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Sample records for f-substituted hydroxyapatite nanopowders

  1. Si-substituted hydroxyapatite nanopowders: Synthesis, thermal stability and sinterability

    SciTech Connect

    Bianco, Alessandra Cacciotti, Ilaria; Lombardi, Mariangela Montanaro, Laura

    2009-02-04

    Synthetic hydroxyapatites incorporating small amounts of Si have shown improved biological performances in terms of enhanced bone apposition, bone in-growth and cell-mediated degradation. This paper reports a systematic investigation on Si-substituted hydroxyapatite (Si 1.40 wt%) nanopowders produced following two different conventional wet methodologies: (a) precipitation of Ca(NO{sub 3}){sub 2}.4H{sub 2}O and (b) titration of Ca(OH){sub 2}. The influence of the synthesis process on composition, thermal behaviour and sinterability of the resulting nanopowders is studied. Samples were characterised by electron microscopy, induced coupled plasma atomic emission spectroscopy, thermal analysis, infrared spectroscopy, N{sub 2} adsorption measurements, X-ray diffraction and dilatometry. Semicrystalline Si-substituted hydroxyapatite powders made up of needle-like nanoparticles were obtained, the specific surface area ranged between 84 and 110 m{sup 2}/g. Pure and Si-substituted hydroxyapatite nanopowders derived from Ca(NO{sub 3}){sub 2}.4H{sub 2}O decomposed around 1000 deg. C. Si-substituted hydroxyapatite nanopowders obtained from Ca(OH){sub 2} were thermally stable up to 1200 deg. C and showed a distinct decreased thermal stability with respect to the homologous pure sample. Si-substituted hydroxyapatites exhibited higher sintering temperature and increased total shrinkage with respect to pure powders. Nanostructured dense ceramics were obtained by sintering at 1100 deg. C Si-substituted hydroxyapatites derived from Ca(OH){sub 2}.

  2. Surfactant-assisted hydrothermal synthesis of hydroxyapatite nanopowders.

    PubMed

    Bricha, Meriame; Belmamouni, Younes; Essassi, El Mokhtar; Ferreira, José M F; El Mabrouk, Khalil

    2012-10-01

    Rod-like hydroxyapatite nanoparticles (n-HAp) with a highly ordered nanostructure were prepared by hydrothermal synthesis from calcium chloride, and phosphoric acid, as calcium and phosphorus sources, respectively. Various surfactant families such as cationic (CTAB), anionic (SDS) and nonionic (Triton X-100) were used as regulators of the nucleation and crystal growth. The synthesized nanopowders were characterized using X-ray diffraction (XRD), Fourier transform infrared spectrograph (FTIR) and transmission electron microscopy (TEM). The rod-like morphology was obtained regardless of the surfactant used during the hydrothermal treatment, but the aspect ratio of the crystals was found to be surfactant dependent. The mechanism of crystal growth as well-oriented nanostructure is discussed. PMID:23421176

  3. Bio-nanoplatforms based on carbon dots conjugating with F-substituted nano-hydroxyapatite for cellular imaging.

    PubMed

    Zhao, Yafei; Shi, Liyi; Fang, Jianhui; Feng, Xin

    2015-12-21

    Carbon dots (CDs) have shown great promise in a wide range of bioapplications due to their tunable optical properties and noncytotoxicity. For the first time, a rational strategy was designed to construct new bio-nanoplatforms based on carboxylic acid terminated CDs (CDs-COOH) conjugating with amino terminated F-substituted nano-hydroxyapatite (NFAp) via EDC/NHS coupling chemistry. The monodisperse NFAp nanorods were functionalized with o-phosphoethanolamine (PEA) to provide them with amino groups and render them hydrophilic with respect to the ligand exchange process. The CDs-COOH@PEA-NFAp conjugates exhibits bright blue fluorescence under UV illumination, excellent photostability and colloidal stability. Due to their low cytotoxicity and good biocompatibility as determined by methyl thiazolyl tetrazolium (MTT) assay, the CDs-COOH@PEA-NFAp conjugates were successfully applied as bio-nanoplatforms to MCF-7 breast cancer cells for cellular imaging in vitro. More importantly, the functional CDs conjugated to NFAp provide an extended and general approach to construct different water-soluble NFAp bio-nanoplatforms for other easily functionalised luminescent materials. Therefore, these green nanoplatforms may be a prospective candidate for applications in bioimaging or targeted biological therapy and drug delivery. PMID:26568461

  4. Bio-nanoplatforms based on carbon dots conjugating with F-substituted nano-hydroxyapatite for cellular imaging

    NASA Astrophysics Data System (ADS)

    Zhao, Yafei; Shi, Liyi; Fang, Jianhui; Feng, Xin

    2015-11-01

    Carbon dots (CDs) have shown great promise in a wide range of bioapplications due to their tunable optical properties and noncytotoxicity. For the first time, a rational strategy was designed to construct new bio-nanoplatforms based on carboxylic acid terminated CDs (CDs-COOH) conjugating with amino terminated F-substituted nano-hydroxyapatite (NFAp) via EDC/NHS coupling chemistry. The monodisperse NFAp nanorods were functionalized with o-phosphoethanolamine (PEA) to provide them with amino groups and render them hydrophilic with respect to the ligand exchange process. The CDs-COOH@PEA-NFAp conjugates exhibits bright blue fluorescence under UV illumination, excellent photostability and colloidal stability. Due to their low cytotoxicity and good biocompatibility as determined by methyl thiazolyl tetrazolium (MTT) assay, the CDs-COOH@PEA-NFAp conjugates were successfully applied as bio-nanoplatforms to MCF-7 breast cancer cells for cellular imaging in vitro. More importantly, the functional CDs conjugated to NFAp provide an extended and general approach to construct different water-soluble NFAp bio-nanoplatforms for other easily functionalised luminescent materials. Therefore, these green nanoplatforms may be a prospective candidate for applications in bioimaging or targeted biological therapy and drug delivery.Carbon dots (CDs) have shown great promise in a wide range of bioapplications due to their tunable optical properties and noncytotoxicity. For the first time, a rational strategy was designed to construct new bio-nanoplatforms based on carboxylic acid terminated CDs (CDs-COOH) conjugating with amino terminated F-substituted nano-hydroxyapatite (NFAp) via EDC/NHS coupling chemistry. The monodisperse NFAp nanorods were functionalized with o-phosphoethanolamine (PEA) to provide them with amino groups and render them hydrophilic with respect to the ligand exchange process. The CDs-COOH@PEA-NFAp conjugates exhibits bright blue fluorescence under UV illumination

  5. Study the adsorption of phenol from aqueous solution on hydroxyapatite nanopowders.

    PubMed

    Lin, Kaili; Pan, Jiayong; Chen, Yiwei; Cheng, Rongming; Xu, Xuecheng

    2009-01-15

    In this study, the hydroxyapatite (HAp) nanopowders prepared by chemical precipitation method were used as the adsorbent, and the potential of HAp nanopowders for phenol adsorption from aqueous solution was studied. The effect of contact time, initial phenol concentration, pH, adsorbent dosage, solution temperature and adsorbent calcining temperature on the phenol adsorption, and the adsorption kinetic, equilibrium and thermodynamic parameters were investigated. The results showed that the HAp nanopowders possessed good adsorption ability to phenol. The adsorption process was fast, and it reached equilibrium in 2h of contact. The initial phenol concentration, pH and the adsorbent calcining temperature played obvious effects on the phenol adsorption capacity onto HAp nanopowders. Increase in the initial phenol concentration could effectively increase the phenol adsorption capacity. At the same time, increase in the pH to high-acidity or to high-alkalinity also resulted in the increase in the phenol adsorption capacity. Increase in the HAp dosage could effectively increase the phenol adsorption percent. However, the higher calcining temperature of HAp nanopowders could obviously decrease the adsorption capacity. The maximum phenol adsorption capacity was obtained as 10.33mg/g for 400mg/L initial phenol concentrations at pH 6.4 and 60 degrees C. The adsorption kinetic and the isotherm studies showed that the pseudo-second-order model and the Freundlich isotherm were the best choices to describe the adsorption behaviors. The thermodynamic parameters suggested that the adsorption of phenol onto HAp was physisorption, spontaneous and endothermic in nature. PMID:18573599

  6. O2/Ar Plasma Treatment for Enhancing the Biocompatibility of Hydroxyapatite Nanopowder and Polycaprolactone Composite Film.

    PubMed

    Ko, Yeong-Mu; Myung, Sung-Woon; Kim, Byung-Hoon

    2015-08-01

    In this study we performed O2/Ar plasma treatment to remove the polycaprolactone on hydroxyapatite nanopowder and polycaprolactone (HAp-NP/PCL) composite film. After plasma ashing, the HAp-NP was exposed on the composite film. The 25 wt% HAp-NP/PCL treated with plasma showed the hydrophilic surface property with reducing the aging effect. The MTT and ALP results indicated that the plasma etching increased the biocompatibility of HAp-NP/PCL composite film. The present simple plasma etching technique can be applicable in a development of biomaterials. PMID:26369196

  7. Antimicrobial properties of silver-doped hydroxyapatite nano-powders and thin films

    NASA Astrophysics Data System (ADS)

    Sygnatowicz, Michael; Keyshar, Kunttal; Tiwari, Ashutosh

    2010-07-01

    Silver-doped hydroxyapatite nanopowders were prepared using a solution based sol-gel method and thoroughly characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Antibacterial tests showed silver-doped HAP powders prevented the growth and reproduction of bacteria. Silver-doped HAP powders were pressed into pellets and on these pellets a pulsed laser deposition (PLD) technique was employed to grow amorphous and crystalline thin films on sapphire substrates. Crystalline films had silver nano-particles present within the HAP matrix. Film stability tests showed crystalline films to be far more stable in prolonged solution submersion than their amorphous counterparts.

  8. Reverse micelle mediated synthesis, processing, mechanical and biological characterization of hydroxyapatite nanopowders for bone graft application

    NASA Astrophysics Data System (ADS)

    Banerjee, Ashis

    Hydroxyapatite (HA) is the most widely used bioceramic material in bone graft applications because of its compositional similarity with natural bone. However, synthetic HA does not show similar mechanical and biological properties to the inorganic component of bone. Properties of ceramic material depend on starting materials, processing techniques, densification and microstructure of the final product. The objective of this research was to process HA whisker reinforced HA composite using HA nanopowders and whiskers. HA nanopowders with different length scale and morphology were synthesized by reverse micelle system using NP5 and NP12 as surfactants and cyclohexane as organic solvent. The lowest average aspect ratio was 1.357+/-0.39 with average particle size of 66 nm and the highest average aspect ratio was 7.277+/-3.227 with average length of 150 nm and width of 20 nm, were synthesized. Micron sized HA whiskers with aspect ratio between 20 and 50, average particle length of 15 mum and width of 400 nm was synthesized using urea as a precipitating agent. Desired microstructure was obtained after sintering with spherical HA nanopowder and whiskers along with dopants. Addition of whiskers decreased density of the sintered compacts. However, at 10 wt% whisker content sample showed microhardness and fracture toughness of 3.6 GPa and 1.5 MPa.m1/2, respectively, and a compressive strength of 80 MPa was obtained. Mineralization study in simulated body fluid (SBF) showed formation of apatite layer on the dense HA compacts indicating a good tendency of bond formation with natural bone. Cytotoxicity results showed excellent cell attachment on the HA surface. In the Appendices, 3 journal articles have been attached which describe synthesis, processing and characterization of undoped and doped PZT nanopowders. Free standing and agglomerated PZT nanopowders were synthesized by the sucrose templated method and the citrate nitrate autocombustion method. Particle size in the range

  9. Porous hydroxyapatite-TiO2 nanocomposites from natural phosphates and their decolorization properties. Photoactive hydroxyapatite-TiO2 nanopowders

    NASA Astrophysics Data System (ADS)

    Bouyarmane, H.; Saoiabi, S.; El Hanbali, I.; El Karbane, M.; Rami, A.; Masse, S.; Laghzizil, A.; Coradin, T.

    2015-07-01

    Titanium dioxide-hydroxyapatite nanopowders were prepared by the simultaneous gelation of a titanium alkoxide and precipitation of a redisolved natural phosphate mineral. Evolution of the crystallinity, porous features and surface reactivity of these powders as a function of Ti content and heating was studied. Optimal conditions were found for the preparation of a low-cost nanocomposite powder that was as effective as pure titania for the decolorization of methylene blue solutions.

  10. nanopowders

    NASA Astrophysics Data System (ADS)

    Janbutrach, Yutana; Hunpratub, Sitchai; Swatsitang, Ekaphan

    2014-09-01

    La1 - x Al x FeO3 ( x = 0.0, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5) nanopowders were prepared by polymerization complex method. All prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and UV-vis spectrophotometry (UV-vis). The magnetic properties were investigated using a vibrating sample magnetometer (VSM). The X-ray results of all samples show the formation of an orthorhombic phase with the second phase of α-Fe2O3 in doped samples. The crystallite sizes of nanoparticles decreased with increasing Al content, and they are found to be in the range of 58.45 ± 5.90 to 15.58 ± 4.64 nm. SEM and TEM images show the agglomeration of nanoparticles with average particle size in the range of 60 to 75 nm. The FT-IR spectra confirm the presence of metal oxygen bonds of O-Fe-O and Fe-O in the FeO6 octahedra. The UV-vis spectra show strong absorption peaks at approximately 285 nm, and the calculated optical band gaps are found to be in the range of 2.05 to 2.09 eV with increasing Al content. The M-H loop of the pure sample is antiferromagnetic, whereas those of the doped samples tend to be ferromagnetic with increasing Al content. The magnetization, remanent magnetization, and coercive field of the Al-doped sample with x = 0.5 are enhanced to 1.665 emu/g, 0.623 emu/g, and 4,087.0 Oe, respectively.

  11. Synthesis, characterization and antimicrobial activity of copper and zinc-doped hydroxyapatite nanopowders

    NASA Astrophysics Data System (ADS)

    Stanić, Vojislav; Dimitrijević, Suzana; Antić-Stanković, Jelena; Mitrić, Miodrag; Jokić, Bojan; Plećaš, Ilija B.; Raičević, Slavica

    2010-08-01

    Antimicrobial materials based on hydroxyapatite are potentially attractive in a wide variety of medical applications. The synthesis of copper and zinc-doped hydroxyapatite was done by neutralization method. This method consists of dissolving CuO or ZnO in solution of H 3PO 4, and the slow addition to suspension of Ca(OH) 2 for obtaining monophasic product. Characterization studies from XRD, SEM, TEM and FTIR spectra showed that particles of all samples are of nano size and they do not contain any discernible crystalline impurity. The quantitative elemental analysis showed that the copper and zinc ions fully incorporated into the hydroxyapatite. The antimicrobial effects of doped hydroxyapatite powders against pathogen bacterial strains Escherichia coli, Staphylococcus aureus and pathogen yeast Candida albicans were tested in solid and liquid media. Quantitative test in liquid media clearly showed that copper and zinc-doped samples had viable cells reduction ability for all tested strains.

  12. Synthesis of antimicrobial monophase silver-doped hydroxyapatite nanopowders for bone tissue engineering

    NASA Astrophysics Data System (ADS)

    Stanić, Vojislav; Janaćković, Djordje; Dimitrijević, Suzana; Tanasković, Sladjana B.; Mitrić, Miodrag; Pavlović, Mirjana S.; Krstić, Aleksandra; Jovanović, Dragoljub; Raičević, Slavica

    2011-02-01

    Monophase silver-doped hydroxyapatite (AgxCa10-x(PO4)6(OH)2; 0.002 ≤ x ≤ 0.04) nanoparticles were prepared using a neutralization method and investigated with respect to potential medical applications. This method consists of dissolving Ag2O in solution of H3PO4, and the slow addition to suspension of Ca(OH)2 was applied for the purpose of homogenous distribution of silver ions. Characterization studies from XRD, TEM and FTIR spectra showed that obtained crystals are monophase hydroxyapatites and that particles of all samples are of nano size, with average length of 70 nm and about 15-25 nm in diameter. Antimicrobial studies have demonstrated that all silver-doped hydroxyapatite samples exhibit excellent antimicrobial activity in vitro against the following pathogens: Staphylococcus aureus, Escherichia coli and Candida albicans. The hydroxyapatite sample with the highest content of silver has shown the highest antimicrobial activity; killed all cells of E. coli and brought to more than 99% reduction in viable counts of S. aureus and C. albicans. The atomic force microscopic studies illustrate that silver-doped hydroxyapatite sample causes considerable morphological changes of microorganism cells which might be the cause of cells' death. Hemolysis ratios of the silver-doped hydroxyapatite samples were below 3%, indicating good blood compatibility and that are promising as biomaterials.

  13. Synthesis of fluorine substituted hydroxyapatite nanopowders and application of the central composite design for determination of its antimicrobial effects

    NASA Astrophysics Data System (ADS)

    Stanić, Vojislav; Dimitrijević, Suzana; Antonović, Dušan G.; Jokić, Bojan M.; Zec, Slavica P.; Tanasković, Sladjana T.; Raičević, Slavica

    2014-01-01

    Synthetic biomaterials based on fluorine substituted hydroxyapatite are potentially attractive for orthopedic and dental implant applications. The new synthesis of fluorine substituted hydroxyapatite samples were done by neutralization, which consists of adding the solution of HF and H3PO4 in suspension of Ca(OH)2. Characterization studies from XRD, SEM and FTIR spectra showed that crystals are obtained with apatite structure and those particles of all samples are nano size, with an average length of 80 nm and about 15-25 nm in diameter. The central composite design was used in order to determine the optimal conditions for the antimicrobial activity of the synthesized samples. In order to evaluate the influence of operating parameters on the percent of viable cell reduction of Streptococcus mutans, three independent variables were chosen: exposure time, pH of saline and floride concentration in apatite samples. The experimental and predicted antimicrobial activities were in close agreement. Antimicrobial activity of the samples increases with the increase of fluoride concentration and the decreased pH of saline. The maximum antimicrobial activity was achieved at the initial pH of 4.

  14. Rheological behavior of oxide nanopowder suspensions

    NASA Astrophysics Data System (ADS)

    Cinar, Simge

    Ceramic nanopowders offer great potential in advanced ceramic materials and many other technologically important applications. Because a material's rheological properties are crucial for most processing routes, control of the rheological behavior has drawn significant attention in the recent past. The control of rheological behavior relies on an understanding of how different parameters affect the suspension viscosities. Even though the suspension stabilization mechanisms are relatively well understood for sub-micron and micron size particle systems, this knowledge cannot be directly transferred to nanopowder suspensions. Nanopowder suspensions exhibit unexpectedly high viscosities that cannot be explained with conventional mechanisms and are still a topic of investigation. This dissertation aims to establish the critical parameters governing the rheological behavior of concentrated oxide nanopowder suspensions, and to elucidate the mechanisms by which these parameters control the rheology of these suspensions. Aqueous alumina nanopowders were chosen as a model system, and the findings were extrapolated to other oxide nanopowder systems such as zirconia, yttria stabilized zirconia, and titania. Processing additives such as fructose, NaCl, HCl, NaOH, and ascorbic acid were used in this study. The effect of solids content and addition of fructose on the viscosity of alumina nanopowder suspensions was investigated by low temperature differential scanning calorimetry (LT-DSC), rheological, and zeta potential measurements. The analysis of bound water events observed in LT-DSC revealed useful information regarding the rheological behavior of nanopowder suspensions. Because of the significance of interparticle interactions in nanopowder suspensions, the electrostatic stabilization was investigated using indifferent and potential determining ions. Different mechanisms, e.g., the effect of the change in effective volume fraction caused by fructose addition and electrostatic

  15. Incorporation of aluminum nanopowder into NTO.

    SciTech Connect

    Lee, K. Y.; Kennedy, J. E.; Peterson, P. D.; Asay, B. W.

    2004-01-01

    Most insensitive high explosives have relatively low output and the user is forced to choose between enhancing operational safety and meeting ordnance performance requirements. The goals of this project are to investigate ways to incorporate Al nanopowder in NTO and to devise formulations that are insensitive and that exhibit high performance. In this paper, the novel method for the preparation of nanoNTO and its formulation with Al nanopowder will be presented, together with the characterization test results. Data from minisandwich velocity test on NTO and NTO/Al mix and the techniques used to verify the potential encapsulation of Al in NTO will also be presented.

  16. Method of preparation of silver nanopowder

    NASA Astrophysics Data System (ADS)

    Jarosz, Mateusz; Mlozniak, Anna; Jakubowska, Malgorzata

    2010-09-01

    In recent years we observe the rapid growth of nanotechnology, including materials, technologies and devices development. Going from micro- to nanoscale can result in new, specific physicochemical, mechanical, optical, electrical, magnetic or catalytical properties. It all emerges from quantum effects and high contribution of surface atoms causing high reactivity. Among others it can cause a reduction of the melting-temperature. The goal of our work was to obtain a silver nanopowder from a thermal decomposition of silver salts of fatty acids.

  17. Production and properties of electrosprayed sericin nanopowder

    NASA Astrophysics Data System (ADS)

    Hazeri, Najmeh; Tavanai, Hossein; Moradi, Ali Reza

    2012-06-01

    Sericin is a proteinous substrate that envelops fibroin (silk) fiber, and its recovery provides significant economical and social benefits. Sericin is an antibacterial agent that resists oxidation and absorbs moisture and UV light. In powder form, sericin has a wide range of applications in food, cosmetics and drug delivery. Asides from other techniques of producing powder, such as precipitation and spray drying, electrospraying can yield solid nanoparticles, particularly in the submicron range. Here, we report the production of sericin nanopowder by electrospraying. Sericin sponge was recovered from Bombyx mori cocoons through a high-temperature, high-pressure process, followed by centrifugation and freeze drying of the sericin solution. The electrospraying solution was prepared by dissolving the sericin sponge in dimethyl sulfoxide. We demonstrate that electrospraying is capable of producing sericin nanopowder with an average particle size of 25 nm, which is by far smaller than the particles produced by other techniques. The electrosprayed sericin nanopowder consists of small crystallites and exhibits a high moisture absorbance.

  18. Preparation of hydroxyapatite/zirconia bioceramic nanocomposites for orthopaedic and dental prosthesis applications

    NASA Astrophysics Data System (ADS)

    Sung, Yun-Mo; Shin, Young-Keun; Ryu, Jae-Jun

    2007-02-01

    Homogeneous mixtures of hydroxyapatite (HAp) and yttria-stabilized zirconia (YSZ) nanoparticles were successfully synthesized using chemical co-precipitation and subsequent calcination. For the synthesis of HAp/YSZ nanopowder, the Ca/P atomic ratio was 1.73 to obtain high-content stoichiometric hydroxyapatite phase and to suppress β-tricalcium phosphate (β-TCP) formation. The agglomerated crystalline powders were milled using YSZ ball media to obtain well-separated nanoparticles. The final particle size of the HAp and YSZ was ~50-70 and ~15-30 nm, respectively. The crystallinity and morphological feature of the nanopowder was analysed using x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) analyses. The ball-milled nanopowder mixture was hot pressed at 1100 °C for 1 h under 20 MPa in vacuum atmosphere. The sintered HAp/YSZ nanocomposites exhibited approximately 99% of the theoretical density, due not only to the fine nanoscale of the particles, but also to the homogeneous distribution of the nanoparticle mixture. They also showed fine grain structures of the HAp phase due to the suppressed grain growth by YSZ particles. The nanocomposites showed improved mechanical properties, flexural strength of ~155 MPa and fracture toughness of ~2.1 MP m1/2, due to the YSZ contribution to the HAp matrix.

  19. Oxidation and melting of aluminum nanopowders.

    PubMed

    Trunov, Mikhaylo A; Umbrajkar, Swati M; Schoenitz, Mirko; Mang, Joseph T; Dreizin, Edward L

    2006-07-01

    Recently, nanometer-sized aluminum powders became available commercially, and their use as potential additives to propellants, explosives, and pyrotechnics has attracted significant interest. It has been suggested that very low melting temperatures are expected for nanosized aluminum powders and that such low melting temperatures could accelerate oxidation and trigger ignition much earlier than for regular, micron-sized aluminum powders. The objective of this work was to investigate experimentally the melting and oxidation behavior of nanosized aluminum powders. Powder samples with three different nominal sizes of 44, 80, and 121 nm were provided by Nanotechnologies Inc. The particle size distributions were measured using small-angle X-ray scattering. Melting was studied by differential scanning calorimetry where the powders were heated from room temperature to 750 degrees C in an argon environment. Thermogravimetric analysis was used to measure the mass increase indicative of oxidation while the powders were heated in an oxygen-argon gas mixture. The measured melting curves were compared to those computed using the experimental particle size distributions and thermodynamic models describing the melting temperature and enthalpy as functions of the particle size. The melting behavior predicted by different models correlated with the experimental observations only qualitatively. Characteristic stepwise oxidation was observed for all studied nanopowders. The observed oxidation behavior was well interpreted considering the recently established kinetics of oxidation of micron-sized aluminum powders. No correlation was found between the melting and oxidation of aluminum nanopowders. PMID:16805619

  20. Characterization of hydroxyapatite by time-resolved luminescence and FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Grigorjeva, L.; Millers, D.; Smits, K.; Jankovica, Dz; Pukina, L.

    2013-12-01

    Time-resolved luminescence and FTIR absorption spectra of undoped and Eu and Ce doped hydroxyapatite nanocrystalline powders prepared by sol-gel method were studied. The luminescence band at 350-400 nm was detected and two decay times (11 ns and 38 ns) was determinated for Ce doped samples. The luminescence spectra and decay kinetics were analized for Eu doped nanopowders. The Eu3+ ion was incorporated in different Ca sites. The process of energy transfer to Eu3+ excited state (5D0) was detected from luminescence decay kinetics.

  1. Preparation and reactivity of aluminum nanopowders coated by hydroxyl-terminated polybutadiene (HTPB)

    NASA Astrophysics Data System (ADS)

    Guo, Liangui; Song, Wulin; Hu, Mulin; Xie, Changsheng; Chen, Xia

    2008-02-01

    HTPB-coated aluminum (Al) nanopowders were prepared by laser-induction complex heating. The characterization of the nanopowders was revealed using transmission electronic microscopy (TEM), high-resolution transmission electronic microscopy (HRTEM), X-ray diffraction analysis (XRD) and Fourier transform infrared (FTIR) spectrometry. Results showed that HTPB-coated Al nanopowders have a core-shell structure with size ranging from 30 to 100 nm and organic HTPB exists in HTPB-coated Al nanopowders. Differential scanning calorimeter (DSC) and thermal gravimeter (TG) analysis of the HTPB-coated Al nanopowders and Al 2O 3-passivated Al nanopowders stored for 2 years in ambient environment indicated that the reactivity and stability of HTPB-coated Al nanopowders outperform Al 2O 3-passivated Al nanopowders. These findings demonstrate that HTPB is a suitable surface coating material for Al nanopowders.

  2. Growth model of binary alloy nanopowders for thermal plasma synthesis

    SciTech Connect

    Shigeta, Masaya; Watanabe, Takayuki

    2010-08-15

    A new model is developed for numerical analysis of the entire growth process of binary alloy nanopowders in thermal plasma synthesis. The model can express any nanopowder profile in the particle size-composition distribution (PSCD). Moreover, its numerical solution algorithm is arithmetic and straightforward so that the model is easy to use. By virtue of these features, the model effectively simulates the collective and simultaneous combined process of binary homogeneous nucleation, binary heterogeneous cocondensation, and coagulation among nanoparticles. The effect of the freezing point depression due to nanoscale particle diameters is also considered in the model. In this study, the metal-silicon systems are particularly chosen as representative binary systems involving cocondensation processes. In consequence, the numerical calculation with the present model reveals the growth mechanisms of the Mo-Si and Ti-Si nanopowders by exhibiting their PSCD evolutions. The difference of the materials' saturation pressures strongly affects the growth behaviors and mature states of the binary alloy nanopowder.

  3. Pulsed wire discharge apparatus for mass production of copper nanopowders.

    PubMed

    Suematsu, H; Nishimura, S; Murai, K; Hayashi, Y; Suzuki, T; Nakayama, T; Jiang, W; Yamazaki, A; Seki, K; Niihara, K

    2007-05-01

    A pulsed wire discharge (PWD) apparatus for the mass production of nanopowders has been developed. The apparatus has a continuous wire feeder, which is operated in synchronization with a discharging circuit. The apparatus is designed for operation at a maximum repetition rate of 1.4 Hz at a stored energy of 160 J. In the present study, Cu nanopowder was synthesized using the PWD apparatus and the performance of the apparatus was examined. Cu nanopowder of 2.0 g quantity was prepared in N(2) gas at 100 kPa for 90 s. The particle size distribution of the Cu nanopowder was analyzed by transmission electron microscopy and the mean surface diameter was determined to be 65 nm. The ratio of the production mass of the powder to input energy was 362 g/kW h. PMID:17552867

  4. Studies on synthesis of alumina nanopowder from synthetic Bayer liquor

    SciTech Connect

    Mazloumi, Mahyar; Arami, Hamed; Khalifehzadeh, Razieh; Sadrnezhaad, S.K. . E-mail: sadrnezh@sharif.edu

    2007-06-05

    Procedure for synthesis of alumina nanopowder from Bayer liquor (synthetic sodium aluminate solution) is investigated. Cooling, ageing and then addition of 3 ml/l Tiron (1,2-dihydroxy-3,5-benzene disulfonic acid disodium salt) to the supersaturated liquor affect purity and fineness of the nanopowder product. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray (EDAX) analyses indicate that purity of the alumina nanopowder increases with the aging time. Experimental observations show that highly pure alumina nanopowders could be produced by direct calcination of cold gelatinous sodium aluminate solution followed by careful washing at a Tiron concentration of 3 ml/l NaOH.

  5. The processing of nanopowders by thermal plasma technology

    NASA Astrophysics Data System (ADS)

    Tong, Lirong; Reddy, Ramana G.

    2006-04-01

    The thermal plasma synthesis of nanopowders is a relatively new technology with great potential for future industrial applications. This article introduces research carried out in the plasma processing laboratory at the University of Alabama in Tuscaloosa, Alabama. Ceramic nanopowders and nanofibers (SiC, TiC, and B4C) and nanocomposite powders (TiC-Al(Ti), TiC-Fe(Ti), and TiN-Fe (Ti)) were successfully synthesized by thermal plasma technology.

  6. The chemical vapor synthesis of inorganic nanopowders

    NASA Astrophysics Data System (ADS)

    Sohn, Hong Yong; Ryu, Taegong; Choi, Jin Won; Hwang, Kyu Sup; Han, Gilsoo; Choi, Young Joon; Fang, Zhigang Zak

    2007-12-01

    Chemical vapor synthesis (CVS) is a process for making fine solid particles by the vapor-phase chemical reactions of precursors. At the University of Utah, this process has been applied to the synthesis of the aluminides of titanium and nickel, other metallic and intermetallic powders, and subsequently aluminum nanopowder and WC-Co nanocomposite powder. This work has demonstrated that it is possible to prepare fine particles of 5-200 nm size by CVS. Further, it has been shown that this technique has a unique capability to produce uniformly mixed powders of different solids. This is possible because the reactants are perfectly mixed in the gas phase. More recently, the CVS process has been carried out in a plasma reactor. This system has shown considerable promise for many applications as a method of producing nanosized powders.

  7. Microemulsion synthesis and magnetic properties of hydroxyapatite-encapsulated nano CoFe2O4

    NASA Astrophysics Data System (ADS)

    Foroughi, Firoozeh; Hassanzadeh-Tabrizi, S. A.; Amighian, Jamshid

    2015-05-01

    Hydroxyapatite-encapsulated cobalt ferrite (CoFe2O4) nanopowders were synthesized by one step microemulsion method. The powders were characterized by X-ray Diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometer. TEM results showed that nanoparticles calcined at 700 °C have core-shell morphology. It was found that the resultant phases, morphology and magnetic properties of the samples depend on calcining temperature. The synthesized nanoparticles showed a maximum saturation magnetization of 7.8 emu/g with a wasp-waisted hysteresis loop. The magnetion was reduced by increasing calcining temperature to 900 °C. This reduction is due to the reaction of cobalt ferrite with hydroxyapatite which leads to CaFe12(PO4)8(OH)12 phase.

