear bond strengths of a range of veneering resin composites bonded to all-ceramic core material using different adh...

  13. Synthesis of ZrN–sialon composites from zircon and alumina by carbothermal reduction–nitridation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yuetong [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China); Huang, Zhaohui, E-mail: huang118@cugb.edu.cn [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China); Xu, Youguo; Fang, Minghao; Liu, Yan-gai [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China); Yang, Jingzhou [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China); School of Mechanical and Chemical Engineering, The University of Western Australia, Perth, WA 6009 (Australia); Hu, Xiaozhi [School of Mechanical and Chemical Engineering, The University of Western Australia, Perth, WA 6009 (Australia)

    2012-11-15

    Highlights: ► ZrN–sialon composites were directly synthesized from zircon and γ-Al{sub 2}O{sub 3}. ► The morphologies and phase compositions of products changed with the temperature. ► The comprehensive and systematic thermodynamic relation of the reaction process was analyzed comprehensively. ► This new technique for synthesizing ZrN–sialon composites can reduce the cost and energy consumption. -- Abstract: ZrN–sialon composites were synthesized from zircon and γ-Al{sub 2}O{sub 3} via carbothermal reduction–nitridation. The effects of reaction temperature on the phase compositions and product morphologies were studied. The equilibrium relationship curves of the condensed phases were drawn and the temperature dependence of the phase stability was investigated. The results show that products with different phase compositions and morphologies can be obtained at different temperatures. The optimum temperature for acquiring ZrN–sialon composites was 1550 °C. Granular ZrN and short prismatic β-sialon (Si{sub 3}Al{sub 3}O{sub 3}N{sub 5}) were formed at 1500 °C, accompanied by surplus Al{sub 2}O{sub 3} and ZrO{sub 2}. The dominant products at 1550 °C were ZrN and Si{sub 3}Al{sub 3}O{sub 3}N{sub 5}, whereas they were ZrN and 15R-SiAl{sub 4}O{sub 2}N{sub 4} at 1600 °C. β-sialon had perfect crystals with a long-column morphology, whereas 15R-SiAl{sub 4}O{sub 2}N was plate-like.

  14. Synthesis of ZrN–sialon composites from zircon and alumina by carbothermal reduction–nitridation

    International Nuclear Information System (INIS)

    Highlights: ► ZrN–sialon composites were directly synthesized from zircon and γ-Al2O3. ► The morphologies and phase compositions of products changed with the temperature. ► The comprehensive and systematic thermodynamic relation of the reaction process was analyzed comprehensively. ► This new technique for synthesizing ZrN–sialon composites can reduce the cost and energy consumption. -- Abstract: ZrN–sialon composites were synthesized from zircon and γ-Al2O3 via carbothermal reduction–nitridation. The effects of reaction temperature on the phase compositions and product morphologies were studied. The equilibrium relationship curves of the condensed phases were drawn and the temperature dependence of the phase stability was investigated. The results show that products with different phase compositions and morphologies can be obtained at different temperatures. The optimum temperature for acquiring ZrN–sialon composites was 1550 °C. Granular ZrN and short prismatic β-sialon (Si3Al3O3N5) were formed at 1500 °C, accompanied by surplus Al2O3 and ZrO2. The dominant products at 1550 °C were ZrN and Si3Al3O3N5, whereas they were ZrN and 15R-SiAl4O2N4 at 1600 °C. β-sialon had perfect crystals with a long-column morphology, whereas 15R-SiAl4O2N was plate-like.

  15. 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.

  16. Microstructure and Some Properties of Aluminum-Silicon Matrix Composites Reinforced by Alumina or Chromia

    Directory of Open Access Journals (Sweden)

    Ahmed A. Moosa

    2010-01-01

    Full Text Available In this work, yttrium oxide particles (powder reinforced AL-Si matrix composites (Y2O3/Al-Si and Chromium oxide particles reinforced AL-Si matrix composites (Cr2O3/AL-Si were prepared by direct squeeze casting. The volume percentages of yttrium oxide used are (4, 8.1, 12.1, 16.1 vol % and the volume percentages of the chromium oxide particles used are (3.1, 6.3, 9.4, 12.5 vol. %. The parameters affecting the preparation of Y2O3/Al-Si and Cr2O3/AL-Si composites by direct squeeze casting process were studied. The molten Al-Si alloy with yttrium oxide particles or with chromium oxide particles was stirred again using an electrical stirrer at speed 500 rpm and the molten alloy was poured into the squeeze die cavity. The pouring temperature that used for all castings is (700˚C. The required squeeze pressure, 53 MPa, was then applied for 30 seconds at a delay time of 5. The die temp is (200˚C. The Y2O3/Al-Si composites and Cr2O3/Al-Si composites produced by squeeze casting have more microstructure refinement, higher hardness and lower wear rate than the unreinforced alloy.

  17. Microstructure and Tensile Properties of Yttria Coated-Alumina Particulates Reinforced Aluminum Matrix Composites

    Institute of Scientific and Technical Information of China (English)

    Zhiqiang YU; Gaohui WU; Longtao JIANG; Dongli SUN

    2005-01-01

    The liquid-phase coating method was used to deposit Y2O3 ceramic on the surface of α-Al2O3. The coatedAl2O3p/6061Al composites were produced using squeeze casting technology. The microstructure and tensile properties of the composites were analysed and studied. The results showed that the coated Al2O3 particles are able to disperse homogeneously in the aluminum liquid. The microstructure of the composites is more even in comparison with that of as-received powders. The tensile testing indicated that mechanical properties of the coated-Al2O3p/6061Alcomposites are better than those of uncoated particles. In the composite with 30% volume fraction, the tensile strength, yield strength as well as elongation is increased by 29.8%, 38.4% and 10.3%, respectively. The SEM analysis of fracture indicated that the dimples of the coated-Al2O3p/6061Al composites are more even.

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

    International Nuclear Information System (INIS)

    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 Al2O3 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 μm2 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)

  19. 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...

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

    DEFF Research Database (Denmark)

    Toft Sørensen, O.; Li, W.-Y.

    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...

  1. Composite silicone rubber of high piezoresistance repeatability filled with nanoparticles

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The ruthenium oxide nanoparticles with size less than 20 nm were fabricated by annealing the metallic ruthenium nanoparticles in air,which were synthesized by using the thermal reduction in the polyol solution.The rutile structure of the ruthenium oxide was proved by using transmission electron microscopy(TEM)and X-ray photoelectron spectroscopy(XPS).The oxide has good electron conductivity. The surface of the ruthenium oxide was modified by a vinyl silane coupling agent.The assembling of the silane to the oxide surface was proved by Infrared(IR)absorption spectroscopy.By mixing the nanoparticles with poly(methylvinylsiloxane)(PMVS)silicone rubber,a composite filled with dispersive conducting phase was fabricated.The temperature dependent conductivity shows that the electron transportation through composite is mainly dominated by tunneling.The measurement of piezoresistance shows that the composite at low strain has high piezoresistance repeatability.The 3D reconstruction images of the composite filled with carbon black or ruthenium oxide show that the aggregation of the nanoparticles differs much for two composites.The narrow distribution range of the particle size was thought to be the main factor for the high piezoresistance recurrence.

  2. 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.

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

    International Nuclear Information System (INIS)

    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

  4. Fabrication and properties of Al matrix composites strengthened by in situ alumina particulates

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    New aluminum matrix composites strengthened by Al2O3 particulates through stirring cast by adding NH4Al(SO4)2 to the molten aluminum have been fabricated. TEM observation shows that in-situ Al2O3 particulates are generally spherical and they are uniformly distributed in the Al matrix. Dry sliding wear test results show that the volume loss of the unreinforced Al matrix is about three times that of the Al2O3 reinforced metal matrix composite (MMC) and the volume loss of the MMC fabricated by adding Al2O3 is larger than that of the MMC by adding NH4Al(SO4)2. Lubricating sliding wear test results show that the volume loss of the MMCs increases more slowly than that of the matrix with the increasing of the load.

  5. Processing, microstructure, and properties of co-continuous alumina-aluminum composites

    Energy Technology Data Exchange (ETDEWEB)

    Breslin, M.C. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering; Ringnalda, J. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering; Xu, L. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering; Fuller, M. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering; Seeger, J. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering; Daehn, G.S. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering; Otani, T. [Department of Mechanical Engineering, College of Industrial Technology, Nihon University, Tokyo (Japan); Fraser, H.L. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering

    1995-06-01

    A novel co-continuous composite of Al{sub 2}O{sub 3} and Al has been developed, consisting of approximately 65% (by volume) of the ceramic phase. It is formed by a liquid phase displacement reaction, involving the displacement of Si from SiO{sub 2} and its replacement by Al. A model for the formation mechanism is presented, based on the reaction thermodynamics and the associated experimentally determined transformation kinetics. It is shown that the process is essentially near-net shape, in which the features of the SiO{sub 2} precursors are faithfully reproduced in the composie product. Various physical and mechanical properties that are exhibited by this composite have been determined and are presented. ((orig.))

  6. Interfacial characterization of silicon carbide fiber/lithia-alumina-silica glass matrix composites

    International Nuclear Information System (INIS)

    The development of the carbon-rich interphase in Nicalon SiC fiber/Li2O-Al2O3SiO2 glass matrix composites has been examined as a function of processing parameters with the use of high-resolution scanning electron microscopy and Auger electron spectroscopy. Specifically, hot-pressing temperatures (1000 degrees, and 1200 degrees C) and times (15, 30, 60, and 240 min) were systematically varied in such a manner so as to fabricate dense composites suitable for evaluation of reaction kinetics. Carbon-rich interphase thickness, which ranged from 1400 to 5400 angstrom (140 to 540 nm), was observed to increase with either increasing times at constant temperature or increasing temperatures at constant time. The kinetics of formation of the carbon-rich interphase followed a diffusion-controlled model, with an activation energy of 25.4 kcal/mol

  7. 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; Wu, Yuehua; Mogensen, Mogens Bjerg

    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...

  8. 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_

  9. Computer simulation of grain growth and Ostwald ripening in alumina-zirconia two-phase composites

    International Nuclear Information System (INIS)

    The kinetics of grain growth and Ostwald ripening in Al2O3-ZrO2 two-phase composites was systematically investigated using two-dimensional (2-D) computer simulations, based on a diffuse-interface field model. Using average values for the experimentally measured ratios of the grain boundary energies to the interphase boundary energy as the input, the predicted 2-D microstructural features and their evolution are in excellent qualitative agreement with experimental observations on 2-D cross sections of 3-D Al2O3-ZrO2 two-phase composite microstructures. It was found that the coupled grain growth in Al2O3-ZrO2 composites is controlled by long-range diffusion and the average size (Rt) as a function of time (t) follows the power-growth law, Rtm - R0m = kt with m = 3, which is independent of the initial microstructures and volume fractions of the two phases. The predicted variation of the kinetic coefficient (k) on the volume fraction follows a trend similar to that experimentally measured through the entire range of volume fractions. The scaling of grain size distributions is observed at a given volume fraction, i.e., they are time-invariant in the steady state. However, the characteristics of size distributions vary with the initial microstructures and the volume fractions. The relationship between matrix grain size and second-phase grain size is discussed

  10. 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.

  11. 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.

  12. 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.

  13. Corrosion protection of cold-rolled steel with alkyd paint coatings composited with submicron-structure types polypyrrole-modified nano-size alumina and carbon nanotubes

    International Nuclear Information System (INIS)

    Highlights: ► Alumina/carbon nanotube (CNT) supported polypyrrole (PPy) particles were prepared. ► Various paint compositions with alkyd binder were immersion tested. ► Alumina-supported PPy based coating provided steel protection in NaCl solution. ► Polyelectrolyte modified CNT embedded coating afforded long-term stable protection. ► sulphonated CNT loaded coating indicated firm corrosion resistance in HCL solution. ► Results are interpreted on the basis of nano and microstructure of the particles. - Abstract: This paper is focused on studying corrosion protection of cold-rolled steel with alkyd paint coatings comprising nano-size alumina and either polystyrene-sulphonate (PSS) modified or sulphonated multi-walled carbon nanotube (MWCNT) supported polypyrrole (PPy). Single layer coatings (in thickness of 40 ± 5 μm) comprising PPy deposited alumina and PSS modified MWCNT supported PPy afforded viable protection during the 1 M sodium chloride test. The coatings containing PSS modified and weakly sulphonated MWCNTs (at volume fractions of 9.9 × 10−4 and 2.5 × 10−4) with PPy volume fractions of 3.5 × 10−3 and 2.5 × 10−3 provided effective corrosion prevention during the 1 M sodium chloride and hydrochloric acid solution tests. While inhibitor particles were characterised by infrared spectroscopy, corrosion products formed at the paint–steel interface were studied by X-ray photoelectron spectroscopy. Apart from the electron microscopy observations, rheology study of three-dimensional structure of the inhibitor particles was performed in dispersions at similar compositions to those used for the paint formulations. Thus, protection mechanism relating to both types of immersion tests is discussed in terms of properties of the inhibitor particles and their microstructure in the coatings.

  14. Softening Resistance, Dimensional Stability and Corrosion Behaviour of Alumina and Rice Husk Ash Reinforced Aluminium Matrix Composites Subjected to Thermal Cycling

    Directory of Open Access Journals (Sweden)

    K.K. Alaneme

    2015-06-01

    Full Text Available The softening resistance, dimensional stability and corrosion behaviour of stir cast alumina and rice husk ash reinforced aluminium matrix composites subjected to thermal cycling has been investigated. Aluminium hybrid composites having 10 wt% reinforcement consisting of alumina (Al2O3 and rice husk ash (RHA in weight ratios of 1:0, 3:1, 1:1, 1:3, and 0:1 respectively were produced. The composites were subjected to varying thermal cycles of 3, 6, 9 and 12 from room temperature to 200 oC repeatedly. Hardness, linear change in dimensions, microstructural examination and corrosion test were used to characterize the composites produced. From the results, no obvious change in the microstructure could be discerned with thermal cycling. There were only marginal changes in hardness with increase in thermal cycling also less than 2 % change in linear dimensions was observed with thermal cycling. The composites were also observed to be very resistant to corrosion in 3.5 % NaCl solution with no appreciable change in corrosion resistance noted with increase in thermal cycling. However, in 0.3M H2SO4 solution, the corrosion resistance increased with increase in RHA content and samples subjected to 9 and 12 thermal cycles exhibited a relatively higher susceptibility to corrosion.

  15. Methods, compositions and kits for imaging cells and tissues using nanoparticles and spatial frequency heterodyne imaging

    Energy Technology Data Exchange (ETDEWEB)

    Rose-Petruck, Christoph; Wands, Jack R.; Rand, Danielle; Derdak, Zoltan; Ortiz, Vivian

    2016-04-19

    Methods, compositions, systems, devices and kits are provided herein for preparing and using a nanoparticle composition and spatial frequency heterodyne imaging for visualizing cells or tissues. In various embodiments, the nanoparticle composition includes at least one of: a nanoparticle, a polymer layer, and a binding agent, such that the polymer layer coats the nanoparticle and is for example a polyethylene glycol, a polyelectrolyte, an anionic polymer, or a cationic polymer, and such that the binding agent that specifically binds the cells or the tissue. Methods, compositions, systems, devices and kits are provided for identifying potential therapeutic agents in a model using the nanoparticle composition and spatial frequency heterodyne imaging.

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

    International Nuclear Information System (INIS)

    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-Al2O3 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

  17. Effect of emulsion composition on gel strength and porosity in the preparation of macroporous alumina ceramics by freeze gelcasting

    Directory of Open Access Journals (Sweden)

    Sujith Vijayan

    2015-09-01

    Full Text Available The freeze gelcasting of hydrogenated vegetable oil-in-aqueous alumina slurry (HVO-in-AAS emulsions of HVO to AAS volume ratios in the range of 1.34–2.69 prepared from slurries of various alumina concentrations were studied to prepare macroporous ceramics of high porosity. The compressive strength (20–150 kPa and Young's modulus (120–1550 kPa of the gelled emulsion bodies increased with an increase in alumina slurry concentration and HVO to AAS volume ratio. Easy HVO removal from gelled emulsion bodies by extraction at room temperature with petroleum ether, a less toxic solvent, was achieved. The highest porosity achieved at a HVO to AAS volume ratio of 2.69 increased from 84 to 92.5% when the alumina concentrations in the slurry decreased from 30 to 10 vol.%. The cell size and cell interconnectivity of the ceramics depended on the alumina slurry concentration and HVO to AAS volume ratio. The Young's modulus of the macroporous ceramics modelled using the equation proposed by Gibson and Ashby showed large deviation in the model parameters, n and C, from the proposed values.

  18. Synthesis and Microstructure of Doped Alumina Composite Membrane by Sol-Gel Process

    Institute of Scientific and Technical Information of China (English)

    XU Xiao-hong; ZHANG Ying; WU Jian-feng; BAI Zhan-liang

    2003-01-01

    The supported membranes of Al2O3 and its modification membranes were prepared.Al2O3,Al2O3-SiO2-TiO2 and Al2O3-SiO2-TiO2-ZrO2 membranes were mamufatured by the slip-casting process using mixing boehmite,silicate,titania and zirconia sols under proper conditions,then the composite membrane was prepared.The structure and characteristics of the membrane were determined by XRD,SEM and AFM measurement.The conditions of preparation of the membrane are discussed.The thickness of the layer is about 1-2μm,the diameter of an average pore is 200-300nm and has a narrow pore distribution without crack forming.By changing the ratios of Al∶Si∶Ti∶Zr(mol),variations of surface pore size of Al2O3-SiO2-TiO2-ZrO2 membrane can be gained.

  19. Collective plasmon modes in a compositionally asymmetric nanoparticle dimer

    Directory of Open Access Journals (Sweden)

    Fuyi Chen

    2011-09-01

    Full Text Available The plasmon coupling phenomenon of heterodimers composed of silver, gold and copper nanoparticles of 60 nm in size and spherical in shape were studied theoretically within the scattered field formulation framework. In-phase dipole coupled σ-modes were observed for the Ag-Au and Ag-Cu heterodimers, and an antiphase dipole coupled π-mode was observed for the Ag-Au heterodimer. These observations agree well with the plasmon hybridization theory. However, quadrupole coupled modes dominate the high energy wavelength range from 357-443 nm in the scattering cross section of the D=60 nm Ag-Au and Ag-Cu heterodimer. We demonstrate for the first time that collective plasmon modes in a compositionally asymmetric nanoparticle dimer have to be predicted from the dipole-dipole approximation of plasmon hybridization theory together with the interband transition effect of the constitutive metals and the retardation effect of the nanoparticle size.

  20. Multifunctional composite core-shell nanoparticles

    Science.gov (United States)

    Wei, Suying; Wang, Qiang; Zhu, Jiahua; Sun, Luyi; Lin, Hongfei; Guo, Zhanhu

    2011-11-01

    In this review paper, the state-of-the-art knowledge of the core-shell multifunctional nanoparticles (MNPs), especially with unique physiochemical properties, is presented. The synthesis methods were summarized from the aspects of both the advantages and the demerits. The core includes the inexpensive and easily oxidized metals and the noble shells include the relatively noble metals, carbon, silica, other oxides, and polymers. The properties including magnetic, optical, anti-corrosion and the surface chemistry of the NPs are thoroughly reviewed. The current status of the applications is reviewed with the detailed examples including the catalysis, giant magnetoresistance (GMR) sensing, electromagnetic interface shielding or microwave absorption, biomedical drug delivery, and the environmental remediation.

  1. Transport properties of alumina nanofluids

    International Nuclear Information System (INIS)

    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

  2. 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.

  3. 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

  4. Entrapment of Radionuclides in Nanoparticle Compositions

    DEFF Research Database (Denmark)

    2012-01-01

    radionuclides,for example 61Cu and 64Cu copper isotopes. The invention further relates to a novel method for loading delivery systems, such as liposome compositions, with metal entities such as radionuclides, and the use of liposomes for targeted diagnosis and treatment of a target site, such as cancerous...

  5. EMI shielding composites based on magnetic nanoparticles and nanocarbons

    OpenAIRE

    Crespo Ribadeneyra, María

    2014-01-01

    The response of nanocomposites towards electromagnetic (EM) radiation can be tailored through the electrical conductivity, permittivity and magnetic permeability. Several composites with singular microstructures and containing either conductive nanoinclusions, magnetic nanoparticles or the combination of both, have been prepared and characterized. The performance of our materials as EM interference (EMI) shields, has been determined from 1 to 18 GHz and elucidated in terms of their electric a...

  6. 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.

  7. Composite silicone rubber of high piezoresistance repeatability filled with nanoparticles

    Institute of Scientific and Technical Information of China (English)

    WU JuYing; ZHOU ChengXi; ZHU QingWen; LI EnRong; DAI Ge; BA Long; HUANG YuHong; Mei Jun

    2009-01-01

    The ruthenium oxide nanoparUcles with size less than 20 nm were fabricated by annealing the metallic ruthenium nanoparUcles in air,which were synthesized by using the thermal reduction in the polyol solution.The rutile structure of the ruthenium oxide was proved by using transmission electron microscopy(TEM)and X-ray photoelectron spectroscopy(XPS).The oxide has good electron conductivity.The surface of the ruthenium oxide was modified by a vinyl silane coupling agent.The assembling of the silane to the oxide surface was proved by Infrared(IR)absorption spectroscopy.By mixing the nanoparticles with poly(methylvinylsiloxane)(PMVS)silicone rubber,a composite filled with dispersive conducting phase was fabricated.The temperature dependent conductivity shows that the electron transportation through composite is mainly dominated by tunneling.The measurement of piezoresistance shows that the composite at low strain has high piezoresistance repeatability.The 3D reconstruction images of the composite filled with carbon black or ruthenium oxide show that the aggregation of the nanoparticles differs much for two composites.The narrow distribution range of the particle size was thought to be the main factor for the high piezoresistance recurrence.

  8. Candle soot nanoparticles-polydimethylsiloxane composites for laser ultrasound transducers

    Science.gov (United States)

    Chang, Wei-Yi; Huang, Wenbin; Kim, Jinwook; Li, Sibo; Jiang, Xiaoning

    2015-10-01

    Generation of high power laser ultrasound strongly demands the advanced materials with efficient laser energy absorption, fast thermal diffusion, and large thermoelastic expansion capabilities. In this study, candle soot nanoparticles-polydimethylsiloxane (CSNPs-PDMS) composite was investigated as the functional layer for an optoacoustic transducer with high-energy conversion efficiency. The mean diameter of the collected candle soot carbon nanoparticles is about 45 nm, and the light absorption ratio at 532 nm wavelength is up to 96.24%. The prototyped CSNPs-PDMS nano-composite laser ultrasound transducer was characterized and compared with transducers using Cr-PDMS, carbon black (CB)-PDMS, and carbon nano-fiber (CNFs)-PDMS composites, respectively. Energy conversion coefficient and -6 dB frequency bandwidth of the CSNPs-PDMS composite laser ultrasound transducer were measured to be 4.41 × 10-3 and 21 MHz, respectively. The unprecedented laser ultrasound transduction performance using CSNPs-PDMS nano-composites is promising for a broad range of ultrasound therapy applications.

  9. 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.

  10. Separation and preconcentration of trace quantities of copper ion using modified alumina nanoparticles, and its determination by flame atomic absorption spectrometry

    International Nuclear Information System (INIS)

    We report on a sensitive, reliable and relatively fast method for separation, preconcentration and determination of trace quantities of copper(II) ion. It is making use of nanometer-sized γ-alumina nanoparticles modified with sodium dodecyl sulfate (SDS). The adsorptive potential was assessed via a Langmuir isotherm and the maximal sorption capacity was found to be 138 mg g-1. The effects of pH values, amount of ligand, flow rate, type of eluting agent, volume of eluent, and the volume of sample were examined. The effects of interfering ions on the recovery of the analyte were also investigated. Copper ion was then determined by flame atomic absorption spectrometry. The relative standard deviation for five replicate determinations (at 50 μg L-1 of copper) is 3.3%. The detection limit (at 3 s) is 2.5 μg L-1. This method was validated with a certified reference material of oyster tissue (NIST SRM 1566b) and the results coincided well with the certified values. The procedure was successfully applied to the determination of Cu in water and food samples. (author)

  11. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Juan; Wang, Ruiyu [State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200433 (China); Tjiu, Weng Weei; Pan, Jisheng [Institute of Materials Research and Engineering, A-STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602 (Singapore); Liu, Tianxi, E-mail: txliu@fudan.edu.cn [State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200433 (China)

    2012-07-30

    Graphical abstract: Fe nanoparticles-graphene composites (FGC) are successfully synthesized by forming a complex Fe{sup 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: Black-Right-Pointing-Pointer Graphene oxide (GO) and Fe{sup 3+} are used as precursors. Black-Right-Pointing-Pointer By adding NaBH{sub 4}, Fe{sup 3+} and GO are in situ reduced to Fe and graphene, respectively, thus forming FGC hybrids. Black-Right-Pointing-Pointer Fe nanoparticles with size of about 5 nm are finely dispersed on graphene sheets. Black-Right-Pointing-Pointer 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{sup 3+} to form Fe{sup 3+}-GO complexes. Then, by adding NaBH{sub 4} solution, Fe{sup 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

  13. 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.

  14. Some observations on the paper influence of tin dioxide interphase on the residual stresses in alumina fiber/glass composites by S.N. Patankar, C. Suryanarayana and F.H. Froes

    International Nuclear Information System (INIS)

    Patankar et al. have recently evaluated thermal stress distribution in alumina fiber (PRD-166)/N51A glass and alumina/SnO2/glass composites using models due to Hsueh et al. and Vedula et al. They concluded that these models predict compressive stresses at the SnO2/glass interface which would adversely affect the toughness. In this paper, the authors discuss some of the errors involved in Ref. 1 as well as point out our results of stress distribution in this composite system

  15. Directed self assembly of polymer/nanoparticle composites controlled by internal and external fields

    OpenAIRE

    Lewin, Christian

    2016-01-01

    In this thesis the influence of solvent vapor annealing and external electric fields on poly-mer / nanoparticle composites has been investigated. Gold nanoparticle composite films were prepared with an SV block copolymer polymer as well as with PS and PMMA homopolymers and PS:PMMA blends.In the first part of this thesis SV block copolymer polymer / gold nanoparticle composite films were exposed to an external electric field. In situ SAXS measurements were performed to investigate the kinetics...