  8. Hydroxyapatite with environmental applications

    SciTech Connect

    Popa, C. L.; Ciobanu, C. S.; Predoi, D.; Petre, C. C.; Jiga, G.; Motelica-Heino, M.; Iconaru, S. L.

    2014-05-15

    The aim of this study was to synthetize new nanoparticles based on methyltrimethoxysilane coated hydroxyapatite (MTHAp) for lead removal in aqueous solutions. The morphological and compositional analysis of MTHAp was investigated by scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometer (EDS). Removal experiments of Pb{sup 2+} ions were carried out in aqueous solutions with controlled concentration of Pb{sup 2+} and at fixed pH of 5. After the removal experiment of Pb{sup 2+} ions from solutions, porous hydroxyapatite nanoparticles were transformed into PbMTHAp-5 via the adsorption of Pb{sup 2+} ions followed by a cation exchange reaction. Our results demonstrate that the porous hydroxyapatite nanoparticles can be used as an adsorbent for removing Pb{sup 2+} ions from aqueous solution.

  9. Transformations in Sol-Gel Synthesized Nanoscale Hydroxyapatite Calcined Under Different Temperatures and Time Conditions

    NASA Astrophysics Data System (ADS)

    Seema, Kapoor; Uma, Batra; Suchita, Kohli

    2012-08-01

    Nano-hydroxyapatite (HAP) has been synthesized using sol-gel technique. Calcium nitrate tetrahydrate and potassium dihydrogen phosphate were used as precursors for calcium and phosphorus, respectively. A detailed study on its transformation during calcination at two crucial temperatures has been undertaken. The synthesized nanopowder was calcined at 600 and 800 °C for different time periods. The results revealed that the obtained powders after calcining at 600 and 800 °C are composed of hydroxyapatite nanoparticles. The nano-HAP powders were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, thermal gravimetric analysis (TGA), and BET surface area analyzer techniques. The results indicate that crystallite size as well as crystallinity of synthesized HAP nanopowders increase with increase in calcination temperature as well as calcination time, but the effect of temperature is more prominent as compared to that of calcination time. TEM micrograph revealed the presence of majority of HAP powder particles as agglomerates and a few as individual particles. It also revealed that HAP produced after sintering at 600 °C is 26-45 nm in size, which is well in agreement with the crystallite size calculated using XRD data. TGA study showed the thermal stability of the as-synthesized nano-HAP powder. The BET surface area decreased with increase in calcination temperature and time. The results clearly demonstrate the significant role of calcination parameters on the characteristics of nano-HAP powders.

  10. Characterization of porous hydroxyapatite.

    PubMed

    Hing, K A; Best, S M; Bonfield, W

    1999-03-01

    Hydroxyapatite has been considered for use in the repair of osseous defects for the last 20 years. Recent developments have led to interest in the potential of porous hydroxyapatite as a synthetic bone graft. However, despite considerable activity in this field, regarding assessment of the biological response to such materials, the basic materials characterization is often inadequate. This paper documents the characterization of the chemical composition, mechanical integrity, macro- and microstructure of a porous hydroxyapatite, Endobon (E. Merck GmbH), intended for the bone-graft market. Specimens possesed a range of apparent densities from 0.35 to 1.44 g cm(-3). Chemical analysis demonstrated that the natural apatite precursor of Endobon was not converted to pure hydroxyapatite, but retained many of the ionic substituents found in bone mineral, notably carbonate, sodium and magnesium ions. Investigation of the microstructure illustrated that the struts of the material were not fully dense, but had retained some traces of the network of osteocyte lacunae. Macrostructural analysis demonstrated the complex inter-relationship between the structural features of an open pore structure. Both pore size and connectivity were found to be inversely dependent on apparent density. Furthermore, measurement of pore aspect ratio and orientation demonstrated a relationship between apparent density and the degree of macrostructural anisotropy within the specimens, while, it was also noted that pore connectivity was sensitive to anisotropy. Compression testing demonstrated the effect of apparent density and macrostructural anisotropy on the mechanical properties. An increase in apparent density from 0.38 to 1.25 g cm(-3) resulted in increases in ultimate compressive stress and compressive modulus of 1 to 11 MPa and 0.2 to 3.1 GPa, respectively. Furthermore, anisotropic high density (> 0.9 g cm(-3)) specimens were found to possess lower compressive moduli than isotropic specimens

  11. Characterisations of collagen-silver-hydroxyapatite nanocomposites

    NASA Astrophysics Data System (ADS)

    Ciobanu, C. S.; Popa, C. L.; Petre, C. C.; Jiga, G.; Trusca, R.; Predoi, D.

    2016-05-01

    The XRD analysis were performed to confirm the formation of hydroxyapatite structure in collagen-silver-hydroxyapatite nanocomposites. The molecular interaction in collagen-hydroxyapatite nanocomposites was highlighted by Fourier transform infrared spectroscopy (FTIR) analysis. The SEM showed a nanostructure of collagen-silverhydroxyapatite nanocomposites composed of nano needle-like particles in a veil with collagen texture. The presence of vibrational groups characteristics to the hydroxyapatite structure in collagen-silver-hydroxyapatite (AgHApColl) nanocomposites was investigated by FTIR.

  12. Ignition and explosion of nanopowders: something new under the dust

    NASA Astrophysics Data System (ADS)

    Dufaud, Olivier; Vignes, Alexis; Henry, François; Perrin, Laurent; Bouillard, Jacques

    2011-07-01

    This work deals with the study of ignition and explosion characteristics of nanoparticles. It has been carried out on various powders: zinc, aluminum, carbon blacks... Specific behaviours have been highlighted during the first phase of this project (Nanosafe 2). For instance, it has been demonstrated that there mainly exists two combustion regimes that are either kinetically controlled, for small size particles, or diffusion controlled, for large size particles (generally with diameters greater than 1 or 2 μm). It has been found that as the particle size decreases, minimum ignition temperature and minimum ignition energy decrease (even lower than 1 mJ), indicating higher potential inflammation and explosion risks for metallic nanopowders. Moreover, the presence of agglomerates in the nanopowders could modify their reactivity. Thus, the explosion severity of Al powders tends to increase as the specific surface area decreases, before reaching a peak for 1 μm particle size. These results are essential for industries producing or handling nanopowders in order to propose/design new and proper prevention and protection means. Nevertheless, the validity of the classical characterization tools with regard to nanopowders should be discussed. For example, the experimental laminar flame velocity of Al dusts has been compared to a theoretical one, determined by Huang's model, which assumes that the propagation of the flame is run mainly by conduction. It has shown a good agreement. However, under certain conditions, the Al flame propagation is expected to be mainly conducted by radiation. Two hypotheses can then be made. On the one hand, it can be assumed that the 20 L sphere probably disturbs the flame propagation and thermal mechanisms by absorbing radiation (wall quenching effect). On the other hand, it has been observed, thanks to the use of a high speed camera that the preheating zone is smaller for some nanopowders than for micro-particles (figure below). It could

  13. Laser transfer of diamond nanopowder induced by metal film blistering

    NASA Astrophysics Data System (ADS)

    Kononenko, T. V.; Alloncle, P.; Konov, V. I.; Sentis, M.

    2009-03-01

    Blister-based laser induced forward transfer (BB-LIFT) is a promising technique to produce surface microstructures of various advanced materials including inorganic and organic micro/nanopowders, suspensions and biological micro-objects embedded in life sustaining medium. The transferred material is spread over a thin metal film irradiated from the far side by single laser pulses through a transparent support. Interaction of the laser pulse with the metal-support interface under optimized conditions causes formation of a quickly expanding blister. Fast movement of the free metal surface provides efficient material transfer, which has been investigated for the case of diamond nanopowder and diamond-containing suspension. The unique features of the given technique are universality, simplicity and efficient isolation of the transferred material from the ablation products and laser heating.

  14. Raman scattering and luminescence of yttria nanopowders and ceramics

    NASA Astrophysics Data System (ADS)

    Osipov, V. V.; Solomonov, V. I.; Spirina, A. V.; Vovkotrub, E. G.; Strekalovskii, V. N.

    2014-06-01

    We have studied Raman scattering in yttria nanopowders and ceramics that was excited by radiation at wavelengths of 514.5 and 632.8 nm. We show that, in undoped nanopowders and cubic phase of doped yttria ceramics, only the Raman scattering by phonons is observed, with no other Raman scattering centers having been revealed. In nanopowders of the monoclinic phase, we have observed an additional Raman line with a Raman shift of 1093 ± 4 cm-1. If all the objects under investigation are excited by the radiation at a wavelength of 514.5 nm, their spectra exhibit four series of photoluminescence lines, two of which (at λ = 521-523 and 538-564 nm) are emitted by Er3+ ions, "impurity" dopants, while the other two lines (at λ = 607-635 and 644-684 nm) are emitted by intrinsic centers. Under excitation by the radiation at a wavelength of 632.8 nm, only a series of bands at λ = 644-684 nm is emitted. In addition to these photoluminescence bands, neodymium-doped ceramics show photoluminescence bands of Nd3+ ions. We have shown that intrinsic luminescence centers, which occur in all the examined specimens, are capable of acting as acceptors with respect to neodymium ions excited to the upper laser level.

  15. Synthesis and Photoluminescence Properties of SnO2 Nanopowder

    NASA Astrophysics Data System (ADS)

    Arai, Takahiro; Adachi, Sadao

    2012-10-01

    SnO2 nanopowder was synthesized by calcining metastannic salt (SnO2·H2O) prepared by chemically etching metallic Sn in aqueous HNO3 solution. The calcined SnO2 nanopowder was investigated by X-ray diffraction (XRD) measurement and photoluminescence (PL) spectroscopy. The XRD and PL intensities increased with increasing calcining temperature, yielding an activation energy of ˜0.65 eV. The PL spectra of the calcined SnO2 nanopowder exhibited green (G) and red (R) emission bands with peaks at ˜2.5 and ˜2.0 eV, respectively, that were clearly dependent not only on the excitation light wavelength but also on the sample temperature. The temperature dependence of the PL intensity between 20 and 300 K was explained by the thermal quenching with activation energies of ˜15 meV (T=20-60 K) and ˜0.12-0.18 eV (T ≥100 K). The G and R emission states were found to originate from the Jahn-Teller effect of the 5s2 (Sn2+) ions in the SnO2 matrix and were similar to those generally observed in many ns2-doped alkali halides and SnCl2.

  16. Hydroxyapatite for Keratoprosthesis Biointegration

    PubMed Central

    Wang, Liqiang; Jeong, Kyung Jae; Chiang, Homer H.; Zurakowski, David; Behlau, Irmgard; Chodosh, James; Dohlman, Claes H.; Langer, Robert

    2011-01-01

    Purpose. Integration of keratoprosthesis with the surrounding cornea is very important in preventing bacterial invasion, which may cause ocular injury. Here the authors investigated whether hydroxyapatite (HAp) coating can improve keratoprosthesis (KPro) biointegration, using polymethyl methacrylate (PMMA)—the principal component of the Boston KPro—as a model polymer. Methods. HAp coatings were induced on PMMA discs after treatment with concentrated NaOH and coating with poly-dopamine (PDA) or polydopamine and then with 11-mercaptoundecanoic acid (11-MUA). Coatings were characterized chemically (Fourier transform infrared spectroscopy [FTIR], energy dispersive X-ray spectroscopy [EDX]) and morphologically (SEM) and were used as substrates for keratocyte growth in vitro. Cylinders of coated PMMA were implanted in porcine corneas ex vivo for 2 weeks, and the force required to pull them out was measured. The inflammatory reaction to coated discs was assessed in the rabbit cornea in vivo. Results. FTIR of the coatings showed absorption bands characteristic of phosphate groups, and EDX showed that the Ca/P ratios were close to those of HAp. By SEM, each method resulted in morphologically distinct HAp films; the 11-MUA group had the most uniform coating. The hydroxyapatite coatings caused comparable enhancement of keratocyte proliferation compared with unmodified PMMA surfaces. HAp coating significantly increased the force and work required to pull PMMA cylinders out of porcine corneas ex vivo. HAp coating of implants reduced the inflammatory response around the PMMA implants in vivo. Conclusions. These results are encouraging for the potential of HAp-coated surfaces for use in keratoprostheses. PMID:21849419

  17. Magnesium incorporation into hydroxyapatite.

    PubMed

    Laurencin, Danielle; Almora-Barrios, Neyvis; de Leeuw, Nora H; Gervais, Christel; Bonhomme, Christian; Mauri, Francesco; Chrzanowski, Wojciech; Knowles, Jonathan C; Newport, Robert J; Wong, Alan; Gan, Zhehong; Smith, Mark E

    2011-03-01

    The incorporation of Mg in hydroxyapatite (HA) was investigated using multinuclear solid state NMR, X-ray absorption spectroscopy (XAS) and computational modeling. High magnetic field (43)Ca solid state NMR and Ca K-edge XAS studies of a ∼10% Mg-substituted HA were performed, bringing direct evidence of the preferential substitution of Mg in the Ca(II) position. (1)H and (31)P solid state NMR show that the environment of the anions is disordered in this substituted apatite phase. Both Density Functional Theory (DFT) and interatomic potential computations of Mg-substituted HA structures are in agreement with these observations. Indeed, the incorporation of low levels of Mg in the Ca(II) site is found to be more favourable energetically, and the NMR parameters calculated from these optimized structures are consistent with the experimental data. Calculations provide direct insight in the structural modifications of the HA lattice, due to the strong contraction of the M⋯O distances around Mg. Finally, extensive interatomic potential calculations also suggest that a local clustering of Mg within the HA lattice is likely to occur. Such structural characterizations of Mg environments in apatites will favour a better understanding of the biological role of this cation. PMID:21144581

  18. Cements from nanocrystalline hydroxyapatite.

    PubMed

    Barralet, J E; Lilley, K J; Grover, L M; Farrar, D F; Ansell, C; Gbureck, U

    2004-04-01

    Calcium phosphate cements are used as bone substitute materials because they may be moulded to fill a void or defect in bone and are osteoconductive. Although apatite cements are stronger than brushite cements, they are potentially less resorbable in vivo. Brushite cements are three-component systems whereby phosphate ions and water react with a soluble calcium phosphate to form brushite (CaHPO4 x 2H2O). Previously reported brushite cement formulations set following the mixture of a calcium phosphate, such as beta-tricalcium phosphate (beta-TCP), with an acidic component such as H3PO4 or monocalcium phosphate monohydrate (MCPM). Due to its low solubility, hydroxyapatite (HA) is yet to be reported as a reactive component in calcium phosphate cement systems. Here we report a new cement system setting to form a matrix consisting predominantly of brushite following the mixture of phosphoric acid with nanocrystalline HA. As a result of the relative ease with which ionic substitutions may be made in apatite this route may offer a novel way to control cement composition or setting characteristics. Since kinetic solubility is dependent on particle size and precipitation temperature is known to affect precipitated HA crystal size, the phase composition and mechanical properties of cements made from HA precipitated at temperatures between 4 and 60 degrees C were investigated. PMID:15332608

  19. Hydroxyapatite in Physiological Environment

    NASA Astrophysics Data System (ADS)

    Slepko, Alexander; Demkov, Alexander A.

    2011-03-01

    A carbonated form of hydroxyapatite (HA) [ Ca 10 (PO4)6 (OH)2 ] is one of the most abundant materials in mammal bone. It crystallizes within the spaces between tropocollagen protein chains in an aqueous solution and strengthens the bone tissue. An emerging application of synthetic HA is bone repair and replacement. Bulk electronic and chemical properties of HA were studied theoretically recently. However, the absorption of H2 O molecules and amino acids of the tropocollagen chains at HA surfaces remains an area of active research. Using density functional theory we analyze the electronic properties and surface energetics of HA for different orientations and terminations and generate a theoretical surface phase diagram of HA. The reactivity of these surface models is analyzed using the frontier orbital approach. We find two dominant surfaces which are most stable over the widest chemical range. However, we expect them to show little surface reactivity. Using a HA slab with a highly reactive surface we build atomistic models of HA covered with up to one monolayer of water and analyze interactions between this surface and the water molecules.

  20. Synthesis, characterization and luminescence properties of Eu3+-doped hydroxyapatite nanocrystal and the thermal treatment effects

    NASA Astrophysics Data System (ADS)

    Silva, Flávia R. O.; de Lima, Nelson B.; Bressiani, Ana Helena A.; Courrol, Lilia C.; Gomes, Laércio

    2015-09-01

    In this work, we present the synthesis, characterization and the luminescence properties of Ca10(PO4)6(OH)2 (hydroxyapatite/HAp) nanocrystals doped with europium trivalent ions. The most important processes that lead to europium emissions in the visible region were identified. Eu:HAp nanopowder excited at 394 nm (or 460 nm) exhibits several emissions: (i) weak emissions at 579 nm, 592 nm and 616 nm due to the 5D0 → 7F0, 5D0 → 7F1 and 5D0 → 7F2 transitions, respectively, with europium ion occupying site I in hydroxyapatite structure and (ii) strong emissions due to the 5D0 → 7F0 (574 nm), 5D0 → 7F1 (602 nm) and 5D0 → 7F2 (610-630 nm) transitions, when Eu3+ is occupying site II. The emission spectrum and the time-resolved luminescence analysis showed that the HAp nanocrystals (nanopowder) thermally treated at temperature (T) between 500 and 800 °C have a change in the initial Eu3+ site distribution of 100 % of Eu3+ at site I to a more stable one where the majority of europium ions are at site II: 30% remains at site I and 70% migrates to site II. In addition, an enhancement of the Eu3+ emission intensity is observed due to the increasing crystallite size. A time-resolved luminescence investigation using a short pulse laser excitation at 460 nm was employed to measure the luminescence decays and to determine the most important mechanisms involved in the deexcitation process of 5D0 excited state of Eu3+, where it is seen a fast (2.9 μs) energy transfer from Eu3+- site I (donor) to Eu3+- site II (acceptor) in the thermally treated nanopowders with T > 500 °C. The initial presence of 100% of Eu3+ at site I in the synthesized nanocrystals is gradually modified by the thermal treatments with temperatures above 500 °C by thermal activation of Ca2+ vacancy (the charge compensator) diffusion through the HAp lattice, which propitiates the Ca2+- vacancies and Eu3+ ions to exchange positions in the lattice. By this thermal activated mechanism, Eu3+ ion migrates

  1. Green upconversion in Y2O3:Yb nanopowder

    NASA Astrophysics Data System (ADS)

    Horvat, Darja; Lazar, Dušan; Možina, Janez; Križan, Janez; Diaci, Janez; Terzić, Mira

    2015-01-01

    Green emission lines, in addition to the blue and the red, were observed upon 980 nm excitation in yttrium oxide (Y2O3) nanopowder codoped with Yb and Tm, synthesized by the chemical combustion method. Upconversion emission studies suggest that the number and characteristics of the green lines are influenced by the annealing temperature as well as by the Yb/Tm concentration ratio, opening possibilities for new customized applications. The chromaticity properties of the upconversion spectra were quantified by the Commission Internationale de l'éclairage coordinate analysis.

  2. Synthesis, characterization and gas sensing properties of tin oxide nanopowder

    NASA Astrophysics Data System (ADS)

    Choudhary, Meenakshi; Mishra, V. N.; Dwivedi, R.

    2013-06-01

    In the present work, tin oxide nanopowder has been synthesized by solid-state reaction technique. The as-prepared pure and palladium doped (0.5 and 1%) powders have been used for the fabrication of thick film sensors. The influence of particle size of powders and morphology of the thick films has been studied on the sensing performance of thick film sensor. It is observed that the sensors produced from the SnO2 doped with 1% palladium have an excellent ability for the detection of hydrogen gas.

  3. Incorporation of chromium into TiO{sub 2} nanopowders

    SciTech Connect

    Kollbek, Kamila; Sikora, Marcin; Kapusta, Czesław; Szlachetko, Jakub; Radecka, Marta; Lyson-Sypien, Barbara; Zakrzewska, Katarzyna

    2015-04-15

    Highlights: • Nanopowders of TiO{sub 2}:Cr with different amount of Cr dopant were obtained by flame spray synthesis, FSS. • Increase in the optical absorption and a shift of the absorption edge were observed upon Cr doping. • HERFD-XANES measurements indicated that the average valence state of titanium ions was preserved. • Increasing magnetic susceptibility of a paramagnetic character was observed upon Cr doping. - Abstract: The paper reports on the results of a study of optical, electronic and magnetic properties of TiO{sub 2} nanopowders doped with Cr ions. Diffused reflectance spectra reveal an increase in the optical absorption and a shift of the absorption edge towards lower energies upon Cr doping. Direct information on the Ti electronic state and the symmetry of its nearest environment is obtained from XANES Ti K-edge spectra. Magnetic behaviour is probed by means of the temperature dependence of DC magnetic susceptibility. Increasing magnetic susceptibility of a paramagnetic character is observed upon increasing chromium doping. The Curie constant of TiO{sub 2}:10 at.% Cr sample (0.12 emu K/mol Oe) is lower than that expected for Cr{sup 3+} (0.1875 emu K/mol Oe) possibly due to the appearance of Cr{sup 4+} or the presence of the orbital contribution to the magnetic moment.

  4. Hydroxyapatite ceramics from hydrothermally prepared powders

    SciTech Connect

    Lin, C.H.; Huang, C.W.; Chang, S.C.

    1994-12-31

    Hydroxyapatite (Ca{sub 5}(PO{sub 4}){sub 3}(OH)) is an effective material for artificial human bone production. Hydroxyapatite powders were hydrothermally produced in this work by reacting Ca(OH){sub 2} with Na{sub 3}PO{sub 4}{center_dot}12H{sub 2}O in an autoclave at various temperature and for various times. The particle size of hydroxyapatite was observed to be very fine, uniform, around 50 nm, as well as independent of reaction time. The hydroxyapatite powders were compacted and sintered at various temperatures for 2 hrs. The density, grain size, and hardness of the hydroxyapatite ceramics were measured and compared with those of the hydroxyapatite ceramics produced by the powders from the commercial source. The hydroxyapatite ceramics from the hydrothermal powders were found to have a higher density, smaller grain size, and higher hardness. After the hydroxyapatite ceramics were dipped in a simulated biological body liquid for 10 days, the density and hardness of the hydroxyapatite ceramics from the hydrothermal powders were less deteriorated than those of the hydroxyapatite ceramics from the commercial powder.

  5. Spark plasma sintering of alumina nanopowders produced by electrical explosion of wires.

    PubMed

    An, Vladimir; Khasanov, Alexey; de Izarra, Charles

    2015-01-01

    Alumina nanopowders produced by electrical explosion of wires were sintered using the spark plasma sintering technique. The results of XRD analysis show that the main phase in the compacted nanopowders is α-Al2O3. According to the SEM observations, the sintered alumina nanopowder consists of micron-sized faceted grains and nano-sized necked grains. The increase in sintering temperature resulted in a higher density of the sintered powders: from 78.44 to 98.21 % of theoretical density. PMID:26543716

  6. Coralline hydroxyapatite in complex acetabular reconstruction.

    PubMed

    Wasielewski, Ray C; Sheridan, Kate C; Lubbers, Melissa A

    2008-04-01

    This retrospective study examined whether a coralline hydroxyapatite bone graft substitute adequately repaired bone defects during complex acetabular reconstructions. Seventeen patients who underwent acetabular revision using Pro Osteon 500 were assessed to determine whether any cups required re-revision, whether bone had incorporated into the coralline hydroxyapatite grafts, and whether the coralline hydroxyapatite grafts resorbed with time. At latest follow-up, no cups required re-revision, but 1 had failed. Radiographic evidence of bone incorporation was observed in every coralline hydroxyapatite graft. Graft resorption was not observed. PMID:19292282

  7. Crystallization of modified hydroxyapatite on titanium implants

    NASA Astrophysics Data System (ADS)

    Golovanova, O. A.; Izmailov, R. R.; Ghyngazov, S. A.; Zaits, A. V.

    2016-02-01

    Carbonated-hydroxyapatite (CHA) and Si-hydroxyapatite (Si-HA) precipitation have been synthesized from the model bioliquid solutions (synovial fluid and SBF). It is found that all the samples synthesized from the model solutions are single-phase and represent hydroxyapatite. The crystallization of the modified hydroxyapatite on alloys of different composition, roughness and subjected to different treatment techniques was investigated. Irradiation of the titanium substrates with the deposited biomimetic coating can facilitate further growth of the crystal and regeneration of the surface.

  8. Synthesis and characterization of porous hydroxyapatite and hydroxyapatite coatings

    SciTech Connect

    Nieh, T G; Choi, B W; Jankowski, A F

    2000-10-25

    A technique is developed to construct bulk hydroxyapatite (HAp) with different cellular structures. The technique involves the initial synthesis of nanocrystalline hydroxyapatite powder from an aqueous solution using water-soluble compounds and then followed by spray drying into agglomerated granules. The granules were further cold pressed and sintered into bulks at elevated temperatures. The sintering behavior of the HAp granules was characterized and compared with those previously reported. Resulting from the fact that the starting HAp powders were extremely fine, a relatively low activation energy for sintering was obtained. In the present study, both porous and dense structures were produced by varying powder morphology and sintering parameters. Porous structures consisting of open cells were constructed. Sintered structures were characterized using scanning electron microscopy and x-ray tomography. In the present paper, hydroxyapatite coatings produced by magnetron sputtering on silicon and titanium substrates will also be presented. The mechanical properties of the coatings were measured using nanoindentation techniques and microstructures examined using transmission electron microscopy.

  9. Chemical vapor synthesis and characterization of aluminum nanopowder

    NASA Astrophysics Data System (ADS)

    Choi, Jin Won; Sohn, Hong Yong; Choi, Young Joon; Fang, Zhigang Zak

    Aluminum is a component in many promising hydrogen storage materials such as aluminum hydride and complex aluminum hydrides. In this research, Al and TiAl 3-containing Al nanopowders were prepared by a chemical vapor synthesis (CVS) process using Mg as the reducing agent. XRD and EDS results indicated that the produced powder was composed of Al or Al with TiAl 3. The shape of the powder was spherical with the average size in the range of 10-50 nm measured by SEM, TEM, BET and ZetaPALS compared with the typically larger than 100 nm for commercially available fine Al powders. In addition, the effects of the operating conditions such as Ar flow rate, precursor feed rate and reaction temperature on the properties of the product powder were investigated.

  10. Cementless Hydroxyapatite Coated Hip Prostheses

    PubMed Central

    Herrera, Antonio; Mateo, Jesús; Gil-Albarova, Jorge; Lobo-Escolar, Antonio; Ibarz, Elena; Gabarre, Sergio; Más, Yolanda

    2015-01-01

    More than twenty years ago, hydroxyapatite (HA), calcium phosphate ceramics, was introduced as a coating for cementless hip prostheses. The choice of this ceramic is due to its composition being similar to organic apatite bone crystals. This ceramic is biocompatible, bioactive, and osteoconductive. These qualities facilitate the primary stability and osseointegration of implants. Our surgical experience includes the implantation of more than 4,000 cementless hydroxyapatite coated hip prostheses since 1990. The models implanted are coated with HA in the acetabulum and in the metaphyseal area of the stem. The results corresponding to survival and stability of implants were very satisfactory in the long-term. From our experience, HA-coated hip implants are a reliable alternative which can achieve long term survival, provided that certain requirements are met: good design selection, sound choice of bearing surfaces based on patient life expectancy, meticulous surgical technique, and indications based on adequate bone quality. PMID:25802848

  11. Effect of deposition parameters on the structural properties of ZnO nanopowders prepared by microwave-assisted hydrothermal synthesis

    NASA Astrophysics Data System (ADS)

    Caglar, Yasemin; Gorgun, Kamuran; Aksoy, Seval

    2015-03-01

    ZnO nanopowders were synthesized via microwave-assisted hydrothermal method at different deposition (microwave irradiation) times and pH values. The effects of pH and deposition (microwave irradiation) time on the crystalline structure and orientation of the ZnO nanopowders have been investigated by X-ray diffraction (XRD) study. XRD observations showed that the crystalline quality of ZnO nanopowders increased with increasing pH value. The crystallite size and texture coefficient values of ZnO nanopowders were calculated. The structural quality of ZnO nanopowder was improved by deposition parameters. Field emission scanning electron microscope (FESEM) was used to analyze the surface morphology of the ZnO nanopowders. Microwave irradiation time and pH value showed a significant effect on the surface morphology.

  12. Structural and physical properties of antibacterial Ag-doped nano-hydroxyapatite synthesized at 100°C

    PubMed Central

    2011-01-01

    Synthesis of nanosized particle of Ag-doped hydroxyapatite with antibacterial properties is in the great interest in the development of new biomedical applications. In this article, we propose a method for synthesized the Ag-doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionized water. Other phase or impurities were not observed. Silver-doped hydroxyapatite nanoparticles (Ag:HAp) were performed by setting the atomic ratio of Ag/[Ag + Ca] at 20% and [Ca + Ag]/P as 1.67. The X-ray diffraction studies demonstrate that powders made by co-precipitation at 100°C exhibit the apatite characteristics with good crystal structure and no new phase or impurity is found. The scanning electron microscopy (SEM) observations suggest that these materials present a little different morphology, which reveals a homogeneous aspect of the synthesized particles for all samples. The presence of calcium (Ca), phosphor (P), oxygen (O), and silver (Ag) in the Ag:HAp is confirmed by energy dispersive X-ray (EDAX) analysis. FT-IR and FT-Raman spectroscopies revealed that the presence of the various vibrational modes corresponds to phosphates and hydroxyl groups. The strain of Staphylococcus aureus was used to evaluate the antibacterial activity of the Ca10-xAgx(PO4)6(OH)2 (x = 0 and 0.2). In vitro bacterial adhesion study indicated a significant difference between HAp (x = 0) and Ag:HAp (x = 0.2). The Ag:Hap nanopowder showed higher inhibition. PMID:22136671

  13. Electron microscopy of biomaterials based on hydroxyapatite

    SciTech Connect

    Suvorova, E. I. Klechkovskaya, V. V.; Komarov, V. F.; Severin, A. V.; Melikhov, I. V.; Buffat, P. A.

    2006-10-15

    Three types of biomaterials based on hydroxyapatite are synthesized and investigated. Hydroxyapatite nanocrystals or microcrystals precipitated from low-temperature aqueous solutions serve as the initial material used for preparing spherical porous granules approximately 300-500 {mu}m in diameter. Sintering of hydroxyapatite crystals at a temperature of 870 deg. C for 2 h or at 1000 deg. C (for 3 h) + 1200 deg. C (for 2 h) brings about the formation of solid ceramics with different internal structures. According to the electron microscopic data, the ceramic material prepared at 870 deg. C is formed by agglomerated hydroxyapatite nanocrystals, whereas the ceramics sintered at 1200 deg. C (with a bending strength of the order of 100 MPa) are composed of crystal blocks as large as 2 {mu}m. It is established that all the biomaterials have a single-phase composition and consist of the hydroxyapatite with a structure retained up to a temperature of 1200 deg. C.

  14. Mechanical and cytotoxicity evaluation of nanostructured hydroxyapatite-bredigite scaffolds for bone regeneration.

    PubMed

    Eilbagi, Marjan; Emadi, Rahmatollah; Raeissi, Keyvan; Kharaziha, Mahshid; Valiani, Ali

    2016-11-01

    Despite the attractive characteristics of three-dimensional pure hydroxyapatite (HA) scaffolds, due to their weak mechanical properties, researches have focused on the development of composite scaffolds via introducing suitable secondary components. The aim of this study was to develop, for the first time, three-dimensional HA-bredigite (Ca7MgSi4O16) scaffolds containing various amounts of bredigite nanopowder (0, 5, 10 and 15wt.%) using space holder technique. Transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction spectroscopy were applied in order to study the morphology, fracture surface and phase compositions of nanopowders and scaffolds. Furthermore, the effects of scaffold composition on the mechanical properties, bioactivity, biodegradability, and cytotoxicity were also evaluated. Results showed that the composite scaffolds with average pore size in the range of 220-310μm, appearance porosity of 63.1-75.9% and appearance density of 1.1±0.04g/cm(3) were successfully developed, depending on bredigite content. Indeed, the micropore size of the scaffolds reduced with increasing bredigite content confirming that the sinterability of the scaffolds was improved. Furthermore, the compression strength and modulus of the scaffolds significantly enhanced via incorporation of bredigite content from 0 to 15wt.%. The composite scaffolds revealed superior bioactivity and biodegradability with increasing bredigite content. Moreover, MTT assay confirmed that HA-15wt.% bredigite scaffold significantly promoted cell proliferation compared to tissue culture plate (control) and HA scaffold. Based on these results, three-dimensional HA-bredigite scaffolds could be promising replacements for HA scaffolds in bone regeneration. PMID:27524060

  15. Synthesis and spectral characterizations of trivalent ions (Cr3+, Fe3+) doped CdO nanopowders.

    PubMed

    Aswani, T; Babu, B; Manjari, V Pushpa; Stella, R Joyce; Rao, G Thirumala; Krishna, Ch Rama; Ravikumar, R V S S N

    2014-01-01

    Trivalent transition metal ions (Cr(3+), Fe(3+)) doped CdO nanopowders via sonication in the presence of Sodium lauryl sulfate as stabilizing agent were synthesized and characterized. Powder XRD studies indicate that the obtained CdO has a cubic phase and concluded that the trivalent ions doping induced the lattice constants to change some extent. Optical absorption spectra exhibited the characteristic bands of Cr(3+) and Fe(3+) ions in octahedral site symmetry. Crystal field (Dq) and inter-electronic repulsion (B and C) parameters are evaluated for Cr(3+) doped CdO nanopowders as Dq=1540, B=619 and C=3327 cm(-1) and for Fe(3+) doped CdO nanopowders Dq=920, B=690, C=2750 cm(-1). EPR spectra of the Cr(3+) and Fe(3+) doped CdO nanopowders exhibited resonances at g=1.973 and g=2 respectively which indicate distorted octahedral site for both ions with the host. Photoluminescence spectra shows the emission bands in violet and bluish green regions for Cr(3+) doped CdO, ultraviolet and blue emissions for Fe(3+) doped CdO nanopowders. The CIE chromaticity coordinates were also evaluated from the emission spectrum. FT-IR spectra indicate the presence of various functional groups of host lattice. PMID:24291431

  16. Preparation, structural and linear optical properties of Zn doped CdS nanopowders

    NASA Astrophysics Data System (ADS)

    Sekhar, H.; Rakesh Kumar, Y.; Narayana Rao, D.

    2015-02-01

    A series of Zn doped cadmium sulfide (CdS:Zn) nanopowders were prepared by a simple co-precipitation method at room temperature by mixing the stoichiometric amount of reactants in a Milli Q water solvent. The composition of nanopowders was accurately adjusted by controlling the molar ratio of Cd, Zn acetate in the mixed reactants. Spectroscopic studies on as prepared nanopowders were investigated by using XRD, Raman, UV-Vis absorption, FE- SEM-EDAX and photoluminescence. Extremely broad reflections of XRD peaks of as prepared powders establish the nanometer scale dimensions and cubic structure. Doping with Zn in CdS does not lead to any structural phase transformation but introduces a decrease in the lattice constants. Two characteristics of LO phonon peaks were observed in pure and Zn doped CdS samples. Raman peaks of Zn doped CdS nanopowders shifts slightly towards higher energy side compared to the pure CdS nanopowders. Exciton-phonon confinement factor (S) varies in between 0.3-0.4. At lower wavelength excitation we observed a broad emission peak maximum centered at 404 nm is attributed to localized band edge emission.

  17. Shock induced reaction of Ni/Al nanopowder mixture.

    PubMed

    Meng, C M; Wei, J J; Chen, Q Y

    2012-11-01

    Nanopowder Ni/Al mixture (mixed in Al:Ni = 2:1 stoichiometry) was shock compressed by employing single and two-stage light gas gun. The particle size of Al and Ni are 100-200 nm and 50-70 nm respectively, morphologies of Al and Ni are sphere like either. Recovered product was characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. According to the XRD spectrum, the mixed powder undergo complete reaction under shock compression, reaction product consist of Ni2Al3, NiAl and corundum structure Al2O3 compound. Grain size of Ni-Al compound is less than 100 nm. With the shock pressure increasing, the ratio of Ni2Al3 decreased obviously. The corundum crystal size is 400-500 nm according to the SEM observation. The results of shock recovery experiments and analysis show that the threshold pressure for reaction of nano size powder Ni/Al mixture is much less than that of micro size powder. PMID:23421276

  18. Nanopowder production by gas-embedded electrical explosion of wire

    NASA Astrophysics Data System (ADS)

    Zou, Xiao-Bing; Mao, Zhi-Guo; Wang, Xin-Xin; Jiang, Wei-Hua

    2013-04-01

    A small electrical explosion of wire (EEW) setup for nanopowder production is constructed. It consists of a low inductance capacitor bank of 2 μF-4 μF typically charged to 8 kV-30 kV, a triggered gas switch, and a production chamber housing the exploding wire load and ambient gas. With the EEW device, nanosize powders of titanium oxides, titanium nitrides, copper oxides, and zinc oxides are successfully synthesized. The average particle size of synthesized powders under different experimental conditions is in a range of 20 nm-80 nm. The pressure of ambient gas or wire vapor can strongly affect the average particle size. The lower the pressure, the smaller the particle size is. For wire material with relatively high resistivity, such as titanium, whose deposited energy Wd is often less than sublimation energy Ws due to the flashover breakdown along the wire prematurely ending the Joule heating process, the synthesized particle size of titanium oxides or titanium nitrides increases with overheat coefficient k (k = Wd/Ws) increasing.

  19. A System to Create Stable Nanoparticle Aerosols from Nanopowders.

    PubMed

    Ding, Yaobo; Riediker, Michael

    2016-01-01

    Nanoparticle aerosols released from nanopowders in workplaces are associated with human exposure and health risks. We developed a novel system, requiring minimal amounts of test materials (min. 200 mg), for studying powder aerosolization behavior and aerosol properties. The aerosolization procedure follows the concept of the fluidized-bed process, but occurs in the modified volume of a V-shaped aerosol generator. The airborne particle number concentration is adjustable by controlling the air flow rate. The system supplied stable aerosol generation rates and particle size distributions over long periods (0.5-2 hr and possibly longer), which are important, for example, to study aerosol behavior, but also for toxicological studies. Strict adherence to the operating procedures during the aerosolization experiments ensures the generation of reproducible test results. The critical steps in the standard protocol are the preparation of the material and setup, and the aerosolization operations themselves. The system can be used for experiments requiring stable aerosol concentrations and may also be an alternative method for testing dustiness. The controlled aerosolization made possible with this setup occurs using energy inputs (may be characterized by aerosolization air velocity) that are within the ranges commonly found in occupational environments where nanomaterial powders are handled. This setup and its operating protocol are thus helpful for human exposure and risk assessment. PMID:27501179

  20. Ce, Gd codoped YAG nanopowder for white light emitting device.

    PubMed

    Schiopu, Vasilica; Matei, Alina; Dinescu, Adrian; Danila, Mihai; Cernica, Ileana

    2012-11-01

    In the last years white light emitting devices have received increased attention and have been used in a wide range of applications due to their long lifetime, high luminescence efficiency, low power consumption and environment friendliness, compared to conventional light sources. The discovery and improvement of inorganic phosphors that can be excited by a GaN chip in the wavelength range 370-470 nm is essential for the efficiency and quality of the emitted light. In the white light emitting device technology, the phosphor preparation step is the most important and it's quality defines the "whiteness". The tunable yellow emission property of YAG:Ce phosphor may be improved by the incorporation of an additional codoping element. Ce, Gd codoped YAG phosphor nanopowder with an average grain size of 40 nm has been synthesized by a sol-gel method. Well-crystallized fine nanoparticles and the formation of the garnet phase have been obtained at 1000 degrees C. The chemical structure and morphology of YAG:Ce, Gd was studied. PMID:23421297

  1. Substituted Hydroxyapatites with Antibacterial Properties

    PubMed Central

    Kolmas, Joanna; Groszyk, Ewa; Kwiatkowska-Różycka, Dagmara

    2014-01-01

    Reconstructive surgery is presently struggling with the problem of infections located within implantation biomaterials. Of course, the best antibacterial protection is antibiotic therapy. However, oral antibiotic therapy is sometimes ineffective, while administering an antibiotic at the location of infection is often associated with an unfavourable ratio of dosage efficiency and toxic effect. Thus, the present study aims to find a new factor which may improve antibacterial activity while also presenting low toxicity to the human cells. Such factors are usually implemented along with the implant itself and may be an integral part of it. Many recent studies have focused on inorganic factors, such as metal nanoparticles, salts, and metal oxides. The advantages of inorganic factors include the ease with which they can be combined with ceramic and polymeric biomaterials. The following review focuses on hydroxyapatites substituted with ions with antibacterial properties. It considers materials that have already been applied in regenerative medicine (e.g., hydroxyapatites with silver ions) and those that are only at the preliminary stage of research and which could potentially be used in implantology or dentistry. We present methods for the synthesis of modified apatites and the antibacterial mechanisms of various ions as well as their antibacterial efficiency. PMID:24949423

  2. Sintering Effects on Morphology, Thermal Stability and Surface Area of Sol-Gel Derived Nano-Hydroxyapatite Powder

    NASA Astrophysics Data System (ADS)

    Kapoor, Seema; Batra, Uma; Kohli, Suchita

    2011-12-01

    Hydroxyapatite (HAP) ceramics have been recognized as substitute materials for bone and teeth in orthopedic and dentistry field due to their chemical and biological similarity to human hard tissue. The nanosized and nanocrystalline forms of HAP have great potential to revolutionize the hard tissue-engineering field, starting from bone repair and augmentation to controlled drug delivery systems. This paper reports the synthesis of biomimetic nano-hydroxyapatite (HAP) by sol-gel method using calcium nitrate tetrahydrate (CNT) and potassium dihydrogen phosphate (KDP) as calcium and phosphorus precursors, respectively to obtain a desired Ca/P ratio of 1.67. Deionized water was used as a diluting media for HAP sol preparation and ammonia was used to adjust the pH to 11. After aging, the HAP gel was dried at 55 °C and sintered to different temperatures (200 °C, 400 °C, 600 °C, 800 °C, 1000 °C and 1200 °C). The dried and sintered powders were characterized for phase composition using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The particle size and morphology was studied using transmission electron microscopy (TEM). The thermal behavior of the dried HAP nanopowder was studied in the temperature range of 55 °C to 1000 °C using thermal gravimetric analyser (TGA). The BET surface area of absorbance was determined by Nitrogen adsorption using Brunauer-Emmett-Teller (BET) method. The presence of characteristic peaks of the phosphate and OH groups in FTIR spectrums confirmed the formation of pure HAP in dried as well as sintered powders. XRD results also confirmed the formation of stoichiometric nano-HAP. Sintering revealed that with increase in temperature, both the crystallinity and crystallite size of nano-HAP particles increased. The synthesized nano-HAP powder was found to be stable upto 1000 °C without any additional phase other than HAP, whereas peak of β-TCP (tricalcium phosphate) was observed at 1200 °C. Photomicrograph of

  3. Sintering Effects on Morphology, Thermal Stability and Surface Area of Sol-Gel Derived Nano-Hydroxyapatite Powder

    SciTech Connect

    Kapoor, Seema; Batra, Uma; Kohli, Suchita

    2011-12-12

    Hydroxyapatite (HAP) ceramics have been recognized as substitute materials for bone and teeth in orthopedic and dentistry field due to their chemical and biological similarity to human hard tissue. The nanosized and nanocrystalline forms of HAP have great potential to revolutionize the hard tissue-engineering field, starting from bone repair and augmentation to controlled drug delivery systems. This paper reports the synthesis of biomimetic nano-hydroxyapatite (HAP) by sol-gel method using calcium nitrate tetrahydrate (CNT) and potassium dihydrogen phosphate (KDP) as calcium and phosphorus precursors, respectively to obtain a desired Ca/P ratio of 1.67. Deionized water was used as a diluting media for HAP sol preparation and ammonia was used to adjust the pH to 11. After aging, the HAP gel was dried at 55 deg. C and sintered to different temperatures (200 deg. C, 400 deg. C, 600 deg. C, 800 deg. C, 1000 deg. C and 1200 deg. C). The dried and sintered powders were characterized for phase composition using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The particle size and morphology was studied using transmission electron microscopy (TEM). The thermal behavior of the dried HAP nanopowder was studied in the temperature range of 55 deg. C to 1000 deg. C using thermal gravimetric analyser (TGA). The BET surface area of absorbance was determined by Nitrogen adsorption using Brunauer-Emmett-Teller (BET) method. The presence of characteristic peaks of the phosphate and OH groups in FTIR spectrums confirmed the formation of pure HAP in dried as well as sintered powders. XRD results also confirmed the formation of stoichiometric nano-HAP. Sintering revealed that with increase in temperature, both the crystallinity and crystallite size of nano-HAP particles increased. The synthesized nano-HAP powder was found to be stable upto 1000 deg. C without any additional phase other than HAP, whereas peak of {beta}-TCP (tricalcium phosphate) was observed

  4. Influence of Obtaining Conditions on Kinetics of the Initial Sintering Stage of Zirconia Nanopowders

    NASA Astrophysics Data System (ADS)

    Lakusta, Marharyta; Danilenko, Igor; Konstantinova, Tetyana; Volkova, Galina

    2016-05-01

    The present paper is devoted to the problem of sintering ceramics based on yttria-stabilized zirconia (Y-TZP). In this paper, we studied the effect of two obtaining methods (co-precipitation and technical hydrolysis) on sintering kinetics of Y-TZP nanopowders. We used the constant rate of heating (CRH) method at different heating rates for determining the sintering mechanisms. The basic mechanism and activation energy ( Q) of diffusion at the initial sintering stage were estimated using the sintering rate equations that are applicable to the CRH data. We found that nanopowder 3Y-TZP produced by the co-precipitation method (DIPE) was sintered according to the volume diffusion mechanism ( n = 1/2) and nanopowder TZ-3Y (TOSOH) produced by the technical hydrolysis was sintered according to the grain boundary diffusion mechanism ( n = 1/3).

  5. Influence of Obtaining Conditions on Kinetics of the Initial Sintering Stage of Zirconia Nanopowders.

    PubMed

    Lakusta, Marharyta; Danilenko, Igor; Konstantinova, Tetyana; Volkova, Galina

    2016-12-01

    The present paper is devoted to the problem of sintering ceramics based on yttria-stabilized zirconia (Y-TZP). In this paper, we studied the effect of two obtaining methods (co-precipitation and technical hydrolysis) on sintering kinetics of Y-TZP nanopowders. We used the constant rate of heating (CRH) method at different heating rates for determining the sintering mechanisms. The basic mechanism and activation energy (Q) of diffusion at the initial sintering stage were estimated using the sintering rate equations that are applicable to the CRH data. We found that nanopowder 3Y-TZP produced by the co-precipitation method (DIPE) was sintered according to the volume diffusion mechanism (n = 1/2) and nanopowder TZ-3Y (TOSOH) produced by the technical hydrolysis was sintered according to the grain boundary diffusion mechanism (n = 1/3). PMID:27142876

  6. Bio-ecological consequences of crop seeds treatment with metal nano-powders

    NASA Astrophysics Data System (ADS)

    Churilov, G.

    2015-11-01

    As a result of our investigations we have determined the optimal concentrations of ferrum, cobalt and cuprum nano-powders recommended to be used as micro-fertilizers increasing the yield and feed value of crops at the expense of accumulating biologically active combinations by 25-35%. In unfavorable climate conditions, for example in a case of excess moisture or heat and drought, the plants development and ripening suffer. Our investigations have shown that the stimulating effect of nano-powders has lowered the effect of stress situations on plants development and simultaneously increased the rape seeds yield and quality. Treating the seeds with the drugs being studied has provided the high crop protection. If consider that the maximum efficiency of protectants Chinuk, SK (20 kg/t of seeds) and Cruiser, KS (10 kg/t of seeds) then for the same effect one needs nano-powders 0.1 g per hectare norm of seeds planting.

  7. Copper and Graphene activated ZnO nanopowders for enhanced photocatalytic and antibacterial activities

    NASA Astrophysics Data System (ADS)

    Ravichandran, K.; Chidhambaram, N.; Gobalakrishnan, S.

    2016-06-01

    ZnO, ZnO:Cu and ZnO:Cu:Graphene nanopowders were synthesized via a facile wet chemical method. The XRD studies show that the synthesized samples have hexagonal wurtzite structure. It is found that graphene addition induces a decrease in crystallite size. UV-vis absorption spectra of the samples show sharp absorption edges around 380 nm. Photoluminescence studies reveal that the incorporation of copper and graphene in ZnO facilitates the efficient photo generated electron-hole pair separation. It is found that the ZnO:Cu and ZnO:Cu:Graphene nanopowder exhibit improved photocatalytic efficiency for the photodegradation of Methylene Blue (MB) under visible light irradiation. Moreover, improved antibacterial activity of ZnO:Cu:Graphene nanopowder against Escherichia coli and Staphylococcus aureus bacteria is observed.

  8. Dissolution studies of hydroxyapatite and glass-reinforced hydroxyapatite ceramics

    SciTech Connect

    Queiroz, A.C.; Santos, J.D.; Monteiro, F.J.; Prado da Silva, M.H

    2003-03-15

    In the continuous agitation assays, glass-reinforced hydroxyapatite (GR-HA) was shown to form a calcium phosphate (CaP) layer, but hydroxyapatite (HA) only formed dispersed precipitates. The formation of this layer was first detected on the GR-HA with a 7.5% glass addition (7.5 GR-HA) after only 3 days of immersion in simulated body fluid (SBF). The time required for layer formation decreased as the amount of glass added to the HA increased. The dissolution rate of the materials followed a similar pattern, i.e. the dissolution rate for GR-HA was higher than for HA, and increased with the addition of glass. The immersion of 7.5 GR-HA in water showed almost linear dissolution kinetics over the immersion periods (3, 7, 15, 30 and 60 days). The concentration of calcium ions in solution and the scanning electron microscopy (SEM) analysis of the 7.5 GR-HA specimens immersed in water and in SBF revealed a clear competition between the material dissolution and the precipitation of a CaP phase. Fourier transformed infrared spectroscopy with alternated total reflectance (FTIR-ATR) analysis indicated that the CaP phase that formed during longer immersion times (30 and 60 days) could be a carbonate-substituted CaP precipitate. As expected from previous work, the GR-HA behavior in terms of its in vitro bioactivity is higher than HA because a homogeneous CaP layer is formed and the precipitation occurs faster. From the dissolution test and in accordance with the chemical composition of the samples, GR-HA was more soluble than HA.

  9. Corundum ceramic materials modified with silica nanopowders: structure and mechanical properties

    NASA Astrophysics Data System (ADS)

    Kostytsyn, M. A.; Muratov, D. S.; Lysov, D. V.; Chuprunov, K. O.; Yudin, A. G.; Leybo, D. V.

    2016-01-01

    Filtering elements are often used in the metallurgy of rare earth metals. Corundum ceramic is one of the most suitable materials for this purpose. The process of formation and the properties of nanomodified ceramic materials, which are proposed as filtering materials with tunable effective porosity, are described. A silica nanopowder is used as a porosity-increasing agent. Vortex layer apparatus is used for mixing of precursor materials. The obtained results show that nanomodification with the vortex layer apparatus using 0.04 wt. % silica nanopowder as a modifying agent leads to an increase in the compression strength of corundum ceramic by the factor of 1.5.

  10. Optical property degradation of titanium dioxide micro- and nanopowders under irradiation

    NASA Astrophysics Data System (ADS)

    Mikhailov, M. M.; Li, Chundong; Neshchimenko, V. V.

    2014-08-01

    Diffuse reflection spectra and absorption spectra of titanium dioxide (anatase) micro- and nanopowders induced by exposure to 100 keV protons and electrons were analyzed at wavelengths between 250 and 2500 nm. It is established that the radiation stability of the nanopowders is higher than the micropowders in the absorption region λ > 500 nm for proton and electron exposure. This effect is caused by the high concentration of radiation defects in micropowders, which is associated with defects of interstitial titanium ions (Tiirad rad rad , Tiirad rad rad rad ), titanium vacancies (VTi⁗, VTi‴ ) and oxygen vacancies VOX.

  11. Radiation stability of SiO2 micro- and nanopowders under electron and proton exposure

    NASA Astrophysics Data System (ADS)

    Li, Chundong; Mikhailov, M. M.; Neshchimenko, V. V.

    2014-01-01

    The effects of proton and electron (E = 100 keV, F = 5 × 1015 сm-2) exposure on the reflective spectra of SiO2 micro- and nanopowders in wavelength range from 250 to 2500 nm have been investigated. It has been established that the reflectance and radiation stability of nanopowders is less than that of micropowders. This effect is caused by the high concentration of radiation defects, which act as surface absorption centers (Es‧ centers) near the energies 5.47 and 4.45 eV, and peroxide silicon defects (tbnd Sisbnd Osbnd Osbnd Sitbnd) near the energy 3.84 eV.

  12. Far-infrared spectra of dysprosium doped yttrium aluminum garnet nanopowder

    NASA Astrophysics Data System (ADS)

    Trajić, J.; Rabasović, M. S.; Savić-Šević, S.; Ševic, D.; Babić, B.; Romčević, M.; Ristić-Djurović, J. L.; Paunović, N.; Križan, J.; Romčević, N.

    2016-07-01

    The solution combustion synthesis was used to prepare nanopowders of yttrium aluminum garnet (YAG) and YAG doped with dysprosium ions, Dy3+, (YAG:Dy). The morphology, specific surface area, texture, and optical properties of the prepared materials were studied by the means of scanning electron microscopy (SEM), nitrogen adsorption method, and far-infrared spectroscopy at room temperature in the spectral region between 80 and 600 cm-1. It was established that all the examined samples were microporous. The Maxwell-Garnet formula was used to model dielectric function of YAG and YAG:Dy nanopowders as mixtures of homogenous spherical inclusions in air.

  13. On the anisotropic elastic properties of hydroxyapatite.

    NASA Technical Reports Server (NTRS)

    Katz, J. L.; Ukraincik, K.

    1971-01-01

    Experimental measurements of the isotropic elastic moduli on polycrystalline specimens of hydroxyapatite and fluorapatite are compared with elastic constants measured directly from single crystals of fluorapatite in order to derive a set of pseudo single crystal elastic constants for hydroxyapatite. The stiffness coefficients thus derived are given. The anisotropic and isotropic elastic properties are then computed and compared with similar properties derived from experimental observations of the anisotropic behavior of bone.

  14. Detection of Hydroxyapatite in Calcified Cardiovascular Tissues

    PubMed Central

    Lee, Jae Sam; Morrisett, Joel D.; Tung, Ching-Hsuan

    2012-01-01

    Objective The objective of this study is to develop a method for selective detection of the calcific (hydroxyapatite) component in human aortic smooth muscle cells in vitro and in calcified cardiovascular tissues ex vivo. This method uses a novel optical molecular imaging contrast dye, Cy-HABP-19, to target calcified cells and tissues. Methods A peptide that mimics the binding affinity of osteocalcin was used to label hydroxyapatite in vitro and ex vivo. Morphological changes in vascular smooth muscle cells were evaluated at an early stage of the mineralization process induced by extrinsic stimuli, osteogenic factors and a magnetic suspension cell culture. Hydroxyapatite components were detected in monolayers of these cells in the presence of osteogenic factors and a magnetic suspension environment. Results Atherosclerotic plaque contains multiple components including lipidic, fibrotic, thrombotic, and calcific materials. Using optical imaging and the Cy-HABP-19 molecular imaging probe, we demonstrated that hydroxyapatite components could be selectively distinguished from various calcium salts in human aortic smooth muscle cells in vitro and in calcified cardiovascular tissues, carotid endarterectomy samples and aortic valves, ex vivo. Conclusion Hydroxyapatite deposits in cardiovascular tissues were selectively detected in the early stage of the calcification process using our Cy-HABP-19 probe. This new probe makes it possible to study the earliest events associated with vascular hydroxyapatite deposition at the cellular and molecular levels. This target-selective molecular imaging probe approach holds high potential for revealing early pathophysiological changes, leading to progression, regression, or stabilization of cardiovascular diseases. PMID:22877867

  15. Brushite-based calcium phosphate cement with multichannel hydroxyapatite granule loading for improved bone regeneration.

    PubMed

    Sarkar, Swapan Kumar; Lee, Byung Yeol; Padalhin, Andrew Reyas; Sarker, Avik; Carpena, Nathaniel; Kim, Boram; Paul, Kallyanshish; Choi, Hwan Jun; Bae, Sang-Ho; Lee, Byong Taek

    2016-01-01

    In this work, we report brushite-based calcium phosphate cement (CPC) system to enhance the in vivo biodegradation and tissue in-growth by incorporation of micro-channeled hydroxyapatite (HAp) granule and silicon and sodium addition in calcium phosphate precursor powder. Sodium- and silicon-rich calcium phosphate powder with predominantly tri calcium phosphate (TCP) phase was synthesized by an inexpensive wet chemical route to react with mono calcium phosphate monohydrate (MCPM) for making the CPC. TCP nanopowder also served as a packing filler and moderator of the reaction kinetics of the setting mechanism. Strong sintered cylindrical HAp granules were prepared by fibrous monolithic (FM) process, which is 800 µm in diameter and have seven micro-channels. Acid sodium pyrophosphate and sodium citrate solution was used as the liquid component which acted as a homogenizer and setting time retarder. The granules accelerated the degradation of the brushite cement matrix as well as improved the bone tissue in-growth by permitting an easy access to the interior of the CPC through the micro-channels. The addition of micro-channeled granule in the CPC introduced porosity without sacrificing much of its compressive strength. In vivo investigation by creating a critical size defect in the femur head of a rabbit model for 1 and 2 months showed excellent bone in-growth through the micro-channels. The granules enhanced the implant degradation behavior and bone regeneration in the implanted area was significantly improved after two months of implantation. PMID:26333790

  16. Microwave processed nanocrystalline hydroxyapatite: Simultaneous enhancement of mechanical and biological properties

    PubMed Central

    Bose, Susmita; Dasgupta, Sudip; Tarafder, Solaiman; Bandyopadhyay, Amit

    2010-01-01

    Despite excellent bioactivity of hydroxyapatite (HA) ceramics, poor mechanical strength has limited its applications primarily to coatings and other non-load bearing areas as bone grafts. Using synthesized HA nanopowder, dense compacts with grain sizes in nanometers to micrometers were processed via microwave sintering between 1000 and 1150 °C for 20 minutes. Here we demonstrate that mechanical properties, such as compressive strength, hardness and indentation fracture toughness of HA compacts increased with a decrease in grain size. HA with 168± 86 nm grain size showed the highest compressive strength of 395±42 MPa, hardness of 8.4±0.4 GPa and indentation fracture toughness of 1.9 ±0.2 MPam1/2. To study the in vitro biological properties, HA compacts with grain size between 168 nm and 1.16 µm were assessed for in vitro bone cell-materials interactions with human osteoblast cell line. Vinculin protein expression for cell attachment and bone cell proliferation using MTT assay showed surfaces with finer grains provided better bone cell-materials interactions than coarse grained samples. Our results indicate simultaneous improvements in mechanical and biological properties in microwave sintered HA compacts with nanoscale grain size. PMID:20230922

  17. Fostering hydroxyapatite bioactivity and mechanical strength by Si-doping and reinforcing with multiwall carbon nanotubes.

    PubMed

    Belmamouni, Younes; Bricha, Meriame; Essassi, El Mokhtar; Ferreira, José M F; El Mabrouk, Khalil

    2014-06-01

    The aim of the present study was to prepare resorbable hydroxyapatite (HA) based bone graft materials reinforced with carbon nanotubes as a way to cope with the inability of pure HA to resorb and its intrinsic brittleness and poor strength that restrict its clinical applications under load-bearing conditions. With this purpose, a Si-doped HA nanopowder (n-Si0.8HA) was prepared by chemical synthesis and used as composite matrix reinforced with different amounts of functionalized multiwall carbon nanotubes (MWCNTs). The effect of the added amounts of MWCNTs on the mechanical properties of nanocomposites and their in vitro biomineralization was assessed by bending strength measurements, immersing tests in simulated body fluid solution (SBF), scanning electron microscopy (SEM), and inductively coupled plasma atomic emission spectroscopy analysis (ICP-AES). The bioactivity and bending strength were enhanced, reaching maximum balanced values for an optimum addition of 3 wt.% f-MWCNTs. These results might contribute to broaden the potential applications of HA-based bone grafts. PMID:24738405

  18. Use of Hydroxyapatite Doping to Enhance Responsiveness of Heat-Inducible Gene Switches to Focused Ultrasound.

    PubMed

    Fabiilli, Mario L; Phanse, Rahul A; Moncion, Alexander; Fowlkes, J Brian; Franceschi, Renny T

    2016-03-01

    Recently, we demonstrated that ultrasound-based hyperthermia can activate cells containing a heat-activated and ligand-inducible gene switch in a spatio-temporally controlled manner. These engineered cells can be incorporated into hydrogel scaffolds (e.g., fibrin) for in vivo implantation, where ultrasound can be used to non-invasively pattern transgene expression. Due to their high water content, the acoustic attenuation of fibrin scaffolds is low. Thus, long ultrasound exposures and high acoustic intensities are needed to generate sufficient hyperthermia for gene activation. Here, we demonstrate that the attenuation of fibrin scaffolds and the resulting hyperthermia achievable with ultrasound can be increased significantly by doping the fibrin with hydroxyapatite (HA) nanopowder. The attenuation of a 1% (w/v) fibrin scaffold with 5% (w/v) HA was similar to soft tissue. Transgene activation of cells harboring the gene switch occurred at lower acoustic intensities and shorter exposures when the cells were encapsulated in HA-doped fibrin scaffolds versus undoped scaffolds. Inclusion of HA in the fibrin scaffold did not affect the viability of the encapsulated cells. PMID:26712417

  19. Passivation of the surface of aluminum nanopowders by protective coatings of the different chemical origin

    NASA Astrophysics Data System (ADS)

    Kwon, Young-Soon; Gromov, Alexander A.; Strokova, Julia I.

    2007-04-01

    The results of investigation and analysis of electro-exploded aluminum nanopowders, whose surface were passivated with the following substances: liquids - nitrocellulose (NC), oleic acid (C 17H 33COOH) and stearic acid (C 17H 35COOH), suspended in kerosene and ethanol, fluoropolymer; solids - boron and nickel; gases - N 2, CO 2 and air (for a comparison) are discussed. The surface protection for the aluminum nanopowders by coatings of different chemical origins leads to the some advantages of the powders properties for an application in energetic systems, e.g. solid propellants and "green" propellants (Al-H 2O). Aluminum nanopowders with a protected surface showed the increased stability to oxidation in air during the storage period and higher reactivity by heating. The TEM-visual diagram of the formation and stabilization of the coatings on the particles has been proposed on the basis of experimental results. The kinetics of the interaction of aluminum nanopowders with air has been discussed. The recommendations concerning an efficiency of the protective "non-Al 2O 3" layers on aluminum nanoparticles were proposed.