  16. Growth of Co-doped ZnO nanoparticles by porous alumina assisted sol–gel route: Structural optical and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Karak, Nantu [Department of Physics, Visva-Bharati University, Santiniketan 731235, West Bengal (India); Pal, Bappaditya; Sarkar, D. [Department of Physics, Gauhati University, Guwahati 781014, Assam (India); Kundu, Tapas Kumar, E-mail: tapaskumar.kundu@visva-bharati.ac.in [Department of Physics, Visva-Bharati University, Santiniketan 731235, West Bengal (India)

    2015-10-25

    We report a simple sol–gel method with spin coating to grow Co-doped ZnO nanoparticles (NPs) using porous alumina template. X-ray diffraction analysis confirms the wurtzite hexagonal structure for the Zn{sub 1−x}Co{sub x}O NPs. Transmission electron microscopy (TEM) micrograph reveals clearly the formation of NPs with average diameter in the range 40–50 nm. High resolution TEM lattice images and the electron diffraction (SAED) pattern show that the NPs are single crystalline with lattice plane spacing of 2.47 Å for the (101) plane. UV–Vis absorption spectra show a slight blue shift in the absorption edge due to doping related modification in the band structure. PL spectra show a band edge related UV emission around 378 nm at low temperature, while defect (Zn{sub i}, O{sub V}) related visible emission dominates at room temperature. Room temperature ferromagnetism (RTFM) is observed in Zn{sub 1−x}Co{sub x}O NPs with the moment of 450–750 memu/g. The temperature dependent magnetization (M-T) curve shows high transition temperature (T{sub c}) as 750 K. The observed FM is explained using a bound magnetic polaron model and expected to arise from the intrinsic exchange interaction of Co ions and Zn{sub i}, O{sub V} related defects. This study provides an effective way to obtain HTFM with lower doping concentration as well as to have control over NP size by alumina pores in the Zn{sub 1−x}Co{sub x}O system. - Highlights: • Zn{sub 1−x}Co{sub x}O NPs of controlled sizes are grown by Sol-gel route using porus templates. • High density point defects (Zn{sub i}, O{sub V}) are observed in the RT PL spectra. • High temperature FM is observed in the Zn{sub 1−x}Co{sub x}O NPs for low doping concentration. • The observed FM is quantitatively analysed and explained using a BMP model. • FM arises from the intrinsic exchange interaction of Co ions and O{sub V}, Zn{sub i} defects.

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

    International Nuclear Information System (INIS)

    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

  18. 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.

  19. Identification of the mechanical behaviour and damage mechanisms of a Nextel™610/alumina ceramic matrix composite subjected to tensile loading.

    OpenAIRE

    Ben Ramdane, C.; Jankowiak, A.; Parlier, M.; Valle, R.; Martin, E.; Diss, P.

    2015-01-01

    (x ± y % = 4 words → counted as 1 , z % = 2 words → counted as 1 → total: < 150 words) The present study was aimed at determining the mechanical behaviour of a weak matrix oxide/oxide CMC subjected to monotonic and cyclic tensile loading in fibre direction and in ±45° fibre orientation and at identifying the damage mechanisms. The material consisted of Nextel™610 fibres (8 HSW) embedded in an alumina matrix, with a fibre volume fraction of 49 % and 24 ± 2 % porosity. The average ultimate tens...

  20. Effect of alumina short fiber and air-cooling processing on solidification microstructure and tensile properties of Al2O3/Al-15Si composites

    Institute of Scientific and Technical Information of China (English)

    张学习; 王德尊; 姚忠凯

    2002-01-01

    The effect of microstructure variation by addition of alumina short fiber and optimization of tensile properties by air-cooling processing in Al2O3/Al-15Si composites were studied. The results show that in Al-15Si alloy matrix composites with 14% and 30%(volume fraction) fiber, the primary silicon is hardly refined, but the eutectic silicon is effectively refined and granulated. Granulation of some eutectic silicon mainly happens in fiber segregation areas. Refining and granulation of the eutectic silicon are related to the physical constraint arising from the fiber. After the 30%Al2O3/Al-15Si composite was remelted and air-cooled, the number of the eutectic silicon on the surface of the fiber increases, which results in the improvement of fiber/matrix interface and tensile properties for the as-cast composite. Air-cooling processing may be reliable for the optimization of the microstructure and properties of fiber reinforced hypereutectic Al-15Si alloy composites.

  1. Reconstruction and visualization of nanoparticle composites by transmission electron tomography

    Energy Technology Data Exchange (ETDEWEB)

    Wang, X.Y. [National Institute for Nanotechnology, 11421 Saskatchewan Drive, Edmonton, Canada T6H 2M9 (Canada); Department of Physics, University of Alberta, Edmonton, Canada T6G 2G7 (Canada); Lockwood, R. [National Institute for Nanotechnology, 11421 Saskatchewan Drive, Edmonton, Canada T6H 2M9 (Canada); Malac, M., E-mail: marek.malac@nrc-cnrc.gc.ca [National Institute for Nanotechnology, 11421 Saskatchewan Drive, Edmonton, Canada T6H 2M9 (Canada); Department of Physics, University of Alberta, Edmonton, Canada T6G 2G7 (Canada); Furukawa, H. [SYSTEM IN FRONTIER INC., 2-8-3, Shinsuzuharu bldg. 4F, Akebono-cho, Tachikawa-shi, Tokyo 190-0012 (Japan); Li, P.; Meldrum, A. [National Institute for Nanotechnology, 11421 Saskatchewan Drive, Edmonton, Canada T6H 2M9 (Canada)

    2012-02-15

    This paper examines the limits of transmission electron tomography reconstruction methods for a nanocomposite object composed of many closely packed nanoparticles. Two commonly used reconstruction methods in TEM tomography were examined and compared, and the sources of various artefacts were explored. Common visualization methods were investigated, and the resulting 'interpretation artefacts' ( i.e., deviations from 'actual' particle sizes and shapes arising from the visualization) were determined. Setting a known or estimated nanoparticle volume fraction as a criterion for thresholding does not in fact give a good visualization. Unexpected effects associated with common built-in image filtering methods were also found. Ultimately, this work set out to establish the common problems and pitfalls associated with electron beam tomographic reconstruction and visualization of samples consisting of closely spaced nanoparticles. -- Highlights: Black-Right-Pointing-Pointer Electron tomography limits were explored by both experiment and simulation. Black-Right-Pointing-Pointer Reliable quantitative volumetry using electron tomography is not presently feasible. Black-Right-Pointing-Pointer Volume rendering appears to be better choice for visualization of composite samples.

  2. DNA-based nanoparticle composite materials for EMI shielding

    Science.gov (United States)

    Zang, De Yu; Grote, James

    2012-03-01

    Composite materials, such as polymer-matrix containing conductive fillers, are very attractive for shielding electromagnetic interference (EMI) due to their high shielding efficiency and seamlessness, processability, flexibility, light-weight and low-cost. Here, we report a development of novel, DNA-based EMI-shielding materials (DESM), consisting of DNA and metal nanoparticles. It has been shown that a thin DESM layer (typically ~30 - 50 μm) could block EMI radiations up to 60 dB effectively over an RF frequency range from KHz to tens GHz, exhibiting excellent EMI shielding efficiency. A wide selection of metal nanoparticle fillers for DESM has been tested for their performance in EMI shielding efficiency. Among them, silver and carbon-based nanoparticles have demonstrated the best performance and were selected for further investigation. The silver-doped DESM films could be also non-conductive while their EMI shielding efficiency is still well-preserved. The nonconductive DESM could have a great potential in the microelectronics industries for EMI shielding on electronic devices and circuit boards.

  3. Optical Characterization of Semiconducting Natural Rubber Nanoparticles and its Composites

    Science.gov (United States)

    Neena, P.; Mathew, Anisha Mary

    2011-10-01

    The present work explains optical properties of semiconducting natural rubber nanoparticles from pristine natural rubber by doping. The studies give evidence that the SbCl5 is an efficient dopant for natural rubber. The mechanism of conduction predominantly involves the formation of conjugated sequence of unsaturated double bond in the polymer backbone. Examination of the UV/Vis study reveals the formation of charge transfer complexes in the polymer back bone. Particle filled elastomeric composites have become attractive owing to their low cost and widespread industrial applications. The arrival of nanometer fillers to polymer materials is a promising channel for their property modification. Natural rubber composite is prepared by mixing the pristine natural rubber with semiconducting natural rubber powder.

  4. CHARACTERIZATION OF MANGANESE PHTHALOCYANINE-Fe3O4 NANOPARTICLE COMPOSITE AND ITS ELECTROMAGNETORHEOLOGICAL FLUID

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Manganese phthalocyanine (MnPc)-Fe3O4 nanoparticles composite was prepared and characterized. The results show that MnPc are complexed on the surface of Fe3O4 nanoparticles in the state of single molecule. There is effective composite between MnPc and Fe3O4 nanoparticles which can improve the antioxidization ability of Fe3O4 nanoparticles greatly. The composite was dispersed into chlorinated paraffin oil to form electromagnetorheological (EMR) fluid with high activity,and the EMR properties of this EMR fluid are studied.

  5. Multiple percolation tunneling staircase in metal-semiconductor nanoparticle composites

    International Nuclear Information System (INIS)

    Multiple percolation transitions are observed in a binary system of RuO2-CaCu3Ti4O12 metal-semiconductor nanoparticle composites near percolation thresholds. Apart from a classical percolation transition, associated with the appearance of a continuous conductance path through RuO2 metal oxide nanoparticles, at least two additional tunneling percolation transitions are detected in this composite system. Such behavior is consistent with the recently emerged picture of a quantum conductivity staircase, which predicts several percolation tunneling thresholds in a system with a hierarchy of local tunneling conductance, due to various degrees of proximity of adjacent conducting particles distributed in an insulating matrix. Here, we investigate a different type of percolation tunneling staircase, associated with a more complex conductive and insulating particle microstructure of two types of non-spherical constituents. As tunneling is strongly temperature dependent, we use variable temperature measurements to emphasize the hierarchical nature of consecutive tunneling transitions. The critical exponents corresponding to specific tunneling percolation thresholds are found to be nonuniversal and temperature dependent.

  6. 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.

  7. A room temperature Na/S battery using a β″ alumina solid electrolyte separator, tetraethylene glycol dimethyl ether electrolyte, and a S/C composite cathode

    Science.gov (United States)

    Kim, Icpyo; Park, Jin-Young; Kim, Chang Hyeon; Park, Jin-Woo; Ahn, Jae-Pyoung; Ahn, Jou-Hyeon; Kim, Ki-Won; Ahn, Hyo-Jun

    2016-01-01

    To realize a high-performance room temperature Na/S battery with an elemental sulfur cathode, it is important that sodium polysulfides stay within the cathode and that they have room enough to react freely. In this work, sodium polysulfides are confined to the cathode using a β″ alumina solid electrolyte separator and an optimal amount of tetraethylene glycol dimethyl ether (TEGDME) electrolyte. In addition, an activated carbon material, in the form of a sulfur/carbon (S/C) composite, with high surface area, porosity, and pore volume is employed in the cathode. The resulting Na/S battery shows a high first discharge capacity of 855 mAh g-1 and coulombic efficiency close to 100%, as well as stable cyclability, with a discharge capacity of 521 mAh g-1 at the 104th discharge.

  8. Characterization of thermochemical properties of Al nanoparticle and NiO nanowire composites

    OpenAIRE

    Wen, John Z.; Ringuette, Sophie; Bohlouli-Zanjani, Golnaz; Hu, Anming; Nguyen, Ngoc Ha; Persic, John; Petre, Catalin F; Zhou, Y. Norman

    2013-01-01

    Thermochemical properties and microstructures of the composite of Al nanoparticles and NiO nanowires were characterized. The nanowires were synthesized using a hydrothermal method and were mixed with these nanoparticles by sonication. Electron microscopic images of these composites showed dispersed NiO nanowires decorated with Al nanoparticles. Thermal analysis suggests the influence of NiO mass ratio was insignificant with regard to the onset temperature of the observed thermite reaction, al...

  9. Corrosion behavior of a cerium-based conversion coating on alumina borate whisker-reinforced AA6061 composite pre-treated by hydrogen fluoride

    International Nuclear Information System (INIS)

    Highlights: → Hydrogen fluoride pre-treatment prior to cerium conversion coating was studied. → Both 'defect-free' and cracked coatings were prepared. → The corrosion resistance of 'defect-free' coating is higher than that of cracked one. → A self-healing effect was observed only on 'defect-free' coating. - Abstract: Cerium-based conversion coatings have been made on alumina borate whisker-reinforced AA6061 composite pre-treated with hydrogen fluoride. The pre-treatment prior to coating significantly affects the microstructure and the corrosion behavior of the ultimate coated composites. The coating deposited on composite pre-treated for 20 s provides better corrosion protection than that pre-treated for 180 s. A self-healing effect is observed on the coated composite with pre-treatment for 20 s in the early stage of immersion, while no self-healing effect appears with pre-treatment for 180 s. It is largely because the morphologies of the coatings are remarkably different under the two pre-treatment conditions.

  10. 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 nanopart......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...... template and structure directing agent and isolating the resulting zeolite, zeolite-like or zeotype encapsulated metal nanoparticles...

  11. Enhanced stab resistance of armor composites with functionalized silica nanoparticles

    Science.gov (United States)

    Mahfuz, Hassan; Clements, Floria; Rangari, Vijaya; Dhanak, Vinod; Beamson, Graham

    2009-03-01

    Traditionally shear thickening fluid (STF) reinforced with Kevlar has been used to develop flexible armor. At the core of the STF-Kevlar composites is a mixture of polyethylene glycol (PEG) and silica particles. This mixture is often known as STF and is consisted of approximately 45 wt % PEG and 55 wt % silica. During rheological tests, STF shows instantaneous spike in viscosity above a critical shear rate. Fabrication of STF-Kevlar composites requires preparation of STF, dilution with ethanol, and then impregnation with Kevlar. In the current approach, nanoscale silica particles were dispersed directly into a mixture of PEG and ethanol through a sonic cavitation process. Two types of silica nanoparticles were used in the investigation: 30 nm crystalline silica and 7 nm amorphous silica. The admixture was then reinforced with Kevlar fabric to produce flexible armor composites. In the next step, silica particles are functionalized with a silane coupling agent to enhance bonding between silica and PEG. The performance of the resulting armor composites improved significantly. As evidenced by National Institute of Justice spike tests, the energy required for zero-layer penetration (i.e., no penetration) jumped twofold: from 12 to 25 J cm2/g. The source of this improvement has been traced to the formation of siloxane (Si-O-Si) bonds between silica and PEG and superior coating of Kevlar filaments with particles. Fourier transform infrared, x-ray photoemission spectroscopy, and scanning electron microscopy studies were performed to examine chemical bonds, elemental composition, and particle dispersion responsible for such improvement. In summary, our experiments have demonstrated that functionalization of silica particles followed by direct dispersion into PEG resulted in superior Kevlar composites having much higher spike resistance.

  12. Silver, Gold, Palladium Nanoparticles: Ligand Design, Synthesis and Polymer Composites

    Science.gov (United States)

    Iqbal, Muhammad

    Metal nanoparticles, especially gold nanoparticles (AuNPs), have been extensively studied due to their interesting optical properties and potential applications in emerging technologies like drug delivery, cancer therapy, catalysis, chemical and bio-sensing and microelectronics devices. Alkyl thiol ligands in the form of self assembled monolayers are often used to stabilize and functionalize the gold nanoparticles while other types of ligands have been rarely employed and the properties of AuNPs protected by different types of ligands have not been studied comprehensively and comparatively. This dissertation reports the first comparative studies on the thermal and chemical stability of AuNPs protected by alkyl thiolates, alkyl selenolates, dialkyl dithiophosphinates, and dialkyl dithiophosphates (Chapters 2 and 3). AuNPs protected by dialkyl dithiophosphinates and dialkyl dithiophosphates are unprecedented. All AuNPs were prepared from amine protected precursor AuNPs by ligand exchange to ensure similar size, size distribution, and chemical composition. They were extensively characterized by solution 1H-NMR and UV-VIS spectroscopy, transmission electron microscopy (TEM), thermal analysis, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) analysis. For the first time, thermal stability was investigated by differential scanning calorimetry (DSC) that provided more accurate decomposition temperatures and enthalpies, whereas chemical stability was tested as the availability of the gold surface towards etching with cyanide in different solvents. Surprisingly, alkyl selenolate protected AuNPs are thermally less stable than alkyl thiolate protected AuNPs despite their proposed stronger binding to the gold surface and a much more crystalline monolayer, which suggests that different decomposition mechanisms apply to alkyl thiolate and alkyl selenolate protected AuNPs. Dialkyl dithiophosphinates and dialkyl dithiophosphates protected AuNPs are thermally

  13. Fabrication of composite nano-particles by radiations

    International Nuclear Information System (INIS)

    Realization of composite nano-materials using radiation technology is reported to demonstrate one of the author's experimental results on noble-metallic nano-particles having the diameter less than 10 nm which are dispersed homogeneously with high density on a catalyst-supporting particle. Keeping away as such from coagulation of noble metals, thus keeping its high specific surface, functional materials, for example, magnetic materials can be used as a supporting particle. The method is to irradiate the solutions containing starting materials. Since water containing 2-propanol is decomposed by radiolysis to produce the reducing and oxidizing species, metallic ions will be reduced to metals and sometimes in the presence of polyvinyl alcohol to noble-metal colloidal solutions which has been further applied to synthesis of Au/γ-Fe2O3 composite particle. Moreover, other metals as Ag, Pt, Pd, Rh, with other supporting materials as Al2O3, TiO2, Fe3O4, ZnO, ZrO2, and CeO2 were found to be realized. Au/iron oxides magnetic composite particles were also synthesized by γ- or electron irradiation to be used magnetically separate the mixture of amino acids and DNA. (S. Ohno)

  14. Study on the Properties of Metallophthalocyanine-Fe3O4 Nanoparticles Composite

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The solubility,antioxidation ability,thermal stability,coercivity Hc and long term stability of MPc-Fe3O4-nanoparticles composite(M=Co,Cu,Ni,Mn) have been studied.The results show that MPc-Fe3O4 nanoparticles composite can be easily dissolved in dilute acid.The dissolving rate of different MPc-Fe3O4 nanoparticles composite is in the following order:M=Mn~M=Co<M=Cu<M=Ni.The antioxidation ability of Fe3O4 nanoparticles are improved greatly after their complex with MPc and there is good relationship between Toxidation of Fe3O4 nanoparticles and n ,the complex layers of MPc on the surface of the composite.The results also show that the thermal stability of Fe3O4 nanoparticles increases greatly and the Hc of them decreases dramatically after Fe3O4 nanoparticles form nanoscale composite with MPc.MPc-Fe3O4 nanoparticles composite have high long term stability.

  15. Preparation and Thermal Property of Liquid Crystal Epoxy Grafted Alumina/Epoxy Resin Composite%环氧液晶接枝氧化铝/环氧树脂复合材料的制备与热性能

    Institute of Scientific and Technical Information of China (English)

    何子海; 虞锦洪

    2015-01-01

    将支化环氧液晶接枝到氧化铝纳米颗粒表面,再将其加入到环氧树脂中制备成复合材料,并对环氧液晶接枝氧化铝/环氧树脂复合材料的热性能进行研究。结果表明:加入环氧液晶接枝氧化铝纳米颗粒后,环氧树脂复合材料的导热系数从纯环氧树脂的0.16 W/(m·K)提高到BLCE-g-Al2O3含量为30%时的0.238 W/(m·K),增加了48.75%;复合材料的初始储能模量比纯环氧树脂的初始储能模量提高了181 MPa,玻璃化转变温度提高了24℃。随着Al2O3填充量的增加,复合材料的热膨胀系数逐渐减小。%Alumina nanoparticles were grafted by branched liquid crystal epoxy (BLCE-g-Al2O3), and BLCE-g-Al2O3/EP composites were prepared through adding the BLCE-g-Al2O3 into epoxy matrix, and then their thermal properties were investigated. The results show that the thermal conductivity of the com-posites increases from 0.16 W/(m·K) of pure epoxy resin to 0.238 W/(m·K) with 30% of BLCE-g-Al2O3 content, and the thermal conductivity increases by 48.75%. The storage modulus and glass transition temperature of the epoxy composites increase by 181 MPa and 24℃, respectively. With the increase of BLCE-g-Al2O3 content, the thermal expansion coefficient of the epoxy composites decreases.

  16. 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. PMID:27315331

  17. The influence of heat treatment on mechanical and fracture properties of an alumina microsphere reinforced aluminium matrix composite

    Energy Technology Data Exchange (ETDEWEB)

    Hadianfard, M.J.; Healy, J.C.; Mai, Y.W. [Univ. of Sydney, NSW (Australia). Dept. of Mechanical Engineering

    1993-12-31

    The effects of aging on the mechanical and fracture toughness properties of a 6061 Al reinforced with 20 vol % alumina microsphere (Comral-85) were studied. Fractographic examination combined with X-ray mapping and image analysis were used to investigate the fracture micro-mechanisms. Hardness and tensile strength were found to increase with aging time reaching a maximum value after approximately 8 hours aging at 175{degree}C. Although elongation to failure decreased with aging time the fracture toughness showed little variation. Specimens for all heat treated conditions (peak-aged, under-aged and over-aged) exhibited ductile fracture consisting of void formation and coalescence. However, the matrix aging condition and particulate distribution significantly affected the fracture mechanisms. Fracture was characterized by particulate distribution significantly affected the fracture mechanisms. Fracture was characterized by particle cracking and matrix failure in the under-aged condition and by decohesion at the matrix/particle interface in the over-aged condition. Image analysis indicated that regions of particulate clusters were preferential sites for crack initiation and subsequent growth for all heat treated conditions. These results are discussed in terms of the effects on matrix microstructure due to accelerated aging and the local density of particulates.

  18. Cascade synthesis of a gold nanoparticle-network polymer composite

    Science.gov (United States)

    Grubjesic, Simonida; Ringstrand, Bryan S.; Jungjohann, Katherine L.; Brombosz, Scott M.; Seifert, Sönke; Firestone, Millicent A.

    2016-01-01

    The multi-step, cascade synthesis of a self-supporting, hierarchically-structured gold nanoparticle hydrogel composite is described. The composite is spontaneously prepared from a non-covalent, lamellar lyotropic mesophase composed of amphiphiles that support the reactive constituents, a mixture of hydroxyl- and acrylate-end-derivatized PEO117-PPO47-PEO117 and [AuCl4]-. The reaction sequence begins with the auto-reduction of aqueous [AuCl4]- by PEO117-PPO47-PEO117 which leads to both the production of Au NPs and the free radical initiated polymerization and crosslinking of the acrylate end-derivatized PEO117-PPO47-PEO117 to yield a network polymer. Optical spectroscopy and TEM monitored the reduction of [AuCl4]-, formation of large aggregated Au NPs and oxidative etching into a final state of dispersed, spherical Au NPs. ATR/FT-IR spectroscopy and thermal analysis confirms acrylate crosslinking to yield the polymer network. X-ray scattering (SAXS and WAXS) monitored the evolution of the multi-lamellar structured mesophase and revealed the presence of semi-crystalline PEO confined within the water layers. The hydrogel could be reversibly swollen without loss of the well-entrained Au NPs with full recovery of composite structure. Optical spectroscopy shows a notable red shift (Δλ ~ 45 nm) in the surface plasmon resonance between swollen and contracted states, demonstrating solvent-mediated modulation of the internal NP packing arrangement.The multi-step, cascade synthesis of a self-supporting, hierarchically-structured gold nanoparticle hydrogel composite is described. The composite is spontaneously prepared from a non-covalent, lamellar lyotropic mesophase composed of amphiphiles that support the reactive constituents, a mixture of hydroxyl- and acrylate-end-derivatized PEO117-PPO47-PEO117 and [AuCl4]-. The reaction sequence begins with the auto-reduction of aqueous [AuCl4]- by PEO117-PPO47-PEO117 which leads to both the production of Au NPs and the free radical

  19. In situ preparation of Nanoparticles/polymer composites

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Nanoparticle (NP) is the matter between molecule and bulk material. It has attracted much attention in catalysis, optoelectronics and biology due to its unique physical and chemical properties. Incorporation of these NPs into the polymer matrix is one of the best methods to display their special functions, which not only stabilize the NPs but also realize the functional assembly of NPs and polymers. However, reali- zation of this idea depends largely on the compatibility of NPs and polymers as well as the interaction between them. Therefore, many methods have been developed to prepare the composites of NPs and polymers in order to obtain the function ex- pected. In this review, we mainly focus on the combination of in situ method with other methods to synthesize different functional one-dimension, two-dimension as well as bulk composites, which has been recently developed by our group. The most striking character of our method is the excellent compatibility between NPs and polymers which ensures a homogeneous distribution of NPs in the polymer matrix. The existence of the polymer network makes the NPs more stable, and is significant for displaying their functions.

  20. In situ preparation of Nanoparticles/polymer composites

    Institute of Scientific and Technical Information of China (English)

    SUN HaiZhu; YANG Bai

    2008-01-01

    Nanoparticle (NP) is the matter between molecule and bulk material. It has attracted much attention in catalysis, optoelectronics and biology due to its unique physical and chemical properties. Incorporation of these NPs into the polymer matrix is one of the best methods to display their special functions, which not only stabilize the NPs but also realize the functional assembly of NPs and polymers. However, reali-zation of this idea depends largely on the compatibility of NPs and polymers as well as the interaction between them. Therefore, many methods have been developed to prepare the composites of NPs and polymers in order to obtain the function ex-pected. In this review, we mainly focus on the combination of in situ method with other methods to synthesize different functional one-dimension, two-dimension as well as bulk composites, which has been recently developed by our group. The most striking character of our method is the excellent compatibility between NPs and polymers which ensures a homogeneous distribution of NPs in the polymer matrix. The existence of the polymer network makes the NPs more stable, and is significant for displaying their functions.

  1. Bioactivity of fluorapatite/alumina composite coatings deposited on Ti6Al4V substrates by laser cladding

    Science.gov (United States)

    Chien, C. S.; Liu, C. W.; Kuo, T. Y.; Wu, C. C.; Hong, T. F.

    2016-04-01

    Hydroxyapatite (HA) is one of the most commonly used coating materials for metal implants. However, following high-temperature deposition, HA easily decomposes into an unstable phase or forms an amorphous phase, and hence, the long-term stability of the implant is reduced. Accordingly, the present study investigates the use of fluorapatite (FA) fortified with 20 wt% alumina (α-Al2O3) as an alternative biomedical coating material. The coatings are deposited on Ti6Al4V substrates using a Nd:YAG laser cladding process performed with laser powers and travel speeds of 400 W/200 mm/min, 800 W/400 mm/min and 1200 W/600 mm/min, respectively. The results show that for all of the specimens, a strong metallurgical bond is formed at the interface between the coating layer and the transition layer due to melting and diffusion. The XRD analysis results reveal that the cladding layers in all of the specimens consist mainly of FA, β-TCP, CaF2, Ti and θ-Al2O3 phases. In addition, the cladding layers of the specimens prepared using laser powers of 400 and 800 W also contain CaTiO3 and CaAl2O4, while that of the specimen clad using a power of 1200 W contains TTCP and CaO. Following immersion in simulated body fluid for 14 days, all of the specimens precipitate dense bone-like apatite and exhibit excellent bioactivity. However, among all of the specimens, the specimen that is prepared with a laser power of 800 W shows the best biological activity due to the presence of residual FA, apatite-generating CaTiO3 and a rough cladding layer surface.