  20. Lower sintering temperature of nanostructured dense ceramics compacted from dry nanopowders using powerful ultrasonic action

    NASA Astrophysics Data System (ADS)

    Khasanov, O.; Reichel, U.; Dvilis, E.; Khasanov, A.

    2011-10-01

    Nanostructured high dense zirconia ceramics have been sintered from dry nanopowders compacted by uniaxial pressing with simultaneous powerful ultrasonic action (PUA). Powerful ultrasound with frequency of 21 kHz was supplied from ultrasonic generator to the mold, which was the ultrasonic wave-guide. Previously the mold was filled by non-agglomerated zirconia nanopowder having average particle size of 40 nm. Any binders or plasticizers were excluded at nanopowder processing. Compaction pressure was 240 MPa, power of ultrasonic generator at PUA was 1 kW and 3 kW. The fully dense zirconia ceramics has been sintered at 1345°C and high-dense ceramics with a density of 99.1%, the most grains of which had the sizes Dgr <= 200 nm, has been sintered at low sintering temperature (1325°C). Applied approach prevents essential grain growth owing to uniform packing of nanoparticles under vibrating PU-action at pressing, which provides the friction forces control during dry nanopowder compaction without contaminating binders or plasticizers.

  1. Workplace Exposure to Titanium Dioxide Nanopowder Released from a Bag Filter System

    PubMed Central

    Ji, Jun Ho; Kim, Jong Bum; Lee, Gwangjae; Noh, Jung-Hun; Yook, Se-Jin; Cho, So-Hye; Bae, Gwi-Nam

    2015-01-01

    Many researchers who use laboratory-scale synthesis systems to manufacture nanomaterials could be easily exposed to airborne nanomaterials during the research and development stage. This study used various real-time aerosol detectors to investigate the presence of nanoaerosols in a laboratory used to manufacture titanium dioxide (TiO2). The TiO2 nanopowders were produced via flame synthesis and collected by a bag filter system for subsequent harvesting. Highly concentrated nanopowders were released from the outlet of the bag filter system into the laboratory. The fractional particle collection efficiency of the bag filter system was only 20% at particle diameter of 100 nm, which is much lower than the performance of a high-efficiency particulate air (HEPA) filter. Furthermore, the laboratory hood system was inadequate to fully exhaust the air discharged from the bag filter system. Unbalanced air flow rates between bag filter and laboratory hood systems could result in high exposure to nanopowder in laboratory settings. Finally, we simulated behavior of nanopowders released in the laboratory using computational fluid dynamics (CFD). PMID:26125024

  2. Workplace Exposure to Titanium Dioxide Nanopowder Released from a Bag Filter System.

    PubMed

    Ji, Jun Ho; Kim, Jong Bum; Lee, Gwangjae; Noh, Jung-Hun; Yook, Se-Jin; Cho, So-Hye; Bae, Gwi-Nam

    2015-01-01

    Many researchers who use laboratory-scale synthesis systems to manufacture nanomaterials could be easily exposed to airborne nanomaterials during the research and development stage. This study used various real-time aerosol detectors to investigate the presence of nanoaerosols in a laboratory used to manufacture titanium dioxide (TiO2). The TiO2 nanopowders were produced via flame synthesis and collected by a bag filter system for subsequent harvesting. Highly concentrated nanopowders were released from the outlet of the bag filter system into the laboratory. The fractional particle collection efficiency of the bag filter system was only 20% at particle diameter of 100 nm, which is much lower than the performance of a high-efficiency particulate air (HEPA) filter. Furthermore, the laboratory hood system was inadequate to fully exhaust the air discharged from the bag filter system. Unbalanced air flow rates between bag filter and laboratory hood systems could result in high exposure to nanopowder in laboratory settings. Finally, we simulated behavior of nanopowders released in the laboratory using computational fluid dynamics (CFD). PMID:26125024

  3. Liquid-feed flame spray pyrolysis synthesis of oxide nanopowders for the processing of ceramic composites

    NASA Astrophysics Data System (ADS)

    Taylor, Nathan John

    In the liquid-feed flame spray pyrolysis (LF-FSP) process, alcohol solutions of metalloorganic precursors are aerosolized by O2 and combusted. The metal oxide combustion products are rapidly quenched (< 10 ms) from flame temperatures of 1500°C to temperatures < 400° C, limiting particle growth. The resulting nanopowders are typically agglomerated but unaggregated. Here, we demonstrate two processing approaches to dense materials: nanopowders with the exact composition, and mixed single metal oxide nanopowders. The effect of the initial degree of phase separation on the final microstructures was determined by sintering studies. Our first studies included the production of yttrium aluminum garnet, Y3Al5O12 (YAG), tubes which we extruded from a thermoplastic/ceramic blend. At equivalent final densities, we found finer grain sizes in the from the mixed Y2O3 and Al2 O3 nanopowders, which was attributed to densification occurring before full transformation to the YAG phase. The enhanced densification in production of pure YAG from the reactive sintering process led us to produce composites in the YAG/alpha-Al 2O3 system. Finally, a third Y2O3 stabilized ZrO2 (YSZ) phase was added to further refine grain sizes using the same two processing approaches. In a separate study, single-phase metastable Al2O3 rich spinels with the composition MO•3Al 2O3 where M = Mg, Ni, and Co were sintered to produce dense MAl2O4/alpha-Al2O3 composites. All of these studies provide a test of the bottom-up approach; that is, how the initial length scale of mixing affects the final composite microstructure. Overall, the length scale of mixing is highly dependent upon the specific oxide composites studied. This work provides a processing framework to be adopted by other researchers to further refine microstructural size. LF-FSP flame temperatures were mapped using different alcohols with different heats of combustion: methanol, ethanol, 1-propanol, and n-butanol. The effect of different

  4. High elastic modulus nanopowder reinforced resin composites for dental applications

    NASA Astrophysics Data System (ADS)

    Wang, Yijun

    2007-12-01

    Dental restorations account for more than $3 billion dollars a year on the market. Among them, all-ceramic dental crowns draw more and more attention and their popularity has risen because of their superior aesthetics and biocompatibility. However, their relatively high failure rate and labor-intensive fabrication procedure still limit their application. In this thesis, a new family of high elastic modulus nanopowder reinforced resin composites and their mechanical properties are studied. Materials with higher elastic modulus, such as alumina and diamond, are used to replace the routine filler material, silica, in dental resin composites to achieve the desired properties. This class of composites is developed to serve (1) as a high stiffness support to all-ceramic crowns and (2) as a means of joining independently fabricated crown core and veneer layers. Most of the work focuses on nano-sized Al2O3 (average particle size 47 nm) reinforcement in a polymeric matrix with 50:50 Bisphenol A glycidyl methacrylate (Bis-GMA): triethylene glycol dimethacrylate (TEGDMA) monomers. Surfactants, silanizing agents and primers are examined to obtain higher filler levels and enhance the bonding between filler and matrix. Silane agents work best. The elastic modulus of a 57.5 vol% alumina/resin composite is 31.5 GPa compared to current commercial resin composites with elastic modulus <15 GPa. Chemical additives can also effectively raise the hardness to as much as 1.34 GPa. Besides>alumina, diamond/resin composites are studied. An elastic modulus of about 45 GPa is obtained for a 57 vol% diamond/resin composite. Our results indicate that with a generally monodispersed nano-sized high modulus filler, relatively high elastic modulus resin-based composite cements are possible. Time-dependent behavior of our resin composites is also investigated. This is valuable for understanding the behavior of our material and possible fatigue testing in the future. Our results indicate that with

  5. Characterisation of Suspension Precipitated Nanocrystalline Hydroxyapatite Powders

    NASA Astrophysics Data System (ADS)

    Mallik, P. K.; Swain, P. K.; Patnaik, S. C.

    2016-02-01

    Hydroxyapatite (HA) is a well-known biomaterial for coating on femoral implants, filling of dental cavity and scaffold for tissue replacement. Hydroxyapatite possess limited load bearing capacity due to their brittleness. In this paper, the synthesis of nanocrystalline hydroxyapatite powders was prepared by dissolving calcium oxide in phosphoric acid, followed by addition of ammonia liquor in a beaker. The prepared solution was stirred by using magnetic stirrer operated at temperature of 80°C for an hour. This leads to the formation of hydroxyapatite precipitate. The precipitate was dried in oven for overnight at 100°C. The dried agglomerated precipitate was calcined at 800°C in conventional furnace for an hour. The influence of calcium oxide concentration and pH on the resulting precipitates was studied using BET, XRD and SEM. As result, a well-defined sub-rounded morphology of powders size of ∼41 nm was obtained with a salt concentration of 0.02 M. Finally, it can be concluded that small changes in the reaction conditions led to large changes in final size, shape and degree of aggregation of the hydroxyapatite particles.

  6. Growth of hydroxyapatite nanoparticles on silica gels.

    PubMed

    Rivera-Muñoz, E M; Huirache-Acuña, R; Velázquez, R; Alonso-Núñez, G; Eguía-Eguía, S

    2011-06-01

    Synthetic, hydroxyapatite nanoparticles were grown on the surface of silica gels. The synthesis of those nanoparticles was obtained by immersing silica gels in a simulated body fluid (SBF) at 37 degrees C. The SBF was replaced every week to keep constant the Ca and P ion concentration and subsequent growth of hydroxyapatite was evaluated after 1-6 weeks of total soaking time in SBF. Hydroxyapatite nanoparticles were observed by scanning electron microscopy (SEM) on the surface of silica gel samples and confirmed by energy dispersive X-ray spectroscopy (EDS), Fourier Transform Infra Red Spectroscopy (FTIR) and powder X-ray Diffractometry (XRD) analysis. These particles show a regular shape and uniform size every week, keeping within the nanoscale always. Both the size and morphology of hydroxyapatite nanoparticles obtained are the result of the use of different chemical additives in the synthesis of silica gels, since they affect the liquid-to-solid interface, and the growth could correspond to a diffusion limited aggregation (DLA) process. A more detailed analysis, with higher magnifications, showed that hydroxyapatite nanoparticles are not solid spheres, showing a branched texture and their size depends on the scale and resolution of the measure instrument. PMID:21770224

  7. Monoclonal antibody purification with hydroxyapatite.

    PubMed

    Gagnon, Pete

    2009-06-01

    Hydroxyapatite (HA) has been used for IgG purification since its introduction in the 1950s. Applications expanded to include IgA and IgM in the 1980s, along with elucidation of its primary binding mechanisms and the development of ceramic HA media. With the advent of recombinant monoclonal antibodies, HA was demonstrated to be effective for removal of antibody aggregates, as well as host cell proteins and leached protein A. HA's inherent abilities have been enhanced by the development of elution strategies that permit differential control of its primary binding mechanisms: calcium metal affinity and phosphoryl cation exchange. These strategies support reduction of antibody aggregate content from greater than 60% to less than 0.1%, in conjunction with enhanced removal of DNA, endotoxin, and virus. HA also has a history of discriminating various immunological constructs on the basis of differences in their variable regions, or discriminating Fab fragments from Fc contaminants in papain digests of purified monoclonal IgG. Continuing development of novel elution strategies, alternative forms of HA, and application of robotic high throughput screening systems promise to expand HA's utility in the field. PMID:19491046

  8. Bioactive Surface Modification of Hydroxyapatite

    PubMed Central

    Okazaki, Yohei; Hiasa, Kyou; Yasuda, Keisuke; Nogami, Keisuke; Mizumachi, Wataru; Hirata, Isao

    2013-01-01

    The purpose of this study was to establish an acid-etching procedure for altering the Ca/P ratio of the nanostructured surface of hydroxyapatite (HAP) by using surface chemical and morphological analyses (XPS, XRD, SEM, surface roughness, and wettability) and to evaluate the in vitro response of osteoblast-like cells (MC3T3-E1 cells) to the modified surfaces. This study utilized HAP and HAP treated with 10%, 20%, 30%, 40%, 50%, or 60% phosphoric acid solution for 10 minutes at 25°C, followed by rinsing 3 times with ultrapure water. The 30% phosphoric acid etching process that provided a Ca/P ratio of 1.50, without destruction of the grain boundary of HAP, was selected as a surface-modification procedure. Additionally, HAP treated by the 30% phosphoric acid etching process was stored under dry conditions at 25°C for 12 hours, and the Ca/P ratio approximated to 1.00 accidentally. The initial adhesion, proliferation, and differentiation (alkaline phosphatase (ALP) activity and relative mRNA level for ALP) of MC3T3-E1 cells on the modified surfaces were significantly promoted (P < 0.05 and 0.01). These findings show that the 30% phosphoric acid etching process for the nanostructured HAP surface can alter the Ca/P ratio effectively and may accelerate the initial adhesion, proliferation, and differentiation of MC3T3-E1 cells. PMID:23862150

  9. Finite Element Simulation of Diametral Strength Test of Hydroxyapatite

    SciTech Connect

    Ozturk, Fahrettin; Toros, Serkan; Evis, Zafer

    2011-01-17

    In this study, the diametral strength test of sintered hydroxyapatite was simulated by the finite element software, ABAQUS/Standard. Stress distributions on diametral test sample were determined. The effect of sintering temperature on stress distribution of hydroxyapatite was studied. It was concluded that high sintering temperatures did not reduce the stress on hydroxyapatite. It had a negative effect on stress distribution of hydroxyapatite after 1300 deg. C. In addition to the porosity, other factors (sintering temperature, presence of phases and the degree of crystallinity) affect the diametral strength of the hydroxyapatite.

  10. Fe{sub 2}O{sub 3} nanopowders prepared by a thermal plasma process for water oxidation

    SciTech Connect

    Lee, Dongeun; Choi, Yong-Wook; Na, Ye-Seul; Choi, Soo-Suk; Park, Dong-Wha; Choi, Jinsub

    2015-08-15

    Highlights: • Hematite nanopowders with a high purity were synthesized by a DC thermal plasma process. • Fe{sub 3}O{sub 4} is formed during the formation of Fe{sub 2}O{sub 3} by thermal plasma with iron and oxygen sources. • Hematite nanopowders with a high purity show higher PEC performance compared to mixed oxides. - Abstract: Hematite (Fe{sub 2}O{sub 3}) nanopowders were synthesized from commercially available micro-sized iron powders by a DC thermal plasma process at atmospheric pressure. The micro-sized iron powders were vaporized in the plasma region, after which the plasma processing equipment was rapidly quenched, resulting in the formation of iron nanopowders with a size of less than 100 nm. Subsequently, the iron nanopowders were heated to convert hematite with a high purity, which was then formed into a thin film with a binder for preparation of electrodes for photoelectrochemical water oxidation. Iron oxide nanopowders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), particle size analysis (PSA) and transmission electron microscopy (TEM). The photoelectrochemical properties of the Fe{sub 2}O{sub 3} film were characterized in 1 M NaOH under AM 1.5 conditions.

  11. Permeability, drying, and sintering of pressure filtered ceramic nanopowders

    NASA Astrophysics Data System (ADS)

    Sweeney, Sean M.

    2002-01-01

    point of drying (when fracture is most likely during drying). Agreement between maximum safe drying stresses and measured sample strengths is found to be good (to within better than a factor of 2) for boehmite samples, but not very good (off by a factor of ˜7) for nanocrystalline 3Y-TZP samples. Sub-critical crack growth is indicated as the source of this deviation in nanocrystalline 3Y-TZP samples. Literature studies of the sintering of chloride-derived 3Y-TZP nanopowders have documented numerous sintering problems including inability to reach full density, desintering, cracking, and the formation of a dense shell with less dense interior. To explain the poor sintering behavior of samples of one nanocrystalline 3Y-TZP powder, the origin of such a dense shell microstructure is determined. Three possible reasons for a dense shell microstructure are examined and rejected: exothermic reactions with the sintering atmosphere, pre-existing density gradients in the green compact, and thermal gradients occurring during sintering. A combination of gas flow/diffusion, thermodynamic, and sintering calculations are used to show that the evolution of a structure-coarsening gas (hydrogen chloride) during sintering causes the formation of a dense shell microstructure, and explains the poor densification behavior of this system. Two solutions to the problem are compared: (1) a thermal treatment composed of an extended hold at 1000°C to allow HCl gas removal before the onset of closed porosity (at about 90-93% of theoretical density), and (2) a chemical treatment performed by washing pre-sintered (500°C/30 min) samples at room temperature using a concentrated ammonium hydroxide solution to remove chlorides. The thermal treatment is found to be superior for removing residual chlorine and allowing full density to be achieved during sintering.

  12. Preparation of irregular mesoporous hydroxyapatite

    SciTech Connect

    Wang Hualin Zhai Linfeng; Li Yanhong; Shi Tiejun

    2008-06-03

    An irregular mesoporous hydroxyapatite (meso-HA), Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}, is successfully prepared from Ca(NO{sub 3}){sub 2}.4H{sub 2}O and NH{sub 4}H{sub 2}PO{sub 4} using surfactant cetyltrimethyl ammonium bromide (CTAB) as template. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) results reveal that the positive head of CTAB is assembled on the surface precipitated HA and much NH{sub 4}{sup +} is enclosed in precipitated HA before calcination. Field scanning electron microscope (FSEM) reveals that there exist many interconnected pores throughout the HA reticular skeleton. Nitrogen adsorption-desorption experiment exhibits a mesoporous material type IV curve, and pore size distribution calculated from the desorption branch of the isotherms based on Barrett-Joyner-Halenda (BJH) model shows that most pores throughout the HA reticular skeleton are sized at about 40 nm, but the pores are not uniform on the whole, owning to decomposition of the 'organic' CTAB templating structures and ammonium salt enclosed in the precipitated HA. The specific surface area of irregular meso-HA is calculated to be 37.6 m{sup 2}/g according to the Brunauer-Emmett-Teller (BET) equation. Moreover, after polylactic acid/meso-HA (PLA/meso-HA) composites degraded 12 weeks in normal saline at 37 deg. C, the interconnected pores throughout the HA skeleton were enlarged and sized in micron degree, which resemble trabecular bone structure very much.

  13. Highly biocompatible, nanocrystalline hydroxyapatite synthesized in a solvothermal process driven by high energy density microwave radiation.

    PubMed

    Smolen, Dariusz; Chudoba, Tadeusz; Malka, Iwona; Kedzierska, Aleksandra; Lojkowski, Witold; Swieszkowski, Wojciech; Kurzydlowski, Krzysztof Jan; Kolodziejczyk-Mierzynska, Małgorzata; Lewandowska-Szumiel, Małgorzata

    2013-01-01

    A microwave, solvothermal synthesis of highly biocompatible hydroxyapatite (HAp) nanopowder was developed. The process was conducted in a microwave radiation field having a high energy density of 5 W/mL and over a time less than 2 minutes. The sample measurements included: powder X-ray diffraction, density, specific surface area, and chemical composition. The morphology and structure were investigated by scanning electron microscopy as well as transmission electron microscopy (TEM). The thermal behavior analysis was conducted using a simultaneous thermal analysis technique coupled with quadruple mass spectrometry. Additionally, Fourier transform infrared spectroscopy tests of heated samples were performed. A degradation test and a biocompatibility study in vitro using human osteoblast cells were also conducted. The developed method enables the synthesis of pure, fully crystalline hexagonal HAp nanopowder with a specific surface area close to 240 m(2)/g and a Ca/P molar ratio equal to 1.57. TEM measurements showed that this method results in particles with an average grain size below 6 nm. A 28-day degradation test conducted according to the ISO standard indicated a 22% loss of initial weight and a calcium ion concentration at 200 μmol/dm(3) in the tris(hydroxymethyl)aminomethane hydrochloride test solution. The cytocompatibility of the obtained material was confirmed in a culture of human bone derived cells, both in an indirect test using the material extract, and in direct contact. A quantitative analysis was based on the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide. Viability assay as well as on DNA content measurements in the PicoGreen test. Indirect observations were performed at one point in time according to the ISO standard for in vitro cytotoxicity (ie, after 24 hours of cell exposure to the extracts). The direct contact tests were completed at three time points: after 24 hours, on day 7, and on day 14 of a culture in an

  14. Highly biocompatible, nanocrystalline hydroxyapatite synthesized in a solvothermal process driven by high energy density microwave radiation

    PubMed Central

    Smolen, Dariusz; Chudoba, Tadeusz; Malka, Iwona; Kedzierska, Aleksandra; Lojkowski, Witold; Swieszkowski, Wojciech; Kurzydlowski, Krzysztof Jan; Kolodziejczyk-Mierzynska, Małgorzata; Lewandowska-Szumiel, Małgorzata

    2013-01-01

    A microwave, solvothermal synthesis of highly biocompatible hydroxyapatite (HAp) nanopowder was developed. The process was conducted in a microwave radiation field having a high energy density of 5 W/mL and over a time less than 2 minutes. The sample measurements included: powder X-ray diffraction, density, specific surface area, and chemical composition. The morphology and structure were investigated by scanning electron microscopy as well as transmission electron microscopy (TEM). The thermal behavior analysis was conducted using a simultaneous thermal analysis technique coupled with quadruple mass spectrometry. Additionally, Fourier transform infrared spectroscopy tests of heated samples were performed. A degradation test and a biocompatibility study in vitro using human osteoblast cells were also conducted. The developed method enables the synthesis of pure, fully crystalline hexagonal HAp nanopowder with a specific surface area close to 240 m2/g and a Ca/P molar ratio equal to 1.57. TEM measurements showed that this method results in particles with an average grain size below 6 nm. A 28-day degradation test conducted according to the ISO standard indicated a 22% loss of initial weight and a calcium ion concentration at 200 μmol/dm3 in the tris(hydroxymethyl)aminomethane hydrochloride test solution. The cytocompatibility of the obtained material was confirmed in a culture of human bone derived cells, both in an indirect test using the material extract, and in direct contact. A quantitative analysis was based on the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide. Viability assay as well as on DNA content measurements in the PicoGreen test. Indirect observations were performed at one point in time according to the ISO standard for in vitro cytotoxicity (ie, after 24 hours of cell exposure to the extracts). The direct contact tests were completed at three time points: after 24 hours, on day 7, and on day 14 of a culture in an osteogenic

  15. Thickness of hydroxyapatite nanocrystal controls mechanical properties of the collagen-hydroxyapatite interface.

    PubMed

    Qin, Zhao; Gautieri, Alfonso; Nair, Arun K; Inbar, Hadass; Buehler, Markus J

    2012-01-31

    Collagen-hydroxyapatite interfaces compose an important building block of bone structures. While it is known that the nanoscale structure of this elementary building block can affect the mechanical properties of bone, a systematic understanding of the effect of the geometry on the mechanical properties of this interface between protein and mineral is lacking. Here we study the effect of geometry, different crystal surfaces, and hydration on the mechanical properties of collagen-hydroxyapatite interfaces from an atomistic perspective, and discuss underlying deformation mechanisms. We find that the presence of hydroxyapatite significantly enhances the tensile modulus and strength compared with a tropocollagen molecule alone. The stiffening effect is strongly dependent on the thickness of the mineral crystal until a plateau is reached at 2 nm crystal thickness. We observe no significant differences due to the mineral surface (Ca surface vs OH surface) or due to the presence of water. Our result shows that the hydroxyapatite crystal with its thickness confined to the nanometer size efficiently increases the tensile modulus and strength of the collagen-hydroxyapatite composite, agreeing well with experimental observations that consistently show the existence of extremely thin mineral flakes in various types of bones. We also show that the collagen-hydroxyapatite interface can be modeled with an elastic network model which, based on the results of atomistic simulations, provides a good estimate of the surface energy and other mechanical features. PMID:22208454

  16. Structural and Optical Characterization of Synthesized TiO2 Nanopowder Using Sol-Gel Technique

    NASA Astrophysics Data System (ADS)

    Lourduraj, S.; Williams, R. Victor

    2016-02-01

    The nanocrystalline TiO2 powder was synthesized by sol-gel method. The XRD analysis reveals that TiO2 powder was highly crystalline (anatase phase) and nanostructured with tetragonal system. The average crystallite size after calcined at 673K is found to be 7.7nm. The surface morphological studies using scanning electron microscopy (SEM) exhibit that the formation of nanosized TiO2 particles with less densification nature. Atomic force microscopy (AFM) topography exhibits the uniform distribution of spherical-shaped particles. The energy dispersive X-ray spectroscopy (EDX) confirms the presence of Titanium and Oxygen in synthesized TiO2 nanopowder. The value of optical bandgap of TiO2 nanopowder calculated from UV-Visible spectrum is 3.45eV. The presence of TiO2 particles is confirmed from the dominant fourier transform infrared (FTIR) peaks at 621cm-1 and 412cm-1.

  17. Synthesis of the thermoelectric nanopowder recovered from the used thermoelectric modules.

    PubMed

    Lee, Kun-Jae; Jin, Yun-Ho; Kong, Man-Sik

    2014-10-01

    We fabricated the thermoelectric powder using the used thermoelectric modules in a vehicle. As a starting material, the used thermoelectric modules were collected and separated to substrate, electrode, solder, and thermoelectric parts by a thermal process. The separation process was performed in a wet process at the critical temperature. The solder in the module was the neighbor part of the thermoelectric material with the lowest melting temperature in the module. We focused on the thermal property of the solder to separate the thermoelectric chips in the module. After the separation process, we prepared the pure thermoelectric material by the chemical etching for an impurity removal. Also the thermoelectric nanopowder was fabricated by a chemical reduction reaction using the recycled thermoelectric materials. The recovered nanopowder was confirmed to the phase of bismuth telluride (Bi2Te3) with the particle size of -15 nm. PMID:25942894

  18. Thermal and Mechanical Characteristics of Polymer Composites Based on Epoxy Resin, Aluminium Nanopowders and Boric Acid

    NASA Astrophysics Data System (ADS)

    Nazarenko, O. B.; Melnikova, T. V.; Visakh, P. M.

    2016-01-01

    The epoxy polymers are characterized by low thermal stability and high flammability. Nanoparticles are considered to be effective fillers of polymer composites for improving their thermal and functional properties. In this work, the epoxy composites were prepared using epoxy resin ED-20, polyethylene polyamine as a hardener, aluminum nanopowder and boric acid fine powder as flame-retardant filler. The thermal characteristics of the obtained samples were studied using thermogravimetric analysis and differential scanning calorimetry. The mechanical characteristics of epoxy composites were also studied. It was found that an addition of all fillers enhances the thermal stability and mechanical characteristics of the epoxy composites. The best thermal stability showed the epoxy composite filled with boric acid. The highest flexural properties showed the epoxy composite based on the combination of boric acid and aluminum nanopowder.

  19. Technology for production of magnetic carbon nanopowders doped with iron and cobalt nanoclusters

    NASA Astrophysics Data System (ADS)

    Gegechkori, T.; Mamniashvili, G.; Kutelia, E.; Rukhadze, L.; Maisuradze, N.; Eristavi, B.; Gventsadze, D.; Akhalkatsi, A.; Gavasheli, T.; Daraselia, D.; Japaridze, D.; Shengelaya, A.

    2015-01-01

    Complex scanning electron microscope and Auger electron spectroscope structure and composition measurements, along with the vibrating sample magnetometer and NMR studies, were carried out on carbon nanoparticles doped with magnetic clusters, which were synthesized by a technology which combines the ethanol vapor pyrolysis method and the chemical vapor deposition process in a horizontal continuous reactor with certain temperature gradients and controlled partial oxygen pressure. The structure and composition data of the synthesized magnetic carbon nanopowders showed that the nanopowders consisted of randomly distributed carbon nanoparticle aggregations that are 200 nm in diameter doped with magnetic clusters. The magnetometry and NMR data are in agreement with the results of the structure analysis, pointing to the existence of a significant superparamagnetic contribution to the synthesized carbon nanoparticles doped with cobalt nanoclusters.

  20. Fast microstructure and phase analyses of nanopowders using combined analysis of transmission electron microscopy scattering patterns.

    PubMed

    Boullay, P; Lutterotti, L; Chateigner, D; Sicard, L

    2014-09-01

    The full quantitative characterization of nanopowders using transmission electron microscopy scattering patterns is shown. This study demonstrates the feasibility of the application of so-called combined analysis, a global approach for phase identification, structure refinement, characterization of anisotropic crystallite sizes and shapes, texture analysis and texture variations with the probed scale, using electron diffraction patterns of TiO2 and Mn3O4 nanocrystal aggregates and platinum films. Electron diffraction pattern misalignments, positioning, and slight changes from pattern to pattern are directly integrated and refined within this approach. The use of a newly developed full-pattern search-match methodology for phase identification of nanopowders and the incorporation of the two-wave dynamical correction for diffraction patterns are also reported and proved to be efficient. PMID:25176993

  1. Production of nickel and iron nanopowders by hydrogen reduction from salts

    NASA Astrophysics Data System (ADS)

    Oglezneva, S. A.; Bulanov, V. Ya.; Kontsevoi, Yu. V.; Ignat'ev, I. E.

    2012-07-01

    The formation of nickel and iron nanoparticles produced by a chemical—metallurgical method and steels made of composite iron powders with nanosized nickel additions is studied. A procedure is developed for calculating the nanopowder particle size and the activation energy of sintering. The results obtained make it possible to decrease the temperature of the process of powder production, to decrease the energy consumed for powder sintering, and to predict the powder nanoparticle size.

  2. Irradiation creep of nano-powder sintered silicon carbide at low neutron fluences

    SciTech Connect

    Koyanagi, Takaaki; Shimoda, Kazuya; Kondo, Sosuke; Hinoki, Tatsuya; Ozawa, Kazumi; Katoh, Yutai

    2014-12-01

    The irradiation creep behavior of nano-powder sintered silicon carbide was investigated using the bend stress relaxation method under neutron irradiation up to 1.9 dpa. The creep deformation was observed at all temperatures ranging from 380 to 1180 °C mainly from the irradiation creep but with the increasing contributions from the thermal creep at higher temperatures. Microstructural observation and data analysis were performed.

  3. [Adsorption of Congo red from aqueous solution on hydroxyapatite].

    PubMed

    Zhan, Yan-Hui; Lin, Jian-Wei

    2013-08-01

    The adsorption of Congo red (CR) from aqueous solution on hydroxyapatite was investigated using batch experiments. The hydroxyapatite was effective for CR removal from aqueous solution. The adsorption kinetics of CR on hydroxyapatite well followed a pseudo-second-order model. The equilibrium adsorption data of CR on hydroxyapatite could be described by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated and showed that the adsorption of CR on hydroxyapatite was spontaneous and exothermic in nature. The CR adsorption capacity for hydroxyapatite decreased significantly with increasing pH from 8 to 10. Thermal regeneration showed that hydroxyapatite could be used for six desorption-adsorption cycles with high removal efficiency for CR in each cycle. The mechanisms for CR adsorption on hydroxyapatite with pH value below the pH at point of zero charge (pH(PZC)) include electrostatic attraction, hydrogen bonding and Lewis acid-base interaction. The mechanisms for CR adsorption on hydroxyapatite with pH value above its pH(PZC) include hydrogen bonding and Lewis acid-base interaction. Results of this work indicate that hydroxyapatite is a promising adsorbent for CR removal from aqueous solution. PMID:24191561

  4. Nutrient-substituted hydroxyapatites: synthesis and characterization

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, D. W.

    1999-01-01

    Incorporation of Mg, S, and plant-essential micronutrients into the structure of synthetic hydroxyapatite (HA) may be advantageous for closed-loop systems, such as will be required on Lunar and Martian outposts, because these apatites can be used as slow-release fertilizers. Our objective was to synthesize HA with Ca, P, Mg, S, Fe, Cu, Mn, Zn, Mo, B, and Cl incorporated into the structure, i.e., nutrient-substituted apatites. Hydroxyapatite, carbonate hydroxyapatite (CHA), nutrient-substituted hydroxyapatite (NHA), and nutrient-substituted carbonate hydroxyapatite (NCHA) were synthesized by precipitating from solution. Chemical and mineralogical analysis of precipitated samples indicated a considerable fraction of the added cations were incorporated into HA, without mineral impurities. Particle size of the HA was in the 1 to 40 nm range, and decreased with increased substitution of nutrient elements. The particle shape of HA was elongated in the c-direction in unsubstituted HA and NHA but more spherical in CHA and NCHA. The substitution of cations and anions in the HA structure was confirmed by the decrease of the d[002] spacing of HA with substitution of ions with an ionic radius less than that of Ca or P. The DTPA-extractable Cu ranged from 8 to 8429 mg kg-1, Zn ranged from 57 to 1279 mg kg-1, Fe from 211 to 2573 mg kg-1, and Mn from 190 to 1719 mg kg-1, depending on the substitution level of each element in HA. Nutrient-substituted HA has the potential to be used as a slow-release fertilizer to supply micronutrients, S, and Mg in addition to Ca and P.

  5. Ultrasonic deagglomeration of aluminum nanopowders with multi-walled carbon nanotube mixtures

    SciTech Connect

    Kozulin, Alexander A. Vorozhtsov, Sergey A. Kulkov, Sergey S.; Kulkov, Sergey N.; Teipel, U.

    2015-10-27

    Comprehensive investigations of aluminum nanopowders, multi-walled carbon nanotubes, and aluminum mixtures with multi-walled carbon nanotubes subjected to ultrasonic deagglomeration in a liquid medium were performed, using microstructural, X-ray diffraction, thermogravimetric, and calorimetric analyses, and specific surface area measurements. The regime of ultrasonic deagglomeration of aluminum nanopowders with multi-walled carbon nanotubes in a liquid medium is described, during which the division of large agglomerates and creation of homogeneous distribution of mixtures components in the volume takes place. It was determined that ultrasonic treatment influences the morphology and crystalline structure of investigated mixtures, contributes to the appearance of X-ray amorphous phase, decreases the specific surface area of the aluminum nanopowder from 13 to 12 m{sup 2}/g, and increases the pore volume and average size from 0.04 to 0.06 cm{sup 3}/g and from 12 to 19 nm, respectively. The size of coherently-diffracting domain was determined by the X-ray diffraction analysis is close to that estimated from the specific surface area and corresponds to average crystallites size in the materials under study.

  6. Impact of isoelectric points of nanopowders in electrolytes on electrochemical characteristics of dye sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Mohanty, Shyama Prasad; Bhargava, Parag

    2012-11-01

    Nanoparticle loaded quasi solid electrolytes are important from the view point of developing electrolytes for dye sensitized solar cells (DSSCs) having long term stability. The present work shows the influence of isoelectric point of nanopowders in electrolyte on the photoelectrochemical characteristics of DSSCs. Electrolytes with nanopowders of silica, alumina and magnesia which have widely differing isoelectric points are used in the study. Adsorption of ions from the electrolyte on the nanopowder surface, characterized by zeta potential measurement, show that cations get adsorbed on silica, alumina surface while anions get adsorbed on magnesia surface. The electrochemical characteristics of nanoparticulate loaded electrolytes are examined through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). DSSCs fabricated using liquid, silica or alumina loaded electrolytes exhibit almost similar performance. But interestingly, the magnesia loaded electrolyte-based cell show lower short circuit current density (JSC) and much higher open circuit voltage (VOC), which is attributed to adsorption of anions. Such anionic adsorption prevents the dark reaction in magnesia loaded electrolyte-based cell and thus, enhances the VOC by almost 100 mV as compared to liquid electrolyte based cell. Also, higher electron life time at the titania/electrolyte interface is observed in magnesia loaded electrolyte-based cell as compared to others.

  7. Ultrasonic deagglomeration of aluminum nanopowders with multi-walled carbon nanotube mixtures

    NASA Astrophysics Data System (ADS)

    Kozulin, Alexander A.; Vorozhtsov, Sergey A.; Kulkov, Sergey S.; Teipel, U.; Kulkov, Sergey N.

    2015-10-01

    Comprehensive investigations of aluminum nanopowders, multi-walled carbon nanotubes, and aluminum mixtures with multi-walled carbon nanotubes subjected to ultrasonic deagglomeration in a liquid medium were performed, using microstructural, X-ray diffraction, thermogravimetric, and calorimetric analyses, and specific surface area measurements. The regime of ultrasonic deagglomeration of aluminum nanopowders with multi-walled carbon nanotubes in a liquid medium is described, during which the division of large agglomerates and creation of homogeneous distribution of mixtures components in the volume takes place. It was determined that ultrasonic treatment influences the morphology and crystalline structure of investigated mixtures, contributes to the appearance of X-ray amorphous phase, decreases the specific surface area of the aluminum nanopowder from 13 to 12 m2/g, and increases the pore volume and average size from 0.04 to 0.06 cm3/g and from 12 to 19 nm, respectively. The size of coherently-diffracting domain was determined by the X-ray diffraction analysis is close to that estimated from the specific surface area and corresponds to average crystallites size in the materials under study.

  8. Photoluminescent BaMoO{sub 4} nanopowders prepared by complex polymerization method (CPM)

    SciTech Connect

    Azevedo Marques, Ana Paula de . E-mail: apamarques@liec.ufscar.br; Melo, Dulce M.A. de; Paskocimas, Carlos A.; Pizani, Paulo S.; Joya, Miryam R.; Leite, Edson R.; Longo, Elson

    2006-03-15

    The BaMoO{sub 4} nanopowders were prepared by the Complex Polymerization Method (CPM). The structure properties of the BaMoO{sub 4} powders were characterized by FTIR transmittance spectra, X-ray diffraction (XRD), Raman spectra, photoluminescence spectra (PL) and high-resolution scanning electron microscopy (HR-SEM). The XRD, FTIR and Raman data showed that BaMoO{sub 4} at 300 deg. C was disordered. At 400 deg. C and higher temperature, BaMoO{sub 4} crystalline scheelite-type phases could be identified, without the presence of additional phases, according to the XRD, FTIR and Raman data. The calculated average crystallite sizes, calculated by XRD, around 40 nm, showed the tendency to increase with the temperature. The crystallite sizes, obtained by HR-SEM, were around of 40-50 nm. The sample that presented the highest intensity of the red emission band was the one heat treated at 400 deg. C for 2 h, and the sample that displayed the highest intensity of the green emission band was the one heat treated at 700 deg. C for 2 h. The CPM was shown to be a low cost route for the production of BaMoO{sub 4} nanopowders, with the advantages of lower temperature, smaller time and reduced cost. The optical properties observed for BaMoO{sub 4} nanopowders suggested that this material is a highly promising candidate for photoluminescent applications.

  9. Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon

    PubMed Central

    Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojtaś, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

    2013-01-01

    Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics. PMID:23884324

  10. Ferroelectric polarization in nanocrystalline hydroxyapatite thin films on silicon.

    PubMed

    Lang, S B; Tofail, S A M; Kholkin, A L; Wojtaś, M; Gregor, M; Gandhi, A A; Wang, Y; Bauer, S; Krause, M; Plecenik, A

    2013-01-01

    Hydroxyapatite nanocrystals in natural form are a major component of bone--a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics. PMID:23884324

  11. Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon

    NASA Astrophysics Data System (ADS)

    Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojtaś, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

    2013-07-01

    Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics.

  12. Synthesis of Si, Mg substituted hydroxyapatites and their sintering behaviors.

    PubMed

    Kim, S R; Lee, J H; Kim, Y T; Riu, D H; Jung, S J; Lee, Y J; Chung, S C; Kim, Y H

    2003-04-01

    Si, Mg-substituted hydroxyapatites, alone and co-substituted, have been prepared to obtain biomaterials having an improved biocompatibility. From FT-IR, XRD and ICP analyses, it was confirmed that single phases of hydroxyapatite substituted by Si alone or co-substituted by Si, Mg. The XRD data indicated the absence of extra phases related to silicon and magnesium oxide or other calcium phosphate species. Si-substituted hydroxyapatite of up to 2 wt% for Si and Si, Mg co-substituted hydroxyapatite of 1 wt% for the each ion keep their original structures intact for the sintering temperatures of up to 1200 degrees C. However, it is observed that ion substitutions by an amount higher than the above ratios for each hydroxyapatite lead to destabilization of original structures of the hydroxyapatite and to the production of tricalcium phosphate and calcium phosphate silicate phases when the samples were sintered at 1100 degrees C or higher. PMID:12527280

  13. Simple route for nano-hydroxyapatite properties expansion.

    PubMed

    Rojas, L; Olmedo, H; García-Piñeres, A J; Silveira, C; Tasic, L; Fraga, F; Montero, M L

    2015-09-01

    Simple surface modification of nano-hydroxyapatite, through acid-basic reactions, allows expanding the properties of this material. Introduction of organic groups such as hydrophobic alkyl chains, carboxylic acid, and amide or amine basic groups on the hydroxyapatite surface systematically change the polarity, surface area, and reactivity of hydroxyapatite without modifying its phase. Physical and chemical properties of the new derivative particles were analyzed. The biocompatibility of modified Nano-Hap on Raw 264.7 cells was also assessed. PMID:26481455

  14. Porous hydroxyapatite and gelatin/hydroxyapatite microspheres obtained by calcium phosphate cement emulsion.

    PubMed

    Perez, Roman A; Del Valle, Sergio; Altankov, George; Ginebra, Maria-Pau

    2011-04-01

    Hydroxyapatite and hybrid gelatine/hydroxyapatite microspheres were obtained through a water in oil emulsion of a calcium phosphate cement (CPC). The setting reaction of the CPC, in this case the hydrolysis of α-tricalcium phosphate, was responsible for the consolidation of the microspheres. After the setting reaction, the microspheres consisted of an entangled network of hydroxyapatite crystals, with a high porosity and pore sizes ranging between 0.5 and 5 μm. The size of the microspheres was tailored by controlling the viscosity of the hydrophobic phase, the rotation speed, and the initial powder size of the CPC. The incorporation of gelatin increased the sphericity of the microspheres, as well as their size and size dispersion. To assess the feasibility of using the microspheres as cell microcarriers, Saos-2 cells were cultured on the microspheres. Fluorescent staining, SEM studies, and LDH quantification showed that the microspheres were able to sustain cell growth. Cell adhesion and proliferation was significantly improved in the hybrid gelatin/hydroxyapatite microspheres as compared to the hydroxyapatite ones. PMID:21290594

  15. Morphology and electronic structure of nanoscale powders of calcium hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Kurgan, Nataly; Karbivskyy, Volodymyr; Kasyanenko, Vasyl

    2015-02-01

    Atomic force microscopy, infrared spectroscopy and NMR studied morphological and physicochemical properties of calcium hydroxyapatite powders produced by changing the temperature parameters of synthesis. Features of morphology formation of calcium hydroxyapatite nanoparticles with an annealing temperature within 200°C to 1,100°C were determined. It is shown that the particle size of the apatite obtained that annealed 700°C is 40 nm corresponding to the particle size of apatite in native bone. The effect of dimension factor on structural parameters of calcium hydroxyapatite is manifested in a more local symmetry of the PO4 3- tetrahedra at nanodispersed calcium hydroxyapatite.

  16. Mechanical properties and biocompatibility of the sputtered Ti doped hydroxyapatite.

    PubMed

    Vladescu, A; Padmanabhan, S C; Ak Azem, F; Braic, M; Titorencu, I; Birlik, I; Morris, M A; Braic, V

    2016-10-01

    The hydroxyapatite enriched with Ti were prepared as possible candidates for biomedical applications especially for implantable devices that are in direct contact to the bone. The hydroxyapatites with different Ti content were prepared by RF magnetron sputtering on Ti-6Al-4V alloy using pure hydroxyapatite and TiO2 targets. The content of Ti was modified by changing the RF power fed on TiO2 target. The XPS and FTIR analyses revealed the presence of hydroxyapatite structure. The hardness and elastic modulus of the hydroxyapatite were increased by Ti addition. After 5 days of culture, the cell viability of the Ti-6Al-4V was enhanced by depositing with undoped or doped hydroxyapatite. The Ti additions led to an increase in cell viability of hydroxyapatite, after 5 days of culture. The electron microscopy showed the presence of more cells on the surface of Ti-enriched hydroxyapatite than those observed on the surface of the uncoated alloys or undoped hydroxyapatite. PMID:27450034

  17. Fabrication of alpha-Fe2O3 nanopowder modified glassy carbon electrode for applications in electrochemical sensing.

    PubMed

    Goyal, Rajendra N; Pandey, Ashish K; Kaur, Davinder; Kumar, Ashvani

    2009-08-01

    In the present study, Fe2O3 nanopowder has been grown by Ultrasonic mist chemical vapor deposition (UM-CVD), which is a promising method for large area deposition at low temperatures taking in to account of its simplicity, inexpensiveness and safety. Room temperature XRD results revealed prominent hematite phase with intense (104) reflection and was also in agreement with the HR-TEM results. In situ high temperature X-ray diffraction (XRD) studies clearly indicated the change of phase from hematite to magnetite as the temperature increases above 300 degrees C. The surface morphology and particle size distribution of Fe2O3 nanopowder were characterized using field emission scanning electron microscope (FE-SEM) and high resolution transmission electron microscope (HR-TEM), which revealed that the particles were spherical in nature and distributed in range of 50-100 nm. SQUID magnetometry results indicate the ferromagnetic nature of the nanopowder with crystallite size of 6 nm as calculated from M-H curve. Transmittance of approximately 55% and estimated direct band gap of 2.5 eV was observed. Further, the nanopowder was used to modify glassy carbon electrode (GCE) and the modified electrode was found to exhibit electrocatalytic activity for the oxidation of dopamine. It is expected that the nanopowder will exhibit promising applications in the development of sensors. PMID:19928136

  18. Synthesis of hollow cobalt oxide nanopowders by a salt-assisted spray pyrolysis process applying nanoscale Kirkendall diffusion and their electrochemical properties.

    PubMed

    Ju, Hyeon Seok; Cho, Jung Sang; Kim, Jong Hwa; Choi, Yun Ju; Kang, Yun Chan

    2015-12-21

    A new concept for preparing hollow metal oxide nanopowders by salt-assisted spray pyrolysis applying nanoscale Kirkendall diffusion is introduced. The composite powders of metal oxide and indecomposable metal salt are prepared by spray pyrolysis. Post-treatment under a reducing atmosphere and subsequent washing using distilled water produce aggregation-free metal nanopowders. The metal nanopowders are then transformed into metal oxide hollow nanopowders by nanoscale Kirkendall diffusion. Co3O4 hollow nanopowders are prepared as first target materials. A cobalt oxide-NaCl composite powder prepared by spray pyrolysis transforms into several Co3O4 hollow nanopowders by several treatment processes. The discharge capacities of the Co3O4 nanopowders with filled and hollow structures at a current density of 1 A g(-1) for the 150th cycle are 605 and 775 mA h g(-1), respectively. The hollow structure formed by nanoscale Kirkendall diffusion improves the lithium-ion storage properties of Co3O4 nanopowders. PMID:26571144

  19. Reactive hydroxyapatite fillers for pectin biocomposites.

    PubMed

    Munarin, Fabiola; Petrini, Paola; Barcellona, Giulia; Roversi, Tommaso; Piazza, Laura; Visai, Livia; Tanzi, Maria Cristina

    2014-12-01

    In this work, a novel injectable biocomposite hydrogel is produced by internal gelation, using pectin as organic matrix and hydroxyapatite either as crosslinking agent and inorganic reinforcement. Tunable gelling kinetics and rheological properties are obtained varying the hydrogels' composition, with the final aim of developing systems for cell immobilization. The reversibility by dissolution of pectin-hydroxyapatite hydrogels is achieved with saline solutions, to possibly accelerate the release of the cells or active agents immobilized. Texture analysis confirms the possibility of extruding the biocomposites from needles with diameters from 20 G to 30 G, indicating that they can be implanted with minimally-invasive approaches, minimizing the pain during injection and the side effects of the open surgery. L929 fibroblasts entrapped in the hydrogels survive to the immobilization procedure and exhibit high cell viability. On the overall, these systems result to be suitable supports for the immobilization of cells for tissue regeneration applications. PMID:25491814

  20. Biomineralization of nanoscale single crystal hydroxyapatite.

    PubMed

    Omokanwaye, Tiffany; Wilson, Otto C; Gugssa, Ayelle; Anderson, Winston

    2015-11-01

    The chemical and physical characteristics of nanocrystalline hydroxyapatite particles which formed during the subcutaneous implantation of crab shell in Sprague-Dawley rats were studied using selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM). The initial SAED characterization evidence indicated the presence of an amorphous calcium phosphate phase. The electron dense nanophase particles which formed in the wound healing zone displayed broad diffuse rings which usually indicate a low crystalline order or amorphous phase. High resolution transmission electron microscopy (HRTEM) revealed that these mineralized regions contained discrete single crystal particles less than 5nm in size. Micrographs taken at successively higher magnifications revealed very small nanoparticles with a hexagonal arrangement of ion channels with characteristic spacing of 0.54nm and 0.23nm. This study revealed that single crystal hydroxyapatite nanoparticles consisting of only a few unit cells formed via a biomineralization directed process. PMID:26249568

  1. Mechanical properties of hydroxyapatite/mica composite.

    PubMed

    Nordström, E G; Herø, H; Jørgensen, R B

    1994-01-01

    Bend specimens of the inorganic synthetic materials hydroxyapatite (HA) and a composite of hydroxyapatite/muscovite mica have been prepared and tested mechanically. Sintering followed by hot isostatic pressing (HIP) without encapsulation gave an increased strength for HA alone, but no significant increase in strength compared with sintering alone for HA/mica composites. The bend strength of the HA/mica composite was inferior to that of HA alone, the reason being inadequate bonding between HA and mica. HIP in glass capsules and an increased cold compaction pressure tended to improve the bend strength of the composite. Corrosion in tris for 7 d did not affect the bend strength of the investigated materials significantly. PMID:7950878

  2. Fracture toughness of hydroxyapatite/mica composite, packed hydroxyapatite, alumina ceramics, silicon nitride and -carbide.

    PubMed

    Nordström, E G; Yokobori, A T; Yokobori, T; Aizawa, Y

    1998-01-01

    By using the fracture toughness estimation method based on two-dimensional map, it was found that the ductility of the high porosity hydroxyapatite/mice composite was comparable with silicon carbide. It was measured to be higher than that of packed hydroxyapatite. Alumina ceramics with more than 96% aluminium oxide showed a higher fracture toughness than the composite material. When bending strength was compared, the strength of the composite was two or three times lower than that of packed hydroxyapatite and much lower than the other studied materials. The composite material showed high porosity, which in turn gives it a lower bending strength. However, the high porosity is more favourable for biocompatibility. PMID:9713684

  3. Identification of hydroxyapatite crystals in synovial fluid.

    PubMed

    Halverson, P B; McCarty, D J

    1979-04-01

    A semiquantitative technique employing (14C) ethane-1-hydroxy 1, -1-diphosphonate (EHDP) binding has been used to detect crystals, presumably hydroxyapatite, in human synovial fluid samples which were handled to prevent the formation of artifactual mineral phase. Binding material was found in 29% of non-inflammatory and in none of inflammatory joint fluids. Nuclide binding material was strongly correlated with the presence of CPPD crystals and with radiographic evidence of cartilaginous degeneration. PMID:106859

  4. Chemical characterization of silicon-substituted hydroxyapatite.

    PubMed

    Gibson, I R; Best, S M; Bonfield, W

    1999-03-15

    Bioceramic specimens have been prepared by incorporating a small amount of silicon (0.4 wt %) into the structure of hydroxyapatite [Ca10(PO4)6(OH)2, HA] via an aqueous precipitation reaction to produce a silicon-substituted hydroxyapatite (Si-HA). The results of chemical analysis confirmed the proposed substitution of the silicon (or silicate) ion for the phosphorus (or phosphate) ion in hydroxyapatite. The Si-HA was produced by first preparing a silicon-substituted apatite (Si-Ap) by a precipitation process. A single-phase Si-HA was obtained by heating/calcining the as-prepared Si-Ap to temperatures above 700 degrees C; no secondary phases, such as tricalcium phosphate (TCP), tetracalcium phosphate (TeCP), or calcium oxide (CaO), were observed by X-ray diffraction analysis. Although the X-ray diffraction patterns of Si-HA and stoichiometric HA appeared to be identical, refinement of the diffraction data revealed some small structural differences between the two materials. The silicon substitution in the HA lattice resulted in a small decrease in the a axis and an increase in the c axis of the unit cell. This substitution also caused a decrease in the number of hydroxyl (OH) groups in the unit cell, which was expected from the proposed substitution mechanism. The incorporation of silicon in the HA lattice resulted in an increase in the distortion of the PO4 tetrahedra, indicated by an increase in the distortion index. Analysis of the Si-HA by Fourier transform infrared (FTIR) spectroscopy indicated that although the amount of silicon incorporated into the HA lattice was small, silicon substitution appeared to affect the FTIR spectra of HA, in particular the P-O vibrational bands. The results demonstrate that phase-pure silicon-substituted hydroxyapatite may be prepared using a simple precipitation technique. PMID:10397946

  5. Electrophoretic deposition of composite hydroxyapatite-chitosan coatings

    SciTech Connect

    Pang Xin; Zhitomirsky, Igor . E-mail: zhitom@mcmaster.ca

    2007-04-15

    Cathodic electrophoretic deposition has been utilized for the fabrication of composite hydroxyapatite-chitosan coatings on 316L stainless steel substrates. The addition of chitosan to the hydroxyapatite suspensions promoted the electrophoretic deposition of the hydroxyapatite nanoparticles and resulted in the formation of composite coatings. The obtained coatings were investigated by X-ray diffraction, thermogravimetric and differential thermal analysis, scanning and transmission electron microscopy, potentiodynamic polarization measurements, and electrochemical impedance spectroscopy. It was shown that the deposit composition can be changed by a variation of the chitosan or hydroxyapatite concentration in the solutions. Experimental conditions were developed for the fabrication of hydroxyapatite-chitosan nanocomposites containing 40.9-89.8 wt.% hydroxyapatite. The method enabled the formation of adherent and uniform coatings of thicknesses up to 60 {mu}m. X-ray studies revealed that the preferred orientation of the hydroxyapatite nanoparticles in the chitosan matrix increases with decreasing hydroxyapatite content in the composite coatings. The obtained coatings provided the corrosion protection for the 316L stainless steel substrates00.

  6. Optical properties and radiation stability of submicro- and nanopowders titanium dioxide measured in situ

    NASA Astrophysics Data System (ADS)

    Mikhailov, M. M.; Neshchimenko, V. V.; Yuryev, S. A.

    2016-04-01

    This study carried out an in situ and external investigation on the reflective spectra of micro- and nanopowders titanium dioxide before and after irradiation by 30 keV electrons. The particle sizes range from 60-240 nm. It was established that the decrease in the particle size leads to an increase in intrinsic defects. The particles with intrinsic defects are then transformed into absorption centers during irradiation as a result of optical degradation of TiO2 powders. High radiation stability has particle sizes range from 80-160 nm.

  7. Photocatalytic degradation of betamethasone sodium phosphate in aqueous solution using ZnO nanopowder

    NASA Astrophysics Data System (ADS)

    Giahi, M.; Taghavi, H.; Habibi, S.

    2012-12-01

    The photocatalytic degradation of betamethasone sodium phosphate has been investigated in aqueous phase by using ultraviolet (UV) light and ZnO nanopowder. The effect of catalyst loading, irradiation time, pH, addition of oxidizers, effect of alcohol and anion presence on the reaction rate was ascertained and optimum conditions for maximum degradation were determined. The photocatalytic degradation of betamethasone sodium phosphate was strongly influenced by these parameters. The optimum amount of the photocatalyst used is 0.44 g/L. The efficiency of betamethasone sodium phosphate increases with the photo-degradation increase of the irradiation time.

  8. Silicide Nanopowders as Low-Cost and High-Performance Thermoelectric Materials

    NASA Astrophysics Data System (ADS)

    Chen, Renkun

    2013-06-01

    Thermoelectric devices directly convert heat into electricity and are very attractive for waste heat recovery and solar energy utilization. If thermoelectric devices can be made sufficiently efficient and inexpensive, then they will become a transformative energy technology that can tap a significant portion (10-20%) of the vast amount of heat existing in nature as well as industrial processes. Nanopowders of Earth-abundant, silicide-based materials, such as Mg2Si and its alloys, provide a unique opportunity to realize this goal. This article will present an overview of recent advances in the synthesis and thermoelectric properties of silicide-based nanostructured materials.

  9. Microstructural and optical characterization of PZT nanopowder prepared at low temperature

    NASA Astrophysics Data System (ADS)

    Ghasemifard, M.; Hosseini, S. M.; Khorsand Zak, A.; Khorrami, Gh. H.

    2009-01-01

    Lead zirconate titanate (PZT) nanopowders were synthesized by the metal organic and salt precursor's sol-gel combustion technique. Single-phase perovskite PZT powders were obtained after heat treatment at temperature of 500 °C. The effects of calcination temperature on lattice parameters and tetragonality of PZT powders have been discussed. The average particles size is estimated to be around 70-80 nm by SEM observations. The absorption coefficient ( α) and the band-gap energy ( Eg) of the perovskite oxide have been estimated using Fourier transform infrared (FTIR) spectroscopy.

  10. Plasma Synthesized Doped Boron Nanopowder for MgB2 Superconductors

    SciTech Connect

    James V. Marzik

    2012-03-26

    Under this program, a process to synthesize nano-sized doped boron powder by a plasma synthesis process was developed and scaled up from 20 gram batches at program start to over 200 grams by program end. Over 75 batches of boron nanopowder were made by RF plasma synthesis. Particle sizes were typically in the 20-200 nm range. The powder was synthesized by the reductive pyrolysis of BCl{sub 3} in hydrogen in an RF plasma. A wide range of process parameters were investigated including plasma power, torch geometry, gas flow rates, and process pressure. The powder-in-tube technique was used to make monofilament and multifilament superconducting wires. MgB{sub 2} wire made with Specialty Materials plasma synthesized boron nanopowder exhibited superconducting properties that significantly exceeded the program goals. Superconducting critical currents, J{sub c}, in excess of 10{sup 5} A cm{sup -2} at magnetic fields of 8 tesla were reproducibly achieved. The upper critical magnetic field in wires fabricated with program boron powder were H{sub c2}(0) = 37 tesla, demonstrating the potential of these materials for high field magnet applications. T{sub c} in carbon-doped MgB{sub 2} powder showed a systematic decrease with increasing carbon precursor gas flows, indicating the plasma synthesis process can give precise control over dopant concentrations. Synthesis rates increased by a factor of 400% over the course of the program, demonstrating the scalability of the powder synthesis process. The plasma synthesis equipment at Specialty Materials has successfully and reproducibly made high quality boron nanopowder for MgB{sub 2} superconductors. Research and development from this program enabled Specialty Materials to successfully scale up the powder synthesis process by a factor of ten and to double the size of its powder pilot plant. Thus far the program has been a technical success. It is anticipated that continued systematic development of plasma processing parameters, dopant

  11. Spatio-temporal dynamics behind the shock front from compacted metal nanopowders.

    PubMed

    Leela, Ch; Venkateshwarlu, P; Singh, Raja V; Verma, Pankaj; Kiran, P Prem

    2014-03-10

    Laser ablated shock waves from compacted metal nanoenergetic powders of Aluminum (Al), Nickel coated Aluminum (Ni-Al) was characterized using shadowgraphy technique and compared with that from Boron Potassium Nitrate (BKN), Ammonium Perchlorate (AP) and Potassium Bromide (KBr) powders. Ablation is created by focused second harmonic (532 nm, 7 ns) of Nd:YAG laser. Time resolved shadowgraphs of propagating shock front and contact front revealed dynamics and the precise time of energy release of materials under extreme ablative pressures. Among the different compacted materials studied, Al nanopowders have maximum shock velocity and pressure behind the shock front compared to others. PMID:24800282

  12. Spatio-temporal dynamics behind the shock front from compacted metal nanopowders.

    PubMed

    Leela, Ch; Venkateshwarlu, P; Singh, Raja V; Verma, Pankaj; Kiran, P Prem

    2014-03-10

    Laser ablated shock waves from compacted metal nanoenergetic powders of Aluminum (Al), Nickel coated Aluminum (Ni-Al) was characterized using shadowgraphy technique and compared with that from Boron Potassium Nitrate (BKN), Ammonium Perchlorate (AP) and Potassium Bromide (KBr) powders. Ablation is created by focused second harmonic (532 nm, 7 ns) of Nd:YAG laser. Time resolved shadowgraphs of propagating shock front and contact front revealed dynamics and the precise time of energy release of materials under extreme ablative pressures. Among the different compacted materials studied, Al nanopowders have maximum shock velocity and pressure behind the shock front compared to others. PMID:24922235

  13. Adhesion to and decalcification of hydroxyapatite by carboxylic acids.

    PubMed

    Yoshida, Y; Van Meerbeek, B; Nakayama, Y; Yoshioka, M; Snauwaert, J; Abe, Y; Lambrechts, P; Vanherle, G; Okazaki, M

    2001-06-01

    Fundamental to the processes of decalcification of or adhesion to mineralized tissues is the molecular interaction of acids with hydroxyapatite. This study was undertaken to chemically analyze the interaction of 1 mono-, 2 di-, 1 tri-, and 2 polycarboxylic acids with hydroxyapatite in an attempt to elucidate the underlying mechanism. Maleic, citric, and lactic acid decalcified hydroxyapatite, in contrast to oxalic acid and the two polycarboxylic acids that were chemically bonded to hydroxyapatite. Solubility tests showed that the calcium salts of the former were very soluble, whereas those of the latter could hardly be dissolved in the respective acid solutions. Based on these data, an adhesion/decalcification concept was advanced that predicts that carboxylic acids, regardless of concentration/pH, either adhere to or decalcify hydroxyapatite, depending on the dissolution rate of the respective calcium salts in the acid solution. This contrasting behavior of organic acids most likely results from their differential structural conformations. PMID:11499514

  14. Methods of synthesizing hydroxyapatite powders and bulk materials

    DOEpatents

    Luo, P.

    1999-01-12

    Methods are provided for producing non-porous controlled morphology hydroxyapatite granules of less than 8 {micro}m by a spray-drying process. Solid or hollow spheres or doughnuts can be formed by controlling the volume fraction and viscosity of the slurry as well as the spray-drying conditions. Methods of providing for homogeneous cellular structure hydroxyapatite granules are also provided. Pores or channels or varying size and number can be formed by varying the temperature at which a hydroxyapatite slurry formed in basic, saturated ammonium hydroxide is spray-dried. Methods of providing non-porous controlled morphology hydroxyapatite granules in ammonium hydroxide are also provided. The hydroxyapatite granules and bulk materials formed by these methods are also provided. 26 figs.

  15. Methods of synthesizing hydroxyapatite powders and bulk materials

    DOEpatents

    Luo, Ping

    1999-01-12

    Methods are provided for producing non-porous controlled morphology hydroxyapatite granules of less than 8 .mu.m by a spray-drying process. Solid or hollow spheres or doughnuts can be formed by controlling the volume fraction and viscosity of the slurry as well as the spray-drying conditions. Methods of providing for homogenous cellular structure hydroxyapatite granules are also provided. Pores or channels or varying size and number can be formed by varying the temperature at which a hydroxyapatite slurry formed in basic, saturated ammonium hydroxide is spray-dried. Methods of providing non-porous controlled morphology hydroxyapatite granules in ammonium hydroxide are also provided. The hydroxyapatite granules and bulk materials formed by these methods are also provided.