  2. Enhanced removal of Cd(II) and Pb(II) by composites of mesoporous carbon stabilized alumina

    Science.gov (United States)

    Yang, Weichun; Tang, Qiongzhi; Wei, Jingmiao; Ran, Yajun; Chai, Liyuan; Wang, Haiying

    2016-04-01

    A novel adsorbent of mesoporous carbon stabilized alumina (MC/Al2O3) was synthesized through one-pot hard-templating method. The adsorption potential of MC/Al2O3 for Cd(II) and Pb(II) from aqueous solution was investigated compared with the mesoporous carbon. The results indicated the MC/Al2O3 showed excellent performance for Cd(II) and Pb(II) removal, the adsorption capacity reached 49.98 mg g-1 for Cd(II) with initial concentration of 50 mg L-1 and reached 235.57 mg g-1 for Pb(II) with initial concentration of 250 mg L-1, respectively. The kinetics data of Cd(II) adsorption demonstrated that the Cd(II) adsorption rate was fast, and the removal efficiencies with initial concentration of 10 and 50 mg L-1 can reach up 99% within 5 and 20 min, respectively. The pseudo-second-order kinetic model could describe the kinetics of Cd(II) adsorption well, indicating the chemical reaction was the rate-controlling step. The mechanism for Cd(II) and Pb(II) adsorption by MC/Al2O3 was investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared spectroscopy (FTIR), and the results indicated that the excellent performance for Cd(II) and Pb(II) adsorption of MC/Al2O3 was mainly attributed to its high surface area and the special functional groups of hydroxy-aluminum, hydroxyl, carboxylic through the formation of strong surface complexation or ion-exchange. It was concluded that MC/Al2O3 can be recognized as an effective adsorbent for removal of Cd(II) and Pb(II) in aqueous solution.

  3. ON THE EFFECT OF NANO-PARTICLE CLUSTERING ON TOUGHENING OF NANO-COMPOSITE CERAMICS

    Institute of Scientific and Technical Information of China (English)

    董照旭; 方岱宁; 苏爱嘉

    2002-01-01

    In this paper, two and three-dimensional clustering models are developed to characterize the effect of nano-particle clustering on toughening of nanocomposite ceramics. It is found that crack pinning toughens the nano-composite ceramics because a higher stress intensity factor is needed for crack to propagate around or to pull-out the nano-particle. The nano-particle along the grain boundary steers the crack into the matrix grain due to the strong cohesion between the nanoparticle and the matrix. Since the fracture resistance of the grain boundary is lower than that of the grain lattice, the higher the probability of transgranular fracture induced by nano-particles, the tougher is the nano-composite. However, both crack pinning and transgranular fracture are affected by nano-particle clustering. Nanoparticle clustering, which increases with increasing volume fraction of nano-particles,leads to reduction of both the strength and toughness of the nano-composite ceramics. The larger the size of the clustered particle, and the more defects it contains, the easier it is for the crack to pass through the clustered particle, which means that the nano-particle clustering can reduce toughening induced by crack pinning and transgranular fracture. The theoretical prediction, based on the combination of the three mechanisms of nano-particles, is in agreement with the experimental data.

  4. Synthesis of agarose-metal/semiconductor nanoparticles having superior bacteriocidal activity and their simple conversion to metal-carbon composites

    Indian Academy of Sciences (India)

    K K R Datta; B Srinivasan; H Balaram; M Eswaramoorthy

    2008-11-01

    Agarose, a naturally occurring biopolymer is used for the stabilization of metal, semiconductor nanoparticles. Ag and Cu nanoparticles stabilized in agarose matrix show excellent antibacterial activity against E. coli bacteria. The well dispersed metal nanoparticles within the agarose composite films can be readily converted to carbon-metal composites of catalytic importance.

  5. Effect of co-existing ions during the preparation of alumina by electrolysis with aluminum soluble electrodes: Structure and defluoridation activity of electro-synthesized adsorbents

    International Nuclear Information System (INIS)

    Highlights: • pH increases during electrocoagulation with aluminum electrodes are rationalized. •Composition of electrogenerated aluminas is dependent upon the electrolyte used. • All the electrogenerated aluminas contained nanoparticles of boehmite AlOOH. • The defluoridation activity of the aluminas was dependent upon the electrolyte used. -- Abstract: The electrochemical dissolution of aluminum was carried out to prepare hydrated aluminas which were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), chemical titrations and defluoridation activities. Aluminas were obtained at controlled pH depending upon the counter cations of the electrolyte. A boehmite AlOOH phase was isolated mainly in ammonium solution, while aluminas synthesized in the other media contained a mixture of phases, usually both boehmite and bayerite γ-Al(OH)3. All the boehmite phases contained nano-crystallites of less than 3 nm. Batch defluoridation experiments revealed a second influence of the original electrolyte. Aluminas were very effective in defluoridation with abatement rates of 99.5%, 98.5% and 97.3% from neutral fluoride solution at 10 mg L−1 when they were prepared in solution of (NH4)2SO4, (NH4)HCO2 and NH4Cl, respectively. The maximum fluoride capacities were 46.94; 10.25 and 12.18 mg g−1 for aluminas prepared in solution of (NH4)2SO4; (NH4)HCO2 and NH4Cl, respectively. The amount of dissolved Al was found to be less than 0.19 mg L−1 at neutral pH. These results show that a defluoridation with electro-synthesized aluminas would be more efficient and safe than a direct electrocoagulation

  6. Effect of co-existing ions during the preparation of alumina by electrolysis with aluminum soluble electrodes: Structure and defluoridation activity of electro-synthesized adsorbents

    Energy Technology Data Exchange (ETDEWEB)

    Tchomgui-Kamga, Eric, E-mail: etchomgui@yahoo.fr [UMR CNRS n°6226 Institut des Sciences Chimiques de Rennes, ENSCR, Avenue du Général Leclerc, CS 50837 - 35708 Rennes Cedex 7 (France); Laboratoire de Chimie Analytique, Faculté des Sciences, Université de Yaoundé-I, BP 812 Yaoundé (Cameroon); Audebrand, Nathalie, E-mail: nathalie.audebrand@univ-rennes1.fr [UMR CNRS n°6226 Institut des Sciences Chimiques de Rennes, Université de Rennes-1, Avenue du Général Leclerc, 35042 Rennes Cedex (France); Darchen, André, E-mail: Andre.Darchen@ensc-rennes.fr [UMR CNRS n°6226 Institut des Sciences Chimiques de Rennes, ENSCR, Avenue du Général Leclerc, CS 50837 - 35708 Rennes Cedex 7 (France)

    2013-06-15

    Highlights: • pH increases during electrocoagulation with aluminum electrodes are rationalized. •Composition of electrogenerated aluminas is dependent upon the electrolyte used. • All the electrogenerated aluminas contained nanoparticles of boehmite AlOOH. • The defluoridation activity of the aluminas was dependent upon the electrolyte used. -- Abstract: The electrochemical dissolution of aluminum was carried out to prepare hydrated aluminas which were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), chemical titrations and defluoridation activities. Aluminas were obtained at controlled pH depending upon the counter cations of the electrolyte. A boehmite AlOOH phase was isolated mainly in ammonium solution, while aluminas synthesized in the other media contained a mixture of phases, usually both boehmite and bayerite γ-Al(OH){sub 3}. All the boehmite phases contained nano-crystallites of less than 3 nm. Batch defluoridation experiments revealed a second influence of the original electrolyte. Aluminas were very effective in defluoridation with abatement rates of 99.5%, 98.5% and 97.3% from neutral fluoride solution at 10 mg L{sup −1} when they were prepared in solution of (NH{sub 4}){sub 2}SO{sub 4}, (NH{sub 4})HCO{sub 2} and NH{sub 4}Cl, respectively. The maximum fluoride capacities were 46.94; 10.25 and 12.18 mg g{sup −1} for aluminas prepared in solution of (NH{sub 4}){sub 2}SO{sub 4}; (NH{sub 4})HCO{sub 2} and NH{sub 4}Cl, respectively. The amount of dissolved Al was found to be less than 0.19 mg L{sup −1} at neutral pH. These results show that a defluoridation with electro-synthesized aluminas would be more efficient and safe than a direct electrocoagulation.

  7. Structural, electrical and gas-sensing properties of In2O3 : Ag composite nanoparticle layers

    Indian Academy of Sciences (India)

    B R Mehta; V N Singh

    2005-11-01

    The central objective of this study is to investigate (i) size-dependent properties of In2O3 nanoparticles and (ii) the role of metal additives in enhancing the gas sensing response. For this purpose, In2O3 : Ag composite nanoparticle layers having well-defined individual nanoparticle size and composition have been grown by a two step synthesis method. Thermogravimetric analysis, X-ray diffraction and transmission electron microscopy have been used to study the effect of post-synthesis heat treatment on the size and structure of the nanoparticles. A first-time unambiguous observation of size-dependent lowering of transformation temperature has been explained in terms of lower cohesive energy of surface atoms and increase in surface-to-volume ratio with decrease in nanoparticle size. The gas sensing studies of In2O3 as well as the In2O3 : Ag composite nanoparticle layers have been studied as a function of size and composition. In2O3 : Ag composite nanoparticle layers with 15% silver show a sensitivity of 436 and response time of 6 s for 1000 ppm of ethanol in air. Ag additives form a p-type Ag2O, which interact with n-type In2O3 to produce an electron-deficient space-charge layer. In the presence of ethanol, interfacial Ag2O reduces to Ag, creating an accumulation layer in In2O3 resulting in increased sensitivity.

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

    OpenAIRE

    Kasraei, Shahin; Sami, Lida; Hendi, Sareh; AliKhani, Mohammad-Yousef; Rezaei-Soufi, Loghman; Khamverdi, Zahra

    2014-01-01

    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 prepa...

  9. PREPARATION,COMPLEX MECHANISM AND STRUCTURE MODEL OF METALLOPHTHALOC- YANINE-Fe3O4 NANOPARTICLES COMPOSITE

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    MPc-Fe3O4-nanoparticles composite(M=Co, Cu, Ni, Mn) have been prepared and the factors that influence their mean size have been studied. The mean size of the nanoparticles composite increase with the increase of complex temperature. The interaction of MPc with Fe3O4 nanoparticles has been studied. There are M-O covalent bonding and ionic bonding between MPc and Fe3O4 nanoparticles. The intensities of M-O bonding and ionic bonding are in vestigated .The complex mechanism of MPc with Fe3O4 nanoparticles have been studied. First, there are complex between MPc and all Fe3O4 nanoparticles. Then, Fe3O4 nanoparticles accumulate together to form the accumulators, MPc have the function of cohering Fe3O4 nanoparticles. A considerable number of MPc combine with Fe3O4 nanoparticles on the surface of the accumulators to form MPc-Fe3O4 nanoparticles composite. All the above proesses take place spontaneously. The structure model of MPc-Fe3O4 nanoparticles composite has also been investigated. Inside the MPc-Fe3O4 nanoparticles composite, Fe3O4 nanoparticles accumulate together without order, on the surface of the composite, MPc form molecular dispersion layer. The threshold of molecular dispersion layer are also investigated.

  10. 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.

  11. Slow crack growth resistance and bridging stress determination in alumina-rich magnesium aluminate spinel/tungsten composites

    International Nuclear Information System (INIS)

    The slow crack growth (SCG) resistance (V-KI diagrams) of magnesium aluminate spinel and its tungsten composites with different metallic content (7, 10, 14 and 22 vol.%) is reported. It is found that tungsten plays a crucial role in the composite by increasing crack resistance: the higher the W content, the higher the stress intensity factor needed for crack extension at a given rate. The reinforcement is due to the bridging mechanism performed by metal particles, as it strongly affects the compliance of cracked specimens. Its magnitude is estimated by a compliance function Φ(a) from a double torsion test. From the compliance function, R-curve behaviour is predicted for the composite with highest tungsten content. It explains the effect of metal particles on SCG curves. The W-MgAl2O4 interface is believed to influence the reinforcement mechanism

  12. Slow crack growth resistance and bridging stress determination in alumina-rich magnesium aluminate spinel/tungsten composites

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Suarez, T.; Lopez-Esteban, S.; Pecharroman, C. [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), C/ Sor Juana Ines de la Cruz, 3, 28049 Cantoblanco, Madrid (Spain); Moya, J.S. [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), C/ Sor Juana Ines de la Cruz, 3, 28049 Cantoblanco, Madrid (Spain)], E-mail: jsmoya@icmm.csic.es; El Attaoui, H.; Benaqqa, C.; Chevalier, J. [Universite de Lyon, INSA-Lyon, MATEIS, UMR CNRS 5510, 20 avenue Albert Einstein, Villeurbanne F-69621 (France)

    2009-04-15

    The slow crack growth (SCG) resistance (V-K{sub I} diagrams) of magnesium aluminate spinel and its tungsten composites with different metallic content (7, 10, 14 and 22 vol.%) is reported. It is found that tungsten plays a crucial role in the composite by increasing crack resistance: the higher the W content, the higher the stress intensity factor needed for crack extension at a given rate. The reinforcement is due to the bridging mechanism performed by metal particles, as it strongly affects the compliance of cracked specimens. Its magnitude is estimated by a compliance function {phi}(a) from a double torsion test. From the compliance function, R-curve behaviour is predicted for the composite with highest tungsten content. It explains the effect of metal particles on SCG curves. The W-MgAl{sub 2}O{sub 4} interface is believed to influence the reinforcement mechanism.

  13. EFFECT OF SPINEL ADDITION ON THE SINTERING BEHAVIOR AND MICROSTRUCTURE OF ALUMINA-SPINEL CERAMICS

    OpenAIRE

    Emre Yalamac

    2014-01-01

    Sintering behaviors of alumina-spinel powder mixtures were investigated up to 1600oC using a vertical dilatometer. Final density and microstructure of pure alumina, magnesium aluminate spinel (MgAl2O4) ceramics and ceramic composites with different alumina-spinel ratio were examined. As a result, the densification and final density of alumina-spinel composites were affected by addition of 10 wt. % and 20 wt. % spinel into alumina. Non-stoichiometric alumina-rich spinel phase was d...

  14. Metal Nanoparticle/Block Copolymer Composite Assembly and Disassembly.

    Science.gov (United States)

    Li, Zihui; Sai, Hiroaki; Warren, Scott C; Kamperman, Marleen; Arora, Hitesh; Gruner, Sol M; Wiesner, Ulrich

    2009-01-01

    Ligand-stabilized platinum nanoparticles (Pt NPs) were self-assembled with poly(isoprene-block-dimethylaminoethyl methacrylate) (PI-b-PDMAEMA) block copolymers to generate organic-inorganic hybrid materials. High loadings of NPs in hybrids were achieved through usage of N,N-di-(2-(allyloxy)ethyl)-N-3-mercaptopropyl-N-3-methylammonium chloride as the ligand, which provided high solubility of NPs in various solvents as well as high affinity to PDMAEMA. From NP synthesis, existence of sub-1 nm Pt NPs was confirmed by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images. Estimations of the Pt NP ligand head group density based on HAADF-STEM images and thermogravimetric analysis (TGA) data yielded results comparable to what has been found for alkanethiol self-assembled monolayers (SAMs) on flat Pt {111} surfaces. Changing the volume fraction of Pt NPs in block copolymer-NP composites yielded hybrids with spherical micellar, wormlike micellar, lamellar and inverse hexagonal morphologies. Disassembly of hybrids with spherical, wormlike micellar, and lamellar morphologies generated isolated metal-NP based nano-spheres, cylinders and sheets, respectively. Results suggest the existence of powerful design criteria for the formation of metal-based nanostructures from designer blocked macromolecules. PMID:21103025

  15. Membrane deformation controlled by monolayer composition of embedded amphiphilic nanoparticles

    Science.gov (United States)

    van Lehn, Reid; Alexander-Katz, Alfredo

    2014-03-01

    In recent work, we have shown that charged, amphiphilic nanoparticles (NPs) can spontaneously insert into lipid bilayers, embedding the NP in a conformation resembling a transmembrane protein. Many embedded membrane proteins exert an influence on surrounding lipids that lead to deformation and membrane-mediated interactions that may be essential for function. Similarly, embedded NPs will also induce membrane deformations related to the same physicochemical forces. Unlike many transmembrane proteins, however, the highly charged NPs may exert preferential interactions on surrounding lipid head groups. In this work, we use atomistic molecular dynamics simulations to show that the membrane around embedded particles may experience local thinning, head group reorientation, and an increase in lipid density depending on the size and surface composition of the NP. We quantify the extent of these deformations and illustrate the complex interplay between lipid tail group and head group interactions that go beyond pure thickness deformations that may be expected from coarse-grained or continuum models. This work thus suggests guidelines for the design of particles that spontaneously partition into lipid bilayers and influence local membrane mechanical properties in a targeted manner.

  16. Nanoparticle Filtration in a RTM Processed Epoxy/Carbon Fiber Composite

    Science.gov (United States)

    Miller, Sandi G.; Micham, Logan; Copa, Christine C.; Criss, James M., Jr.; Mintz, Eric A.

    2011-01-01

    Several epoxy matrix composite panels were fabricated by resin transfer molding (RTM) E862/W resin onto a triaxially braided carbon fiber pre-form. Nanoparticles including carbon nanofiber, synthetic clay, and functionalized graphite were dispersed in the E862 matrix, and the extent of particle filtration during processing was characterized. Nanoparticle dispersion in the resin flashing on both the inlet and outlet edges of the panel was compared by TEM. Variation in physical properties such as Tg and moisture absorption throughout the panel were also characterized. All nanoparticle filled panels showed a decrease in Tg along the resin flow path across the panel, indicating nanoparticle filtration, however there was little change in moisture absorption. This works illustrates the need to obtain good nano-particle dispersion in the matrix resin to prevent particle agglomeration and hence particle filtration in the resultant polymer matrix composites (PMC).

  17. 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

  18. In situ measurement of reinforcement stress in an aluminum-alumina metal matrix composite under compressive loading

    International Nuclear Information System (INIS)

    The phenomena of stress partitioning between the matrix and the reinforcements in a loaded metal matrix composite dominate the mechanical behavior of these materials. Numerical models for estimating the stress in the matrix and the reinforcement under load are well developed. However, direct experimental measurements (e.g. measurement of reinforcement stress) are more difficult and have not been widely undertaken at present. The objective of the present work was to measure in situ the hydrostatic stress in the ceramic reinforcements in a continuously reinforced metal matrix composite loaded under transverse compression (i.e. loading perpendicular to the fiber axis). A single crystal sapphire reinforced AA6061 matrix model composite (reinforcement volume fraction ∼10%) was used for the measurements, which were undertaken at applied strains of 5, 10 and 20%. The stress measurements utilized the piezo-spectroscopic property of the Cr3+ ions which were present as impurities in the sapphire reinforcements. The compressive deformation of the composite was simulated using an isotropic, plane strain finite element model. The reinforcement hydrostatic stress estimates from the isotropic FEM model were suitably modified to incorporate the effects of anisotropy in properties of the sapphire single crystal. The mean values of the experimental measurements of reinforcement hydrostatic stress matched well with the numerical estimates

  19. Progress in insulating thermal conductive polymer/alumina composites%聚合物/Al2O3导热绝缘复合材料研究进展

    Institute of Scientific and Technical Information of China (English)

    董丽娜; 周文英; 睢雪珍; 王子君; 张溟涛

    2015-01-01

    Alumina is a kind of important heat conductive filler to prepare high thermal conductive composites due to its low price and excellent comprehensive properties,such as superior electrical insulation and high thermal conductivity. In this paper,the authors discussed the research progress in insulting thermal conductive polymer/alumina composites,the influences of content,shape,particle size and surface modification of alumina,hybrid fillers and processing methods,etc. on the thermal conductivity and other properties were emphasized to supply references for preparing polymer/alumina composites with good comprehensive properties.%Al2O3以其优越电绝缘性及良好导热能力、价格低廉等综合性能成为目前制备导热绝缘复合材料的一类重要填料.综述了聚合物/Al2O3导热绝缘复合材料的研究进展,重点阐述了氧化铝的用量、形状、粒径、表面改性、混杂填充及加工方法等对聚合物/Al2O3复合材料热导率及其他性能的影响,为制备综合性能优良的聚合物/Al2O3复合材料提供有益参考.

  20. Compositional disorder and its effect on the thermoelectric performance of Zn₃P₂ nanowire-copper nanoparticle composites.

    Science.gov (United States)

    Brockway, Lance; Vasiraju, Venkata; Vaddiraju, Sreeram

    2014-03-28

    Recent studies indicated that nanowire format of materials is ideal for enhancing the thermoelectric performance of materials. Most of these studies were performed using individual nanowires as the test elements. It is not currently clear whether bulk assemblies of nanowires replicate this enhanced thermoelectric performance of individual nanowires. Therefore, it is imperative to understand whether enhanced thermoelectric performance exhibited by individual nanowires can be extended to bulk assemblies of nanowires. It is also imperative to know whether the addition of metal nanoparticle to semiconductor nanowires can be employed for enhancing their thermoelectric performance further. Specifically, it is important to understand the effect of microstructure and composition on the thermoelectric performance on bulk compound semiconductor nanowire-metal nanoparticle composites. In this study, bulk composites composed of mixtures of copper nanoparticles with either unfunctionalized or 1,4-benzenedithiol (BDT) functionalized Zn₃P₂ nanowires were fabricated and analyzed for their thermoelectric performance. The results indicated that use of BDT functionalized nanowires for the fabrication of composites leads to interface-engineered composites that have uniform composition all across their cross-section. The interface engineering allows for increasing their Seebeck coefficients and electrical conductivities, relative to the Zn₃P₂ nanowire pellets. In contrast, the use of unfunctionalized Zn₃P₂ nanowires for the fabrication of composite leads to the formation of composites that are non-uniform in composition across their cross-section. Ultimately, the composites were found to have Zn₃P₂ nanowires interspersed with metal alloy nanoparticles. Such non-uniform composites exhibited very high electrical conductivities, but slightly lower Seebeck coefficients, relative to Zn₃P₂ nanowire pellets. These composites were found to show a very high zT of 0.23 at 770

  1. Compositional disorder and its effect on the thermoelectric performance of Zn3P2 nanowire–copper nanoparticle composites

    International Nuclear Information System (INIS)

    Recent studies indicated that nanowire format of materials is ideal for enhancing the thermoelectric performance of materials. Most of these studies were performed using individual nanowires as the test elements. It is not currently clear whether bulk assemblies of nanowires replicate this enhanced thermoelectric performance of individual nanowires. Therefore, it is imperative to understand whether enhanced thermoelectric performance exhibited by individual nanowires can be extended to bulk assemblies of nanowires. It is also imperative to know whether the addition of metal nanoparticle to semiconductor nanowires can be employed for enhancing their thermoelectric performance further. Specifically, it is important to understand the effect of microstructure and composition on the thermoelectric performance on bulk compound semiconductor nanowire–metal nanoparticle composites. In this study, bulk composites composed of mixtures of copper nanoparticles with either unfunctionalized or 1,4-benzenedithiol (BDT) functionalized Zn3P2 nanowires were fabricated and analyzed for their thermoelectric performance. The results indicated that use of BDT functionalized nanowires for the fabrication of composites leads to interface-engineered composites that have uniform composition all across their cross-section. The interface engineering allows for increasing their Seebeck coefficients and electrical conductivities, relative to the Zn3P2 nanowire pellets. In contrast, the use of unfunctionalized Zn3P2 nanowires for the fabrication of composite leads to the formation of composites that are non-uniform in composition across their cross-section. Ultimately, the composites were found to have Zn3P2 nanowires interspersed with metal alloy nanoparticles. Such non-uniform composites exhibited very high electrical conductivities, but slightly lower Seebeck coefficients, relative to Zn3P2 nanowire pellets. These composites were found to show a very high zT of 0.23 at 770 K, orders of

  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. 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. PMID:25046646

  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

    2016-01-01

    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. PMID:26783258

  5. 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

    2016-01-01

    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.

  6. 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

    2016-01-01

    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. PMID:26783258

  7. A study on heat transfer characteristics of spherical and fibrous alumina nanofluids

    International Nuclear Information System (INIS)

    Highlights: ► Spherical and fibrous alumina nanoparticles were prepared by pulsed wire evaporation and hydrolysis methods. ► Fibrous alumina nanofluid exhibited higher thermal conductivity enhancement than spherical one due to entangled structure of nanofibers with high aspect-ratio. ► Decreasing rate of viscosity with temperature for fibrous alumina nanofluid was much larger than that for spherical one. - Abstract: Ethylene glycol based nanofluids containing spherical/fibrous alumina nanoparticles were synthesized by pulsed wire evaporation and hydrolysis methods. The crystallographic and morphological properties of the prepared nanoparticles were analyzed by X-ray diffraction, nitrogen gas adsorption and transmission electron microscopy. The average diameter of spherical alumina nanoparticles was about 80 nm and the alumina nanofibers exhibited a high aspect ratio (length/width). The viscosity and thermal conductivity of the spherical/fibrous alumina nanofluids were experimentally measured in the temperature range from 25 to 80 °C. For the fibrous alumina nanofluid, the increase of temperature raised thermal conductivity but lowered viscosity. On the other hand, for the spherical alumina nanofluid, both thermal conductivity and viscosity were decreased with increasing temperature. In particular, the fibrous alumina nanofluid exhibited a higher enhancement of thermal conductivity than the spherical one due to the well-connected structure between entangled nanofibers with high aspect ratio.

  8. Bauxite and alumina

    Science.gov (United States)

    Bray, E.L.

    2009-01-01

    The article provides information on bauxite and alumina mining. U.S. states like Alabama, Arkansas and Georgia produced small amounts of bauxite and bauxitic clays for nonmetallurgical uses. Total metallurgical-grade bauxite imports in 2008 is cited. The leading suppliers of bauxite to the U.S. are Jamaica, Guinea and Brazil. The estimated domestic production of alumina in 2008 is mentioned. It also discusses consumption and prices of both bauxite and alumina.

  9. Porous Alumina Films with Width-Controllable Alumina Stripes

    Directory of Open Access Journals (Sweden)

    Huang Shi-Ming

    2010-01-01

    Full Text Available Abstract Porous alumina films had been fabricated by anodizing from aluminum films after an electropolishing procedure. Alumina stripes without pores can be distinguished on the surface of the porous alumina films. The width of the alumina stripes increases proportionally with the anodizing voltage. And the pores tend to be initiated close to the alumina stripes. These phenomena can be ascribed to the electric field distribution in the alumina barrier layer caused by the geometric structure of the aluminum surface.

  10. Porous Alumina Films with Width-Controllable Alumina Stripes

    OpenAIRE

    Huang Shi-Ming; Pu Lin; Shi Yi; Huang Kai; Wu Zhi-Ming; Ji Li; Kang Jun-Yong

    2010-01-01

    Abstract Porous alumina films had been fabricated by anodizing from aluminum films after an electropolishing procedure. Alumina stripes without pores can be distinguished on the surface of the porous alumina films. The width of the alumina stripes increases proportionally with the anodizing voltage. And the pores tend to be initiated close to the alumina stripes. These phenomena can be ascribed to the electric field distribution in the alumina barrier layer caused by the geometric structure o...

  11. Photocurrent Enhancement in Porphyrin-Silver Nanoparticle Composite Films Using Nanostructures of Silver Nanoparticles

    Science.gov (United States)

    Matsumoto, Ryuji; Yamada, Sunao; Yonemura, Hiroaki

    2013-04-01

    The fabrication of tetraphenyl porphyrin (TPP)-silver nanoparticle (AgP) composite films on indium-tin oxide (ITO) electrodes was carried out by the electrostatic layer-by-layer adsorption technique. Maximum enhancement in photocurrent action spectra as well as in fluorescence emission spectra was observed at an immersion time of 2 h. The effects of AgP on photocurrent and fluorescence suggested the effects of enhanced electric fields resulting from a localized surface plasmon resonance on the enhancement of photocurrent and fluorescence signals. The effect of AgP on the lifetime of the singlet excited state of TPP (1TPP*) indicated that the lifetime of 1TPP* decreases as compared with that in the absence of AgP substrate. The results on fluorescence lifetime suggested that the difference between the effects of AgP on photocurrent and fluorescence is most likely ascribed to the notion that the energy transfer from 1TPP* to surface plasmons due to AgP aggregates competes with photoinduced electron transfer from 1TPP* to O2 during photocurrent measurement.

  12. Perovskite ceramic nanoparticles in polymer composites for augmenting bone tissue regeneration

    International Nuclear Information System (INIS)

    There is increasing interest in the use of nanoparticles as fillers in polymer matrices to develop biomaterials which mimic the mechanical, chemical and electrical properties of bone tissue for orthopaedic applications. The objective of this study was to prepare poly(ϵ-caprolactone) (PCL) nanocomposites incorporating three different perovskite ceramic nanoparticles, namely, calcium titanate (CT), strontium titanate (ST) and barium titanate (BT). The tensile strength and modulus of the composites increased with the addition of nanoparticles. Scanning electron microscopy indicated that dispersion of the nanoparticles scaled with the density of the ceramics, which in turn played an important role in determining the enhancement in mechanical properties of the composite. Dielectric spectroscopy revealed improved permittivity and reduced losses in the composites when compared to neat PCL. Nanofibrous scaffolds were fabricated via electrospinning. Induction coupled plasma-optical emission spectroscopy indicated the release of small quantities of Ca+2, Sr+2, Ba+2 ions from the scaffolds. Piezo-force microscopy revealed that BT nanoparticles imparted piezoelectric properties to the scaffolds. In vitro studies revealed that all composites support osteoblast proliferation. Expression of osteogenic genes was enhanced on the nanocomposites in the following order: PCL/CT > PCL/ST > PCL/BT > PCL. This study demonstrates that the use of perovskite nanoparticles could be a promising technique to engineer better polymeric scaffolds for bone tissue engineering. (paper)

  13. Properties and Strengthening Mechanism of Brush Plated Nanoparticle Reinforced Composite Coatings

    Institute of Scientific and Technical Information of China (English)

    DONG Shi-yun; XU Bin-shi; MA Shi-ning; TU Wei-yi

    2004-01-01

    Nanoparticle reinforced nickel matrix composite coatings, such as n-Al2O3/Ni, n-SiO2/Ni, n-SiC/Ni and n-TiO2/Ni, were fabricated by brush plating technique. Hardness, wear resistance and contact-fatigue resistance of the composite coatings were determined, and strengthening mechanism of the composite coatings was discussed. Results showed that the composite coatings had superior properties to the Ni metal coating. Compared with properties of brush plated Ni metal coating, the composite coatings had hardness over 1.5 times and wear resistance capability of about 2.5 times. The strengthening mechanism of the composite coatings mainly included fine-crystal grain effect, nanoparticle dispersion effect and dislocation effect.

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

    International Nuclear Information System (INIS)

    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 m2 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. Modifications of interface chemistry of LSM–YSZ composite by ceria nanoparticles

    DEFF Research Database (Denmark)

    Knöfel, Christina; Wang, Hsiang-Jen; Thydén, Karl Tor Sune; Mogensen, Mogens Bjerg

    2011-01-01

    crystal structure. Low concentrations of lanthanum and manganese originating from LSM were detected within SDC particles. It was also observed that the relative atomic concentration of strontium increased on the LSM–YSZ surface with increasing amount of SDC nanoparticles. These findings are related to the...... applied nanoparticle impregnation method. It is indicated that interactions between surfactant, nanoparticles, impregnation solution and the LSM–YSZ composite take place which can locally affect the surface and interface chemistry of the investigated materials.......A porous composite electrode LSM–YSZ (lanthanum strontium manganite and yttria stabilized zirconia) was impregnated with different amounts of SDC (samarium substituted ceria) nanoparticles. The materials were investigated with X-ray diffraction, scanning electron microscopy, transmission electron...

  16. Carbon nanotubes/laser ablation gold nanoparticles composites

    International Nuclear Information System (INIS)

    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

  17. Mechanical properties of dispersed ceramic nanoparticles in polymer composites for orthopedic applications

    Directory of Open Access Journals (Sweden)

    Huinan Liu

    2010-04-01

    Full Text Available Huinan Liu, Thomas J WebsterDivision of Engineering, Brown University, Providence, RI, USAAbstract: Ceramic/polymer composites have been considered as third-generation orthopedic biomaterials due to their ability to closely match properties (such as surface, chemistry, biological, and mechanical of natural bone. It has already been shown that the addition of nanophase compared with conventional (or micron-scale ceramics to polymers enhances bone cell functions. However, in order to fully take advantage of the promising nanometer size effects that nanoceramics can provide when added to polymers, it is critical to uniformly disperse them in a polymer matrix. This is critical since ceramic nanoparticles inherently have a strong tendency to form larger agglomerates in a polymer matrix which may compromise their properties. Therefore, in this study, model ceramic nanoparticles, specifically titania and hydroxyapatite (HA, were dispersed in a model polymer (PLGA, poly-lactic-co-glycolic acid using high-power ultrasonic energy. The mechanical properties of the resulting PLGA composites with well-dispersed ceramic (either titania or HA nanoparticles were investigated and compared with composites with agglomerated ceramic nanoparticles. Results demonstrated that well-dispersed ceramic nanoparticles (titania or HA in PLGA improved mechanical properties compared with agglomerated ceramic nanoparticles even though the weight percentage of the ceramics was the same. Specifically, well-dispersed nanoceramics in PLGA enhanced the tensile modulus, tensile strength at yield, ultimate tensile strength, and compressive modulus compared with the more agglomerated nanoceramics in PLGA. In summary, supplemented by previous studies that demonstrated greater osteoblast (bone-forming cell functions on well-dispersed nanophase ceramics in polymers, the present study demonstrated that the combination of PLGA with well-dispersed nanoceramics enhanced mechanical properties

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

    OpenAIRE

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

    2016-01-01

    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...

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

    Science.gov (United States)

    Kasraei, Shahin; Sami, Lida; Hendi, Sareh; AliKhani, Mohammad-Yousef; Rezaei-Soufi, Loghman

    2014-01-01

    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. PMID:24790923

  20. Photoresponse from noble metal nanoparticles-multi walled carbon nanotube composites

    Energy Technology Data Exchange (ETDEWEB)

    Scarselli, M.; Camilli, L.; Castrucci, P.; De Crescenzi, M. [Dipartimento di Fisica, Universita di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma (Italy); Matthes, L. [Dipartimento di Fisica, Universita di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma (Italy); Institut fuer Festkoepertheorie und optik, Friedrich Schiller Universitaet, Max-Wien Platz 1, Jena (Germany); Pulci, O. [Dipartimento di Fisica, Universita di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma (Italy); ETSF, MIFO, and CNR-ISM, Via del Fosso del Cavaliere, Roma (Italy); Gatto, E.; Venanzi, M. [Dipartimento di Scienze e Tecnologie Chimiche, Universita di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma (Italy)

    2012-12-10

    In this Letter, we investigated the photo-response of multi wall carbon nanotube-based composites obtained from in situ thermal evaporation of noble metals (Au, Ag, and Cu) on the nanotube films. The metal deposition process produced discrete nanoparticles on the nanotube outer walls. The nanoparticle-carbon nanotube films were characterized by photo-electrochemical measurements in a standard three electrode cell. The photocurrent from the decorated carbon nanotubes remarkably increased with respect to that of bare multiwall tubes. With the aid of first-principle calculations, these results are discussed in terms of metal nanoparticle-nanotube interactions and electronic charge transfer at the interface.

  1. Synthesis and characterization of single-crystalline alumina nanowires

    Institute of Scientific and Technical Information of China (English)

    ZHAO Qing; XU Xiang-yu; ZHANG Hong-zhou; CHEN Yao-feng; XU Jun; YU Da-peng

    2005-01-01

    Alumina nanowires were synthesized on large-area silicon substrate via simple thermal evaporation method of heating a mixture of aluminum and alumina powders without using any catalyst or template. The phase structure and the surface morphology of the as-grown sample were analyzed by X-ray diffractometry(XRD) and scanning electron microscopy (SEM), respectively. The chemical composition and the microstructure of the as-grown alumina nanowires were characterized using transmission electron microscope(TEM). The nanowires are usually straight and the single crystalline has average diameter of 40 nm and length of 3 - 5 μm. The growth direction is along the [002] direction. Well aligned alumina nanowire arrays were observed on the surface of many large particles. The catalyst-free growth of the alumina nanowires was explained under the framework of a vapor-solid(VS)growth mechanism. This as-synthesized alumina nanowires could find potential applications in the fabrication of nanodevices.

  2. Microporous alumina ceramic membranes

    Science.gov (United States)

    Anderson, Marc A.; Sheng, Guangyao

    1993-01-01

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  3. Heterocyclic aramid nanoparticle-assisted graphene exfoliation for fabrication of pristine graphene-based composite paper

    Energy Technology Data Exchange (ETDEWEB)

    Mo, Yao; Liu, Qi; Fan, Jinchen, E-mail: Jinchen.fan@shiep.edu.cn; Shi, Penghui; Min, Yulin, E-mail: ahaqmylin@126.com; Xu, Qunjie [Shanghai University of Electric Power, Shanghai Key Laboratory of Materials Protection and Advanced Materials in Electric Power, College of Environmental and Chemical Engineering (China)

    2015-07-15

    Mechanically strong, electrically conductive, and flexible pristine graphene-based composite paper was prepared based on heterocyclic aramid nanoparticle-assisted liquid-phase exfoliation of graphite. The macroscopic heterocyclic aramid yarns were split and assembled into heterocyclic aramid nanoparticles with the size of ∼30 nm by deprotonation in dimethylsulfoxide in the presence of potassium hydroxide. The obtained heterocyclic aramid nanoparticles dimethylsulfoxide dispersion was used as good medium solvent for highly efficiency liquid-phase exfoliation of graphite. The results demonstrated that the concentration of exfoliated graphene can facile reaches ∼2.72 mg/mL after direct sonication of 7 h with assist of heterocyclic aramid nanoparticles. After exfoliation, the self-assembled pristine graphene-based composite paper was fabricated by vacuum-assisted filtration. Due to the introduction of heterocyclic aramid nanoparticles, the self-assembled pristine graphene/heterocyclic aramid nanoparticles composite paper exhibited good mechanical property with tensile strength of ∼129.7 MPa, meantime, has a high electrical conductivity of ∼1.42 × 10{sup 4} S/m.

  4. Composition- and Structure-Tunable Gold-Cobalt Nanoparticles and Electrocatalytic Synergy for Oxygen Evolution Reaction.

    Science.gov (United States)

    Lu, Aolin; Peng, Dong-Liang; Chang, Fangfang; Skeete, Zakiya; Shan, Shiyao; Sharma, Anju; Luo, Jin; Zhong, Chuan-Jian

    2016-08-10

    The increasing energy crisis constitutes an inspiring drive seeking alternative energies such as hydrogen from water splitting which is clean and abundant, but a key challenge for water splitting is the need of highly efficient catalysts for oxygen evolution reaction (OER). This report describes findings of an investigation of the synthesis of gold-cobalt (AuCo) nanoparticles by a facile one-pot and injection method and their use as highly efficient catalysts for OER. While particle size depends on the synthesis method, the composition of the nanoparticles is controlled by feeding ratio of Au and Co precursors in the synthesis. Depending on Co content, the nanoparticles exhibit largely phase-segregated domains with a core (Au)-shell (Co) type of structure at a high level of Co. Upon the thermochemical treatment of carbon-supported AuCo nanoparticles, the redox activity of Co species in the nanoparticles with cycle number is shown to decrease which changes the surface oxidation state of Co species without changing the composition significantly. The electrocatalytic activity for OER in alkaline electrolytes is shown to depend on the bimetallic composition, displaying a maximum activity for an Au:Co ratio of ∼2:3. This dependence is also shown to correlate with the surface oxidation state and redox activities, providing an insight into the electrocatalytic activity. Mechanistic aspects of the electrocataltytic properties are discussed in terms of the bifunctional synergy of Co and Au in the nanoparticle catalysts. PMID:27479685

  5. Heterocyclic aramid nanoparticle-assisted graphene exfoliation for fabrication of pristine graphene-based composite paper

    International Nuclear Information System (INIS)

    Mechanically strong, electrically conductive, and flexible pristine graphene-based composite paper was prepared based on heterocyclic aramid nanoparticle-assisted liquid-phase exfoliation of graphite. The macroscopic heterocyclic aramid yarns were split and assembled into heterocyclic aramid nanoparticles with the size of ∼30 nm by deprotonation in dimethylsulfoxide in the presence of potassium hydroxide. The obtained heterocyclic aramid nanoparticles dimethylsulfoxide dispersion was used as good medium solvent for highly efficiency liquid-phase exfoliation of graphite. The results demonstrated that the concentration of exfoliated graphene can facile reaches ∼2.72 mg/mL after direct sonication of 7 h with assist of heterocyclic aramid nanoparticles. After exfoliation, the self-assembled pristine graphene-based composite paper was fabricated by vacuum-assisted filtration. Due to the introduction of heterocyclic aramid nanoparticles, the self-assembled pristine graphene/heterocyclic aramid nanoparticles composite paper exhibited good mechanical property with tensile strength of ∼129.7 MPa, meantime, has a high electrical conductivity of ∼1.42 × 104 S/m.

  6. 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

  7. Guest–host interaction in ferroelectric liquid crystal–nanoparticle composite system

    Indian Academy of Sciences (India)

    Dharmendra Pratap Singh; Swadesh Kumar Gupta; Satya Prakash Yadav; P K Sharma; A C Pandey; Rajiv Manohar

    2014-05-01

    The present paper deals with the characterization of a ferroelectric liquid crystal–nanoparticle (FLC–NP) composite system. The dielectric, electrical and polarization property of the FLC–NP composite system have been studied as a function of temperature and frequency. Ferroelectric Cu-doped ZnO (Cu–ZnO) nanoparticles have been added to the pure ferroelectric liquid crystal (FLC) Felix 17/100. The nanoparticles are bigger in size as compared to FLC molecules; therefore, they distort the existing geometry of FLC matrix and set up an antiparallel correlation with the dipole moments of the host FLC molecules. This antiparallel correlation of guest–host geometry reduces the net ferroelectricity of the composite system and modifies all the physical properties of the pure FLC. The change in properties has been analysed and explained in the light of guest–host interaction.

  8. Characterization of thermochemical properties of Al nanoparticle and NiO nanowire composites

    Science.gov (United States)

    Wen, John Z.; Ringuette, Sophie; Bohlouli-Zanjani, Golnaz; Hu, Anming; Nguyen, Ngoc Ha; Persic, John; Petre, Catalin F.; Zhou, Y. Norman

    2013-04-01

    Thermochemical properties and microstructures of the composite of Al nanoparticles and NiO nanowires were characterized. The nanowires were synthesized using a hydrothermal method and were mixed with these nanoparticles by sonication. Electron microscopic images of these composites showed dispersed NiO nanowires decorated with Al nanoparticles. Thermal analysis suggests the influence of NiO mass ratio was insignificant with regard to the onset temperature of the observed thermite reaction, although energy release values changed dramatically with varying NiO ratios. Reaction products from the fuel-rich composites were found to include elemental Al and Ni, Al2O3, and AlNi. The production of the AlNi phase, confirmed by an ab initio molecular dynamics simulation, was associated with the formation of some metallic liquid spheres from the thermite reaction.

  9. Pengaruh Temperatur Bath Terhadap Alumina Solubility Pada Tungku Reduksi Di PT Inalum Kuala Tanjung

    OpenAIRE

    Rahman, Syahri

    2010-01-01

    Alumina solubility is maximum aluminium oxide concentration of the cryolite electrolyte depend on its composition. The factors that affect to the quantity of alumina solubility are cryolite temperature (NA3AlF6), %AlF3, and %CaF2 in cryolite. From observation data, know that if cryolite temperature high, so alumina solubility provided high too.

  10. Dual functions of TiC nanoparticles on tribological performance of Al/graphite composites

    Science.gov (United States)

    Fallahdoost, Hamid; Nouri, Alireza; Azimi, Amin

    2016-06-01

    In this study, the effect of TiC nanoparticles as a reinforcement on the mechanical and tribological properties of Aluminum-based self lubricating composite was investigated. The microstructure, relative density, hardness, and tribological properties of Al/graphite and Al/TiC/graphite composites were examined as a function of graphite content. The tribo-surfaces of the samples were analyzed using SEM and EDS elemental mapping. The results indicated that the addition of TiC nanoparticles not only decreased the wear rate and coefficient of friction of the composites, but also facilitated the formation of a stable graphite layer at longer sliding distances and high sliding velocities by forming a durable graphite/TiC composite on the tribo-surface. Therefore, the stability of graphite layer can be considered as a possible cause for decrease in wear rate of the Al/TiC/graphite composite.

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

    International Nuclear Information System (INIS)

    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 NaBH4 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.

  12. Composite materials for medical purposes based on polyvinylpyrrolidone modified with ketoprofen and silver nanoparticles

    Science.gov (United States)

    Nikitin, L. N.; Vasil'Kov, A. Yu.; Banchero, M.; Manna, L.; Naumkin, A. V.; Podshibikhin, V. L.; Abramchuk, S. S.; Buzin, M. I.; Korlyukov, A. A.; Khokhlov, A. R.

    2011-07-01

    A method for obtaining composite medical materials based on polyvinylpyrrolidone (PVP K15) modified with ketoprofen in a medium of supercritical carbon dioxide and with Ag nanoparticles prepared by metal vapor synthesis is developed. A system in which ketoprofen and Ag nanoparticles with an average size of ˜16 nm are uniformly distributed over the bulk of PVP is obtained. It is found that the yield of ketoprofen from the composite in the physiological solution is higher than that for an analogous system obtained by mechanical mixing of the components.

  13. 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.

  14. Effects of yttrium on the sintering and microstructure of alumina-silicon carbide "nanocomposites"

    OpenAIRE

    Cock, AM; Shapiro, IP; Todd, RI; Roberts, SG

    2005-01-01

    Alumina and alumina-based "nanocomposites" with 2 and 5 vol% silicon carbide and varying amounts of yttria (0-1.5 wt%) have been prepared by pressureless sintering in the temperature range 1450°-1650°C. The effects of composition and sintering temperature on density and microstructure are reported. Yttria inhibited sintering in alumina, but enhanced the sinterability of the nanocomposites. It also induced abnormal grain growth in both alumina and nanocomposites, but strongly bimodal grain siz...

  15. Metal Oxide Nanoparticles: The Importance of Size, Shape, Chemical Composition, and Valence State in Determining Toxicity

    Science.gov (United States)

    Dunnick, Katherine

    Nanoparticles, which are defined as a structure with at least one dimension between 1 and 100 nm, have the potential to be used in a variety of consumer products due to their improved functionality compared to similar particles of larger size. Their small size is associated with increased strength, improved catalytic properties, and increased reactivity; however, their size is also associated with increased toxicity in vitro and in vivo. Numerous toxicological studies have been conducted to determine the properties of nanomaterials that increase their toxicity in order to manufacture new nanomaterials with decreased toxicity. Data indicates that size, shape, chemical composition, and valence state of nanomaterials can dramatically alter their toxicity profile. Therefore, the purpose of this dissertation was to determine how altering the shape, size, and chemical composition of various metal oxide nanoparticles would affect their toxicity. Metal oxides are used in variety of consumer products, from spray-sun screens, to food coloring agents; thus, understanding the toxicity of metal oxides and determining which aspects affect their toxicity may provide safe alternatives nanomaterials for continued use in manufacturing. Tungstate nanoparticles toxicity was assessed in an in vitro model using RAW 264.7 cells. The size, shape, and chemical composition of these nanomaterials were altered and the effect on reactive oxygen species and general cytotoxicity was determined using a variety of techniques. Results demonstrate that shape was important in reactive oxygen species production as wires were able to induce significant reactive oxygen species compared to spheres. Shape, size, and chemical composition did not have much effect on the overall toxicity of these nanoparticles in RAW 264.7 cells over a 72 hour time course, implicating that the base material of the nanoparticles was not toxic in these cells. To further assess how chemical composition can affect toxicity

  16. Adsorption and desorption of uranium on nano goethite and nano alumina

    International Nuclear Information System (INIS)

    The nano goethite and nano alumina were synthesized to investigate the effect of nanoscale size on adsorption-desorption of U(VI) from aqueous solution. It was determined that the site densities of nanoparticles are higher than α-alumina and goethite, whereas slight effect of carbonate on adsorption of U(VI) onto nanoparticles was observed. The maximum adsorption capacities of nano alumina and nano goethite were ∼151 and 79 mg/g, respectively. The batch desorption indicated stronger binding affinity of U(VI) for nanoparticles as compared to non-nanoparticles, which were consistent with the results of surface complexation modeling assuming weak and strong sites for nanoparticles while weak sites for α-alumina and goethite. (author)

  17. Fabrication and evaluation of valsartan–polymer–surfactant composite nanoparticles by using the supercritical antisolvent process

    Directory of Open Access Journals (Sweden)

    Kim MS

    2014-11-01

    Full Text Available Min-Soo Kim,1 In-hwan Baek21College of Pharmacy, Pusan National University, Geumjeong-gu, Busan, Republic of Korea; 2College of Pharmacy, Kyungsung University, Daeyeon-dong, Nam-gu, Busan, Republic of KoreaAbstract: The aim of this study was to fabricate valsartan composite nanoparticles by using the supercritical antisolvent (SAS process, and to evaluate the correlation between in vitro dissolution and in vivo pharmacokinetic parameters for the poorly water-soluble drug valsartan. Spherical composite nanoparticles with a mean size smaller than 400 nm, which contained valsartan, were successfully fabricated by using the SAS process. X-ray diffraction and thermal analyses indicated that valsartan was present in an amorphous form within the composite nanoparticles. The in vitro dissolution and oral bioavailability of valsartan were dramatically enhanced by the composite nanoparticles. Valsartan–hydroxypropyl methylcellulose–poloxamer 407 nanoparticles exhibited faster drug release (up to 90% within 10 minutes under all dissolution conditions and higher oral bioavailability than the raw material, with an approximately 7.2-fold higher maximum plasma concentration. In addition, there was a positive linear correlation between the pharmacokinetic parameters and the in vitro dissolution efficiency. Therefore, the preparation of composite nanoparticles with valsartan–hydroxypropyl methylcellulose and poloxamer 407 by using the SAS process could be an effective formulation strategy for the development of a new dosage form of valsartan with high oral bioavailability.Keywords: supersaturation, bioavailability, solid dispersion, dissolution, supercritical fluid

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

    International Nuclear Information System (INIS)

    Fe3O4/Au composite nanoparticles (GoldMag NPs) have received considerable attention because of their advantageous properties arisen from both individual Au and Fe3O4 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. Fe3O4 nanoparticles were prepared by co-precipitation and modified by the citric acid, and then citric acid-coated Fe3O4 nanoparticles were used as seeds in sodium citrate solution to reduce the HAuCl4. 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 Fe3O4/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

  19. 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.

  20. 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 ti

  1. Plasmonic composites of semiconductive polyelectrolytes with metal nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Pfleger, Jiří; Kazim, Samrana; Bondarev, D.; Vohlídal, J.

    Pennington : The Electrochemical Society, 2011. A_1294. [ECS Meeting /219./. 01.05.2011-06.05.2011, Montreal] R&D Projects: GA ČR GAP208/10/0941 Institutional research plan: CEZ:AV0Z40500505 Keywords : plasmonic nanoparticles * polyelectrolytes * conductive polymers Subject RIV: CF - Physical ; Theoretical Chemistry

  2. Optical processes in composites of conjugated polyelectrolyte with silver nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Kazim, Samrana; Bondarev, M.; Hromádková, Jiřina; Vohlídal, J.; Pfleger, Jiří

    Praha : Ústav makromolekulární chemie AV ČR, 2009. L9. ISBN 978-80-85009-60-6. [Workshop: Career in Polymers. 10.07.2009-11.07.2009, Prague] Institutional research plan: CEZ:AV0Z40500505 Keywords : conjugated polyelectrolyte * siílver nanoparticles Subject RIV: CD - Macromolecular Chemistry

  3. 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.

  4. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Hnin Yu Yu [Information Storage Materials Laboratory, Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya 468-8511 (Japan)], E-mail: hnin@toyota-ti.ac.jp; Suzuki, Takao; Nam, Nguyen T.; Phuoc, Nguyen N.; Cao Jiangwei [Information Storage Materials Laboratory, Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya 468-8511 (Japan); Hirotsu, Yoshihiko [ISIR, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

    2008-11-15

    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{sub 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.

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

    International Nuclear Information System (INIS)

    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 L10-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

  7. Thermal diffusivity of nanofluids containing Au/Pd bimetallic nanoparticles of different compositions.

    Science.gov (United States)

    Sánchez-Ramírez, J F; Jiménez Pérez, J L; Cruz Orea, A; Gutierrez Fuentes, R; Bautista-Hernández, A; Pal, U

    2006-03-01

    Colloidal suspensions of bimetallic Au/Pd nanoparticles were prepared by simultaneous reduction of the metal ions from their corresponding chloride salts with polymer (PVP) stabilizer. Thermal properties of water containing bimetallic nanoparticles with different nominal compositions (Au/Pd = 12/1, 5/1, 1/1, 1/5) were measured using the mode mismatched dual-beam thermal lens technique to determine the effect of particle composition on the thermal diffusivity of the nanofluids. The characteristic time constant of the transient thermal lens was estimated by fitting the experimental data to the theoretical expression for transient thermal lens. The thermal diffusivity of the nanofluids (water, containing Au/Pd bimetallic nanoparticles) is seen to be strongly dependent on the composition of the particles. The maximum diffusivity was achieved for the nanoparticles with highest Au/Pd molar ratio. A possible mechanism for such high thermal diffusivity of the nanofluids with bimetallic particles is given. UV-Vis spectroscopy, TEM and high-resolution electron microscopy (HREM) techniques were used to characterize the Au/Pd bimetallic nanoparticles. PMID:16573121

  8. Antibacterial activity of dental composites containing quaternary ammonium polyethylenimine nanoparticles against Streptococcus mutans.