  16. Effect of zeta potentials on bovine serum albumin adsorption to hydroxyapatite surfaces.

    PubMed

    Miyake, Nahoko; Sato, Toru; Maki, Yoshinobu

    2013-01-01

    The aim of the present study was to examine the adsorption of bovine serum albumin (BSA) to hydroxyapatite surfaces by means of zeta potential. The electrophoretic mobility of both hydroxyapatite and BSA were negative, with BSA itself less negative than hydroxyapatite. The zeta potential of the surface of BSA-adsorbed hydroxyapatite was significantly more negative than that of hydroxyapatite alone (p<0.0001). The BSA histogram indicated two negative peaks, and the zeta potential of BSA-adsorbed hydroxyapatite also showed two similar negative peaks. These results suggest that BSA adsorption to hydroxyapatite surfaces is related to electrostatic interaction. PMID:23903580

  17. Ultrastructure of regenerated bone mineral surrounding hydroxyapatite-alginate composite and sintered hydroxyapatite.

    PubMed

    Rossi, Andre L; Barreto, Isabela C; Maciel, William Q; Rosa, Fabiana P; Rocha-Leão, Maria H; Werckmann, Jacques; Rossi, Alexandre M; Borojevic, Radovan; Farina, Marcos

    2012-01-01

    We report the ultrastructure of regenerated bone surrounding two types of biomaterials: hydroxyapatite-alginate composite and sintered hydroxyapatite. Critical defects in the calvaria of Wistar rats were filled with micrometer-sized spherical biomaterials and analyzed after 90 and 120 days of implantation by high-resolution transmission electron microscopy and Fourier transform infrared attenuated total reflectance microscopy, respectively. Infrared spectroscopy showed that hydroxyapatite of both biomaterials became more disordered after implantation in the rat calvaria, indicating that the biological environment induced modifications in biomaterials structure. We observed that the regenerated bone surrounding both biomaterials had a lamellar structure with type I collagen fibers alternating in adjacent lamella with angles of approximately 90°. In each lamella, plate-like apatite crystals were aligned in the c-axis direction, although a rotation around the c-axis could be present. Bone plate-like crystal dimensions were similar in regenerated bone around biomaterials and pre-existing bone in the rat calvaria. No epitaxial growth was observed around any of the biomaterials. A distinct mineralized layer was observed between new bone and hydroxyapatite-alginate biomaterial. This region presented a particular ultrastructure with crystallites smaller than those of the bulk of the biomaterial, and was possibly formed during the synthesis of alginate-containing composite or in the biological environment after implantation. Round nanoparticles were observed in regions of newly formed bone. The findings of this work contribute to a better understanding of the role of hydroxyapatite based biomaterials in bone regeneration processes at the nanoscale. PMID:22057083

  18. Properties of magnesium-substituted hydroxyapatite and the plasma coatings based on it

    NASA Astrophysics Data System (ADS)

    Lyasnikova, A. V.; Pichkhidze, S. Ya.; Dudareva, O. A.; Markelova, O. A.

    2015-11-01

    Magnesium-substituted hydroxyapatite is synthesized and deposited by plasma spraying, and the coating and the products of hydroxyapatite decomposition are analyzed. The phase composition of magnesium- substituted hydroxyapatite deposited by plasma spraying undergoes changes. The coating consisting of molten magnesium-substituted hydroxyapatite powder particles with pores between them has a homogeneous structure over the surface and throughout the internal structure and adhesion characteristics that exceed those of hydroxyapatite coatings.

  19. Synthesis and characterization of NiO nanopowder by sol-gel process

    NASA Astrophysics Data System (ADS)

    Ningsih, Sherly Kasuma Warda

    2015-09-01

    Preparation of nickel oxide (NiO) nanopowder by sol-gel process has been studied. NiO nanopowders were obtained by sol-gel method by using nickel nitrate hexahydrate and sodium hydroxide and aquadest were used as precursor, agent precipitator and solvent, respectively. The powders were formed by drying at 110°C and followed by heating in the furnace at 400°C for 1.5 hours. The product was obtained black powder. The product was characterized by Energy Dispesive X-ray Fluorescence (ED-XRF), X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The ED-XRF pattern shows the composition of NiO produced was 97.1%. The XRD pattern showed NiO forms were produced generally in monoclinic stucture. The crystalline size of NiO was obtained in the range 40-85 nm. SEM micrograph clearly showed that powder had a spherical with uniform distribution size is 0.1-1.0 µm approximately.

  20. Dependence of viscosity of suspensions of ceramic nanopowders in ethyl alcohol on concentration and temperature.

    PubMed

    Zyła, Gaweł; Cholewa, Marian; Witek, Adam

    2012-01-01

    : This work presents results of measurements of viscosity of suspensions including yttrium oxide (Y2O3), yttrium aluminum garnet (Y3Al5O12) and magnesium aluminum spinel (MgAl2O4) nanopowders in ethanol. Nanoparticles used in our research were either commercially available (Baikowski) or nanopowders newly developed in the Institute of Ceramics and Building Materials in Warsaw, Poland. The study was conducted in a wide range of shear rates (0.01 to 2,000 s-1) and temperature interval from -15°C to 20°C. A Haake Mars 2 rheometer from Thermo Fisher, Germany, was used in the Biophysics Laboratory at Rzeszów University of Technology. Most of the samples show a non-Newtonian behaviour. It was confirmed with a Rheo-NMR system from Bruker that 10% by weight of Y2O3 suspension is a non-Newtonian fluid. In this work, we also report an unexpected behaviour of the viscosity of some samples (Y2O3 and Y3Al5O12) due to sedimentation effect. PMID:22824064

  1. Three-dimensional simulations of nanopowder compaction processes by granular dynamics method

    NASA Astrophysics Data System (ADS)

    Boltachev, G. Sh.; Lukyashin, K. E.; Shitov, V. A.; Volkov, N. B.

    2013-07-01

    In order to describe and to study the processes of cold compaction within the discrete element method a three-dimensional model of nanosized powder is developed. The elastic forces of repulsion, the tangential forces of “friction” (Cattaneo-Mindlin), and the dispersion forces of attraction (van der Waals-Hamaker), as well as the formation and destruction of hard bonds between the individual particles are taken into account. The monosized powders with the size of particles in the range 10-40 nm are simulated. The simulation results are compared to the experimental data of the alumina nanopowders compaction. It is shown that the model allows us to reproduce experimental data reliably and, in particular, describes the size effect in the compaction processes. A number of different external loading conditions is used in order to perform the theoretical and experimental researches. The uniaxial compaction (the closed-die compaction), the biaxial (radial) compaction, and the isotropic compaction (the cold isostatic pressing) are studied. The real and computed results are in a good agreement with each other. They reveal a weak sensitivity of the oxide nanopowders to the loading condition (compaction geometry). The application of the continuum theory of the plastically hardening porous body, which is usually used for the description of powders, is discussed.

  2. A study on the effect factors of sol-gel synthesis of yttrium aluminum garnet nanopowders

    NASA Astrophysics Data System (ADS)

    Yang, Lin; Lu, Tiecheng; Xu, Hui; Zhang, Wei; Ma, Benyuan

    2010-03-01

    Yttrium aluminum garnet (YAG) nanopowders were synthesized by sol-gel method using aluminum nitrate, yttrium nitrate, and citric acid as starting materials, de-ionized water, ethanol, and ethylene glycol as solvents, respectively. The phase formation process, state of particle size distribution (PSD), compositions, morphological characteristics, and thermal behavior of the powders were investigated by means of x-ray diffractometry, PSD, Fourier transform infrared, transmission electronic microscope, and thermogravimetry-differential scanning calorimetry. Results indicate that the formation and characteristics of precursor gel and YAG powder, such as the rate of gelation, average particle size, and powder agglomerate state, strongly depend on the stoichiometric amount of citric acid, the solvent composition, and the precalcination process. Highly crystalline, well-dispersed YAG nanopowder was obtained by calcining at 800 °C for 2 h in the presence of citric acid to nitrate ratio of 3, ethanol solvent, and precalcination process. According to the analysis of experimental results, sol-gel chemistry, DLVO theory, and steric effect, the effects of stoichiometric amount of citric acid, solvent composition, and precalcination process on the formation and characteristics of precursor gel and YAG powder have been discussed. Meanwhile, the overall synthesis mechanism in sol-gel method has been suggested.

  3. Aluminum doped zirconia nanopowders: Wet-chemical synthesis and structural analysis by Rietveld refinement

    SciTech Connect

    Srdic, Vladimir V. Rakic, Srdan; Cvejic, Zeljka

    2008-10-02

    Alumina/zirconia nanopowders, with up to 20 mol% Al{sub 2}O{sub 3}, were prepared by wet-chemical synthesis technique, using controlled hydrolysis of alkoxides. The as-synthesized powders are amorphous, have very high specific surface area and the corresponding particle size smaller than 4 nm. Amorphous powders with 0, 10 and 20 mol% Al{sub 2}O{sub 3} crystallize at 460, 692 and 749 deg. C, respectively, as a single-phase tetragonal zirconia, without any traces of alumina phases. Rietvled refinement of X-ray diffraction data, used for the detailed structural analysis of annealed nanopowders, showed that the high-temperature zirconia phase is stabilized due to the formation of ZrO{sub 2}/Al{sub 2}O{sub 3} solid solutions. High solubility of alumina in the tetragonal zirconia (up to 28.6 at% Al{sup 3+}) and stabilization of tetragonal zirconia solid solution up to high temperature (as high as 1150 deg. C) were also confirmed.

  4. Dependence of viscosity of suspensions of ceramic nanopowders in ethyl alcohol on concentration and temperature

    PubMed Central

    2012-01-01

    This work presents results of measurements of viscosity of suspensions including yttrium oxide (Y2O3), yttrium aluminum garnet (Y3Al5O12) and magnesium aluminum spinel (MgAl2O4) nanopowders in ethanol. Nanoparticles used in our research were either commercially available (Baikowski) or nanopowders newly developed in the Institute of Ceramics and Building Materials in Warsaw, Poland. The study was conducted in a wide range of shear rates (0.01 to 2,000 s−1) and temperature interval from -15°C to 20°C. A Haake Mars 2 rheometer from Thermo Fisher, Germany, was used in the Biophysics Laboratory at Rzeszów University of Technology. Most of the samples show a non-Newtonian behaviour. It was confirmed with a Rheo-NMR system from Bruker that 10% by weight of Y2O3 suspension is a non-Newtonian fluid. In this work, we also report an unexpected behaviour of the viscosity of some samples (Y2O3 and Y3Al5O12) due to sedimentation effect. PMID:22824064

  5. Synthesis and characterization of NiO nanopowder by sol-gel process

    SciTech Connect

    Ningsih, Sherly Kasuma Warda

    2015-09-30

    Preparation of nickel oxide (NiO) nanopowder by sol-gel process has been studied. NiO nanopowders were obtained by sol-gel method by using nickel nitrate hexahydrate and sodium hydroxide and aquadest were used as precursor, agent precipitator and solvent, respectively. The powders were formed by drying at 110°C and followed by heating in the furnace at 400°C for 1.5 hours. The product was obtained black powder. The product was characterized by Energy Dispesive X-ray Fluorescence (ED-XRF), X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The ED-XRF pattern shows the composition of NiO produced was 97.1%. The XRD pattern showed NiO forms were produced generally in monoclinic stucture. The crystalline size of NiO was obtained in the range 40-85 nm. SEM micrograph clearly showed that powder had a spherical with uniform distribution size is 0.1-1.0 µm approximately.

  6. EGCG assisted green synthesis of ZnO nanopowders: Photodegradative, antimicrobial and antioxidant activities

    NASA Astrophysics Data System (ADS)

    Suresh, D.; Udayabhanu; Nethravathi, P. C.; Lingaraju, K.; Rajanaika, H.; Sharma, S. C.; Nagabhushana, H.

    2015-02-01

    Zinc oxide nanopowders were synthesized by solution combustion method using Epigallocatechin gallate (EGCG) a tea catechin as fuel. The structure and morphology of the product was characterized by Powder X-ray Diffraction, Scanning Electron Microscopy, photoluminescence and UV-Visible spectroscopy. The nanopowders (Nps) were subjected to photocatalytic and biological activities such as antimicrobial and antioxidant studies. PXRD patterns demonstrate that the formed product belongs to hexagonal wurtzite system. SEM images show that the particles are agglomerated to form sponge like structure and the average crystallite sizes were found to be ∼10-20 nm. PL spectra exhibit broad and strong peak at 590 nm due to the Zn-vacancies, and O-vacancies. The prepared ZnO Nps exhibit excellent photocatalytic activity for the photodegradation of malachite green (MG) and methylene blue (MB) indicating that the ZnO NPs are potential photocatalytic semiconductor materials. ZnO NPs exhibit significant bactericidal activity against Klebsiella aerogenes, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus using the agar well diffusion method. Furthermore, the ZnO nano powders show good antioxidant activity by potentially scavenging DPPH radicals. The study successfully demonstrates synthesis of ZnO NPs by simple ecofriendly route employing EGCG as fuel that exhibit superior photodegradative, antibacterial and antioxidant activities.

  7. Low temperature synthesis of pure cubic ZrO2 nanopowder: Structural and luminescence studies

    NASA Astrophysics Data System (ADS)

    Prakashbabu, D.; Hari Krishna, R.; Nagabhushana, B. M.; Nagabhushana, H.; Shivakumara, C.; Chakradar, R. P. S.; Ramalingam, H. B.; Sharma, S. C.; Chandramohan, R.

    2014-03-01

    Pure cubic zirconia (ZrO2) nanopowder is prepared for the first time by simple low temperature solution combustion method without calcination. The product is characterized by Powder X-ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infra Red spectroscopy (FTIR) and Ultraviolet-Visible spectroscopy (UV-Vis). The PXRD showed the formation of pure stable cubic ZrO2 nanopowders with average crystallite size ranging from 6 to 12 nm. The lattice parameters were calculated from Rietveld refinement method. SEM micrograph shows fluffy, mesoporous, agglomerated particles with large number of voids. TEM micrograph shows honey comb like arrangement of particles with particle size ∼10 nm. The PL emission spectrum excited at 210 nm and 240 nm consists of intense bands centered at ∼365 and ∼390 nm. Both the samples show shoulder peak at ∼420 nm, along with four weak emission bands at ∼484, ∼528, ∼614 and ∼726 nm. TL studies were carried out pre-irradiating samples with γ-rays ranging from 1 to 5 KGy at room temperature. A well resolved glow peak at 377 °C is recorded which can be ascribed to deep traps. With increase in γ radiation there is linear increase in TL intensity which shows the possible use of ZrO2 as dosimetric material.

  8. Synthesis and characterization of InNbO₄ nanopowder for gas sensors.

    PubMed

    Balamurugan, C; Vijayakumar, E; Subramania, A

    2012-01-15

    Indium niobate (InNbO(4)) nanopowder was prepared by a comparatively low temperature niobium citrate complex process. The prepared InNbO(4) was characterized by thermal analysis, X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy, diffuse reflectance spectroscopy (DRS), and impedance studies. It revealed that the well crystalline monoclinic InNbO(4) nanopowder was obtained at the calcination temperature of 600°C. The average particle diameter was 22nm. The optical band gap was found to be 2.66eV. The temperature dependent conductivity obeyed Arrhenius relation. The activation energy of the conductivity process was calculated to be 0.43eV. The gas sensing behaviour of the prepared InNbO(4) was studied by measuring the change in resistance of the sensor material as a function of various concentrations of the test gases such as liquid petroleum gas (LPG), ammonia (NH(3)) and ethanol (C(2)H(5)OH) at their optimized operating temperature. InNbO(4) had a better sensitivity to LPG (0.97) and NH(3) (0.70) gas than ethanol (0.46). The sensor responses of InNbO(4) as a function of gas concentrations and with recovery time were also studied in detail. PMID:22265476

  9. Employing Ti nano-powder dielectric to enhance surface characteristics in electrical discharge machining of AISI D2 steel

    NASA Astrophysics Data System (ADS)

    Marashi, Houriyeh; Sarhan, Ahmed A. D.; Hamdi, Mohd

    2015-12-01

    Manufacturing components with superior surface characteristics is challenging when electrical discharge machining (EDM) is employed for mass production. The aim of this research is to enhance the characteristics of AISI D2 steel surface machined with EDM through adding Ti nano-powder to dielectric under various machining parameters, including discharge duration (Ton) and peak current (I). Surface roughness profilometer, FESEM and AFM analysis were utilized to reveal the machined surface characteristics in terms of surface roughness, surface morphology and surface micro-defects. Moreover, EDX analysis was performed in order to evaluate the atomic deposition of Ti nano-powder on the surface. The concentration of Ti nano-powder in dielectric was also examined using ESEM and EDX. According to the results, the addition of Ti nano-powder to dielectric notably enhanced the surface morphology and surface roughness at all machining parameters except Ton = 340 μs. Of these parameters, maximum enhancement was observed at Ton = 210 μs, where the material removal rate and average surface roughness improved by ∼69 and ∼35% for peak current of 6 and 12 A, respectively. Elemental analysis signified negligible Ti deposition on the machined surface while the atomic concentration of Ti was increased around the crack areas.

  10. Hydroxyapatite-silver nanoparticles coatings on porous polyurethane scaffold.

    PubMed

    Ciobanu, Gabriela; Ilisei, Simona; Luca, Constantin

    2014-02-01

    The present paper is focused on a study regarding the possibility of obtaining hydroxyapatite-silver nanoparticle coatings on porous polyurethane scaffold. The method applied is based on a combined strategy involving hydroxyapatite biomimetic deposition on polyurethane surface using a Supersaturated Calcification Solution (SCS), combined with silver ions reduction and in-situ crystallization processes on hydroxyapatite-polyurethane surface by sample immersing in AgNO3 solution. The morphology, composition and phase structure of the prepared samples were characterized by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements. The data obtained show that a layer of hydroxyapatite was deposited on porous polyurethane support and the silver nanoparticles (average size 34.71 nm) were dispersed among and even on the hydroxyapatite crystals. Hydroxyapatite/polyurethane surface acts as a reducer and a stabilizing agent for silver ions. The surface plasmon resonance peak in UV-Vis absorption spectra showed an absorption maximum at 415 nm, indicating formation of silver nanoparticles. The hydroxyapatite-silver polyurethane scaffolds were tested against Staphylococcus aureus and Escherichia coli and the obtained data were indicative of good antibacterial properties of the materials. PMID:24411349

  11. Hydroxyapatite Reinforced Coatings with Incorporated Detonationally Generated Nanodiamonds

    SciTech Connect

    Pramatarova, L.; Pecheva, E.; Hikov, T.; Fingarova, D.; Dimitrova, R.; Spassov, T.; Krasteva, N.; Mitev, D.

    2010-01-21

    We studied the effect of the substrate chemistry on the morphology of hydroxyapatite-detonational nanodiamond composite coatings grown by a biomimetic approach (immersion in a supersaturated simulated body fluid). When detonational nanodiamond particles were added to the solution, the morphology of the grown for 2 h composite particles was porous but more compact then that of pure hydroxyapatite particles. The nanodiamond particles stimulated the hydroxyapatite growth with different morphology on the various substrates (Ti, Ti alloys, glasses, Si, opal). Biocompatibility assay with MG63 osteoblast cells revealed that the detonational nanodiamond water suspension with low and average concentration of the detonational nanodiamond powder is not toxic to living cells.

  12. In-situ deposition of hydroxyapatite on graphene nanosheets

    PubMed Central

    Neelgund, Gururaj M.; Oki, Aderemi; Luo, Zhiping

    2014-01-01

    Graphene nanosheets were effectively functionalized by in-situ deposition of hydroxyaptite through a facile chemical precipitation method. Prior to grafting of hydroxyapatite, chemically modified graphene nanosheets were obtained by the reduction of graphene oxide in presence of ethylenediamine. The resulting hydroxyapatite functionalized graphene nanosheets were characterized by attenuated total reflection IR spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray energy dispersive spectroscopy, Raman spectroscopy and thermogravimetric analysis. These characterization techniques revealed the successful grafting of hydroxyapatite over well exfoliated graphene nanosheets without destroying their structure. PMID:25110359

  13. Hydroxyapatite Reinforced Coatings with Incorporated Detonationally Generated Nanodiamonds

    NASA Astrophysics Data System (ADS)

    Pramatarova, L.; Pecheva, E.; Dimitrova, R.; Spassov, T.; Krasteva, N.; Hikov, T.; Fingarova, D.; Mitev, D.

    2010-01-01

    We studied the effect of the substrate chemistry on the morphology of hydroxyapatite-detonational nanodiamond composite coatings grown by a biomimetic approach (immersion in a supersaturated simulated body fluid). When detonational nanodiamond particles were added to the solution, the morphology of the grown for 2 h composite particles was porous but more compact then that of pure hydroxyapatite particles. The nanodiamond particles stimulated the hydroxyapatite growth with different morphology on the various substrates (Ti, Ti alloys, glasses, Si, opal). Biocompatibility assay with MG63 osteoblast cells revealed that the detonational nanodiamond water suspension with low and average concentration of the detonational nanodiamond powder is not toxic to living cells.

  14. An X-ray electron study of nanodisperse hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Melikhov, I. V.; Teterin, Yu. A.; Rudin, V. N.; Teterin, A. Yu.; Maslakov, K. I.; Severin, A. V.

    2009-01-01

    Two states of surface valence electrons localized on faces with different molecular reliefs were observed for nanodisperse hydroxyapatite. Thermal treatment of nanocrystals caused a shift Δ E b = 0.5 eV of the spectrum of valence electrons on molecularly rough faces and a shift of 0.8 eV of the spectrum from smooth faces. Similar electron spectrum shifts were observed for sorption, in particular, of sodium succinate. These results are of importance for the diagnostics of various hydroxyapatite kinds, since hydroxyapatite is a constituent mineral component of living organisms, and for the synthesis of medicines with enhanced biological activity used in treatment of various bone diseases.

  15. EXAFS study of structural disorder in carbonate-containing hydroxyapatites.

    PubMed

    Harries, J E; Hasnain, S S; Shah, J S

    1987-12-01

    A structural characterization of pure hydroxyapatite and partially carbonated hydroxyapatites has been performed using EXAFS spectroscopy, X-ray diffraction, and infrared spectroscopy. Our findings show that marked structural changes within the hydroxyapatite unit cell accompany the substitution of the phosphate anion. Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy has shown that the incorporation of carbonate into the phosphate site alters the structural geometry beyond the nearest neighbor oxygen coordination to calcium in a manner consistent with an increase in structural disorder. The nearest neighbor coordination to calcium is not detectably affected by the presence of carbonate. PMID:2830003

  16. Evolving application of biomimetic nanostructured hydroxyapatite

    PubMed Central

    Roveri, Norberto; Iafisco, Michele

    2010-01-01

    By mimicking Nature, we can design and synthesize inorganic smart materials that are reactive to biological tissues. These smart materials can be utilized to design innovative third-generation biomaterials, which are able to not only optimize their interaction with biological tissues and environment, but also mimic biogenic materials in their functionalities. The biomedical applications involve increasing the biomimetic levels from chemical composition, structural organization, morphology, mechanical behavior, nanostructure, and bulk and surface chemical–physical properties until the surface becomes bioreactive and stimulates cellular materials. The chemical–physical characteristics of biogenic hydroxyapatites from bone and tooth have been described, in order to point out the elective sides, which are important to reproduce the design of a new biomimetic synthetic hydroxyapatite. This review outlines the evolving applications of biomimetic synthetic calcium phosphates, details the main characteristics of bone and tooth, where the calcium phosphates are present, and discusses the chemical–physical characteristics of biomimetic calcium phosphates, methods of synthesizing them, and some of their biomedical applications. PMID:24198477

  17. Dissolution of human teeth-derived hydroxyapatite.

    PubMed

    Seo, Dong Seok; Lee, Jong Kook

    2008-01-01

    We have been interested in human teeth which consist of hydroxyapatite (HA), but do not degrade for a long time. In order to overcome dissolution and mechanical degradation of man-made HA, biologically derived hydroxyapatite (BHA) ceramics were prepared from human teeth and their dissolving behavior was investigated in distilled water for 3-14 days and compared with an artificial HA made of synthetic HA powder. BHA ceramics were prepared by calcining freshly extracted human teeth at 900 degrees C and followed by sintering at 1200 degrees C for 2 h. All detectable peaks in the artificial HA are identical to HA lattice planes, whereas BHA consisted of a mixture of HA and beta-tricalcium phosphate (TCP). Although the artificial HA was expected to be stable in water, the surface dissolution initiated at grain boundaries followed by generated many separated grains and their associated pores. On the other hand, BHA showed that definite grains considered as beta-TCP were predominantly dissolved and the grains were separated from the matrix leaving pores. In the mean time, the rest region, mainly consisting of HA, did not show any evidence of dissolution. It indicates that BHA showed rather stable grain boundaries and lack of excessive dissolution in liquid environment. PMID:17943445

  18. Biological reactivity of zirconia-hydroxyapatite composites.

    PubMed

    Silva, Viviane V; Lameiras, Fernando S; Lobato, Zélia I P

    2002-01-01

    Materials and devices intended for end-use applications as implants and medical devices must be evaluated to determine their biocompatibility potential in contact with physiological systems. The use of standard practices of biological testing provides a reasonable level of confidence concerning the response of a living organism to a given material or device, as well as guidance in selecting the proper procedures to be carried out for the screening of new or modified materials. This article presents results from cytotoxicity assays of cell culture, skin irritation, and acute toxicity by systemic and intracutaneous injections for powders, ceramic bodies, and extract liquids of hydroxyapatite (HA), calcia partially stabilized zirconia (ZO), and two types of zirconia-hydroxyapatite composites (Z4H6 and Z6H4) with potential for future use as orthopedic and dental implants. They indicate that these materials present potential for this type of application because they meet the requirements of the standard practices recommended for evaluating the biological reactivity of ATCC cell cultures (CCL1 NCTC clone 929 of mouse connective tissue and CCL 81 of monkey connective tissue) and animals (rabbit and mouse) with direct or indirect patient contact, or by the injection of specific extracts prepared from the material under test. In addition, studies involving short-term intramuscular and long-term implantation assays to estimate the reaction of living tissue to the composites studied, and investigations on long-term effects that these materials can cause on the cellular metabolism, are already in progress. PMID:12209904

  19. Improved mechanical properties of hydroxyapatite/poly(ɛ-caprolactone) scaffolds by surface modification of hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Dai, Jing; Zhang, Qingchun; Xiao, Yan; Lang, Meidong

    2010-08-01

    Scaffolds comprising hydroxyapatite (HAP) or poly(ɛ-caprolactone)-grafted hydroxyapatite (g-HAP) and poly(ɛ-caprolactone) (PCL) were prepared using the thermally induced phase separation/salt leaching technique. The g-HAP nanoparticles were evaluated by Fourier Transformation Infrared Spectroscopy (FTIR) and thermal gravimetric analysis (TGA). Power X-ray Diffraction (XRD) patterns confirmed the successful grafting on the surface of HAP. The effects on mechanical strength, porosity and thermal property of scaffolds by the introduction of nanoparticles were extensively investigated. The compressive modulus of the scaffold was greatly improved by the addition of g-HAP nanoparticles. Especially the compressive modulus of the g-HAP/PCL scaffold containing 20 wt% of g-HAP was 59.4% higher than that of the corresponding HAP/PCL scaffold.

  20. Nanopowders M{sub 2}O{sub 3} (M = Y, La, Yb, Nd) with spherical particles and laser ceramics based on them

    SciTech Connect

    Bagayev, Sergei N; Kaminskii, Alexandr A; Kopylov, Yu L; Kravchenko, V B; Tolmachev, A V; Shemet, V V; Yavetskii, R P

    2013-03-31

    We have considered the problems of agglomeration of yttrium aluminium garnet (YAG) nanopowders prepared by chemical co-precipitation of precursors from aqueous solutions and subsequent calcination. To fabricate YAG and Y{sub 2}O{sub 3} laser ceramic samples with high optical transmittance and reproducible characteristics, we have developed a method for producing non-agglomerated nanopowders of pure and doped Y{sub 2}O{sub 3} by homogeneous chemical precipitation. Nanopowders Y{sub 2}O{sub 3} with La and Yb as well as mixtures of Y{sub 2}O{sub 3} : Nd and several commercial nanopowders of aluminium oxide have been compacted; optimised compacting technique have been selected; ceramic samples (Y, La, Yb){sub 2}O{sub 3} and YAG : Nd with high optical transmittance at a wavelength of 1 {mu}m have been produced by solid-phase synthesis. (extreme light fields and their applications)

  1. Effect of solution combusted TiO2 nanopowder within commercial BaTiO3 dielectric layer on the photoelectric properties for AC powder electroluminescence devices.

    PubMed

    Park, Sung; Choi, Gil Rak; Kim, Youn Cheol; Lee, Jae Chun; Lee, Ju Hyeon

    2013-05-01

    A unique synthesis method was developed, which is called solution combustion method (SCM). TiO2 nanopowder was synthesized by this method. This SCM TiO2 nanopowder (-35 nm) was added to the dielectric layer of AC powder electroluminescence (EL) device. The dielectric layer was made of commercial BaTiO3 powder (-1.2 microm) and binding polymer. 0, 5, 10 and 15 wt% of SCM TiO2 nanopowder was added to the dielectric layer during fabrication of AC powder EL device respectively. Dielectric constant of these four kinds of dielectric layers was measured. The brightness and current density of AC powder EL device were also measured. When 10 wt% of SCM TiO2 nanopowder was added, dielectric constant and brightness were increased by 30% and 101% respectively. Furthermore, the current density was decreased by 71%. This means that the brightness was double and the power consumption was one third. PMID:23858874

  2. Topography, wetting, and corrosion responses of electrodeposited hydroxyapatite and fluoridated hydroxyapatite on magnesium.

    PubMed

    Assadian, Mahtab; Jafari, Hassan; Ghaffari Shahri, Seyed Morteza; Idris, Mohd Hasbullah; Almasi, Davood

    2016-08-12

    In this study, different types of calcium-phosphate phases were coated on NaOH pre-treated pure magnesium. The coating was applied by electrodeposition method in order to provide higher corrosion resistance and improve biocompatibility for magnesium. Thickness, surface morphology and topography of the coatings were analyzed using optical, scanning electron and atomic-force microscopies, respectively. Composition and chemical bonding, crystalline structures and wettability of the coatings were characterized using energy-dispersive and attenuated total reflectance-Fourier transform infrared spectroscopies, grazing incidence X-ray diffraction and contact angle measurement, respectively. Degradation behavior of the coated specimens was also investigated by potentiodynamic polarization and immersion tests. The experiments proved the presence of a porous coating dominated by dicalcium-phosphate dehydrate on the specimens. It was also verified that the developed hydroxyapatite was crystallized by alkali post-treatment. Addition of supplemental fluoride to the coating electrolyte resulted in stable and highly crystallized structures of fluoridated hydroxyapatite. The coatings were found effective to improve biocompatibility combined with corrosion resistance of the specimens. Noticeably, the fluoride supplemented layer was efficient in lowering corrosion rate and increasing surface roughness of the specimens compared to hydroxyapatite and dicalcium-phosphate dehydrates layers. PMID:27567782

  3. Carbonate Hydroxyapatite and Silicon-Substituted Carbonate Hydroxyapatite: Synthesis, Mechanical Properties, and Solubility Evaluations

    PubMed Central

    Bang, L. T.; Long, B. D.; Othman, R.

    2014-01-01

    The present study investigates the chemical composition, solubility, and physical and mechanical properties of carbonate hydroxyapatite (CO3Ap) and silicon-substituted carbonate hydroxyapatite (Si-CO3Ap) which have been prepared by a simple precipitation method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF) spectroscopy, and inductively coupled plasma (ICP) techniques were used to characterize the formation of CO3Ap and Si-CO3Ap. The results revealed that the silicate (SiO44−) and carbonate (CO32−) ions competed to occupy the phosphate (PO43−) site and also entered simultaneously into the hydroxyapatite structure. The Si-substituted CO3Ap reduced the powder crystallinity and promoted ion release which resulted in a better solubility compared to that of Si-free CO3Ap. The mean particle size of Si-CO3Ap was much finer than that of CO3Ap. At 750°C heat-treatment temperature, the diametral tensile strengths (DTS) of Si-CO3Ap and CO3Ap were about 10.8 ± 0.3 and 11.8 ± 0.4 MPa, respectively. PMID:24723840

  4. [Study on an injectable biomimetic hydroxyapatite--atelocollagen composite].