    Science.gov (United States)

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

    2006-07-01

    The antibacterial activity of quaternary ammonium polyethylenimine (PEI) nanoparticles embedded at 1%w/w with clinically used bonding, flowable and hybrid dental composite resins and cured by light polymerization was studied. The antibacterial activity was tested with Streptoccocus mutans by: (i) the agar diffusion test (ADT); (ii) the direct contact test; (iii) bacterial growth in the materials elute; (iv) and scanning electron microscope (SEM). Using the direct contact test, antibacterial activity (p<0.001) was found in all three types of composite resins incorporated with the synthesized nanoparticles. The effect lasted for at least 1 month. SEM demonstrated bacterial debris and no streptococcal chains at 24h of bacterial contact. The addition of 1%w/w of nanoparticles did not affect the flexural modulus and the flexural strength of the dental composite materials. The results indicate that quaternary ammonium PEI nanoparticles immobilized in resin-based materials have a strong antibacterial activity upon contact without leach-out of the nanoparticles and without compromise in mechanical properties. PMID:16564083

  9. Catalytic pyrogenation synthesis of C/Ni composite nanoparticles: controllable carbon structures and high permittivities

    Energy Technology Data Exchange (ETDEWEB)

    Lu, B; Huang, H; Dong, X L; Lei, J P, E-mail: dongxl@dlut.edu.c [School of Materials Science and Engineering, Dalian University of Technology, Dalian, Liaoning 116024 (China)

    2010-03-17

    Catalytic pyrogenation of methane gas in the presence of Ni nanoparticles was employed to synthesize C/Ni composite nanoparticles at various reaction temperatures. The Ni nanoparticles prepared by the arc-discharge method served as a catalyst to decompose the hydrocarbon molecules and also provided isolated templates for the formation of carbon nanocapsules at 400 and 500 {sup 0}C or multi-walled carbon nanotubes at 600 and 650 {sup 0}C. The generation and growth mechanism of the carbon shells are discussed on the basis of structure evolution. By dispersing the nanoparticles homogeneously into a paraffin matrix, the electromagnetic parameters of the nanoparticles have been investigated in the frequency range 2-18 GHz. The samples exhibit high permittivities varying with the microstructures of the nanoparticles. The relationship between the dielectric properties and diverse carbon structures is indicated. The high permittivities of the nanoparticles are attributed to the better conductivity of the carbon shells and the charge polarizations at the defects or interfaces between metal cores and carbon shells.

  10. Characterization of metal nanoparticles/conducting polymer composite films prepared by radiation technique

    International Nuclear Information System (INIS)

    Composites of conducting polymer-metal nanoparticles are of great interest in modern physical and chemical researchers due to their unique physical and chemical properties, which are distinct from those of the bulk metal and molecules .Conducting polymer - metal nanoparticles can be used in diverse fields such as electronics, electrocatalystics and optoelectronics. Conducting polymer and metal nanoparticles blended in polyvinyl Alcohol (PVA) was synthesized by irradiating as films containing monomer and metal salt at different concentrations with gamma radiation technique. In the same time the conducting polymer and metal nanoparticles were formed due to oxidation of monomer and reduction of metal ion respectively by radiation. The structure analysis of conducting polymer-metal nanoparticles films were studied by X-Ray diffraction system which appears different diffraction peak angles respectively .The optical properties were investigated using UV -Vis spectrophotometer that show optical absorbance peak at #lamda# = (780 , 430) nm of conducting polymer and metal nanoparticles respectively. From the UV-spectrum the band gap energy (Eg) was deduced and found to be decreases from (1.4, 2.8) eV at 10 kGy to (1.2,2.52) eV at 50 kGy for conducting polymer and metal nanoparticles respectively. (Author)

  11. Effect of Particle Size and Phase Composition of Titanium Dioxide Nanoparticles on the Photocatalytic Properties

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Hee Dong [Korea Institute of Geoscience and Mineral Resources, Division of Materials Development (Korea, Republic of)], E-mail: hdjang@kigam.re.kr; Kim, Seong-Kil [R and D Center, Samhwa Paint Industry (Korea, Republic of); Kim, Seung-Jin [Korea Institute of Construction Materials, R and D division (Korea, Republic of)

    2001-06-15

    Titanium dioxide (TiO{sub 2}) nanoparticles were prepared by the oxidation of titanium tetrachloride (TiCl{sub 4}) in a diffusion flame reactor. The average diameter of particles was 15-30 nm and mass fraction of anatase ranged from 40% to 80%. Effects of particle size and phase composition of those TiO{sub 2} nanoparticles on photocatalytic properties such as decomposition of methylene blue, bacteria and ammonia gas were investigated. The degree of decomposition of methylene blue by the TiO{sub 2} nanoparticles under the illumination of the black light was directly proportional to the anatase mass fraction, but inversely to the particle size. The decomposition of bacteria and ammonia gas by the TiO{sub 2} nanoparticles under the illumination of the fluorescent light showed the same trend as in the case of the methylene blue.

  12. 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.

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

    OpenAIRE

    Arezou Sezavar; Seyed Mojtaba Zebarjad; Seyed Abdolkarim Sajjadi

    2015-01-01

    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 defor...

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

    International Nuclear Information System (INIS)

    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. Highly coercive cobalt ferrite nanoparticles-CuTl-1223 superconductor composites

    Energy Technology Data Exchange (ETDEWEB)

    Jabbar, Abdul; Qasim, Irfan; Khan, Shahid A.; Nadeem, K.; Waqee-ur-Rehman, M.; Mumtaz, M., E-mail: mmumtaz75@yahoo.com; Zeb, F.

    2015-03-01

    We explored the effects of highly coercive cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles addition on structural, morphological, and superconducting properties of Cu{sub 0.5}Tl{sub 0.5}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10-δ} (CuTl-1223) matrix. Series of (CoFe{sub 2}O{sub 4}){sub x}/CuTl-1223 (x=0 ∼2.0 wt%) composites samples were synthesized and were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) absorption spectroscopy, and dc-resistivity versus temperature measurements. The magnetic behavior of CoFe{sub 2}O{sub 4} nanoparticles was determined by MH-loops with the help of superconducting quantum interference device (SQUID). MH-loops analysis showed that these nanoparticles exhibit high saturation magnetization (86 emu/g) and high coercivity (3350 Oe) at 50 K. The tetragonal structure of host CuTl-1223 superconducting matrix was not altered after the addition of CoFe{sub 2}O{sub 4} nanoparticles, which gave us a clue that these nanoparticles had occupied the inter-granular sites (grain-boundaries) and had filled the pores. The increase of mass density with increasing content of these nanoparticles in composites can also be an evidence of filling up the voids in the matrix. The resistivity versus temperature measurements showed an increase in zero resistivity critical {T_c(0)}, which could be most probably due to improvement of weak-links by the addition of these nanoparticles. But the addition of these nanoparticles beyond an optimum level caused the agglomeration and produced additional stresses in material and suppressed the superconductivity. - Highlights: • T{sub c}(0) increased with increasing CoFe{sub 2}O{sub 4} nanoparticles up to x=1.5. • CoFe{sub 2}O{sub 4} nanoparticles addition has not affected the structure of CuTl-1223. • Addition of CoFe{sub 2}O{sub 4} nanoparticles has improved inter-grains weak links. • Non-monotonic variation of ρ{sub (300} {sub K)} (Ω-cm) is due to

  16. Orientation relationship in WC-Co composite nanoparticles synthesized by in situ reactions

    International Nuclear Information System (INIS)

    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. (paper)

  17. 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.

  18. 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.

  19. Mechanical properties of zirconia-toughened alumina

    International Nuclear Information System (INIS)

    Bend samples of four compositions of zirconia-toughened alumina were heat treated at 10000C for 100 and 500 H and tested for strength and fracture toughness at room temperature. These results are compared with as-received properties, as well as stress rupture and stepped-temperature stress rupture data

  20. Highly coercive cobalt ferrite nanoparticles-CuTl-1223 superconductor composites

    Science.gov (United States)

    Jabbar, Abdul; Qasim, Irfan; Khan, Shahid A.; Nadeem, K.; Waqee-ur-Rehman, M.; Mumtaz, M.; Zeb, F.

    2015-03-01

    We explored the effects of highly coercive cobalt ferrite (CoFe2O4) nanoparticles addition on structural, morphological, and superconducting properties of Cu0.5Tl0.5Ba2Ca2Cu3O10-δ (CuTl-1223} matrix. Series of (CoFe2O4)x/CuTl-1223 (x=0 2.0 wt%) composites samples were synthesized and were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) absorption spectroscopy, and dc-resistivity versus temperature measurements. The magnetic behavior of CoFe2O4 nanoparticles was determined by MH-loops with the help of superconducting quantum interference device (SQUID). MH-loops analysis showed that these nanoparticles exhibit high saturation magnetization (86 emu/g) and high coercivity (3350 Oe) at 50 K. The tetragonal structure of host CuTl-1223 superconducting matrix was not altered after the addition of CoFe2O4 nanoparticles, which gave us a clue that these nanoparticles had occupied the inter-granular sites (grain-boundaries) and had filled the pores. The increase of mass density with increasing content of these nanoparticles in composites can also be an evidence of filling up the voids in the matrix. The resistivity versus temperature measurements showed an increase in zero resistivity critical {Tc(0)}, which could be most probably due to improvement of weak-links by the addition of these nanoparticles. But the addition of these nanoparticles beyond an optimum level caused the agglomeration and produced additional stresses in material and suppressed the superconductivity.

  1. pH-sensitive poly(lactide-co-glycolide) nanoparticle composite microcapsules for oral delivery of insulin

    Science.gov (United States)

    Sun, Shaoping; Liang, Na; Yamamoto, Hiromitsu; Kawashima, Yoshiaki; Cui, Fude; Yan, Pengfei

    2015-01-01

    This study proposes a new concept of pH-sensitive poly(lactide-co-glycolide) (PLGA) nanoparticle composite microcapsules for oral delivery of insulin. Firstly, insulin–sodium oleate complex was prepared by the hydrophobic ion pairing method and then encapsulated into PLGA nanoparticles by the emulsion solvent diffusion method. In order to reduce the burst release of insulin from PLGA nanoparticles and deliver insulin to specific gastrointestinal regions, hence to enhance bioavailability of insulin, the PLGA nanoparticles were further encapsulated into Eudragit® FS 30D to prepare PLGA nanoparticle composite microcapsules by organic spray-drying method. The preparation was evaluated in vitro and in vivo, and the absorption mechanism was discussed. The in vitro drug release studies revealed that the drug release was pH dependent, and the in vivo results demonstrated that the formulation of PLGA nanoparticle composite microcapsules was an effective candidate for oral insulin delivery. PMID:25999713

  2. Synthesis of supported bimetallic nanoparticles with controlled size and composition distributions for active site elucidation

    Energy Technology Data Exchange (ETDEWEB)

    Hakim, Sikander H.; Sener, Canan; Alba Rubio, Ana C.; Gostanian, Thomas M.; O' neill, Brandon J; Ribeiro, Fabio H.; Miller, Jeffrey T.; Dumesic, James A

    2015-08-01

    Elucidation of active sites in supported bimetallic catalysts is complicated by the high level of dispersity in the nanoparticle size and composition that is inherent in conventional methods of catalyst preparation. We present a synthesis strategy that leads to highly dispersed, bimetallic nanoparticles with uniform particle size and composition by means of controlled surface reactions. We demonstrate the synthesis of three systems, RhMo, PtMo, and RhRe, consisting of a highly reducible metal with an oxophilic promoter. These catalysts are characterized by FTIR, CO chemisorption, STEM/EDS, TPR, and XAS analysis. The catalytic properties of these bimetallic nanoparticles were probed for the selective CO hydrogenolysis of (hydroxymethyl)tetrahydropyran to produce 1,6 hexanediol. Based on the characterization results and reactivity trends, the active sites in the hydrogenolysis reaction are identified to be small ensembles of the more noble metal (Rh, Pt) adjacent to highly reduced moieties of the more oxophilic metal (Mo, Re).

  3. Fast response and recovery of hydrogen sensing in Pd-Pt nanoparticle-graphene composite layers

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Rakesh; Varandani, Deepak; Mehta, B R; Singh, V N [Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016 (India); Wen Zhenhai; Feng Xinliang; Muellen, Klaus, E-mail: brmehta@physics.iitd.ernet.in [Max-Planck Institute for Polymer Research, D-55128 Mainz (Germany)

    2011-07-08

    This study reports the fast response and recovery of hydrogen sensing in nanoparticle-graphene composite layers fabricated using chemical methods and comprising of isolated Pd alloy nanoparticles dispersed onto graphene layers. For 2% hydrogen at 40 {sup 0}C and 1 atm pressure, a response time of < 2 s and a recovery time of 18 s are observed. The fast response and recovery observed during sensing are due to hydrogen-induced changes in the work function of the Pd alloy and modification in the distribution of defect states in the graphene band gap due to gas adsorption. The results of hydrogen sensing in the new class of Pd-Pt nanoparticle-graphene composite material are important for understanding the effect of gas adsorption on electronic conduction in graphene layers and for developing a new type of gas sensor based on changes in the electronic properties of the interface.

  4. Poly(methyl methacrylate) Composites with Size-selected Silver Nanoparticles Fabricated Using Cluster Beam Technique

    DEFF Research Database (Denmark)

    Hanif, Muhammad; Juluri, Raghavendra R.; Chirumamilla, Manohar;

    2016-01-01

    based on cluster beam technique allowing the formation of monocrystalline size-selected silver nanoparticles with a +/- 5-7% precision of diameter and controllable embedment into poly (methyl methacrylate). It is shown that the soft-landed silver clusters preserve almost spherical shape with a slight......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...

  5. 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.

  6. 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.

  7. A novel route for fabricating metal-polymer composite nanoparticles with phase-separated structures.

    Science.gov (United States)

    Yabu, Hiroshi; Koike, Kazutaka; Motoyoshi, Kiwamu; Higuchi, Takeshi; Shimomura, Masatsugu

    2010-07-15

    Au nanoparticles (NPs) and polymer composite particles with phase-separation structures were prepared based on phase separation structures. Au NPs were successfully synthesized in amphiphilic block-copolymer micelles, and then composite particles were formed by a simple solvent evaporation process from Au NPs and polymer solution. The phase separated structures (Janus and Core-shell) were controlled by changing the combination of polymers having differing hydrophobicity. PMID:21567522

  8. Inductive heat property of Fe3O4/polymer composite nanoparticles in an ac magnetic field for localized hyperthermia.

    Science.gov (United States)

    Zhao, Dong-Lin; Zhang, Hai-Long; Zeng, Xian-Wei; Xia, Qi-Sheng; Tang, Jin-Tian

    2006-12-01

    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 degrees C and 52.4 degrees C, respectively. The Fe(3)O(4)/PANI composite nanoparticles would be useful as good thermoseeds for localized hyperthermia treatment of cancers. PMID:18458406

  9. Decreased astroglial cell adhesion and proliferation on zinc oxide nanoparticle polyurethane composites

    Directory of Open Access Journals (Sweden)

    Justin T Seil

    2008-11-01

    Full Text Available Justin T Seil, Thomas J WebsterLaboratory for Nanomedicine Research, Division of Engineering, Brown University, Providence, RI, USAAbstract: 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.Keywords: zinc oxide, nanoparticles, astrocytes, neural tissue, nervous system, biomaterials

  10. The influence of self-assembly behavior of nanoparticles on the dielectric polymer composites

    Directory of Open Access Journals (Sweden)

    Xin Lu

    2013-11-01

    Full Text Available To clearify the influence of the distribution of the conductive nanoparticles on the dielectric properties of the corresponding polymer composites, the microstructure and dielectric character of the composites based on the oleic acid modified ferroferric oxide and polyvinylidene fluoride (PVDF polymer have been studied experimentally. It is found that these composites exhibit a normal percolative phase transition over the filler content from insulator to conductor, consistent with the classical percolation theory. However, when the percentage of fillers is at a certain value which is below the percolation threshold, these nanoparticles can assemble into a special porous structure in the PVDF matrix, associated with the enhancement of dielectric constant at low frequency. In addition, the controllable dispersion of conducting nanoparticles in a polymer matrix can prevent premature agglomeration at low filling fractions and avoid the appearance of anomalously early percolation. Therefore, the self-assembly behavior of nanoparticles can be beneficial to preparation of the high dielectric constant and low loss composites for the application of electric energy storage.

  11. 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.

  12. Polypropylene Glycol-Silver Nanoparticle Composites: A Novel Anticorrosion Material for Aluminum in Acid Medium

    Science.gov (United States)

    Solomon, Moses M.; Umoren, Saviour A.; Israel, Aniekemeabasi U.; Ebenso, Eno E.

    2015-11-01

    Admixture of polypropylene glycol and 1 mM AgNO3 together with natural honey as reducing and stabilizing agent was employed to prepare in situ polypropylene glycol/silver nanoparticle (PPG/AgNPs) composite. The prepared PPG/AgNPs composite was characterized by UV-Vis spectroscopy, FTIR, XRD, and EDS, while the morphology of the Ag nanoparticles in the composite was obtained by TEM. TEM results revealed that the Ag nanoparticles were spherical in shape. The anticorrosion property of PPG/AgNPs composite was examined by electrochemical, weight loss, SEM, EDS, and water contact angle measurements. Results obtained show that PPG/AgNPs are effective in retarding the dissolution of Al in an acid-induced corrosive environment. Inhibition efficiency increased with the increasing composite concentration but decreased with the increasing temperature. Potentiodynamic polarization results revealed that PPG/AgNPs functions as a mixed-type corrosion inhibitor. The adsorption of the composite onto Al surface was found to follow El-Awady et al. adsorption isotherm model. SEM, EDS, and water contact angle results confirmed the adsorption of PPG/AgNPs films onto Al surface.

  13. Inter-particle Interactions in Composites of Antiferromagnetic Nanoparticles

    DEFF Research Database (Denmark)

    Frandsen, Cathrine; Mørup, Steen

    2003-01-01

    We have prepared mixtures of alpha-Fe2O3, CoO, and NiO nanoparticles by drying aqueous suspensions of the particles. The magnetic properties were studied by Mossbauer spectroscopy. The measurements showed that interactions with CoO particles suppress the superparamagnetic relaxation of both alpha......-Fe2O3 and Fe-57-doped NiO particles. The effect of NiO particles on alpha-FeA particles was a shorter relaxation time and an induced Morin transition, which usually is absent in alpha-Fe2O3 nanoparticles. Spectra of alpha-Fe2O3 particles, prepared by drying suspensions with added Co2+ and Ni2+ ions...

  14. Innovative Composite Films of Chitosan, Methylcellulose, and Nanoparticles

    OpenAIRE

    Mura, Stefania; Corrias, Francesco; Stara, Giuseppe; Piccinini, Massimo; Secchi, Nicola; Marongiu, Daniela; Innocenzi, Plinio; Irudayaraj, Joseph; Greppi, Gian F.

    2011-01-01

    Plastic is readily available and inexpensive, so it is becoming the main material for packaging. Unfortunately plastics do not biodegrade and, if reduced in small pieces, contaminate soil and waterways. In the present work, natural films composed of chitosan, methylcellulose, and silica (SiO(2)) nanoparticles (NPs) were developed as new packaging materials. The effect of the incorporation of NPs into the polymeric film matrix was evaluated. An excellent improvement of the mechanical propertie...

  15. Room temperature NO2-sensing properties of WO3 nanoparticles/porous silicon

    International Nuclear Information System (INIS)

    WO3 nanoparticles were synthesized by sol–gel method with tungsten hexachloride (WCl6) as precursor and deposited onto porous silicon and alumina substrates by dip-coating. The morphology and crystal structure of samples were investigated by means of field emission scanning electron microscope and X-ray diffractometer. It is the experimental results demonstrated by gas sensing tests that WO3 nanoparticles combining with the substrate of porous silicon presented an improved NO2-sensing property at room temperature. Compared to WO3 deposited on alumina working above 100 °C, the WO3 nanoparticles/porous silicon exhibited higher properties upon exposure to sub-ppm concentrations of NO2 gas at room temperature. Additionally, the NO2-sensing performance of WO3 nanoparticles/porous silicon was enhanced markedly, in comparison to pure porous silicon. The mechanism of WO3/porous silicon composite structure on the NO2 sensing was explained in detail.

  16. Preparation of Antibacterial Nanofibre/Nanoparticle Covered Composite Yarns

    OpenAIRE

    Fatma Yalcinkaya; Michal Komarek; Daniela Lubasova; Filip Sanetrnik; Jiri Maryska

    2016-01-01

    The antibacterial efficiency of nanofibre composite yarns with an immobilized antibacterial agent was tested. This novel type of nanofibrous composite material combines the good mechanical properties of the core yarn with the high specific surface of the nanofibre shell to gain specific targeted qualities. The main advantages of nanofibre covered composite yarns over the standard planar nanofibre membranes include high tensile strength, a high production rate, and their ability to be processe...

  17. 氧化铝复合陶瓷在全髋关节置换中的应用%Alumina matrix composite ceramic-on-ceramic bearings in total hip arthroplasty

    Institute of Scientific and Technical Information of China (English)

    薛孝威; 孙国静; 赵建宁; 周利武; 丁然; 郭亭

    2013-01-01

    目的 为了改善假体的生存率,减少陶瓷部件相关的并发症,新一代氧化铝复合陶瓷开始应用于临床,文中分析氧化铝复合陶瓷对陶瓷全髋关节置换的早期临床疗效.方法 自2009年4月至2011年8月应用第4代氧化铝复合陶瓷对陶瓷对50例(59髋)髋关节疾病患者行全髋关节置换术,应用Harris评分及X线检查进行疗效评定.结果 获得有效随访43例(52髋),平均随访21.4个月(12~40个月).Harris评分由术前平均(43.0±16.3)分(11~64分)提高到末次随访时平均 (92.6±5.3)分(80~100分).未发生陶瓷组件的碎裂及假体脱位,1髋(1.9%)出现异响,1例发生症状性血栓.结论 氧化铝复合陶瓷对陶瓷界面的短期临床效果满意,大头颈陶瓷假体的使用减少了术后脱位率,关节稳定性良好.%Objective A new alumina matrix composite material was developed to improve implant longevity and reduce the risk of component-related complications. The aim of this study was evaluate to retrospectively the short-term clinical results of alumina matrix composite ceramic-on-ceramic bearings in total hip arthroplasty. Methods From April 2009 to August 2011, we performed 59 total hip arthroplasties on 50 patients using alumina matrix composite ceramic-on-ceramic bearings at our institution. The clinical results were evaluated by Hams hip score and X-rays. All patients were evaluated clinically and radiographically at follow-up. Results At the time of the latest follow-up, forty-three( 52 hips ) patients were available for follow-up. Patients had a mean follow-up of 21.4 months ( range, 12 -40 years ). The mean preoperative Harris hip score improved from 43. 0 ± 16. 3( range, 11-64 )points to 92. 6 ± 5. 3( range, 80 - 100 ) points at latest follow-up. There was no ceramic fractures and dislocations; one patient (1.9% )reported squeaking, 1 patient developed symptoms of deep veinthrombosis. Conclusion The early clinical results of alumina matrix

  18. 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.

  19. Synthesis and characterization of hybrid silica/PMMA nanoparticles and their use as filler in dental composites

    Energy Technology Data Exchange (ETDEWEB)

    Canché-Escamilla, G., E-mail: gcanche@cicy.mx [Unidad de Materiales, Centro de Investigación Científica de Yucatán A.C. Calle 43 No. 130 Col. Chuburná de Hidalgo, Mérida, Yucatán 97200 (Mexico); Duarte-Aranda, S. [Unidad de Materiales, Centro de Investigación Científica de Yucatán A.C. Calle 43 No. 130 Col. Chuburná de Hidalgo, Mérida, Yucatán 97200 (Mexico); Toledano, M. [Facultad de Odontología, Universidad de Granada, Campus Universitario de Cartuja s/n, Granada 18071 (Spain)

    2014-09-01

    The effect of hybrid silica/poly(methylmethacrylate) (PMMA) nanoparticles on the properties of composites for dental restoration was evaluated. Hybrid nanoparticles with silica as core and PMMA as shell were obtained by a seeded emulsion polymerization process. Fourier transform infrared spectrum of the hybrid nanoparticles shows an intense peak at 1730 cm{sup −1}, corresponding to carbonyl groups (C=O) of the ester. The thermal stability of the hybrid particles decreases with increasing amounts of PMMA and the residual mass at 700 °C corresponds to the silica content in the hybrid particles. Composites were obtained by dispersing nanoparticles (silica or hybrid), as fillers, in a resin—bis glycidyl dimethacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) (40%/60% (w/w)). The paste was then placed in a mold and polymerized under light irradiation. During the preparation of the composites, with the hybrid nanoparticles, the monomers swell the PMMA shell and after photo-curing, a semi-interpenetrating network (semi-IPN) is obtained around the silica core. The properties of the composites, obtained using the hybrid nanoparticles, depend on the filler content and the amount of PMMA in the semi-IPN matrix. For composites with similar inorganic filler contents, the composites with low amounts of PMMA shell had higher modulus than those in which silica was used as the filler. - Highlights: • Hybrid nanoparticles silica/PMMA were used as fillers in dental composites. • The properties of the hybrid nanoparticle depend on the silica/PMMA content ratio. • A higher content of inorganic filler was obtained using hybrid nanoparticle. • Composites with higher modulus were obtained using hybrid nanoparticles. • A semi-IPN matrix between the PMMA shell and the resin is obtained.

  20. Synthesis and characterization of hybrid silica/PMMA nanoparticles and their use as filler in dental composites

    International Nuclear Information System (INIS)

    The effect of hybrid silica/poly(methylmethacrylate) (PMMA) nanoparticles on the properties of composites for dental restoration was evaluated. Hybrid nanoparticles with silica as core and PMMA as shell were obtained by a seeded emulsion polymerization process. Fourier transform infrared spectrum of the hybrid nanoparticles shows an intense peak at 1730 cm−1, corresponding to carbonyl groups (C=O) of the ester. The thermal stability of the hybrid particles decreases with increasing amounts of PMMA and the residual mass at 700 °C corresponds to the silica content in the hybrid particles. Composites were obtained by dispersing nanoparticles (silica or hybrid), as fillers, in a resin—bis glycidyl dimethacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) (40%/60% (w/w)). The paste was then placed in a mold and polymerized under light irradiation. During the preparation of the composites, with the hybrid nanoparticles, the monomers swell the PMMA shell and after photo-curing, a semi-interpenetrating network (semi-IPN) is obtained around the silica core. The properties of the composites, obtained using the hybrid nanoparticles, depend on the filler content and the amount of PMMA in the semi-IPN matrix. For composites with similar inorganic filler contents, the composites with low amounts of PMMA shell had higher modulus than those in which silica was used as the filler. - Highlights: • Hybrid nanoparticles silica/PMMA were used as fillers in dental composites. • The properties of the hybrid nanoparticle depend on the silica/PMMA content ratio. • A higher content of inorganic filler was obtained using hybrid nanoparticle. • Composites with higher modulus were obtained using hybrid nanoparticles. • A semi-IPN matrix between the PMMA shell and the resin is obtained

  1. Effect of TiO, nanoparticles on the interface in the PET-rubber composites.

    Science.gov (United States)

    Vladuta, Cristina; Andronic, Luminita; Duta, Anca

    2010-04-01

    Usually, ceramic powders (SiO2, ZnO) are used as fillers for enhancing rubber mechanical strength. Poly-ethylene terephthalate (PET)-rubber nanocomposites were prepared by compression molding using titanium oxide (TiO2) nanoparticles as low content fillers (PET-rubber nanocomposites were studied before and after keeping the samples under UV-radiation for a week. UV-radiation has interesting potential for the photochemical modification of polymers and TiO2. The influence of UV radiation on the properties of the interface polymer-TiO2 nanoparticles was evaluated. The impact of nanoparticle aggregates on the nanometer to micrometer organization of PET-rubber composites was studied with Atomic Force Microscopy (AFM). The interface properties were explained by measuring the contact angles and surface tensions. The interactions between components of nanocomposites were investigated with Fourier Transform-Infrared (FTIR) and the effects of TiO2 nanoparticle on the interfaces and composites crystalline structure were evaluated by X-ray diffraction (XRD). The results proved that the TiO2 nanoparticles, in different weight percentages, did not alter the nanocomposites crystallinity or the average crystallites size, but improve the interface properties. PMID:20355456

  2. 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.

  3. Effect of zirconium nanoparticles on the mechanical properties of light-cured resin based dental composites

    International Nuclear Information System (INIS)

    The aim of this study was to evaluate the mechanical properties of conventional composite resins (Solare-P) and the modified composite resin having mixed with zirconium nanoparticles. The composite resins are used to replace the missing tooth structure and improve esthetics. In this study, the composite was filled with increments in a mould which was 4 mm in depth and 3 mm in diameter. After filling, it was polymerized with halogen light curing unit for 20 seconds for each increment. In other experiments, the composite was mixed with zirconium nanoparticles and filled in the moulds with increments and polymerized for 20 seconds with halogen light curing unit for each increment. After keeping the moulds at 37 deg. C for 24 hours their mechanical properties including compressive force, %age elongation, compressive strength and hardness were evaluated. It was seen that by adding zirconium nanoparticles, compressive force, %age elongation, compressive strength and hardness increased significantly. Thus it was concluded that the new materials are better than the conventional compomers. (author)

  4. Metal Nanoparticle/Block Copolymer Composite Assembly and Disassembly

    OpenAIRE

    Li, Zihui; Sai, Hiroaki; Warren, Scott C.; Kamperman, Marleen; Arora, Hitesh; Gruner, Sol M.; Wiesner, Ulrich

    2009-01-01

    Ligand-stabilized platinum nanoparticles (Pt NPs) were self-assembled with poly(isoprene-block-dimethylaminoethyl methacrylate) (PI-b-PDMAEMA) block copolymers to generate organic-inorganic hybrid materials. High loadings of NPs in hybrids were achieved through usage of N,N-di-(2-(allyloxy)ethyl)-N-3-mercaptopropyl-N-3-methylammonium chloride as the ligand, which provided high solubility of NPs in various solvents as well as high affinity to PDMAEMA. From NP synthesis, existence of sub-1 nm P...

  5. Metal nanoparticles containing polymer composites for advanced optoelectronic applications

    Czech Academy of Sciences Publication Activity Database

    Pfleger, Jiří; Podhájecká, Klára; Sharf, Ahmed; Kazim, Samrana

    Luxembourg: Office for Official Publications of the European Communities, 2009 - (Fantechi, S.; Havlíčková, L.; Svobodová, E.; Fryček, R.; Albrecht, V.). s. 218 ISBN 978-92-79-11109-9. [European and International Forum on Nanotechnology: EuroNanoForum 2009 - Nanotechnology for Sustainable Economy . 02.06.2009-05.06.2009, Praha] R&D Projects: GA AV ČR KAN100500652 Institutional research plan: CEZ:AV0Z40500505 Keywords : nanocomposites * metal nanoparticles Subject RIV: CD - Macromolecular Chemistry

  6. Metal nanoparticles containing polymer composites for advanced optoelectronic applications

    Czech Academy of Sciences Publication Activity Database

    Pfleger, Jiří; Podhájecká, Klára; Sharf, Ahmed; Kazim, Samrana

    Luxembourg: Office for Official Publications of the European Communities, 2009 - (Fantechi, S.; Havlíčková, L.; Svobodová, E.; Fryček, R.; Albrecht, V.). s. 218 ISBN 978-92-79-11109-9. [European and International Forum on Nanotechnology: EuroNanoForum 2009 - Nanotechnology for Sustainable Economy . 02.06.2009-05.06.2009, Praha] R&D Projects: GA AV ČR KAN200200651 Institutional research plan: CEZ:AV0Z40500505 Keywords : nanocomposites * metal nanoparticles Subject RIV: CD - Macromolecular Chemistry

  7. Polypyrrole-Au Nanoparticles Composite as Suitable Platform for DNA Biosensor with Electrochemical Impedance Spectroscopy Detection

    International Nuclear Information System (INIS)

    Application of a composite consisting of polypyrrole (PPy) and gold nanoparticles (Au Nps) to the construction of sensing layer in DNA biosensors led to the enhancement of the sensitivity due to the increase in the number of probe DNA strands in the layer by at least two orders of magnitude compared to the regular thiol intermediate layers. The probe DNA strands attached to the Au nanoparticles in the composite layer were fully available for the hybridization process. The examination of the composites containing a constant amount of Au nanoparticles and varying in PPy-layer thickness was done using electrochemical impedance spectroscopy, voltammetry and scanning electron microscopy. The optimal PPy layer thickness was determined to be in the range 10–20 nm. Such thickness of the polymer layer led to the elimination of aggregation of metal nanoparticles electrodeposited at the PPy surface. The sensor response (ΔRct) increased linearly with logarithm of concentration of target DNA in the range 2·10−13–2·10−6 M. The obtained detection limit of target DNA in the sample was circa 8.4·10−13 M. This limit is equivalent to the detection of circa 3.5·106 copies of DNA in a 7-μl droplet or circa 5·1011 DNA copies in one-liter sample

  8. Composite edible films based on hydroxypropyl methylcellulose reinforced with microcrystalline cellulose nanoparticles.

    Science.gov (United States)

    Bilbao-Sáinz, Cristina; Avena-Bustillos, Roberto J; Wood, Delilah F; Williams, Tina G; McHugh, Tara H

    2010-03-24

    It has been stated that hydroxypropyl methyl cellulose (HPMC) based films have promising applications in the food industry because of their environmental appeal, low cost, flexibility and transparency. Nevertheless, their mechanical and moisture barrier properties should be improved. The aim of this work was to enhance these properties by reinforcing the films with microcrystalline cellulose (MCC) at the nano scale level. Three sizes of MCC nanoparticles were incorporated into HPMC edible films at different concentrations. Identical MCC nanoparticles were lipid coated (LC) prior to casting into HPMC/LC-MCC composite films. The films were examined for mechanical and moisture barrier properties verifying how the addition of cellulose nanoparticles affected the water affinities (water adsorption/desorption isotherms) and the diffusion coefficients. The expected reinforcing effect of the MCC was observed: HPMC/MCC and HPMC/LC-MCC films showed up to 53% and 48% increase, respectively, in tensile strength values in comparison with unfilled HPMC films. Furthermore, addition of unmodified MCC nanoparticles reduced the moisture permeability up to 40% and use of LC-MCC reduced this value up to 50%. Water vapor permeability was mainly influenced by the differences in water solubility of different composite films since, in spite of the increase in water diffusivity values with the incorporation of MCC to HPMC films, better moisture barrier properties were achieved for HPMC/MCC and HPMC/LC-MCC composite films than for HPMC films. PMID:20187652

  9. 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. PMID:23262147

  10. Manipulation of combustion waves in carbon-nanotube/fuel composites by highly reactive Mg nanoparticles.

    Science.gov (United States)

    Lee, Kang Yeol; Hwang, Hayoung; Shin, Dongjoon; Choi, Wonjoon

    2015-10-28

    Manipulating the interface of micro/nanostructured materials and chemical fuels can change the fundamental characteristics of combustion waves that are generated during a reaction. In this study, we report that Mg/MgO nanoparticles actively amplify the propagation of combustion waves at the interface of multi-walled carbon nanotubes (MWCNTs) and chemical fuels. Fuel/MWCNT and fuel/MWCNT-Mg/MgO composite films were prepared by a facile synthetic method. We present complete physiochemical characterization of these composite films and evaluate the propagating velocities and real-time surface temperatures of combustion waves. Mg/MgO nanoparticles at the interface enhanced the reaction front velocity by 41%. The resulting explosive reactions supplied additional thermal energy to the chemical fuel, accelerating flame propagation. Furthermore, the surface temperatures of the composites with Mg/MgO nanoparticles were much lower, indicating how the transient heat from the reaction would ignite the unreacted fuels at lower surface temperatures despite not reaching the necessary activation energy for a chain reaction. This mechanism contributed to thermopower waves that amplified the output voltage. Furthermore, large temperature gradients due to the presence of nanoparticles increased charge transport inside the nanostructured material, due to the increased thermoelectric effects. This manipulation could contribute to the active control of interfacially driven combustion waves along nanostructured materials, yielding many potential applications. PMID:26419765

  11. Quantifying the composition of yttrium and oxygen rich nanoparticles in oxide dispersion strengthened steels

    International Nuclear Information System (INIS)

    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. - Highlights: ► First APT analysis of bulk Y2O3 oxide. ► Comparison with the composition of Y--O based nanoclusters in ODS steel. ► Sequence of ion hits on the detector show that there is a bias towards Y loss. ► Nanoparticles are concluded to have a ∼1:1 Y:O ratio

  12. 高抗冲导热绝缘PC/PE/Al2O3复合材料的制备与性能%Development of High Impact and Thermal Conducting Insulating Polycarbonate/Polyethylene/Alumina Composites

    Institute of Scientific and Technical Information of China (English)

    文雯; 刘述梅; 傅轶; 赵建青

    2011-01-01

    Alumina (Al2O3) was filled in linear low density polyethylene (LLDPE) with a polyethylene grafted by maleic anhydride (PE-g-MAH) compatibilizer to produce a conducting master batch, which was then dispersed in polycarbonate (PC). A PC/PE/Al2O3 composite with high impact and thermal conducting properties through such a master batch method was prepared. The effect of blending procedures, compatibilizer, PC/PE ratios and the content of alumina on properties of the composite was investigated. The PC/LLDPE/PE-MAH composite (5/1/1 mass ratios) containing 40% Al2O3 processed a 27.2 kJ/m2 of Izod impact strength and 0.644 W/m·K of the thermal conductivity. The thermal conductivity of the composite with 60% alumina reached 0.895 W/m·K, which was 3.4 times of that of the PC/PE blend (0.260 W/m·K).%以氧化铝(AlO)、线性低密度聚乙烯(LLDPE)和聚乙烯接枝马来酸酐(PE-g-MAH)熔融共混挤出得到AlO导热绝缘母粒,然后再与聚碳酸酯(PC)熔融挤出的母料法(两步法)制得高抗冲导热绝缘PC俩/AlO(PE为LLDPE与PE-g-MAH)复合材料.探讨了相容刑种类、PC/PE比例、AlO用量等因素对PC/PE/AlO复合材料力学性能和导热性能的影响.结果表明,以PE-g-MAH作为相容剂,在PC/LLDPE/PE-g-MAH质量比为5/1/1,AlO用量为40%(质量分数)时,复合材料缺口冲击强度为27.2 kJ/m,导热系数为0.644 W/m·K;当AlO用量增加到60%时,材料的导热系数为0.895 W/m·K,是PC/PE合金(0.260 W/m·K)的3.4倍.

  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. Effect of reinforcement nanoparticles addition on mechanical properties of SBS/curaua fiber composites

    International Nuclear Information System (INIS)

    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)

  15. Slow release of fullerene-like WS2 nanoparticles as a superior solid lubrication mechanism in composite matrices

    International Nuclear Information System (INIS)

    Recently, the efficacy of hollow ''inorganic fullerene-like'' (IF) WS2 nanoparticles as additives for lubrication fluids has been demonstrated. By confining the IF nanoparticles inside a porous and densified solid matrix, prepared by powder metallurgy (PM) techniques, slow release of the IF nanoparticles onto the metal surface alleviates both friction losses and wear, while assuring the mechanical integrity of the composite. The potential ramifications of this work for self-lubricating bearings, gears, etc. are also discussed. (orig.)

  16. Natural weathering studies of oil palm trunk lumber (OPTL) green polymer composites enhanced with oil palm shell (OPS) nanoparticles

    OpenAIRE

    Islam, Md Nazrul; Dungani, Rudi; Abdul Khalil, HPS; Alwani, M Siti; Nadirah, WO Wan; Fizree, H Mohammad

    2013-01-01

    In this study, a green composite was produced from Oil Palm Trunk Lumber (OPTL) by impregnating oil palm shell (OPS) nanoparticles with formaldehyde resin. The changes of physical, mechanical and morphological properties of the OPS nanoparticles impregnated OPTL as a result of natural weathering was investigated. The OPS fibres were ground with a ball-mill for producing nanoparticles before being mixed with the phenol formaldehyde (PF) resin at a concentration of 1, 3, 5 and 10% w/w basis and...

  17. 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.

  18. Optical Properties of Composites Based on a Transparent Matrix and Copper Nanoparticles

    Science.gov (United States)

    Kalenskii, A. V.; Zvekov, A. A.; Nikitin, A. P.; Gazenaur, N. V.

    2016-06-01

    Dependences of the transmittance, absorbance, and reflectance of the composite based on a transparent matrix and copper spherical nanoparticles on the sample thickness and the mass fraction of particles are calculated for radiation of the first and second harmonics of a neodymium laser using the Mie theory and the stationary radiation transfer equation. Distributions of the luminance gain are calculated at different distances from the sample surface. It is shown that the luminance gain increases with nanoparticle radius and radiation wavelength due to multiple scattering. In the limit of a small sample thickness, the luminance gain has a threshold value due to the effect of the total internal reflection. Results obtained are needed for optimization of an optical detonator capsule based on a transparent explosive material and copper nanoparticles.

  19. 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.

  20. Core/shell fluorescent magnetic silica-coated composite nanoparticles for bioconjugation

    International Nuclear Information System (INIS)

    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

  1. Core/shell fluorescent magnetic silica-coated composite nanoparticles for bioconjugation

    Energy Technology Data Exchange (ETDEWEB)

    He Rong; You Xiaogang; Shao Jun; Gao Feng; Pan Bifeng; Cui Daxiang [Department of Bio-Nano Science and Engineering, National Key Laboratory of Nano/Micro Fabrication Technology, Key Laboratory for Thin Film and Microfabrication of Ministry of Education, Institute of Micro and Nano Science and Technology, Shanghai Jiaotong University, Shanghai 200030 (China)

    2007-08-08

    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{sup -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.

  2. Radius ratio rule for surface hydrophilization of polydimethyl siloxane and silica nanoparticle composite

    Energy Technology Data Exchange (ETDEWEB)

    Toutam, Vijaykumar, E-mail: toutamvk@nplindia.org [Quantum Phenomena and Applications Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Jain, Puneet; Sharma, Rina [Quantum Phenomena and Applications Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Bathula, Sivaiah; Dhar, Ajay [Material Physics and Engineering Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India)

    2015-09-15

    Graphical abstract: - Highlights: • Binary hard sphere silica nanoparticle system based PDMS composite. • Enhanced hydrophilization and retainability of the composite. • Restriction of uncured PDMS from diffusion. • Increased Debye length of electrostatic double layer, measured by F-D Spectroscopy. - Abstract: Polydimethyl siloxane (PDMS) and Silica (SiO{sub 2}) nanoparticle composite blocks of three different batches (CB1–CB3) made by varying the size of SiO{sub 2} nanoparticles (NP), are studied for the degree of hydrophilization and retainability after oxidation by contact angle measurements (CA) and force distance spectroscopy (FDS) using Atomic Force Microscope (AFM). While CA measurements have shown high hydrophilization and retainability for CB3, F-D spectroscopy has reiterated the observation and has shown long range interactive forces and high Debye length of the electrostatic double layer formed. These results are in agreement with the radius ratio rule of binary sphere system for high density packing in the composite and thereby for strong hydrophilization and retainability due to reinforcement and restricted diffusion of uncured polymer.

  3. Controllable synthesis and characterization of Fe{sub 3}O{sub 4}/Au composite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Xing, Yan; Jin, Yan-Yan; Si, Jian-Chao [Key Laboratory of Synthetic and Natural Functional Molecular Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi' an 710069 (China); National Engineering Research Center for Miniaturized Detection Systems, Xi' an 710069 (China); Peng, Ming-Li, E-mail: mlpeng@nwu.edu.cn [Key Laboratory of Synthetic and Natural Functional Molecular Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi' an 710069 (China); National Engineering Research Center for Miniaturized Detection Systems, Xi' an 710069 (China); Wang, Xiao-Fang [Key Laboratory of Synthetic and Natural Functional Molecular Chemistry of Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi' an 710069 (China); Chen, Chao [National Engineering Research Center for Miniaturized Detection Systems, Xi' an 710069 (China); College of Life Sciences, Northwest University, Xi' an 710069 (China); Cui, Ya-Li, E-mail: yalicui@nwu.edu.cn [National Engineering Research Center for Miniaturized Detection Systems, Xi' an 710069 (China); College of Life Sciences, Northwest University, Xi' an 710069 (China)

    2015-04-15

    Fe{sub 3}O{sub 4}/Au composite nanoparticles (GoldMag NPs) have received considerable attention because of their advantageous properties arisen from both individual Au and Fe{sub 3}O{sub 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{sub 3}O{sub 4} nanoparticles were prepared by co-precipitation and modified by the citric acid, and then citric acid-coated Fe{sub 3}O{sub 4} nanoparticles were used as seeds in sodium citrate solution to reduce the HAuCl{sub 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{sub 3}O{sub 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.

  4. Core–shell composite particles composed of biodegradable polymer particles and magnetic iron oxide nanoparticles for targeted drug delivery

    International Nuclear Information System (INIS)

    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

  5. 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.

  6. Manipulation of combustion waves in carbon-nanotube/fuel composites by highly reactive Mg nanoparticles

    Science.gov (United States)

    Lee, Kang Yeol; Hwang, Hayoung; Shin, Dongjoon; Choi, Wonjoon

    2015-10-01

    Manipulating the interface of micro/nanostructured materials and chemical fuels can change the fundamental characteristics of combustion waves that are generated during a reaction. In this study, we report that Mg/MgO nanoparticles actively amplify the propagation of combustion waves at the interface of multi-walled carbon nanotubes (MWCNTs) and chemical fuels. Fuel/MWCNT and fuel/MWCNT-Mg/MgO composite films were prepared by a facile synthetic method. We present complete physiochemical characterization of these composite films and evaluate the propagating velocities and real-time surface temperatures of combustion waves. Mg/MgO nanoparticles at the interface enhanced the reaction front velocity by 41%. The resulting explosive reactions supplied additional thermal energy to the chemical fuel, accelerating flame propagation. Furthermore, the surface temperatures of the composites with Mg/MgO nanoparticles were much lower, indicating how the transient heat from the reaction would ignite the unreacted fuels at lower surface temperatures despite not reaching the necessary activation energy for a chain reaction. This mechanism contributed to thermopower waves that amplified the output voltage. Furthermore, large temperature gradients due to the presence of nanoparticles increased charge transport inside the nanostructured material, due to the increased thermoelectric effects. This manipulation could contribute to the active control of interfacially driven combustion waves along nanostructured materials, yielding many potential applications.Manipulating the interface of micro/nanostructured materials and chemical fuels can change the fundamental characteristics of combustion waves that are generated during a reaction. In this study, we report that Mg/MgO nanoparticles actively amplify the propagation of combustion waves at the interface of multi-walled carbon nanotubes (MWCNTs) and chemical fuels. Fuel/MWCNT and fuel/MWCNT-Mg/MgO composite films were prepared by a facile

  7. Synthesis and characterization of hydroxyapatite/Ca-zirconia nanoparticle composites

    Czech Academy of Sciences Publication Activity Database

    Částková, K.; Hadraba, Hynek; Roupcová, P.; Matoušek, A.; Cihlář, J.

    Toledo: ECERS, 2015. ISBN 978-84-606-9257-7. [ECERS 14 - International Conference of the European Ceramic Society /14./. 21.06.2015-25.06.2015, Toledo] R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : hydroxyapatite * zirconia * composite Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

  8. Chemical composition and corrosion protection of silane films modified with CeO2 nanoparticles

    International Nuclear Information System (INIS)

    The present work aims at understanding the role of CeO2 nanoparticles (with and without activation in cerium(III) solutions) used as fillers for hybrid silane coatings applied on galvanized steel substrates. The work reports the improved corrosion protection performance of the modified silane films and discusses the chemistry of the cerium-activated nanoparticles, the mechanisms involved in the formation of the surface coatings and its corrosion inhibition ability. The anti-corrosion performance was investigated using electrochemical impedance spectroscopy (EIS), the scanning vibrating electrode technique (SVET) and d.c. potentiodynamic polarization. The chemical composition of silanised nanoparticles and the chemical changes of the silane solutions due to the presence of additives were studied using X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance spectroscopy (NMR), respectively. The NMR and XPS data revealed that the modified silane solutions and respective coatings have enhanced cross-linking and that silane-cerium bonds are likely to occur. Electrochemical impedance spectroscopy showed that the modified coatings have improved barrier properties and the SVET measurements highlight the corrosion inhibition effect of ceria nanoparticles activated with Ce(III) ions. Potentiodynamic polarization curves demonstrate an enhanced passive domain for zinc, in the presence of nanoparticles, in solutions simulating the cathodic environment.

  9. Electromagnetic properties of NiZn ferrite nanoparticles and their polymer composites

    International Nuclear Information System (INIS)

    The magnetic properties of polycrystalline NiZn ferrite nanoparticles synthesized using a polyol-reduction and coprecipitation reaction methods have been investigated. The effects on magnetization of synthesis approach, chemical composition, processing conditions, and on the size of nanoparticles on magnetization have been investigated. The measured room-temperature magnetization for the as-prepared magnetic nanoparticles (MNP) synthesized via polyol-reduction and coprecipitation is 69 Am2 kg−1 and 14 Am2 kg−1, respectively. X-ray diffraction measurements confirm spinel structure of the particles with an estimated grain size of ∼80 nm obtained from the polyol-reduction and 28 nm obtained from these coprecipitation techniques. Upon calcination under atmospheric conditions at different temperatures between 800 °C and 1000 °C, the magnetization, M, of the coprecipitated MNP increases to 76 Am2 kg−1 with an estimated grain size of 90 nm. The MNP-polymer nanocomposites made from the synthesized MNP in various loading fraction and high density polyethylene exhibit interesting electromagnetic properties. The measured permeability and permittivity of the magnetic nanoparticle-polymer nanocomposites increases with the loading fractions of the magnetic nanoparticles, suggesting control for impedance matching for antenna applications

  10. Electron beam induced synthesis of uranium dioxide nanoparticles: Effect of solvent composition

    Science.gov (United States)

    Rath, M. C.; Keny, S. J.; Naik, D. B.

    2016-09-01

    The effect of various compositions of solvents was investigated on the electron beam induced synthesis of uranium dioxide, UO2 nanoparticles. The synthesis was carried out at different pHs from 2 to 7 in the aqueous solutions containing 10 mM uranyl nitrate and 10% 2-propanol. The formation of UO2 nanoparticles was found to occur only in the pH range from 2.5 to 3.7. Experiments were also carried out in the aqueous solutions containing various other alcohols (10% v/v) such as methanol, ethanol, 1-propanol, 1-butanol or tert-butanol as well as in solutions containing 10 mM sodium formate at pH 3.4. The formation of UO2 nanoparticles in the aqueous solutions was found to occur only in the presence of ethanol, 1-propanol, 2-propanol or 1-butanol. It is therefore confirmed that the electron beam induced synthesis of UO2 nanoparticles strongly depends on the solvent compositions as well as the pH of the medium.

  11. Highly hydrophilic thin-film composite forward osmosis membranes functionalized with surface-tailored nanoparticles.

    Science.gov (United States)

    Tiraferri, Alberto; Kang, Yan; Giannelis, Emmanuel P; Elimelech, Menachem

    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. PMID:22948042

  12. Ferroelectric properties of composites containing BaTiO3 nanoparticles of various sizes

    International Nuclear Information System (INIS)

    Size effects, including the occurrence of superparaelectric phases associated with small scale, are a significant research topic for ferroelectrics. Relevant phenomena have been explored in detail, e.g. for homogeneous, thin ferroelectric films, but the related effects associated with nanoparticles are usually only inferred from their structural properties. In contrast, this paper describes all the steps and concepts necessary for the direct characterization and quantitative assessment of the ferroelectric properties of as-synthesized and as-received nanoparticles. The method adopted uses electrical polarization measurements on polymer matrix composites containing ferroelectric nanoparticles. It is applied to ten different BaTiO3 particle types covering a size range from 10 nm to 0.8 μm. The influence of variations of particle characteristics such as tetragonality and dielectric constant is considered based on measurements of these properties. For composites containing different particle types a clearly differing polarization behaviour is found. For decreasing particle size, increasing electric field is required to achieve a given level of polarization. The size dependence of a measure related to the coercive field revealed by this work is qualitatively in line with the state of the knowledge for ferroelectrics having small dimensions. For the first time, such results and size effects are described based on data from experiments on collections of actual nanoparticles. (paper)

  13. 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.

  14. Second-harmonic generation from bimetal composites doped with metal nanoparticles

    Science.gov (United States)

    Daneshfar, Nader

    2016-05-01

    In the present paper, we study the nonlinear optical response of the bimetal composites doped with metal nanoparticles in the framework of nonlinear Mie theory combined with the Maxwell-Garnett model. We concentrate on the second-order harmonic generation from bimetal nanocomposites including silver and gold particles, since sometimes the nonlinear optical response is sensitive to the more accurate of material structure than linear optical response. We show that optical second harmonic generation is strongly sensitive to temperature as an environmental parameter, interparticle plasmon coupling between Au and Ag nanoparticles (the filling factor of inclusions), the particle size and the surrounding medium. However, this work shows good potential of bimetal composites for nonlinear optics at the nanoscale.

  15. Polypropylene/glass fiber hierarchical composites incorporating inorganic fullerene-like nanoparticles for advanced technological applications

    OpenAIRE

    Díez Pascual, Ana M.; Naffakh Cherradi Hadi, Mohammed

    2013-01-01

    Novel isotactic polypropylene (iPP)/glass fiber (GF) laminates reinforced with inorganic fullerene-like tungsten disulfide (IF-WS2) nanoparticles as environmentally friendly fillers have been successfully fabricated by simple melt-blending and fiber impregnation in a hot-press without the addition of any compatibilizer. The influence of IF-WS2 concentration on the morphology, viscosity. and thermal and mechanical behavior of the hierarchical composites has been investigated. Results revealed ...