    PubMed

    Maier, S S; Pelin, Irina; Bulacovschi, V

    2007-01-01

    The paper presents a procedure for preparing mineralized collagen nanofibrils, mixed with deficient nanoparticulate calcium hydroxyapatite in a ratio close to that found in living bone structures. Such a composition might represent an injectable osteoconductive constituent, used in surgical kits for bone reconstruction. The FT-IR spectra of the prepared composite reveals a weak absorption at 871.82 cm(-1), indicating the nucleation of hydroxy-apatite at the acidic atelocollagen functions. More than that, a 45 cm(-1) ipsochromic shift of carboxylic band suggest a strong ionic interaction with hydroxyapatite. The X-Ray spectra show a high resemblance between the synthetic composite and the Fluka hydroxyapatite, but only for 2theta angles higher than 30 degrees. Below that value the protein presence induce crystalline disorders. PMID:18389809

  5. Formation of pyrophosphate on hydroxyapatite with thioesters as condensing agents

    NASA Technical Reports Server (NTRS)

    Weber, A. L.

    1982-01-01

    'Energy-rich' thioesters are shown to act as condensing agents in the formation of pyrophosphate on hydroxyapatite in the presence of water at ambient temperature. The yield of pyrophosphate based on thioester ranges from 2.5% to 11.4% and depends upon the pH and concentration of reactants. Reaction of 0.130 M hydroxyapatite suspended in a solution of 0.08 M sodium phosphate and 0.20 M imidazole hydrochloride (pH 7.0) with 0.10 M N,S-diacetylcysteamine for 6 days gives the highest yield of pyrophosphate (11.4%). Pyrophosphate formation requires the presence of hydroxyapatite, sodium phosphate and the thioester, N,S-diacetylcysteamine. The related thioester, N,S-diacetylcysteine, also yields pyrophosphate in reactions on hydroxyapatite.

  6. Preparation and characterization of collagen-hydroxyapatite/pectin composite.

    PubMed

    Wenpo, Feng; Gaofeng, Liang; Shuying, Feng; Yuanming, Qi; Keyong, Tang

    2015-03-01

    Pectin, a kind of plant polysaccharide, was introduced into collagen-hydroxyapatite composite system, and prepared collagen-hydroxyapatite/pectin (Col-HA/pectin) composite in situ. The structure of the composite was investigated by XRD, SEM, and FT-IR. The mechanical properties, water absorption, enzyme degradation, and cytotoxicity of the composite were investigated as well. The results show that the inorganic substance in the composite materials is hydroxyapatite in relatively low crystallinity. A new interface appeared by the interaction among hydroxyapatite and collagen-pectin, and formed smooth fine particles. The mechanical properties, water absorption, enzyme degradation, and cytotoxicity indicate a potential use in bone replacement for the new composite. PMID:25485944

  7. Synthesis of mesoporous nano-hydroxyapatite by using zwitterions surfactant

    EPA Science Inventory

    Mesoporous nano-hydroxyapatite (mn-HAP) was successfully synthesized via a novel micelle-templating method using lauryl dimethylaminoacetic acid as zwitterionic surfactant. The systematic use of such a surfactant in combination with microwave energy inputenables the precise contr...

  8. Formation of hydroxyapatite in various aqueous solutions

    NASA Astrophysics Data System (ADS)

    Sturgeon, Jacqueline Lee

    Hydroxyapatite (HAp), Ca10(PO4)6(OH) 2, is important in the field of biomaterials as it is the mineral component of bones and teeth. Biological apatites do not maintain an exact composition and are usually calcium-deficient, represented as Ca(10- x)(HPO 4)x(PO4)(6-x)(OH)(2-x), where x ranges from 0 to 1, with various ion substitutions. Formation of calcium-deficient hydroxyapatites (CDHAp) from solid calcium phosphate precursor materials was performed at physiologic temperature (37°C) in a variety of aqueous solutions. Two cement systems were utilized in these experiments: tetralcium phosphate (TetCP) with dicalcium phosphate anhydrous (DCPA) and beta-tricalcium phosphate (beta-TCP). The kinetics, solution chemistry, phase evolution, and microstructure of the developed apatites were analyzed as appropriate. Reaction of beta-TCP in ammonium fluoride solutions formed HAp substituted with fluoride and calculated to be deficient in calcium. A new ratio of TetCP to DCPA was used with solutions of sodium bicarbonate to form a calcium-deficient carbonate hydroxyapatite. The capacity for sodium dihydrogen phosphate to buffer pH increases and enhance reaction kinetics in this system was also explored. Formation of a highly crystalline CDHAp was achieved by hydrolyzing beta-TCP in water for extended time periods. Lattice parameters were among the features characterized for this apatite. The hydrolysis of beta-TCP in phosphate buffered saline (PBS) and simulated body fluids (SBF) was also investigated; use of SBF was found to completely inhibit formation of HAp in this system while reaction in PBS was slow in comparison to water. The effects of filler materials on the mechanical properties of a calcium phosphate cement were examined using the TetCP/DCPA system. Dense aggregates were not found to decrease compressive strength in comparison to the cement alone. The use of aggregates was found to improve the compressive strength of cement formed using NaHCO3 solution as a

  9. Acetone Sensing Properties of a Gas Sensor Composed of Carbon Nanotubes Doped With Iron Oxide Nanopowder

    PubMed Central

    Tan, Qiulin; Fang, Jiahua; Liu, Wenyi; Xiong, Jijun; Zhang, Wendong

    2015-01-01

    Iron oxide (Fe2O3) nanopowder was prepared by a precipitation method and then mixed with different proportions of carbon nanotubes. The composite materials were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. A fabricated heater-type gas sensor was compared with a pure Fe2O3 gas sensor under the influence of acetone. The effects of the amount of doping, the sintering temperature, and the operating temperature on the response of the sensor and the response recovery time were analyzed. Experiments show that doping of carbon nanotubes with iron oxide effectively improves the response of the resulting gas sensors to acetone gas. It also reduces the operating temperature and shortens the response recovery time of the sensor. The response of the sensor in an acetone gas concentration of 80 ppm was enhanced, with good repeatability. PMID:26569253

  10. Stable Co-Catalyst-Free Photocatalytic H2 Evolution From Oxidized Titanium Nitride Nanopowders.

    PubMed

    Zhou, Xuemei; Zolnhofer, Eva M; Nguyen, Nhat Truong; Liu, Ning; Meyer, Karsten; Schmuki, Patrik

    2015-11-01

    A simple strategy is used to thermally oxidize TiN nanopowder (∼20 nm) to an anatase phase of a TiO2:Ti(3+):N compound. In contrast to the rutile phase of such a compound, this photocatalyst provides activity for hydrogen evolution under AM1.5 conditions, without the use of any noble metal co-catalyst. Moreover the photocatalyst is active and stable over extended periods of time (tested for 4 months). Importantly, to achieve successful conversion to the active anatase polymorph, sufficiently small starting particles of TiN are needed. The key factor for catalysis is the stabilization of the co-catalytically active Ti(3+) species against oxidation by nitrogen present in the starting material. PMID:26427346

  11. Preparation and Characterization of Fine-Particle NTO and Its Formulation with Al Nanopowders

    NASA Astrophysics Data System (ADS)

    Lee, K.-Y.; Kennedy, J. E.; Asay, B. W.; Son, S. F.; Martin, E. S.

    2004-07-01

    We have initiated study of the effect of nano-aluminum on the detonation performance of NTO. A novel method for the preparation of both fine-particle NTO (UF-NTO) and its formulation with Al nanopowder has been developed. Results from small-scale sensitivity tests on both the UF-NTO and aluminized NTO composite indicated that they are insensitive to impact, friction and HESD. The performance of both UF-NTO and NTO/Al mix was evaluated by detonation-spreading floret tests. At the same pressed density, it was found that, when initiated by a 3-mm-diameter flyer plate, the aluminized NTO composite produced a shallower dent on a copper witness plate than neat UF-NTO and thus was inferior to UF-NTO in detonation spreading.

  12. The effect of calcination temperature on the crystallinity of TiO 2 nanopowders

    NASA Astrophysics Data System (ADS)

    Chen, Yung-Fang; Lee, Chi-Young; Yeng, Ming-Yu; Chiu, Hsin-Tien

    2003-01-01

    TiO 2 nanopowders have been prepared using 0.1 M titanium tetraisopropoxide (TTIP) in varied pH aqueous solution containing TMC and NP-204 surfactants. Only the powder acquired from a solution of pH=2 has a regular particle size distribution. Anatase phase powders are obtained by calcination in nitrogen in the 250-500°C temperature range. When calcined at 400°C, the diameter of the nanoparticles is approximately 10 nm with a specific surface area of 106.9 m 2/g. As the calcination temperature is increased, the particle size increases. Rutile phase powders are formed at calcination temperatures above 600°C.

  13. Modelling of laser welding of flat parts using the modifying nanopowders

    NASA Astrophysics Data System (ADS)

    Cherepanov, A. N.; Shapeev, V. P.

    2013-06-01

    A mathematical model is formulated to describe thermophysical processes at laser welding of metal plates for the case when the modifying nanoparticles of refractory compounds have been introduced in the weld pool (the nanopowder seed cultrure fermenters — NSCF). Specially prepared nanoparticles of refractory compounds serve the crystallization centers that is they are in fact the exogenous primers, on the surface of which the individual clusters are grouped. Owing to this, one can control the process of the crystallization of the alloy and the formation of its structure and, consequently, the joint weld properties. As an example, we present the results of computing the butt welding of two plates of aluminum alloy and steel. Computed and experimental data are compared.

  14. Magnetic nanopowder as effective adsorbent for the removal of Congo Red from aqueous solution.

    PubMed

    Paşka, O; Ianoş, R; Păcurariu, C; Brădeanu, A

    2014-01-01

    A magnetic iron oxide nanopowder (MnP), prepared by a simple and efficient combustion synthesis technique, was tested for the removal of the anionic dye Congo Red (CR) from aqueous solution. The influence of solution pH, adsorbent dose, temperature, contact time and initial dye concentration on the adsorption of CR onto MnP were investigated. It was shown that the CR adsorption was pH dependent and the adsorption mechanism was governed by electrostatic forces. The adsorption kinetic was best described by the pseudo-second-order model and the equilibrium data were well fitted to the Langmuir isotherm, yielding maximum adsorption capacity of 54.46 mg g(-1). The undeniable advantages of the MnP adsorbent such as inexpensive preparation method, good adsorption capacity and easy separation using an external magnetic field, recommend it as a promising candidate for the removal of anionic dyes from polluted water. PMID:24647189

  15. Effect of BaTiO3 Nanopowder Concentration on Rheological Behaviour of Ceramic Inkjet Inks

    NASA Astrophysics Data System (ADS)

    Kyrpal, R.; Dulina, I.; Ragulya, A.

    2015-04-01

    The relationship between rheological properties of ceramic inkjet inks based on BaTiO3 nanopowder and solid phase concentration has been investigated. In the ink volume takes place the formation periodic colloidal structures (PCS). The determining factor of structure formation is powder-dispersant ratio. Structural constitution of in the system with the low pigment concentration represented as PCS2, that contains solid particles in deflocculated that stabilized by the presence of adsorption-solvate layers. Dilatant structure formation for such inks explained by constrained conditions of the interaction. Samples with high BaTiO3 concentration have been classified as PKS1. Dilatant properties of the PKS1 resulted in particles rearrangement under the influence of the flow. In the region of some values powder-dispersant ratio take place conversation PKS2 to PKS1 and ink structure transformation from monodisperse to aggregate state.

  16. Acoustic Properties of Polyurethane Composition Reinforced with Carbon Nanotubes and Silicon Oxide Nano-powder

    NASA Astrophysics Data System (ADS)

    Orfali, Wasim A.

    This article demonstrates the acoustic properties of added small amount of carbon-nanotube and siliconoxide nano powder (S-type, P-Type) to the host material polyurethane composition. By adding CNT and/or nano-silica in the form of powder at different concentrations up to 2% within the PU composition to improve the sound absorption were investigated in the frequency range up to 1600 Hz. Sound transmission loss measurement of the samples were determined using large impedance tube. The tests showed that addition of 0.2 wt.% Silicon Oxide Nano-powder and 0.35 wt.% carbon nanotube to polyurethane composition improved sound transmissions loss (Sound Absorption) up to 80 dB than that of pure polyurethane foam sample.

  17. Preparation, structural and optical characterization of ZnO, ZnO: Al nanopowder

    SciTech Connect

    Mohan, R. Raj; Rajendran, K.; Sambath, K.

    2014-01-28

    In this paper, ZnO and ZnO:Al nanopowders have been synthesized by low cost hydrothermal method. Zinc nitrate, hexamethylenetetramine (HMT) and aluminium nitrate are used as precursors for ZnO and AZO with different molar ratios. The structural and optical characterization of doped and un-doped ZnO powders have been investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDAX), photoluminescence (PL) and ultra violet visible (UV-Vis) absorption studies. The SEM results show that the hydrothermal synthesis can be used to obtain nanoparticles with different morphology. It is observed that the grain size of the AZO nanoparticles increased with increasing of Al concentration. The PL measurement of AZO shows that broad range of green emission around 550nm with high intensity. The green emission resulted mainly because of intrinsic defects.

  18. Molten salt synthesis and localized surface plasmon resonance study of vanadium dioxide nanopowders

    SciTech Connect

    Wang Fu; Liu Yun; Liu Chunyan

    2009-12-15

    Rutile-type vanadium dioxide nanopowders with four different sizes were successfully synthesized by carbothermal reducing V{sub 2}O{sub 5} in KCl-LiCl molten salt. XRD and TEM characterizations suggested that vanadium dioxide particles formed by a broken and reunited process of vanadium oxide. Molten salt and organic carbon sources are crucial to the size of final particles. In the presence of the molten salt, the organic carbon with a shorter chain length would induce smaller particles. The UV-VIS-IR spectral measurements for as-prepared vanadium dioxide announced an obvious localized surface plasmon resonance band in the near infrared region at 90 deg. C. - Graphical abstract: Schematic illustration of the formation mechanism of VO{sub 2}(M) nanoparticles in molten salt, particles size can be controlled by choosing organic carbon sources with different chain length.

  19. Physicochemical and sensory properties of milk supplemented with dispersible nanopowdered oyster shell during storage.

    PubMed

    Lee, Y K; Ahn, S I; Chang, Y H; Kwak, H S

    2015-09-01

    The current study was carried out to investigate the dispersibility of powdered oyster shell (POS), nanopowdered oyster shell (NPOS), and Zn-activated nanopowdered oyster shell (Zn-NPOS) in milk and to determine effects of adding oyster shell on the physicochemical and sensory properties of milk during storage at 4°C for 16 d. To ensure dispersibility, 10% (wt/vol) oyster shell was added to distilled water and stirred at 800 rpm for 2 h, and then the emulsifier 0.5% polyglycerol monostearate (PGMS) was added and stirred continually for 24 h. The particle sizes of POS, NPOS, and Zn-NPOS were 180μm, 389 nm, and 257 nm, respectively. The pH values of all milk samples ranged from 6.62 to 6.88 during storage, and the zeta-potential of milks with NPOS and Zn-NPOS added were more stable than that of milk with POS in low concentrations (0.5 and 1.0%, vol/vol) during storage. The L and a color values of the milks were not significantly influenced by treatment; however, the b value (yellow-blue color) significantly increased during storage after adding POS, NPOS, or Zn-NPOS. Sensory analysis revealed that sedimentation score significantly increased with POS-supplemented milk, but the NPOS- and Zn-NPOS-supplemented milks did not show sedimentation until after 8 d of storage. Based on the data obtained, we conclude that dispersible nanosized oyster shell at concentrations of 0.5 and 1.0% (vol/vol) could be supplemented to milk without significant adverse effects on physicochemical and sensory properties. PMID:26162797

  20. Combustion synthesis, characterization and Raman studies of ZnO nanopowders

    NASA Astrophysics Data System (ADS)

    Reddy, A. Jagannatha; Kokila, M. K.; Nagabhushana, H.; Rao, J. L.; Shivakumara, C.; Nagabhushana, B. M.; Chakradhar, R. P. S.

    2011-10-01

    Spherical shaped ZnO nanopowders (14-50 nm) were synthesized by a low temperature solution combustion method in a short time <5 min. Rietveld analysis show that ZnO has hexagonal wurtzite structure with lattice constants a = 3.2511(1) Å, c = 5.2076(2) Å, unit cell volume ( V) = 47.66(5) (Å) 3 and belongs to space group P63mc. SEM micrographs reveal that the particles are spherical in shape and the powders contained several voids and pores. TEM results also confirm spherical shape, with average particle size of 14-50 nm. The values are consistent with the grain sizes measured from Scherrer's method and Williamson-Hall (W-H) plots. A broad UV-vis absorption spectrum was observed at ˜375 nm which is a characteristic band for the wurtzite hexagonal pure ZnO. The optical energy band gap of 3.24 eV was observed for nanopowder which is slightly lower than that of the bulk ZnO (3.37 eV). The observed Raman peaks at 438 and 588 cm -1 were attributed to the E 2 (high) and E 1 (LO) modes respectively. The broad band at 564 cm -1 is due to disorder-activated Raman scattering for the A 1 mode. These bands are associated with the first-order Raman active modes of the ZnO phase. The weak bands observed in the range 750-1000 cm -1 are due to small defects.

  1. Green approach for the synthesis and characterization of ZrSnO4 nanopowder

    NASA Astrophysics Data System (ADS)

    Athar, Taimur; Vishwakarma, Sandeep Kumar; Bardia, Avinash; Alabass, Razzaq; Alqarlosy, Ahmed; Khan, Aleem Ahmed

    2016-06-01

    Well-defined structural framework of ZrSnO4 nanopowder has been synthesized for the fabrications of cost-effective and sensitive devices which give final reproducible result with reliability under ideal conditions. The synthesis was carried out at moderate temperature and then finally dried in the laboratory oven and then followed with calcination at 1000 °C for 4 h to get phase selective product. It was observed that gelation time depends on the concentration of reactants and temperature. The characterization of ZrSnO4 was carried out with XRD, SEM, TEM, UV, thermal analysis, DLS and FT-IR techniques. With adjustment of reaction parameters, the systematic tuning of the particle size, shape and functional properties can be controlled. It was concluded that self-assembly is an integral part for the synthesis and opens a new exciting opportunity for better understanding the formation of nanostructure framework from micro- to nanoscale along with mechanistic via wet chemical approach. ZrSnO4 has vital role in identifying its potential cytotoxicity in the biological systems. The cytotoxicity effects of ZrSnO4 nanopowder in vitro were evaluated in three different human cell types (hepatocytes, mesenchymal stem cells and neuronal cells). Acute exposure of nanoparticles was found to have greater cytotoxic effect at higher concentration (30 µg/ml). However, partial detoxification was observed during nanoparticles exposure at day 6. The study concluded that an initial stress from nanoparticles incorporates sealing or detoxification of nanoparticles which may help to recover cell viability.

  2. Suspension thermal spraying of hydroxyapatite: microstructure and in vitro behaviour.

    PubMed

    Bolelli, Giovanni; Bellucci, Devis; Cannillo, Valeria; Lusvarghi, Luca; Sola, Antonella; Stiegler, Nico; Müller, Philipp; Killinger, Andreas; Gadow, Rainer; Altomare, Lina; De Nardo, Luigi

    2014-01-01

    In cementless fixation of metallic prostheses, bony ingrowth onto the implant surface is often promoted by osteoconductive plasma-sprayed hydroxyapatite coatings. The present work explores the use of the innovative High Velocity Suspension Flame Spraying (HVSFS) process to coat Ti substrates with thin homogeneous hydroxyapatite coatings. The HVSFS hydroxyapatite coatings studied were dense, 27-37μm thick, with some transverse microcracks. Lamellae were sintered together and nearly unidentifiable, unlike conventional plasma-sprayed hydroxyapatite. Crystallinities of 10%-70% were obtained, depending on the deposition parameters and the use of a TiO2 bond coat. The average hardness of layers with low (<24%) and high (70%) crystallinity was ≈3.5GPa and ≈4.5GPa respectively. The distributions of hardness values, all characterised by Weibull modulus in the 5-7 range, were narrower than that of conventional plasma-sprayed hydroxyapatite, with a Weibull modulus of ≈3.3. During soaking in simulated body fluid, glassy coatings were progressively resorbed and replaced by a new, precipitated hydroxyapatite layer, whereas coatings with 70% crystallinity were stable up to 14days of immersion. The interpretation of the precipitation behaviour was also assisted by surface charge assessments, performed through Z-potential measurements. During in vitro tests, HA coatings showed no cytotoxicity towards the SAOS-2 osteoblast cell line, and surface cell proliferation was comparable with proliferation on reference polystyrene culture plates. PMID:24268261

  3. Novel doped hydroxyapatite thin films obtained by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Duta, L.; Oktar, F. N.; Stan, G. E.; Popescu-Pelin, G.; Serban, N.; Luculescu, C.; Mihailescu, I. N.

    2013-01-01

    We report on the synthesis of novel ovine and bovine derived hydroxyapatite thin films on titanium substrates by pulsed laser deposition for a new generation of implants. The calcination treatment applied to produce the hydroxyapatite powders from ovine/bovine bones was intended to induce crystallization and to prohibit the transmission of diseases. The deposited films were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive X-ray spectroscopy. Pull-off adherence and profilometry measurements were also carried out. X-ray diffraction ascertained the polycrystalline hydroxyapatite nature of the powders and films. Fourier transform infrared spectroscopy evidenced the vibrational bands characteristic to a hydroxyapatite material slightly carbonated. The micrographs of the films showed a uniform distribution of spheroidal particulates with a mean diameter of ∼2 μm. Pull-off measurements demonstrated excellent bonding strength values between the hydroxyapatite films and the titanium substrates. Because of their physical-chemical properties and low cost fabrication from renewable resources, we think that these new coating materials could be considered as a prospective competitor to synthetic hydroxyapatite used for implantology applications.

  4. In situ deposition of hydroxyapatite on graphene nanosheets

    SciTech Connect

    Neelgund, Gururaj M.; Oki, Aderemi; Luo, Zhiping

    2013-02-15

    Graphical abstract: A facile chemical precipitation method is reported for effective in situ deposition of hydroxyapatite on graphene nanosheets. Prior to grafting of hydroxyapatite, chemically modified graphene nanosheets were obtained by the reduction of graphene oxide in presence of ethylenediamine. Display Omitted Highlights: ► It is a facile and effective method for deposition of HA on GR nanosheets. ► It avoids the use of harmful reducing agents like hydrazine, NaBH{sub 4} etc. ► GR nanosheets were produced using bio-compatible, ethylenediamine. ► The graphitic structure of synthesized GR nanosheets was high ordered. ► The ratio of Ca to P in HA was 1.64, which is close to ratio in natural bone. -- Abstract: Graphene nanosheets were effectively functionalized by in situ deposition of hydroxyapatite through a facile chemical precipitation method. Prior to grafting of hydroxyapatite, chemically modified graphene nanosheets were obtained by the reduction of graphene oxide in presence of ethylenediamine. The resulting hydroxyapatite functionalized graphene nanosheets were characterized by attenuated total reflection IR spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray energy dispersive spectroscopy, Raman spectroscopy and thermogravimetric analysis. These characterization techniques revealed the successful grafting of hydroxyapatite over well exfoliated graphene nanosheets without destroying their structure.

  5. The Adsorption of Polyelectrolytes on Hydroxyapatite Crystals.

    PubMed

    Tsortos; Nancollas

    1999-01-01

    The adsorption of two polyelectrolytes, poly-L-Glutamate and poly-L-Aspartate, on hydroxyapatite (HAP) crystals was studied both experimentally and theoretically. Langmuir adsorption isotherms were obtained for both these molecules, with binding constants K = 6 x 10(6) and 3 x 10(6) M-1, respectively, at 37.0 degreesC, pH 7.4, and 0.15 M ionic strength. A theoretical analysis of the data, based on a model proposed by Hesselink, suggested a "train-loop" type of adsorption with non-electrostatic energy terms 3.51 and 4.76 (kT) for poly-L-Glu and poly-L-Asp, respectively. Copyright 1999 Academic Press. PMID:9878142

  6. Thermal Diffusivity in Bone and Hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Calderón, A.; Peña Rodríguez, G.; Muñoz Hernández, R. A.; Díaz Gongora, J. A. I.; Mejia Barradas, C. M.

    2004-09-01

    We report thermal diffusivity measurements in bull bone and commercial hydroxyapatite (HA), both in powder form, in order to determinate the thermal compatibility between these materials. Besides this, we report a comparison between these measured values and those of metallic samples frequently used in implants, as high purity titanium and stainless steel. Our results show a good thermal compatibility (74%) between HA and bone, both in powder form. Finally, it was obtained a one order of magnitude difference between the thermal diffusivity values of metallic samples and those corresponding values to bone and HA being this difference greater in titanium than in stainless steel, which is important to consider in some biomedical and dental applications.

  7. Novel method of preparing hydroxyapatite foams.

    PubMed

    Muthutantri, Anushini; Huang, Jie; Edirisinghe, Mohan

    2008-04-01

    Porous scaffolds are considered a key strategy in the concept of bone tissue engineering. Hydroxyapatite, which is a bioceramic has been used as a popular scaffold material due to its bioactive and osteoconductive properties. A combination of slurry-dipping and electrospraying has been used as a new foam fabrication method to produce porous and interconnected foam structures. The combined method has shown to overcome the shortcomings of the individual methods and it has produced open pores in the desired range of 100-350 microm. The porosity which was determined by calculation and microtomography was between 84% and 88%. Reduced cracks and thicker struts were observed in the microstructure, pointing to improved mechanical properties. PMID:18214644

  8. Adhesion behaviors of Escherichia coli on hydroxyapatite.

    PubMed

    Kamitakahara, Masanobu; Takahashi, Shohei; Yokoi, Taishi; Inoue, Chihiro; Ioku, Koji

    2016-04-01

    Optimum design of support materials for microorganisms is required for the construction of bioreactors. However, the effects of support materials on microorganisms are still unclear. In this study, we investigated the adhesion behavior of Escherichia coli (E. coli) on hydroxyapatite (HA), polyurethane (PU), poly(vinyl chloride) (PVC), and carbon (Carbon) to obtain basic knowledge for the design of support materials. The total metabolic activity and number of E. coli adhering on the samples followed the order of HA ≈ Carbon>PVC>PU. On the other hand, the water contact angle of the pellet surfaces followed the order of HA

  9. First principles study of hydroxyapatite surface.

    PubMed

    Slepko, Alexander; Demkov, Alexander A

    2013-07-28

    The biomineral hydroxyapatite (HA) [Ca10(PO4)6(OH)2] is the main mineral constituent of mammal bone. We report a theoretical investigation of the HA surface. We identify the low energy surface orientations and stoichiometry under a variety of chemical environments. The surface most stable in the physiologically relevant OH-rich environment is the OH-terminated (1000) surface. We calculate the work function of HA and relate it to the surface composition. For the lowest energy OH-terminated surface we find the work function of 5.1 eV, in close agreement with the experimentally reported range of 4.7 eV-5.1 eV [V. S. Bystrov, E. Paramonova, Y. Dekhtyar, A. Katashev, A. Karlov, N. Polyaka, A. V. Bystrova, A. Patmalnieks, and A. L. Kholkin, J. Phys.: Condens. Matter 23, 065302 (2011)]. PMID:23902010

  10. Hydroxyapatite deposition disease of the joint.

    PubMed

    Molloy, Eamonn S; McCarthy, Geraldine M

    2003-06-01

    Basic calcium phosphate (BCP) crystals include partially carbonate-substituted hydroxyapatite, octacalcium phosphate, and tricalcium phosphate. They may form deposits, which are frequently asymptomatic but may give rise to a number of clinical syndromes including calcific periarthritis, Milwaukee shoulder syndrome, and osteoarthritis, in and around joints. Recent data suggest that magnesium whitlockite, another form of BCP, may play a pathologic role in arthritis. Data from the past year have provided further understanding of the mechanisms by which BCP crystals induce inflammation and degeneration. There remains no specific treatment to modify the effects of BCP crystals. Although potential drugs are being identified as the complex pathophysiology of BCP crystals is unraveled, much work remains to be done in order to translate research advances to date into tangible clinical benefits. PMID:12744814

  11. Mechanism of incorporation of zinc into hydroxyapatite.

    PubMed

    Matsunaga, Katsuyuki; Murata, Hidenobu; Mizoguchi, Teruyasu; Nakahira, Atsushi

    2010-06-01

    The atomic level mechanism of incorporation of Zn(2+) into hydroxyapatite (HAp), which is a potential dopant to promote bone formation, was investigated, based on first principles total energy calculations and experimental X-ray absorption near edge structure (XANES) analyses. It was found that Zn(2+)-doped HAp tends to have a Ca-deficient chemical composition and substitutional Zn(2+) ions are associated with a defect complex with a Ca(2+) vacancy and two charge compensating protons. Moreover, first principles calculations demonstrated that Zn(2+) incorporation into HAp can take place by occupying the Ca(2+) vacancy of the defect complex. The Ca(2+) vacancy complex is not only the origin of the calcium deficiency in HAp, but also plays a key role in the uptake of trace elements during mineralization. PMID:19944784

  12. Effect of hydroxyapatite microcrystals on macrophage activity.

    PubMed

    Fukuchi, N; Akao, M; Sato, A

    1995-01-01

    Hydroxyapatite (HAp) microcrystals were synthesized by a neutralization reaction of Ca(OH)2 suspension and H3PO4 solution using an ultrasonic homogenizer. The in vitro interaction of HAp microcrystals with rat peritoneal macrophages was investigated by measuring the viability, acid phosphatase (ACP) activity, lactate dehydrogenase (LDH) activity and intracellular calcium content. HAp calcined at 800 degrees C and alpha-alumina particles (alumina) were used as comparative materials. Macrophages actively phagocytosed HAp microcrystals by dissolving them. However, no damage in macrophages exposed to HAp microcrystals was observed by transmission electron microscopy. Macrophages in the presence of HAp microcrystals showed less ACP and LDH activity and higher intracellular calcium content than those in the presence of calcined HAp and alumina. HAp microcrystals had excellent biocompatibility to macrophages as well as sintered HAp. PMID:8785507

  13. Fluoride removal performance of glass derived hydroxyapatite

    SciTech Connect

    Liang, Wen; Zhan, Lei; Piao, Longhua; Russel, Christian

    2011-02-15

    Research highlights: {yields} Novel sodium calcium borate glass derived hydroxyapatite (G-HAP) is prepared. {yields} Micro-G-HAP adsorbs F{sup -} ions in solutions more effectively than commercial nano-HAP. {yields} The adsorption kinetics and isotherms are well fitted by a second order kinetic model and Freundlich isotherm model. -- Abstract: A novel sodium calcium borate glass derived hydroxyapatite (G-HAP) with different ranges of particle size was prepared by immersion sodium calcium borate glass in 0.1 M K{sub 2}HPO{sub 4} solution by the ratio of 50 g L{sup -1} for 7 days. The unique advantage of G-HAP for the adsorption of fluoride ions in solutions was studied. The effects of size and quantity of particles, pH value and adsorption time on adsorption performance were investigated. The maximum adsorption capacity was 17.34 mg g{sup -1} if 5 g L{sup -1}, <100 {mu}m G-HAP was added to a solution with an initial pH value of 6.72 and the adsorption time was 12 h. The results showed that the micro-G-HAP could immobilize F{sup -} in solution more effectively than commercial nano-HAP, which makes potential application of the G-HAP in removing the fluoride ions from wastewater. The adsorption kinetics and isotherms for F{sup -} could be well fitted by a second order kinetic model and Freundlich isotherm model respectively, which could be used to describe the adsorption behavior. The mechanism of G-HAP in immobilizing F{sup -} from aqueous solutions was investigated by the X-ray diffraction (XRD), infrared spectra (IR) and scanning electron microscopy (SEM).