  16. Three-port beam splitter for slow neutrons using holographic nanoparticle-polymer composite diffraction gratings

    OpenAIRE

    Klepp, J.; Tomita, Y; Pruner, C.; Kohlbrecher, J.; Fally, M.

    2012-01-01

    Diffraction of slow neutrons by nanoparticle-polymer composite gratings has been observed. By carefully choosing grating parameters such as grating thickness and spacing, a three-port beam splitter operation for cold neutrons - splitting the incident neutron intensity equally into the plus-minus first and zeroth diffraction orders - was realized. As a possible application, a Zernike three-path interferometer is briefly discussed.

  17. Fabrication and evaluation of valsartan–polymer– surfactant composite nanoparticles by using the supercritical antisolvent process

    OpenAIRE

    Kim MS; Baek IH

    2014-01-01

    Min-Soo Kim,1 In-hwan Baek21College of Pharmacy, Pusan National University, Geumjeong-gu, Busan, Republic of Korea; 2College of Pharmacy, Kyungsung University, Daeyeon-dong, Nam-gu, Busan, Republic of KoreaAbstract: The aim of this study was to fabricate valsartan composite nanoparticles by using the supercritical antisolvent (SAS) process, and to evaluate the correlation between in vitro dissolution and in vivo pharmacokinetic parameters for the poorly water-soluble drug valsartan. Spherical...

  18. Parametric Study of Strain Rate Effects on Nanoparticle-Reinforced Polymer Composites

    OpenAIRE

    Soltannia, B.; Haji Gholami, I.; Masajedian, S.; Mertiny, P.; Sameoto, D.; F. Taheri

    2016-01-01

    Crashworthiness, energy absorption capacity, and safety are important factors in the design of lightweight vehicles made of fiber-reinforced polymer composite (FRP) components. The relatively recent emergence of the nanotechnology industry has presented a novel means to augment the mechanical properties of various materials. As a result, recent attempts have contemplated the use of nanoparticles to further improve the resiliency of resins, especially when resins are used for mating FRP compon...

  19. Nanoparticle and Gelation Stabilized Functional Composites of an Ionic Salt in a Hydrophobic Polymer Matrix

    OpenAIRE

    Demirel, Adem Levent; Kanyas, Selin; Aydın, Derya; Kızılel, Rıza; Kızılel, Seda

    2014-01-01

    Nanoparticle and Gelation Stabilized Functional Composites of an Ionic Salt in a Hydrophobic Polymer Matrix Selin Kanyas1, Derya Aydın2, Riza Kizilel3, A. Levent Demirel1,4, Seda Kizilel1,2* 1 Material Science and Engineering, Koc University, Sariyer, Istanbul, Turkey, 2 Department of Chemical and Biological Engineering, Koc University, Sariyer, Istanbul, Turkey, 3 Koc University-TUPRAS Energy Center (KUTEM), Koc University, Sariyer, Istanbul, Turkey, 4 Department of Chemistry,...

  20. Liquid Crystalline Network Composites Reinforced by Silica Nanoparticles

    Directory of Open Access Journals (Sweden)

    Zhen Li

    2014-07-01

    Full Text Available Liquid crystalline networks (LCNs are a class of polymers, which are able to produce mechanical actuation in response to external stimuli. Recent creation of LCNs with exchangeable links (xLCNs makes LCNs easy moldable. As the xLCNs need to be shaped at a high temperature, it is important to enhance their thermal and mechanical properties. In this paper, a series of xLCNs/SiO2 composites containing 1%–7% SiO2 nanoparitcles (SNP were prepared and their thermal and mechanical properties were examined. The results show that xLCNs/SNP composites have lower liquid crystalline-isotropic phase transition temperature and higher decomposition temperature than pure LCN. The tensile strength and the elongation at break of xLCNs at high temperatures were also enhanced due to the addition of SNPs.

  1. 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

  2. Mechanically-reinforced electrospun composite silk fibroin nanofibers containing hydroxyapatite nanoparticles

    International Nuclear Information System (INIS)

    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

  3. The Effect of Ag Content of the Chitosan-Silver Nanoparticle Composite Material on the Structure and Antibacterial Activity

    Directory of Open Access Journals (Sweden)

    Solmaz Akmaz

    2013-01-01

    Full Text Available The aim of this study is to investigate the antibacterial properties and characterization of chitosan-silver nanoparticle composite materials. Chitosan-silver nanoparticle composite material was synthesized by adding AgNO3 and NaOH solutions to chitosan solution at 95°C. Different concentrations (0,02 M, 0,04 M, and 0,06 M of AgNO3 were used for synthesis. Chitosan-silver nanoparticle composite materials were characterized by Transmission electron microscopy (TEM, X-ray diffraction (XRD, ultraviolet (UV spectrophotometer, and Fourier transform infrared (FTIR spectrometer techniques. Escherichia coli, Acinetobacter baumannii, Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, and Streptococcus pneumoniae were used to test the bactericidal efficiency of synthesized chitosan-Ag nanoparticle composite materials. The biological activity was determined by the minimum bacterial concentration (MBC of the materials. Antibacterial effect of chitosan-silver nanoparticle materials was increased by increasing Ag amount of the composite materials. The presence of small amount of metal nanoparticles in the composite was enough to significantly enhance antibacterial activity as compared with pure chitosan.

  4. Doxorubicin-loaded mesoporous silica nanoparticle composite nanofibers for long-term adjustments of tumor apoptosis

    Science.gov (United States)

    Yuan, Ziming; Pan, Yue; Cheng, Ruoyu; Sheng, Lulu; Wu, Wei; Pan, Guoqing; Feng, Qiming; Cui, Wenguo

    2016-06-01

    There is a high local recurrence (LR) rate in breast-conserving therapy (BCT) and enhancement of the local treatment is promising as a way to improve this. Thus we propose a drug delivery system using doxorubicin (DOX)-loaded mesoporous silica nanoparticle composite nanofibers which can release anti-tumor drugs in two phases—burst release in the early stage and sustained release at a later stage—to reduce the LR of BCT. In the present study, we designed a novel composite nanofibrous scaffold to realize the efficient release of drugs by loading both DOX and DOX-loaded mesoporous silica nanoparticles into an electrospun PLLA nanofibrous scaffold. In vitro results demonstrated that this kind of nanomaterial can release DOX in two phases, and the results of in vivo experiments showed that this hybrid nanomaterial significantly inhibited the tumor growth in a solid tumor model. Histopathological examination demonstrated that the apoptosis of tumor cells in the treated group over a 10 week period was significant. The anti-cancer effects were also accompanied with decreased expression of Bcl-2 and TNF-α, along with up-regulation of Bax, Fas and the activation of caspase-3 levels. The present study illustrates that the mesoporous silica nanoparticle composite nanofibrous scaffold could have anti-tumor properties and could be further developed as adjuvant therapeutic protocols for the treatment of cancer.

  5. Study on Electromagnetorheological Fluid Containing CuPc-Fe3O4 Nanoparticles Composite

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Electromagnetorheological(EMR) fluids containing CuPc-Fe3O4 nanopareticles composite were prepared and their properties were studied.The results show that Δτ of this kind of EMR fluids increases with the increments of applied electric field, magnetic field and volume fraction of the nanoparticles composite. Δτ has an approximate linear relationship with γ.When an electric and magnetic field are applied simultaneously,the EMR fluids have a synergistic effect. The EMR fluids have a good long-term stability.

  6. Fabrication of smart magnetite/reduced graphene oxide composite nanoparticles and their magnetic stimuli-response.

    Science.gov (United States)

    Hong, Cheng Hai; Kim, Min Wook; Zhang, Wen Ling; Moon, Il Jae; Choi, Hyoung Jin

    2016-11-01

    Novel Fe3O4/reduced graphene oxide (RGO) composite nanoparticles were synthesized and confirmed by FT-IR spectra as good candidates for magnetic stimuli-responsive magnetorheological (MR) materials. The morphology of Fe3O4/RGO was observed by both scanning and transmission electron microscopy and their sedimentation stability improved due to a decreased density of the synthesized composites. The MR performance of the Fe3O4/RGO-based fluid was investigated with a rotational rheometer, and the Cho-Choi-Jhon model of the rheological equation of state was adopted to explain their performances for the entire shear rate region. PMID:27475706

  7. 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.

  8. Solid Lubricant For Alumina

    Science.gov (United States)

    Dellacorte, Christopher; Pepper, Stephen V.; Honecy, Frank S.

    1993-01-01

    Outer layer of silver lubricates, while intermediate layer of titanium ensures adhesion. Lubricating outer films of silver deposited on thin intermediate films of titanium on alumina substrates found to reduce sliding friction and wear. Films provide effective lubrication for ceramic seals, bearings, and other hot sliding components in advanced high-temperature engines.

  9. A 'green' chitosan silver nanoparticle composite as a heterogeneous as well as micro-heterogeneous catalyst

    Science.gov (United States)

    Murugadoss, A.; Chattopadhyay, Arun

    2008-01-01

    In this paper, we report on the catalytic activity of a new metal nanoparticle-polymer composite consisting of Ag nanoparticles (NPs) and environmentally friendly ('green') chitosan. The polymer (chitosan) not only acted as the reducing agent for the metal ions, but also stabilized the product NPs by anchoring them. The majority of the particles produced in this way had sizes less than 5 nm. The catalytic activity of the composite was investigated photometrically by monitoring the reduction of 4-nitrophenol (4NP) in the presence of excess NaBH4 in water, under both heterogeneous and micro-heterogeneous conditions. The reaction was first order with respect to the concentration of 4NP. We also observed that the apparent rate constant, kapp, for the reaction was linearly dependent on the amount of Ag NPs present in the composite. Moreover, the turn-over frequency (TOF) of the catalyst was found to be (1.5 ± 0.3) × 10-3 s-1, when the reaction was carried out under heterogeneous conditions. The Ag NPs in the composite retained their catalytic activities even after using them for ten cycles. Our observations also suggest that the catalytic efficiency under micro-heterogeneous conditions is much higher than under heterogeneous conditions. Thus the composite we have represents an ideal case of an environmentally friendly and stable catalyst, which works under heterogeneous as well as micro-heterogeneous conditions with the advantage of nanoscopic particles as the catalyst.

  10. 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.

  11. Composite Electroplating to Obtain Ni-ZrO2 Nanocomposite Coatings Containing Monodispersed ZrO2 Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; HOU Feng-yan; GUO He-tong

    2004-01-01

    The Zirconia nanoparticles are dispersed well in the plating bath using polyelectrolyte dispersant and NiZrO2 nanocomposite coatings containing monodispersed ZrO2 nanoparticles are successfully prepared under DC electrodeposition condition. The effects of the dispersant concentration on the dispersibility of Zirconia nanoparticles in the plating bath and the hardness of nanocomposite coatings have been investigated. The results shows that the hardness of nanocomposite coatings are strongly influenced by the dispersion state of ZrO2 nanoparticles in the composite coatings and only a very low volume percent of monodispered ZrO2 nanoparticles in Ni-ZrO2 composite coatings will result in higher hardness of the coating.

  12. High-performance flexible hydrogen sensor made of WS2 nanosheet–Pd nanoparticle composite film

    Science.gov (United States)

    Kuru, Cihan; Choi, Duyoung; Kargar, Alireza; Liu, Chin Hung; Yavuz, Serdar; Choi, Chulmin; Jin, Sungho; Bandaru, Prabhakar R.

    2016-05-01

    We report a flexible hydrogen sensor, composed of WS2 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 WS2–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 WS2–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.

  13. Injectable Hydrogel Composite Based Gelatin-PEG and Biphasic Calcium Phosphate Nanoparticles for Bone Regeneration

    Science.gov (United States)

    Van, Thuy Duong; Tran, Ngoc Quyen; Nguyen, Dai Hai; Nguyen, Cuu Khoa; Tran, Dai Lam; Nguyen, Phuong Thi

    2016-05-01

    Gelatin hydrogels have recently attracted much attention for tissue regeneration because of their biocompatibility. In this study, we introduce poly-ethylene glycol (PEG)—grafted gelatin containing tyramine moieties which have been utilized for in situ enzyme-mediated hydrogel preparation. The hydrogel can be used to load nanoparticles of biphasic calcium phosphate, a mixture of hydroxyapatite and β-tricalcium phosphate, and forming injectable bio-composites. Proton nuclear magnetic resonance (1H NMR) spectra indicated that tyramine-functionalized polyethylene glycol-nitrophenyl carbonate ester was conjugated to the gelatin. The hydrogel composite was rapidly formed in situ (within a few seconds) in the presence of horseradish peroxidase and hydrogen peroxide. In vitro experiments with bio-mineralization on the hydrogel composite surfaces was well-observed after 2 weeks soaking in simulated body fluid solution. The obtained results indicated that the hydrogel composite could be a potential injectable material for bone regeneration.

  14. 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

    2016-10-01

    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. PMID:27312610

  15. High alumina metamorphic rocks of the Kings Mountain district, North Carolina and South Carolina

    Science.gov (United States)

    Potter, Donald Brandreth

    1954-01-01

    The following evidence suggests that high alumina quartzite in this district is of metasedimentary origin: high alumina quartzite occurs as well defined thin beds that can be traced up to three and one half miles along strike; many outcrops of high alumina quartzite exhibit compositional layering (i.e., kyanigte quartzite is interlayered with staurolite quartzite, and with non-kyanitic magnetiferous quartzite); high alumina quartzite beds occur in a conformable sequence of high alumina metasedimentary and metavolcanic schists. It is suggested that the high alumina quartzite beds are metamorphosed beds of sandy or silty clay; these beds probably represent one stage in the deposition of fine grained clayey clastic sediments. No evidence was found to support the view of Smith and Newcombe (1951) that the kyanite at Henry Knob developed by hudrothermal introduction of alumina. The present study indicates that kyanite in the kyanite quartzite here, as throughout the district, is of metasedimentary origin.

  16. Stable Small Composite Microbubbles Decorated with Magnetite Nanoparticles - A Synergistic Effect between Surfactant Molecules and Nanoparticles.

    Science.gov (United States)

    Ma, Jun; Pourroy, Geneviève; Krafft, Marie Pierre

    2016-05-01

    Three approaches to preparing iron oxide nanoparticle-decorated microbubbles (NP-decoMBs) have been investigated. The size and stability characteristics of these microbubbles (MBs) were investigated by optical microscopy, laser light scattering and an acoustical method, and compared with those of non-decorated MBs. First, magnetite nanoparticles (Fe3O4NPs) grafted with dimyristoylphosphatidylcholine (DMPC) were synthesized and used to prepare MBs by brief sonication under an atmosphere of air saturated with perfluorohexane. These MBs had a rather large mean radius (r ~ 12 µm), and a moderate volume of encapsulated gas. Remarkably, a second approach that consisted of dispersing unbound DMPC molecules in the aqueous phase along with DMPC-grafted Fe3O4NPs prior to sonication was found to drastically change the situation, allowing the obtaining of monomodal populations of much smaller (r ~ 0.6 µm) NP-decoMBs. The latter were echogenic and stable for at least 10 days at room temperature, without significant variation of their size characteristics. In a third approach, NP-decoMBs were directly prepared from dispersions of naked Fe3O4NPs in the presence of DMPC. The resulting NP-decoMBs suspensions consisted of broadly distributed bubble populations mostly containing two populations (with r ~ 5 and ~ 15 µm). Control microbubbles made of DMPC only were small (r ~ 1.3 µm), although not as small as those formed from DMPC-grafted Fe3O4NPs in the presence of free DMPC, and were less stable, with a room temperature half-life of only ~1 day. These observations imply that there is a synergy between the Fe3O4NPs and the DMPC molecules in the air/water interfacial film stabilization process. PMID:27087000

  17. 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

  18. Dielectric performance of polymer-based composites containing core-shell Ag@TiO2 nanoparticle fillers

    Science.gov (United States)

    Liang, Fei; Zhang, Lu; Lu, Wen-Zhong; Wan, Qian-Xing; Fan, Gui-Fen

    2016-02-01

    This paper reports composites prepared by embedding core-shell Ag@TiO2 fillers into polytetrafluoroethylene. Ag nanoparticles were homogeneously coated with TiO2, to give a shell thickness of approximately ˜8-10 nm. The composite containing Ag@TiO2 nanoparticles with rutile shells exhibited better dielectric properties than the composite containing Ag@TiO2 nanoparticles with anatase shells. The relative permittivity (ɛr) of the composite containing 70 vol. % filler was approximately 240 at 100 Hz, which was more than 100 times higher than that of pure polytetrafluoroethylene (ɛr = 2.1). An effective medium percolation theory model is used to account for the dielectric constant of the composite.

  19. 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

    2015-07-01

    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.

  20. 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

    2016-06-01

    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. PMID:27172520

  1. 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.

    2007-02-01

    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 3O 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 3O 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 (MS) of Fe/Fe 3O 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 3O 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.

  2. Effect of Silica Nanoparticles on Compressive Strength of Leaves-Waste Composite

    Science.gov (United States)

    Masturi, Masturi; Aliah, Hasniah; Aji, Mahardika Prasetya; Sagita, Adi Ardian; Bukit, Minsyahril; Sustini, Euis; Khairurrijal, Khairurrijal; Abdullah, Mikrajuddin

    2011-12-01

    The utilization of solid-waste, especially leaves-waste is one of interesting research of environmental field. One of them is making a composite using polyvinyl acetate (PVAc) polymer as binder (matrix) and silica nanoparticles as reinforcement (filler) to improve the strength of composite-produced. Those raw materials preliminary were mixed by simple mixing with varied compositions and then hot-pressed at 36 MPa and 100 °C for 20 minutes. From compressive strength test, it was found that composite with composition 7:8 of PVAc and leaves-waste had maximum compressive strength, i.e. 57.60 MPa. It was also that the enhancement of strength due to PVAc fraction (w/w) increasing is a percolation behavior, even though its mathematical explanation has not been performed. Into composition of maximum strength above, silica with average size is 74 nm then was added to improve the strength and found that at silica weight fraction of 0.79 (%w/w), the composite had optimum compressive strength, i.e. 70.5 MPa, or increased up to 22.4% of that without silica. The final compressive strength was very comparable to some building goods such as sandstones and bricks. The composite density was also measured and obtained that it was about 0.9 g/cm3 that is very close to some usual woods.

  3. 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.

  4. 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

  5. Doxorubicin/heparin composite nanoparticles for caspase-activated prodrug chemotherapy.

    Science.gov (United States)

    Khaliq, Nisar Ul; Sandra, Febrina Carolina; Park, Dal Yong; Lee, Jae Young; Oh, Keun Sang; Kim, Dongkyu; Byun, Youngro; Kim, In-San; Kwon, Ick Chan; Kim, Sang Yoon; Yuk, Soon Hong

    2016-09-01

    Caspase-activated prodrug chemotherapy is introduced and demonstrated using the composite nanoparticles (NPs), which deliver doxorubicin (DOX) and DEVD-S-DOX together to the tumor tissue. DEVD-S-DOX, DOX linked to a peptide moiety (DEVD), is a prodrug that is cleaved into free DOX by caspase-3 upon apoptosis. DEVD-S-DOX has no therapeutic efficacy, but it changes into free DOX with the expression of caspase-3. With the accumulation of the composite NPs in the tumor tissue by the enhanced permeation and retention (EPR) effect, a small exposure of DOX in the tumor cells initiated apoptosis in a localized area of the tumor tissue, which induced caspase-3 activation. Cleavage of DEVD-S-DOX into free DOX by caspase-3 continued with repetitive activation of caspase-3 and cleavage of DEVD-S-DOX at the tumor site. The composite NPs were characterized with transmittance electron microscopy (TEM) and particle size analyzer. We then evaluated the nanoparticle drug release, therapeutic efficacy, and in vivo biodistribution for tumor targeting using a non-invasive live animal imaging technology and the quantification of DOX with high performance liquid chromatography. DOX-induced apoptosis-targeted chemotherapy (DIATC) was verified by in vitro/in vivo DEVD-S-DOX response to free DOX and cellular uptake behavior of the composite NPs with flow cytometry analysis. Significant antitumor efficacy with minimal cardiotoxicity was also observed, which supported DIATC for improved chemotherapy. PMID:27286189

  6. Interface composition between Fe3O4 nanoparticles and GaAs for spintronic applications

    International Nuclear Information System (INIS)

    Recent interest in spintronic applications has necessitated the study of magnetic materials in contact with semiconductor substrates; importantly, the structure and composition of these interfaces can influence both device functionality and the magnetic properties. Nanoscale ferromagnet/semiconductor structures are of particular interest. In this study, the interface structure between a monolayer of ferromagnetic magnetite (Fe3O4) nanoparticles and a GaAs substrate was studied using cross-sectional transmission electron microscopy techniques. It was found that a continuous amorphous oxide interface layer separates the nanoparticles from the GaAs substrate, and that iron diffused into the interface layer forming a compositional gradient. Electron energy-loss near-edge fine structures of the O K absorption edge revealed that the amorphous oxide is composed of γ-Fe2O3 directly underneath the Fe3O4 nanoparticles, followed by a solid solution of Ga2O3 and FeO and mostly Ga2O3 when approaching the buckled oxide/substrate interface. Real-space density functional theory calculations of the dynamical form factor confirmed the experimental observations. The implication of the findings on the optimization of these structures for spin injection is discussed

  7. PREPARATION OF Al₂O₃-CaAl₁₂O₁₉-ZrO₂ COMPOSITE CERAMIC MATERIAL BY THE HYDRATION AND SINTERING OF Ca₇ZrAl₆O₁₈-REACTIVE ALUMINA MIXTURE

    Directory of Open Access Journals (Sweden)

    Dominika Madej

    2016-03-01

    Full Text Available Ceramic material of composition belonging to the Al₂O₃-CaAl₁₂O₁₉-ZrO₂ compatibility field was obtained as a result of hydration and sintering of the mixture of Al₂O₃ and Ca₇ZrAl₆O₁₈ powders. The hydrated Al₂O₃- Ca₇ZrAl₆O₁₈ mixture products were studied by XRD, DTA-TG-EGA and FT-IR after 14 days of curing and hydration at 50°C. C₃AH₆, Al(OH₃ and CaZrO₃ compounds were formed upon hydration. CaZrO₃ and the lime-rich calcium aluminates formed as transient phases during hydration and dehydration processes were converted to CA6 and ZrO₂ in the presence of an excess of Al₂O₃ during sintering at 1500°C. The Al₂O₃-based dense refractory composite material was investigated by XRD, FT-IR, SEM-EDS and mercury porosimetry. The sintered ceramic microstructure consists of a homogeneous distribution of zirconia grains in an alumina matrix reinforced with the calcium hexaaluminate phase. The presence of Al₂O₃, CaAl₁₂O₁₉ and ZrO₂ in the synthesized material was confirmed by XRD and FT-IR techniques. By applying the mercury intrusion porosimetry technique, the heterogeneous pore size distribution of the refractory composite material was determined.

  8. Hexagonal Nanoarchitecture of Composite Monolayer of Magnetite Nanoparticles and Geminus Surfactant 1,3-Propylenebis (dodecyldimethylammonium) Dibromide

    Institute of Scientific and Technical Information of China (English)

    LIU,Ming-Xian; GAN,Li-Hua; HAO,Zhi-Xian; XU,Zi-Jie; ZHU,Da-Zhang; CHEN,Long-Wu

    2008-01-01

    Negatively charged magnetite nanoparticles with an average size of about 10 nm have been synthesized by a chemical coprecipitation method using sodium dodecyl benzene sulphonate as a surface modifying reagent. Composite Langmuir monolayer of Fe3O4 nanoparticles and geminus surfactant 1,3-propylenebis(dodecyldimethylammonium) dibromide (C12-C3-C12) was prepared on the subphase of Fe3O4 nanoparticle hydrosols. In the presence of the magnetite nanoparticles, the collapse pressure of the composite monolayer and the limited mean molecular area of C12-C3-C12 are higher than those on pure water subphase. Transmission electron microscopy observation of a C12-C3-C12/Fe3O4 nanoparticle complex shows that Fe3O4 nanoparticles and geminus surfactant had an unexpected hexagonal nanoarchitecture at the air-liquid interface when the surface pressure of the composite monolayer increased to about 12 mN·m-1. A mechanism for constructing the particular nanopatterned configuration of the C12-C3-C12/Fe3O4 nanoparticle complex in the Langmuir layer directly from the unique molecular structure of the geminus surfactant and the interfacial interactions between C12-C3-C12 and the components in the subphase was proposed.

  9. Characterization of Glasses in One Type of Alumina Rich Fly Ash by Chemical Digestion Methods: Implications for Alumina Extraction

    Directory of Open Access Journals (Sweden)

    Lijun Zhao

    2016-01-01

    Full Text Available In recent years, one type of alumina rich fly ash (ARFA with about 50 wt% of alumina has been extensively investigated for alumina extraction in China. Due to the silica in ARFA, alumina extraction would have to generate a huge amount of solid waste. There is a growing interest in the glasses in ARFA, because they are composed mainly of silica and could be removed prior to alumina extraction. In this work, the glasses in ARFA have been investigated by chemical methods, that is, acid and base digestions. The chemical compositions have been measured by XRF for ARFA from the digestion processes. The K2O standard, XRD, and FTIR spectroscopies were successfully used to define the digestions processes, and size analysis and SEM-EDX provided rich information on particle transformations. As a result, acid and base digestion methods were found to produce very similar results for the glasses in ARFA. The K2O standard was attributed to the formation of glasses by illites, and TiO2 and Fe2O3 were proposed to originate from ilmenite in alumina rich coals (ARC. Some implications of the results were also discussed for the alumina extraction from ARFA.

  10. Modifying the composition of hydrogen-terminated silicon nanoparticles synthesized in a nonthermal rf plasma

    International Nuclear Information System (INIS)

    Hydrogen-terminated silicon nanoparticles were synthesized over a broad range of conditions in a continuous flow, nonthermal rf plasma. The effects of three operating parameters--rf power, reactor pressure, and hydrogen flow rate--were examined in terms of their effects on particle crystallinity, size, and surface composition. Silicon-hydrogen composition was characterized in situ by Fourier transform infrared spectrometry, and particle structural morphology was examined with a transmission electron microscope. Amorphous or crystalline particles could be synthesized by appropriately adjusting the operating parameters. Over the majority of settings examined, the minimum power required to produce discrete crystalline particles was ∼20-30 W. Depending on the parameter settings, particles also exhibited hydrogen coverage ranging from predominantly monohydride (SiH) functional groups to more complex compositions of higher hydrides. Particles with the highest proportion of surface SiH bonds were consistently synthesized in the smallest diameter (4 mm i.d.) tube reactor.

  11. Induction thermal plasma synthesis of lithium oxide composite nanoparticles with a spinel structure

    Science.gov (United States)

    Sone, Hirotaka; Kageyama, Takuya; Tanaka, Manabu; Okamoto, Daisuke; Watanabe, Takayuki

    2016-07-01

    Li–Mn composite oxide nanoparticles are synthesized using an induction thermal plasma, and the formation mechanism is investigated on the basis of the homogenous nucleation rate and thermodynamic considerations. Under a high O2 partial pressure, MnO crystals nucleate and Li oxide condenses on MnO nuclei at a relatively high rate, forming LiMn2O4 in a single phase. On the other hand, under a low partial pressure of O2, LiMnO2 is obtained owing to the low condensation rate of Li oxide. This study presents the successful selective synthesis of LiMn2O4 nanoparticles by controlling the partial pressure of O2.

  12. Composite glycidyl methacrylated dextran (Dex-GMA)/gelatin nanoparticles for localized protein delivery

    Institute of Scientific and Technical Information of China (English)

    Fa-ming CHEN; Zhi-wei MA; Guang-ying DONG; Zhi-fen WU

    2009-01-01

    Aim: Localized delivery of growth factors has significant potential as a future therapeutic strategy in tissue engineering and regenerative medicine. A nanoparticle vehicle was created and evaluated in this study with the intent to deliver growth factors for periodontal regeneration. Methods: Novel composite nanoparticles based on glycidyl methacrylate derivatized dextrans (Dex-GMA) and gelatin were fabricated by a facile method without using any organic solvents. The configurations of the resultant nanoparticles were evaluated by transmission electron microscopy, scanning electron microscopy, and atomic force microscope. Their surfaces were characterized by zeta-potential measurements, after which their properties including swelling, degradation, drug release, and cytotoxicity were also investigated using in vitro models,Results: The particle size of Dex-GMA/gelatin nanoparticles (DG-NPs) ranged from 20 to 100 nm and showed a mono-dis-perse size distribution (mean diameter 53.7 nm) and a strongly negative surface zeta potential (-20 mV). The DC,-NPs were characterized by good swelling and degradation properties in media including dextranase. The in vitro drug release stud-ies showed that the efficient bone morphogenetic protein (BMP) release from DG-NPs was maintained for more than 12 d under degradation conditions, where more than 90% of the loaded BMP was released. No any relevant cell damage caused by DG-NPs was found in the cytotoxicity tests for a period of 24 h.Conclusion: These combined results demonstrate that DG-NPs fulfill the basic prerequisites for growth factor delivery.With further in vivo studies, those nanoparticles may offer a promising vehicle for the delivery of active drugs to the perio-dontium.

  13. Amino acid mediated synthesis of silver nanoparticles and preparation of antimicrobial agar/silver nanoparticles composite films.

    Science.gov (United States)

    Shankar, Shiv; Rhim, Jong-Whan

    2015-10-01

    Silver nanoparticles (AgNPs) were synthesized using amino acids (tyrosine and tryptophan) as reducing and capping agents, and they were incorporated into the agar to prepare antimicrobial composite films. The AgNPs solutions exhibited characteristic absorption peak at 420 nm that showed a red shift to ∼434 nm after forming composite with agar. XRD data demonstrated the crystalline structure of AgNPs with dominant (111) facet. Apparent surface color and transmittance of agar films were greatly influenced by the AgNPs. The incorporation of AgNPs into agar did not exhibit any change in chemical structure, thermal stability, moisture content, and water vapor permeability. The water contact angle, tensile strength, and modulus decreased slightly, but elongation at break increased after AgNPs incorporation. The agar/AgNPs nanocomposite films possessed strong antibacterial activity against Listeria monocytogenes and Escherichia coli. The agar/AgNPs film could be applied to the active food packaging by controlling the food-borne pathogens. PMID:26076636

  14. Effect of Physiochemical Properties and Bath Chemistry on Alumina Dissolution Rate in Cryolite Electrolyte

    Science.gov (United States)

    Yang, Youjian; Gao, Bingliang; Wang, Zhaowen; Shi, Zhongning; Hu, Xianwei

    2015-05-01

    The relationships of dissolution rate to alumina specifications and bath chemistry including electrolyte composition, operating temperature and superheat were investigated. The key physiochemical properties of industrial alumina samples were tested including moisture content, loss on ignition, surface area and phase composition. The dissolution of these samples in several bath compositions was observed through a quartz crucible equipped with a visual recording system. The dissolution rate increased with increasing loss on ignition and surface area. The operating temperatures and existing alumina concentration in the electrolyte had a greater impact on the alumina dissolution rate than the minor change of the bath compositions and superheat. Same trends were also obtained for the lab-calcined alumina samples.

  15. Rheological Properties of Aqueous Nanometric Alumina Suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Chuanping Li

    2004-12-19

    ' 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 {zeta}-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.

  16. Nanoindentation of shock deformed alumina

    International Nuclear Information System (INIS)

    In the current study, the experimental results on the nanoindentation response of both as prepared and shock recovered alumina of 10 μm grain size and identical processing history are presented and analyzed. The shock recovery experiments were deliberately conducted with gas gun arrangements at shock pressures much above the Hugoniot Elastic Limit (HEL) of alumina. The nanoindentation experiments were conducted at 10-1000 mN load with a Berkovich indenter. The nanohardness and Young's modulus value of shock recovered alumina were always lower than those of the as prepared alumina samples. Subsequently, the detailed characterizations of the shock recovered alumina samples by X-ray diffraction, scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were utilized to understand the reasons behind the drop in nanohardness and Young's modulus of shock recovered alumina samples.

  17. Microfluidic assisted synthesis of silver nanoparticle-chitosan composite microparticles for antibacterial applications.

    Science.gov (United States)

    Yang, Chih-Hui; Wang, Lung-Shuo; Chen, Szu-Yu; Huang, Mao-Chen; Li, Ya-Hua; Lin, Yun-Chul; Chen, Pei-Fan; Shaw, Jei-Fu; Huang, Keng-Shiang

    2016-08-30

    Silver nanoparticle (Ag NP)-loaded chitosan composites have numerous biomedical applications; however, fabricating uniform composite microparticles remains challenging. This paper presents a novel microfluidic approach for single-step and in situ synthesis of Ag NP-loaded chitosan microparticles. This proposed approach enables obtaining uniform and monodisperse Ag NP-loaded chitosan microparticles measuring several hundred micrometers. In addition, the diameter of the composites can be tuned by adjusting the flow on the microfluidic chip. The composite particles containing Ag NPs were characterized using UV-vis spectra and scanning electron microscopy-energy dispersive X-ray spectrometry data. The characteristic peaks of Ag NPs in the UV-vis spectra and the element mapping or pattern revealed the formation of nanosized silver particles. The results of antibacterial tests indicated that both chitosan and composite particles showed antibacterial ability, and Ag NPs could enhance the inhibition rate and exhibited dose-dependent antibacterial ability. Because of the properties of Ag NPs and chitosan, the synthesized composite microparticles can be used in several future potential applications, such as bactericidal agents for water disinfection, antipathogens, and surface plasma resonance enhancers. PMID:26780124

  18. Modern views on the composition of anionic oxy-fluoride complexes of aluminium and their rearrangement during the electrolysis of cryolite-alumina melts

    Science.gov (United States)

    Khramov, A. P.; Shurov, N. I.

    2014-08-01

    Some consequences of the hypothesis of the absence of free F- ions in cryolite-alumina melts are observed. The melt at 1 < CR < 3 is assumed to consist of the complexes AlF{6/3-}, AlF{5/2-}, AlF{4/-}, Al2OF{6/2-}, and Al2O2F{4/2-}, and alkali metal cations. A formal-stoichiometric study of the processes occurring during electrolysis is performed on the basis of the accepted hypothesis. Judgments about some of the features of the electrode reactions and chemical reactions in the electrolyte volume are presented. The reaction schemes for the instances with and without the subsequent/preceding chemical reaction near the electrode or in the molten salt volume are given. The mass flows of various forms of ionic complexes through the electrolyte volume are given for these schemes. Definitive conclusions are not made in the study, but the range of possible variants for the electrochemical routes of the overall chemical reaction in the cell is limited.

  19. Electrospun cellulose acetate composites containing supported metal nanoparticles for antifungal membranes.

    Science.gov (United States)

    Quirós, Jennifer; Gonzalo, Soledad; Jalvo, Blanca; Boltes, Karina; Perdigón-Melón, José Antonio; Rosal, Roberto

    2016-09-01

    Electrospun cellulose acetate composites containing silver and copper nanoparticles supported in sepiolite and mesoporous silica were prepared and tested as fungistatic membranes against the fungus Aspergillus niger. The nanoparticles were in the 3-50nm range for sepiolite supported materials and limited by the size of mesopores (5-8nm) in the case of mesoporous silica. Sepiolite and silica were well dispersed within the fibers, with larger aggregates in the micrometer range, and allowed a controlled release of metals to create a fungistatic environment. The effect was assessed using digital image analysis to evaluate fungal growth rate and fluorescence readings using a viability stain. The results showed that silver and copper nanomaterials significantly impaired the growth of fungi when the spores were incubated either in direct contact with particles or included in cellulose acetate composite membranes. The fungistatic effect took place on germinating spores before hyphae growth conidiophore formation. After 24h the cultures were separated from fungistatic materials and showed growth impairment only due to the prior exposure. Growth reduction was important for all the particles and membranes with respect to non-exposed controls. The effect of copper and silver loaded materials was not significantly different from each other with average reductions around 70% for bare particles and 50% for membranes. Copper on sepiolite was particularly efficient with a decrease of metabolic activity of up to 80% with respect to controls. Copper materials induced rapid maturation and conidiation with fungi splitting in sets of subcolonies. Metal-loaded nanomaterials acted as reservoirs for the controlled release of metals. The amount of silver or copper released daily by composite membranes represented roughly 1% of their total load of metals. Supported nanomaterials encapsulated in nanofibers allow formulating active membranes with high antifungal performance at the same time

  20. The thermodynamic properties of hydrated γ-Al2O3 nanoparticles

    International Nuclear Information System (INIS)

    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. Surface modification by metal ion implantation forming metallic nanoparticles in an insulating matrix

    Energy Technology Data Exchange (ETDEWEB)

    Salvadori, M.C., E-mail: mcsalvadori@if.usp.br [Institute of Physics, University of Sao Paulo, C.P. 66318, CEP 05314-970, Sao Paulo, S.P. (Brazil); Teixeira, F.S.; Sgubin, L.G.; Cattani, M. [Institute of Physics, University of Sao Paulo, C.P. 66318, CEP 05314-970, Sao Paulo, S.P. (Brazil); Brown, I.G. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2014-08-15

    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

  2. Magneto-electro-responsive material based on magnetite nanoparticles/polyurethane composites.

    Science.gov (United States)

    Petcharoen, Karat; Sirivat, Anuvat

    2016-04-01

    Multi-functional materials in actuator applications have been developed toward reversibility and sensitivity under various actuating fields. In this work, magneto-electro-responsive materials consisting of a polyurethane (PU) matrix and its composites embedded with magnetite nanoparticles (MNP) as a dispersed phase were fabricated to tailor the electromechanical properties and bending performance under electric, magnetic, and electromagnetic fields. Due to the superior characteristics of MNP over other magnetic materials, the composites fabricated with electronic polarization were highly responsive under electric field. The highest storage modulus sensitivity belonged to the 1.0% v/v MNP/PU composite which possessed the value of 3.46 at the electric field 2 kV mm(-1). Moreover, all of the PU composites behaved as an electrostrictive material in which the stress depended quadratically on the electric field. It was demonstrated that the PU composites also possessed very good recoverability, fast response (<15s) and large bending angle relative to that of pristine PU under applied electric field. Interestingly, the steady state storage modulus response was attained within the first electrical actuation cycle and the PU composite was a fully reversible material. In addition, it was shown that superparamagnetism was a common characteristic of all fabricated composites under magnetic field. The 3.0%v/v MNP/PU composite provided the largest bending distance up to 23.60mm, and 14.10mm under the magnetic field of 5000 G, and the electromagnetic field of 320 G, respectively. In summary, the MNP/PU composite material is a potential candidate to be used as a smart material under the influences of electric and/or magnetic fields over other existing dielectric materials. PMID:26838855

  3. Tensile Mechanical Properties and Strengthening Mechanism of Hybrid Carbon Nanotube and Silicon Carbide Nanoparticle-Reinforced Magnesium Alloy Composites

    OpenAIRE

    Xia Zhou; Depeng Su; Chengwei Wu; Liming Liu

    2012-01-01

    AZ91 magnesium alloy hybrid composites reinforced with different hybrid ratios of carbon nanotubes (CNTs) and silicon carbide (SiC) nanoparticulates were fabricated by semisolid stirring assisted ultrasonic cavitation. The results showed that grains of the matrix in the AZ91/(CNT + SiC) composites were obviously refined after adding hybrid CNTs and SiC nanoparticles to the AZ91 alloy, and the room-temperature mechanical properties of AZ91/(CNT + SiC) hybrid composites were improved comparing ...

  4. 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.

  5. Manipulating fluorescence color and intensity with regular metal nanoparticle-based composite materials

    International Nuclear Information System (INIS)

    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

  6. Effect of impregnation of La0.85Sr0.15MnO3/Yttria Stabilized Zirconia Solid Oxide Fuel Cell cathodes with La0.85Sr0.15MnO3 or Al2O3 nano-particles

    DEFF Research Database (Denmark)

    Kammer Hansen, Kent; Wandel, Marie; Liu, Yi-Lin; Mogensen, Mogens Bjerg

    2010-01-01

    electrodes if the temperature was kept low after the impregnation with strontium substituted lanthanum manganite. On good performing electrodes the effect disappeared on heating. Alumina nano-particles had a detrimental effect on the activity of the strontium substituted lanthanum manganite based electrodes.......Strontium substituted lanthanum manganite and yttria stabilized zirconia solid oxide fuel cell composite electrodes were impregnated with nano-particles of strontium substituted lanthanum manganite or alumina. A clear positive effect was observed on low performing electrodes and on good performing...

  7. Effective Medium Theory Applied to Colloidal Solution of Gold Nanoparticles and Alternating Gold-Silica Multilayer Thin Film Composites

    International Nuclear Information System (INIS)

    Optical modeling of multilayer thin films constructed with oppositely charged nanoparticles help us to understand phenomenon such as surface plasmon resonance, absorbance, transmittance and reflectance. This work reports the application of Maxwell-Garnett effective medium theory in quasi-static limit to colloidal suspensions consisting of host material silica and the inclusion material -gold nanoparticles. Layer-by-layer deposition method was used to self-assemble these nanoparticles to build multilayer composite films. By varying the number and thickness of the layers and the size and spacing of the metal inclusion, a facilitative optical design is modeled to build multilayers of nanosized materials targeted for desired applications. (author)

  8. Active-Transient Liquid Phase (A-TLP) Bonding of Pure Aluminum Matrix Composite Reinforced with Short Alumina Fiber Using Al-12Si-xTi Foils as Active Interlayer

    Science.gov (United States)

    Zhang, Guifeng; Su, Wei; Suzumura, Akio

    2016-02-01

    To optimize both the interlayer composition design route and pressure for joining aluminum matrix composite reinforced with short alumina fiber (as-cast 30 vol pct Al2O3sf/Al), traditional transient liquid phase (TLP) bonding using Al-12Si and Cu interlayer and active-TLP (A-TLP) bonding using an active Ti-containing interlayer (Al-12Si-xTi, x = 0.1, 0.5, and 1 wt pct) under the same condition [883 K (610 °C) × 30 minutes × 1 or 0.015 MPa in flowing argon] were compared in terms of interfacial wettability, bond seam microstructure, shear strength, and fracture path. It was found that not only the Ti content but also the pressure are critical factors affecting interfacial wettability and bond seam microstructure. The improvement in wettability by adding Ti as an active element were confirmed by reduction of expulsion of liquid interlayer, elimination of interfacial gap, higher shear strength and favorable fracture path (partially through bond seam and the composite). Because of the incubation period for wetting, reducing the pressure after melting of the interlayer could further increase joint shear strength by thickening the remaining bond seam of solid-solution matrix and decreasing fraction of the in situ newly formed Al-Si-Ti IMC phase (short bar shape) within the bond seam. The maximum shear strength of 88.6 MPa (99 pct of the as-cast composite) was obtained by adding trace Ti content (0.5 Ti wt pct) addition and using low pressure (0.015 MPa). The results showed that suitable combination of Ti content and pressure pattern is required for improving both wettability and bond seam microstructure.

  9. Active-Transient Liquid Phase (A-TLP) Bonding of Pure Aluminum Matrix Composite Reinforced with Short Alumina Fiber Using Al-12Si- xTi Foils as Active Interlayer

    Science.gov (United States)

    Zhang, Guifeng; Su, Wei; Suzumura, Akio

    2016-06-01

    To optimize both the interlayer composition design route and pressure for joining aluminum matrix composite reinforced with short alumina fiber (as-cast 30 vol pct Al2O3sf/Al), traditional transient liquid phase (TLP) bonding using Al-12Si and Cu interlayer and active-TLP (A-TLP) bonding using an active Ti-containing interlayer (Al-12Si- xTi, x = 0.1, 0.5, and 1 wt pct) under the same condition [883 K (610 °C) × 30 minutes × 1 or 0.015 MPa in flowing argon] were compared in terms of interfacial wettability, bond seam microstructure, shear strength, and fracture path. It was found that not only the Ti content but also the pressure are critical factors affecting interfacial wettability and bond seam microstructure. The improvement in wettability by adding Ti as an active element were confirmed by reduction of expulsion of liquid interlayer, elimination of interfacial gap, higher shear strength and favorable fracture path (partially through bond seam and the composite). Because of the incubation period for wetting, reducing the pressure after melting of the interlayer could further increase joint shear strength by thickening the remaining bond seam of solid-solution matrix and decreasing fraction of the in situ newly formed Al-Si-Ti IMC phase (short bar shape) within the bond seam. The maximum shear strength of 88.6 MPa (99 pct of the as-cast composite) was obtained by adding trace Ti content (0.5 Ti wt pct) addition and using low pressure (0.015 MPa). The results showed that suitable combination of Ti content and pressure pattern is required for improving both wettability and bond seam microstructure.

  10. Properties of Al2O3 nano-particle reinforced copper matrix composite coatings prepared by pulse and direct current electroplating

    International Nuclear Information System (INIS)

    Highlights: → The influence of Al2O3 is studied on morphologies of the DC and PC applied coatings. → The influence of Al2O3 is studied on the DC and PC coating thicknesses. → The influence of Al2O3 is studied on wear resistance. → The effect of Al2O3 is studied on the porosity and corrosion resistance. -- Abstract: Cu-Al2O3 nano-composite coatings have high potential for use in applications in which high mechanical properties together with high corrosion resistance are required. In the present study it is intended to produce copper nano-alumina composite coatings with various nano-alumina contents in order to investigate the effect of alumina reinforcement particles on corrosion resistance and mechanical properties such as hardness and wear resistance. The composite coatings were deposited using direct current (DC) and pulse current (PC) plating. The microstructures of the coatings produced from both methods were examined via scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The wear behaviors, micro hardness, coating thickness, corrosion rate and coating porosity were examined using appropriate methods. Compared to DC deposition, PC plating facilitated higher amounts of particle incorporation with more uniform distribution. The results indicated that the mechanical properties of the applied coatings with incorporated nano-alumina reinforcement were far more superior as compared to its own matrix as well as non-composite copper coatings. It was also found out that increasing the amount of nano-alumina content in the coating, led to enhanced general properties of the coatings.

  11. Synthesis of magnetic composite nanoparticles enveloped in copolymers specified for scale inhibition application

    Science.gov (United States)

    Do, Bao Phuong Huu; Dung Nguyen, Ba; Duy Nguyen, Hoang; Nguyen, Phuong Tung

    2013-12-01

    We report the synthesis of magnetic iron oxide nanoparticles encapsulated in maleic acid-2-acrylamido-2-methyl-1-propanesulfonate based polymer. This composite nanoparticle is specified for the high-pressure/high-temperature (HPHT) oilfield scale inhibition application. The process includes a facile-ultrasound-supported addition reaction to obtain iron oxide nanoparticles with surface coated by oleic acid. Then via inverse microemulsion polymerization with selected monomers, the specifically designed copolymers have been formatted in nanoscale. The structure and morphology of obtained materials were characterized by transmission electron microscopy (TEM), x-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and the thermal stability. The effectiveness of synthesized compounds as a carbonate scale inhibitor was investigated by testing method NACE standard TM 03-074-95 at aging temperature of 70, 90 and 120 °C. The magnetic nanocomposite particles can be easily collected and detected demonstrating their superior monitoring ability, which is absent in the case of conventional copolymer-based scale inhibitor.

  12. Synergistic effect of manganese oxide nanoparticles and graphene nanosheets in composite anodes for lithium ion batteries

    International Nuclear Information System (INIS)

    A graphene-Mn3O4-graphene (GMG) sandwich structure with homogeneous anchoring of Mn3O4 nanoparticles among flexible and conductive graphene nanosheets (GSs) is achieved through dispersion of the GSs in Mn(NO3)2 solution and subsequent calcination. Mn3O4 nanoparticles are 50 ∼ 200 nm clusters consisting of 10 ∼ 20 nm primary particles, and serve as spacers to prevent the re-stacking of the GSs. GSs provide a highly conductive network among Mn3O4 nanoparticles for efficient electron transfer and buffer any volume change during cycling. Due to the strong synergistic effect between Mn3O4 and GSs, the capacity contributions from GSs and Mn3O4 in GMG are much larger than capacities of pure GSs and Mn3O4. Consequently, the GMG composite electrodes show excellent electrochemical properties for lithium ion battery applications, demonstrating a large reversible capacity of 750 mAh g−1 at 0.1 C based on the mass of GMG with no capacity fading after 100 cycles, and high rate abilities of 500 mAh g−1 at 5 C and 380 mAh g−1 at 10 C. (paper)

  13. ZnO nanoparticles obtained by pulsed laser ablation and their composite with cotton fabric: Preparation and study of antibacterial activity

    Science.gov (United States)

    Svetlichnyi, Valery; Shabalina, Anastasiia; Lapin, Ivan; Goncharova, Daria; Nemoykina, Anna

    2016-05-01

    A simple deposition method was used to prepare a ZnO/cotton fabric composite from water and ethanol dispersions of ZnO nanoparticles obtained by the pulsed laser ablation method. The structure and composition of the nanoparticles from dispersions and as-prepared composites were studied using electron microscopy, X-ray diffraction, and spectroscopy. The nanoparticles and composite obtained exhibited antibacterial activity to three different pathogenic microorganisms-Escherichia coli, Staphylococcus aureus, and Bacillus subtilis. An attempt to understand a mechanism of bactericidal effect of ZnO nanoparticles was made. It was shown that zinc ions and hydrogen peroxide were not responsible for antibacterial activity of the particles and the composite, and surface properties of nanoparticles played an important role in antibacterial activity of zinc oxide. The proposed composite is a promising material for use as an antibacterial bandage.

  14. Tribological properties of the synthesis of Cu-BTA composite nanoparticles via the thermal decomposition application in lubricants

    Science.gov (United States)

    Kao, M. J.; Hsu, F. C.; Guo, J. B.; Huang, K. D.; Peng, D. X.

    2013-11-01

    This project investigated the tribological properties of Cu-benzotriazole (BTA) composite nanoparticles as lubricant additives. BTA functions as a stabilizer for the Cu nanoparticles and as a protector from oxidation of the Cu nanoparticles in various test circumstances. Tribological experiments were conducted using a pin-on-disk (ASTM G99) test for the wear scar diameter, friction coefficient, and morphology of worn surfaces. Furthermore, the dispersivity of these Cu-BTA nanoparticles in liquid paraffin oil was measured using a UV/VIS spectrophotometer. The experiment results revealed the dispersion capability of the benzotriazole-capped Cu nanoparticles and indicated the dispersing stability in liquid paraffin oil for the BTA-capped surface of Cu nanoparticles. The testing results demonstrate that the Cu-BTA nanoparticle used as an additive in liquid paraffin oil at an appropriate concentration exhibits better tribological properties than those of pure paraffin oil. Moreover, Cu-BTA functioning as an additive has different anti-wear abilities due to its small size effect. Finally, the repair ability of Cu-BTA nanoparticles on the worn surfaces was observed using SEM and EDS.

  15. 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.

  16. Tuning the dielectric properties of metallic-nanoparticle/elastomer composites by strain

    Science.gov (United States)

    Gaiser, Patrick; Binz, Jonas; Gompf, Bruno; Berrier, Audrey; Dressel, Martin

    2015-02-01

    Tunable metal/dielectric composites are promising candidates for a large number of potential applications in electronics, sensor technologies and optical devices. Here we systematically investigate the dielectric properties of Ag-nanoparticles embedded in the highly flexible elastomer poly-dimethylsiloxane (PDMS). As tuning parameter we use uniaxial and biaxial strain applied to the composite. We demonstrate that both static variations of the filling factor and applied strain lead to the same behavior, i.e., the filling factor of the composite can be tuned by application of strain. In this way the effective static permittivity εeff of the composite can be varied over a very large range. Once the Poisson's ratio of the composite is known, the strain dependent dielectric constant can be accurately described by effective medium theory without any additional free fit parameter up to metal filling factors close to the percolation threshold. It is demonstrated that, starting above the percolation threshold in the metallic phase, applying strain provides the possibility to cross the percolation threshold into the insulating region. The change of regime from conductive phase down to insulating follows the description given by percolation theory and can be actively controlled.

  17. High Temperature Stability of Potassium Beta Alumina

    Science.gov (United States)

    Williams, R. M.; Kisor, A.; Ryan, M. A.

    1996-01-01

    None. From Objectives section: Evaluate the stability of potassium beta alumina under potassium AMTEC operating conditions. Evaluate the stability regime in which potassium beta alumina can be fabricated.

  18. Mechanical performance of alumina reinforced with NbC, TiC and WC

    Directory of Open Access Journals (Sweden)

    Wilson Acchar

    2012-12-01

    Full Text Available The incorporation of refractory hard particles in Al2O3-based composites may inhibit grain growth of the matrix, which could significantly contribute to mechanical performance of the composite. The present study aimed to investigate the potential use of NbC as alumina reinforcing material, as an alternative to other carbides such as TiC and WC. Alumina was mixed with a fixed carbide concentration of 30 wt.(% in a ball mill and uniaxially hot-pressed at 1650 ºC under a load of 30 MPa in an inert atmosphere. X-ray diffraction revealed no oxidation products were present after the sintering process. Microstructure analyses indicate a homogeneous carbide distribution in the alumina matrix. Results obtained in this study show that alumina reinforced with NbC is a composite material with properties comparable to those of alumina reinforced with WC and TiC, thereby making it good reinforcing material.

  19. 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.

  20. A facile synthesis of metal nanoparticle - graphene composites for better absorption of solar radiation

    International Nuclear Information System (INIS)

    Herein, a facile chemical approach has been adopted to prepare silver nanoparticles (AgNPs)- graphene (G) composite to study photothermal effect. Sodium borohydride (SBH), a strong reducing agent has been selected for this work. Effect of SBH concentrations on optical behavior of AgNPs-G composite was also investigated. Resultant materials were characterized by various techniques including X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), optical absorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM micrographs confirm wrapping of AgNPs into graphene whereas XRD analysis reveals their particle size variation between 47 nm to 69 nm. Optical studies throw a light on their strong absorption behavior towards solar radiation