  14. Synthesis of Spongy-Like Mesoporous Hydroxyapatite from Raw Waste Eggshells for Enhanced Dissolution of Ibuprofen Loaded via Supercritical CO2

    PubMed Central

    Ibrahim, Abdul-Rauf; Li, Xiangyun; Zhou, Yulan; Huang, Yan; Chen, Wenwen; Wang, Hongtao; Li, Jun

    2015-01-01

    The use of cheaper and recyclable biomaterials (like eggshells) to synthesize high purity hydroxyapatite (HAp) with better properties (small particle size, large surface area and pore volume) for applications (in environmental remediation, bone augmentation and replacement, and drug delivery systems) is vital since high-purity synthetic calcium sources are expensive. In this work, pure and mesoporous HAp nanopowder with large pore volume (1.4 cm3/g) and surface area (284.1 m2/g) was produced from raw eggshells at room temperature using a simple two-step procedure. The control of precursor droplets could stabilize the pH value of the reaction solution, because of the size of the needle (of the syringe pump used for precursor additions) leading to production of HAp with high surface area and pore size. The as-produced HAp revealed high ibuprofen (as a model drug) loading (1.38 g/g HAp), enhanced dissolution and controllable release of the drug via solute-saturated supercritical carbon dioxide. PMID:25860950

  15. Application of neural network technique to planetary milling process for the production of ZnO nanopowders

    NASA Astrophysics Data System (ADS)

    Lemine, O. M.; Hiazaa, A. F.; Louly, M. A.; Al-Ahmari, A. M.

    2011-10-01

    An artificial-neural-network (ANN) model was developed to estimate the crystalline size of ZnO nanopowder as a function on the planetary milling parameters such as balls to powder ratio and rotation speed. This nanopowder was synthesized by mechanical milling and the required data for training were collected from the experimental results. The synthesized ZnO nanoparticles are characterized by X-ray diffraction (XRD). It was found that artificial neural network was very effective providing a perfect agreement between the outcomes of ANN modeling and experimental results. An optimization model is then developed to find the best milling parameters (rotation speed and balls to powder ratio) producing the minimal average crystalline size.

  16. Polymer complex solution synthesis of (Y xGd 1- x) 2O 3:Eu 3+ nanopowders

    NASA Astrophysics Data System (ADS)

    Andrić, Ž.; Dramićanin, M. D.; Mitrić, M.; Jokanović, V.; Bessière, A.; Viana, B.

    2008-03-01

    Yttrium-gadolinium-europium oxide phosphors are regarded promising for many important optical applications, for example in computed tomography medical imaging and plasma displays. In this work, we investigated procedure for (Y xGd 1- x) 2O 3:Eu 3+ ( x = 0, 0.25, 0.5, 0.75 and 1) nanopowder synthesis using polymer complex solution method (PCS) based on polyethylene glycol fuel (PEG). Structural and emission properties of nanopowders are investigated by X-ray diffraction, electron microscopy and photoluminescence measurements. We obtained particles of about 40 nm having excellent structural ordering in cubic bixbyte type of structure - space group Ia3 for all mixed oxide compositions. Luminescence emission measurements exposed characteristic transition of the trivalent europium ion incorporated into insulating host. 5D 1 and 5D 0 decay time values are measured to obtain information on different kinetic processes occurring for these two emitting levels.

  17. Electrical and optical properties of SrTiO3 nanopowders: Effect of different dopants Ba and Ag

    NASA Astrophysics Data System (ADS)

    Ghasemifard, Mahdi; Ghamari, Misagh; Iziy, Meysam

    2016-05-01

    Using strontium-titanium salts precursor, nanopowders (STO-based-NPs) were successfully synthesized by controlled gel-combustion method. Citric and nitric acids in an optimum ratio were used as the fuel and oxidizer agents, respectively. After heat treatment at 850∘C, the crystalline structure of the products was investigated by X-ray diffraction. The effects of Ba and Ag dopants on particle size distribution were discussed by transmission electron microscopy (TEM). The optical and dielectric parameters such as energy band gap (Eg), real and imaginary parts of refractive index, dielectric function and energy loss function of nanopowders have been investigated by UV-Vis and FTIR spectra. The band gap of SrTiO3 increased with increasing Ba, Ag and Ba-Ag. Different atomic radii of dopants are responsible for changing optical and dielectric parameters due to the altered orbital configuration of the lattice structure.

  18. Ammonia sensing properties of V-doped ZnO:Ca nanopowders prepared by sol–gel synthesis

    SciTech Connect

    Fazio, E.; Hjiri, M.; Dhahri, R.; El Mir, L.; Sabatino, G.; Barreca, F.; Neri, F.; Leonardi, S.G.; Pistone, A.; Neri, G.

    2015-03-15

    V-doped ZnO:Ca nanopowders with different V loading were prepared by sol–gel synthesis and successive drying in ethanol under supercritical conditions. Characterization data of nanopowders annealed at 700 °C in air, revealed that they have the wurtzite structure. Raman features of V-doped ZnO:Ca samples were found to be substantially modified with respect to pure ZnO or binary ZnO:Ca samples, which indicate the substitution of vanadium ions in the ZnO lattice. The ammonia sensing properties of V-doped ZnO:Ca thick films were also investigated. The results obtained demonstrate the possibility of a fine tuning of the sensing characteristics of ZnO-based sensors by Ca and V doping. In particular, their combined effect has brought to an enhanced response towards NH{sub 3} compared to bare ZnO and binary V-ZnO and Ca-ZnO samples. Raman investigation suggested that the presence of Ca play a key role in enhancing the sensor response in these ternary composite nanomaterials. - Graphical abstract: V-doped ZnO:Ca nanopowders prepared by sol–gel synthesis possess enhanced sensing characteristics towards NH{sub 3} compared to bare ZnO. - Highlights: • V-doped ZnO:Ca nanopowders with different V loading were prepared by sol–gel synthesis. • Raman features of V-doped ZnO:Ca samples indicate the substitution of V ions in the ZnO lattice. • Combined effects of dopants have brought to an enhanced response to NH{sub 3} compared to ZnO. • Ca play a key role in enhancing the sensor response of ternary V-doped ZnO:Ca composites.

  19. Synthesis of nanostructured framework of novel ZnBaO2 nanopowder via wet chemical approach and hepatocytotoxicity response

    NASA Astrophysics Data System (ADS)

    Athar, Taimur; Vishwakarma, Sandeep Kumar; Alabass, Razzaq; Alqaralosy, Ahmed; Khan, Aleem Ahmed

    2015-09-01

    Wet synthetic process is an effective and facile method at low cost, environmentally benign process for easy scaling-up and then used for fabrication of multi-utility devices. Self-assembling of nanobrick leads to architecture framework with new functional properties which help to make its vast applications as nanodevices with their intrinsic shape, size and functional properties. The bimetallic oxide nanostructure with phase structure was characterized by FTIR, UV-visible electronic absorption, XRD, thermal studies, SEM, TEM, DLS and fluorescence. Nanocrystalline ZnBaO2 powder can be used due to its chemical stability and excellent transmission in the visible region. It was observed that the annealing rate plays an important role to redefine the structural and other physicochemical properties which finally help to change gel into crystalline functional properties with porosity. Wet chemical approach can be used for the synthesis of other metal oxide nanopowders which can be easily scale up for production level. Along with synthesis and characterization, we also assessed biological responses of human hepatocytes exposed to ZnBaO2 nanopowder. Cell membrane permeability and ammonia detoxification were investigated against various concentrations of nanoparticles on in vitro cultured hepatocytes. Our results suggest that low concentrations (<40 μg/ml) of ZnBaO2 nanopowder have no cytotoxic effect on hepatocytes viability, proliferation and detoxification, whereas concentrations above 40 μg/ml depict significant toxicity on cells.

  20. Synthesis of nanostructured framework of novel ZnBaO2 nanopowder via wet chemical approach and hepatocytotoxicity response

    NASA Astrophysics Data System (ADS)

    Athar, Taimur; Vishwakarma, Sandeep Kumar; Alabass, Razzaq; Alqaralosy, Ahmed; Khan, Aleem Ahmed

    2016-08-01

    Wet synthetic process is an effective and facile method at low cost, environmentally benign process for easy scaling-up and then used for fabrication of multi-utility devices. Self-assembling of nanobrick leads to architecture framework with new functional properties which help to make its vast applications as nanodevices with their intrinsic shape, size and functional properties. The bimetallic oxide nanostructure with phase structure was characterized by FTIR, UV-visible electronic absorption, XRD, thermal studies, SEM, TEM, DLS and fluorescence. Nanocrystalline ZnBaO2 powder can be used due to its chemical stability and excellent transmission in the visible region. It was observed that the annealing rate plays an important role to redefine the structural and other physicochemical properties which finally help to change gel into crystalline functional properties with porosity. Wet chemical approach can be used for the synthesis of other metal oxide nanopowders which can be easily scale up for production level. Along with synthesis and characterization, we also assessed biological responses of human hepatocytes exposed to ZnBaO2 nanopowder. Cell membrane permeability and ammonia detoxification were investigated against various concentrations of nanoparticles on in vitro cultured hepatocytes. Our results suggest that low concentrations (<40 μg/ml) of ZnBaO2 nanopowder have no cytotoxic effect on hepatocytes viability, proliferation and detoxification, whereas concentrations above 40 μg/ml depict significant toxicity on cells.

  1. ZnO nanopowder induced light scattering for improved visualization of emission sites in carbon nanotube films and arrays.

    PubMed

    Mesko, Marcel; Ou, Qiongrong; Matsuda, Takafumi; Ishikawa, Tomokazu; Veis, Martin; Antos, Roman; Ogino, Akihisa; Nagatsu, Masaaki

    2009-06-24

    We report on ZnO nanopowder induced light scattering for improved visualization of emission sites in carbon nanotube films and arrays. We observed a significant reduction of the internal multiple light scattering phenomena, which are characteristic for ZnO micropowders. The microsized grains of the commercially available ZnO:Zn (P 15) were reduced to the nanometre scale by pulsed laser ablation at an oxygen ambient pressure of 10 kPa. Our investigations show no crystalline change and no shift of the broad green emission peak at 500 nm for the ZnO nanopowder. For the application in field emission displays, we demonstrate the possibility of achieving cathodoluminescence with a fine pitch size of 100 microm of the patterned pixels without requiring additional electron beam focusing and without a black matrix. Moreover, the presented results show the feasibility of employing ZnO nanopowder as a detection material for the phosphorus screen method, which is able to localize emission sites of carbon nanotube films and arrays with an accuracy comparable to scanning anode field emission microscopy. PMID:19487805

  2. ZnO nanopowder induced light scattering for improved visualization of emission sites in carbon nanotube films and arrays

    NASA Astrophysics Data System (ADS)

    Meško, Marcel; Ou, Qiongrong; Matsuda, Takafumi; Ishikawa, Tomokazu; Veis, Martin; Antoš, Roman; Ogino, Akihisa; Nagatsu, Masaaki

    2009-06-01

    We report on ZnO nanopowder induced light scattering for improved visualization of emission sites in carbon nanotube films and arrays. We observed a significant reduction of the internal multiple light scattering phenomena, which are characteristic for ZnO micropowders. The microsized grains of the commercially available ZnO:Zn (P 15) were reduced to the nanometre scale by pulsed laser ablation at an oxygen ambient pressure of 10 kPa. Our investigations show no crystalline change and no shift of the broad green emission peak at 500 nm for the ZnO nanopowder. For the application in field emission displays, we demonstrate the possibility of achieving cathodoluminescence with a fine pitch size of 100 µm of the patterned pixels without requiring additional electron beam focusing and without a black matrix. Moreover, the presented results show the feasibility of employing ZnO nanopowder as a detection material for the phosphorus screen method, which is able to localize emission sites of carbon nanotube films and arrays with an accuracy comparable to scanning anode field emission microscopy.

  3. Preparation of Porous Hydroxyapatite Tablets and Porous Hydroxyapatite Coatings for Orthopaedic Use

    NASA Astrophysics Data System (ADS)

    Méndez-González, M.

    2004-09-01

    Porous hydroxyapatite tablets and coatings on metal substrates were obtained by the addition of polymeric additives and liofilization. Both tablets and coatings were characterized by scanning electron microscopy and x-ray diffraction. Coatings obtained by plasma spraying also exhibited interconnected porous of 100 μm while coatings obtained by laser ablation did not show any porosity. The diffraction patterns of the deposited HA were similar to that of the powder obtained by the precipitation method suggesting that no significant changes occurred during the coating procedure.

  4. Selective recovery of pure copper nanopowder from indium-tin-oxide etching wastewater by various wet chemical reduction process: Understanding their chemistry and comparisons of sustainable valorization processes.

    PubMed

    Swain, Basudev; Mishra, Chinmayee; Hong, Hyun Seon; Cho, Sung-Soo

    2016-05-01

    Sustainable valorization processes for selective recovery of pure copper nanopowder from Indium-Tin-Oxide (ITO) etching wastewater by various wet chemical reduction processes, their chemistry has been investigated and compared. After the indium recovery by solvent extraction from ITO etching wastewater, the same is also an environmental challenge, needs to be treated before disposal. After the indium recovery, ITO etching wastewater contains 6.11kg/m(3) of copper and 1.35kg/m(3) of aluminum, pH of the solution is very low converging to 0 and contain a significant amount of chlorine in the media. In this study, pure copper nanopowder was recovered using various reducing reagents by wet chemical reduction and characterized. Different reducing agents like a metallic, an inorganic acid and an organic acid were used to understand reduction behavior of copper in the presence of aluminum in a strong chloride medium of the ITO etching wastewater. The effect of a polymer surfactant Polyvinylpyrrolidone (PVP), which was included to prevent aggregation, to provide dispersion stability and control the size of copper nanopowder was investigated and compared. The developed copper nanopowder recovery techniques are techno-economical feasible processes for commercial production of copper nanopowder in the range of 100-500nm size from the reported facilities through a one-pot synthesis. By all the process reported pure copper nanopowder can be recovered with>99% efficiency. After the copper recovery, copper concentration in the wastewater reduced to acceptable limit recommended by WHO for wastewater disposal. The process is not only beneficial for recycling of copper, but also helps to address environment challenged posed by ITO etching wastewater. From a complex wastewater, synthesis of pure copper nanopowder using various wet chemical reduction route and their comparison is the novelty of this recovery process. PMID:26918838

  5. Electrokinetic properties of hydroxyapatite under flotation conditions.

    PubMed

    Vucinić, Dusica R; Radulović, Dragan S; Deusić, Slaven D

    2010-03-01

    The effect of calcite supernatant, calcium, and carbonate ions on the hydroxyapatite (HA) zeta potential without and in the presence of sodium oleate (1x10(-4) mol L(-1)) was examined within the pH range from 4 to 12. The interpretation of results was based on the HA surface and oleate solution chemistry, and on some floatability tests. HA, with different positive and negative surface sites formed depending on its solubility and pH, had a negative zeta potential over the whole pH range. This mineral is not naturally floatable (flotation recovery, 5%9.3. The HA surface is less negatively charged in calcite supernatant than in water from pH 6.6 to 9.2 due to the adsorption on HA negative surface active centers ([triple bond]HPO(4)(-) and [triple bond]PO(4)(2-)) of the Ca(2+), and CaOH(+) ions (present in the calcite supernatant), producing more surface sites [triple bond]HPO(4)Ca(+), [triple bond]PO(4)Ca, [triple bond]HPO(4)CaOH, and [triple bond]PO(4)(-) CaOH, and new centers [triple bond]HPO(4)CaHCO(3) and [triple bond]PO(4)(-) CaHCO(3). In the presence of 1x10(-3) mol L(-1) CaCl(2), the HA sample has positive zeta potential, the same as calcite from the same deposit, up to IEP at pH 11.25. Carbonate ions (1x10(-3) mol L(-1) Na(2)CO(3)) do not affect the HA zeta potential. However, a possible process can be the ion-exchange reaction between

  6. Osteoinductive hydroxyapatite-coated titanium implants.

    PubMed

    Ripamonti, Ugo; Roden, Laura C; Renton, Louise F

    2012-05-01

    Previous studies have shown that heterotopic induction of bone formation by calcium phosphate-based macroporous constructs is set into motion by the geometry of the implanted substrata, i.e. a sequence of repetitive concavities assembled within the macroporous spaces. The aim of this study was to construct osteoinductive titanium implants that per se, and without the exogenous application of the osteogenic soluble molecular signals of the transforming growth factor-β supergene family, would initiate the induction of bone formation. To generate intrinsically osteoinductive titanium implants for translation in clinical contexts, titanium grade Ti-6A1-4V cylinders of 15 mm in length and 3.85 mm in diameter, with or without concavities, were plasma sprayed with crystalline hydroxyapatite resulting in a uniform layer of 30 μm in thickness. Before coating, experimental titanium implants were prepared with a sequence of 36 repetitive concavities 1600 μm in diameter and 800 μm in depth, spaced a distance of 1000 μm apart. Mandibular molars and premolars were extracted to prepare edentulous mandibular ridges for later implantation. Planar and geometric hydroxyapatite-coated titanium constructs were implanted in the left and right edentulized hemi-mandibles, respectively, after a healing period of 7-8 months, 3 per hemi-mandible. Three planar and three geometric implants were implanted in the left and right tibiae, respectively; additionally, planar and geometric constructs were also inserted in the rectus abdominis muscle. Six animals were euthanized at 30 and 90 days after implantation; one animal had to be euthanized 5 days after surgery and the remaining animal was euthanized 31 months after implantation. Undecalcified longitudinal sections were precision-sawed, ground and polished to 40-60 μm; all sections were stained with a modified Goldner's trichrome. Undecalcified specimen block preparation was performed using the EXAKT precision cutting and grinding system

  7. Nanostructured nickel-free austenitic stainless steel/hydroxyapatite composites.

    PubMed

    Tulinski, Maciej; Jurczyk, Mieczyslaw

    2012-11-01

    In this work Ni-free austenitic stainless steels with nanostructure and their nanocomposites with hydroxyapatite are presented and characterized by means of X-ray diffraction and optical profiling. The samples were synthesized by mechanical alloying, heat treatment and nitriding of elemental microcrystalline powders with addition of hydroxyapatite (HA). In our work we wanted to introduce into stainless steel hydroxyapatite ceramics that have been intensively studied for bone repair and replacement applications. Such applications were chosen because of their high biocompatibility and ability to bond to bone. Since nickel-free austenitic stainless steels seem to have better mechanical properties, corrosion resistance and biocompatibility compared to 316L stainless steels, it is possible that composite made of this steel and HA could improve properties, as well. Mechanical alloying and nitriding are very effective technologies to improve the corrosion resistance of stainless steel. Similar process in case of nanocomposites of stainless steel with hydroxyapatite helps achieve even better mechanical properties and corrosion resistance. Hence nanocrystalline nickel-free stainless steels and nickel-free stainless steel/hydroxyapatite nanocomposites could be promising bionanomaterials for use as a hard tissue replacement implants, e.g., orthopedic implants. In such application, the surface roughness and more specifically the surface topography influences the proliferation of cells (e.g., osteoblasts). PMID:23421285

  8. New Bismuth-Substituted Hydroxyapatite Nanoparticles for Bone Tissue Engineering

    NASA Astrophysics Data System (ADS)

    Ciobanu, Gabriela; Bargan, Ana Maria; Luca, Constantin

    2015-11-01

    New bismuth-substituted hydroxyapatite [Ca10- x Bi x (PO4)6(OH)2 where x = 0-2.5] nanoparticles were synthesized by the co-precipitation method from aqueous solutions. The structural properties of the samples were analyzed by scanning electron microscopy coupled with x-ray analysis, x-ray powder diffraction, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller surface area analysis. The results confirm that bismuth ions have been incorporated into the hydroxyapatite lattice. The prepared nanocrystalline powders consisted of hydroxyapatite as single phase with hexagonal structure, crystal sizes smaller than 60 nm and (Bi + Ca)/P atomic ratio of around 1.67. The hydroxyapatite samples doped with Bi have mesoporous textures with pores size of around 2 nm and specific surface area in the range of 12-25 m2/g. The Bi-substituted hydroxyapatite powders are more effective against Gram-negative Escherichia coli bacteria than Gram-positive Staphylococcus aureus bacteria.

  9. A process for the development of strontium hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Zahra, N.; Fayyaz, M.; Iqbal, W.; Irfan, M.; Alam, S.

    2014-06-01

    A procedure for the preparation of Strontium Hydroxyapatite is adapted to produce high purity and better homogeneity ceramic with good Crystallinity. The strontium substituted bone cement has potential for use in orthopedic surgeries. Ionic Strontium (Sr) in humans shares the same physiological pathway as calcium and can be deposited in the mineral structure of the bone. In the present study, a novel concept of preparing Sr-contained Hydroxyapatite bone cement by using a precipitation method is proposed to get an ideal biomaterial that possesses potential degradability and more excellent pharmacological effect. Chemical analysis, Fourier Transform Infra Red analysis and Thermogravimetric/ Differential Scanning Calorimetric studies were conducted on prepared Strontium Hydroxyapatite sample to characterize the incorporation of 15% Sr2+ into the crystal lattice of Hydroxyapatite. Strontium was quantitatively incorporated into Hydroxyapatite where its substitution for calcium provoked a linear shift of the infrared absorption bands of the hydroxyl and phosphate groups. Thus, the formation of Sr-HAp was confirmed by Chemical Analysis, FT-IR and TGA/DSC results.

  10. Cobalt doped proangiogenic hydroxyapatite for bone tissue engineering application.

    PubMed

    Kulanthaivel, Senthilguru; Roy, Bibhas; Agarwal, Tarun; Giri, Supratim; Pramanik, Krishna; Pal, Kunal; Ray, Sirsendu S; Maiti, Tapas K; Banerjee, Indranil

    2016-01-01

    The present study delineates the synthesis and characterization of cobalt doped proangiogenic-osteogenic hydroxyapatite. Hydroxyapatite samples, doped with varying concentrations of bivalent cobalt (Co(2+)) were prepared by the ammoniacal precipitation method and the extent of doping was measured by ICP-OES. The crystalline structure of the doped hydroxyapatite samples was confirmed by XRD and FTIR studies. Analysis pertaining to the effect of doped hydroxyapatite on cell cycle progression and proliferation of MG-63 cells revealed that the doping of cobalt supported the cell viability and proliferation up to a threshold limit. Furthermore, such level of doping also induced differentiation of the bone cells, which was evident from the higher expression of differentiation markers (Runx2 and Osterix) and better nodule formation (SEM study). Western blot analysis in conjugation with ELISA study confirmed that the doped HAp samples significantly increased the expression of HIF-1α and VEGF in MG-63 cells. The analysis described here confirms the proangiogenic-osteogenic properties of the cobalt doped hydroxyapatite and indicates its potential application in bone tissue engineering. PMID:26478356

  11. Nano-Hydroxyapatite Thick Film Gas Sensors

    SciTech Connect

    Khairnar, Rajendra S.; Mene, Ravindra U.; Munde, Shivaji G.; Mahabole, Megha P.

    2011-12-10

    In the present work pure and metal ions (Co and Fe) doped hydroxyapatite (HAp) thick films have been successfully utilized to improve the structural, morphological and gas sensing properties. Nanocrystalline HAp powder is synthesized by wet chemical precipitation route, and ion exchange process is employed for addition of Co and Fe ions in HAp matrix. Moreover, swift heavy ion irradiation (SHI) technique is used to modify the surface of pure and metal ion exchanged HAp with various ion fluence. The structural investigation of pure and metal ion exchanged HAp thick films are carried out using X-ray diffraction and the presence of functional group is observed by means FTIR spectroscopy. Furthermore, surface morphology is visualized by means of SEM and AFM analysis. CO gas sensing study is carried out for, pure and metal ions doped, HAp thick films with detail investigation on operating temperature, response/recovery time and gas uptake capacity. The surface modifications of sensor matrix by SHI enhance the gas response, response/recovery and gas uptake capacity. The significant observation is here to note that, addition of Co and Fe in HAp matrix and surface modification by SHI improves the sensing properties of HAp films drastically resulting in gas sensing at relatively lower temperatures.

  12. Dip coated silicon-substituted hydroxyapatite films.

    PubMed

    Hijón, Natalia; Victoria Cabañas, M; Peña, Juan; Vallet-Regí, María

    2006-09-01

    Silicon-substituted hydroxyapatites have been deposited onto Ti6Al4V substrates by sol-gel technology. The Ca(10)(PO(4))(6-x-y)(SiO(4))(x)(CO(3))(y)(OH)(2-x+y) coatings obtained, with silicon contents up to x=1 (2.8 wt.%), show a homogeneous and crack-free surface composed of particles smaller than 20 nm. The silicon enters into the apatite structure in the form of SiO(4)(4-) groups that partially substitute the PO(4)(3-) groups. The Si content and the Ca/P molar ratio of the coatings agree with those originally introduced in the sols. Layers with thicknesses around 600 nm show adhesion strengths superior to 20 MPa as determined by a pull-out test. The formation of an apatite layer onto these coatings after immersion in a simulated body fluid is enhanced by the presence of silicon. PMID:16828579

  13. Nano-Hydroxyapatite Thick Film Gas Sensors

    NASA Astrophysics Data System (ADS)

    Khairnar, Rajendra S.; Mene, Ravindra U.; Munde, Shivaji G.; Mahabole, Megha P.

    2011-12-01

    In the present work pure and metal ions (Co and Fe) doped hydroxyapatite (HAp) thick films have been successfully utilized to improve the structural, morphological and gas sensing properties. Nanocrystalline HAp powder is synthesized by wet chemical precipitation route, and ion exchange process is employed for addition of Co and Fe ions in HAp matrix. Moreover, swift heavy ion irradiation (SHI) technique is used to modify the surface of pure and metal ion exchanged HAp with various ion fluence. The structural investigation of pure and metal ion exchanged HAp thick films are carried out using X-ray diffraction and the presence of functional group is observed by means FTIR spectroscopy. Furthermore, surface morphology is visualized by means of SEM and AFM analysis. CO gas sensing study is carried out for, pure and metal ions doped, HAp thick films with detail investigation on operating temperature, response/recovery time and gas uptake capacity. The surface modifications of sensor matrix by SHI enhance the gas response, response/recovery and gas uptake capacity. The significant observation is here to note that, addition of Co and Fe in HAp matrix and surface modification by SHI improves the sensing properties of HAp films drastically resulting in gas sensing at relatively lower temperatures.

  14. Dual functional selenium-substituted hydroxyapatite.

    PubMed

    Wang, Yanhua; Ma, Jun; Zhou, Lei; Chen, Jin; Liu, Yonghui; Qiu, Zhiye; Zhang, Shengmin

    2012-06-01

    Hydroxyapatite (HA) doped with trace elements has attracted much attention recently owing to its excellent biological functions. Herein, we use a facile co-precipitation method to incorporate selenium into HA by adding sodium selenite during synthesis. The obtained selenium-substituted HA products are needle-like nanoparticles which have  size and crystallinity that are similar to those of the pure HA nanoparticles (HANs) when the selenium content is low. HANs are found to have the ability to induce the apoptosis of osteosarcoma cells, and the anti-tumour effects are enhanced after incorporation of selenium. Meanwhile, the nanoparticles can also support the growth of bone marrow stem cells. Furthermore, the flow cytometric results indicate that the apoptosis induction of osteosarcoma cells is caused by the increased reactive oxygen species and decreased mitochondrial membrane potential. These results show that the selenium-substituted HANs are potentially promising bone graft materials in osteosarcoma treatment due to their dual functions of supporting normal cell growth and inducing tumour cell apoptosis. PMID:23741613

  15. Synthesis of carbonated hydroxyapatite nanospheres through nanoemulsion.

    PubMed

    Zhou, W Y; Wang, M; Cheung, W L; Guo, B C; Jia, D M

    2008-01-01

    This study investigated the nanoemulsion technique as a means to synthesize carbonated hydroxyapatite (CHAp) nanospheres which could be used to produce composite tissue engineering scaffolds. CHAp nanospheres were successfully synthesized by mixing an acetone solution of Ca(NO(3))(2).4H(2)O with an aqueous solution of (NH(4))(2)HPO(4) and NH(4)HCO(3). Four reaction temperatures, namely, 4, 25, 37 and 55 degrees C, were investigated and no surfactant was added in all nanoemulsion processes. Wet slurries of CHAp from the nanoemulsions were freeze-dried to obtain dry powders. X-ray diffraction (XRD) results showed that the as-synthesized CHAp nanoparticles were mainly in an amorphous state. After calcination at 900 degrees C, the apatite became well crystallized. Fourier transform infrared (FTIR) spectroscopy showed that the CHAp was B-type substitution. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the CHAp particles were spherical in shape and that their sizes were in the nanometer range. The successful synthesis of CHAp nanospheres is a critical step forward in our efforts to fabricate bone tissue engineering scaffolds using the selective laser sintering technology. PMID:17577636

  16. Chemical characterization of some substituted hydroxyapatites

    PubMed Central

    2011-01-01

    Synthetic multi-substituted hydroxyapatite nano powders containing silicon and or carbonate prepared by a wet chemical method. The process parameters are set up to allow the simultaneous substitution of carbonate and silicon ions in the place of phosphorus. The chemical and structural characterizations of the prepared powders are determined with the aid of; XRF, ICP, XRD and FTIR. The results show that, the ion substitution in the crystal lattice of HA caused a change in the unit cell dimensions and affected the degree of crystallization of the produced powders. The apatite formation abilityy of the prepared discs from the synthesized powders is determined by immersing in SBF solution for different periods. The degree of ion release was determined in the obtained solutions. The examined surface of the immersed discs under SEM and analyzed by CDS showed a more dense HA layer than those of un-substituted ones. The HA with the substituted silicon and carbonate ions, showed the highest solubility with greater rate of ion release, compared with carbonate-free powder. All prepared powders took sodium ion from the SBF solution during immersion, which was not recorded before. PMID:22122971

  17. Elastin-like polypeptide based hydroxyapatite bionanocomposites.

    PubMed

    Wang, Eddie; Lee, Sang-Hyuk; Lee, Seung-Wuk

    2011-03-14

    In nature, organic matrix macromolecules play a critical role in enhancing the mechanical properties of biomineralized composites such as bone and teeth. Designing artificial matrix analogues is promising but challenging because relatively little is known about how natural matrix components function. Therefore, in lieu of using natural components, we created biomimetic matrices using genetically engineered elastin-like polypeptides (ELPs) and then used them to construct mechanically robust ELP-hydroxyapatite (HAP) composites. ELPs were engineered with well-defined backbone charge distributions by periodic incorporation of negative, positive, or neutral side chains or with HAP-binding octaglutamic acid motifs at one or both protein termini. ELPs exhibited sequence-specific capacities to interact with ions, bind HAP, and disperse HAP nanoparticles. HAP-binding ELPs were incorporated into calcium phosphate cements, resulting in materials with improved mechanical strength, injectability, and antiwashout properties. The results demonstrate that rational design of genetically engineered polymers is a powerful system for determining sequence-property relationships and for improving the properties of organic-inorganic composites. Our approach may be used to further develop novel, multifunctional bone cements and expanded to the design of other advanced composites. PMID:21218767

  18. Osteoclasts in the interface with electrospun hydroxyapatite.

    PubMed

    Pasuri, Jenni; Holopainen, Jani; Kokkonen, Hanna; Persson, Maria; Kauppinen, Kyösti; Lehenkari, Petri; Santala, Eero; Ritala, Mikko; Tuukkanen, Juha

    2015-11-01

    Electrospinning is a method to produce lightweight, resorbable and bioinspired scaffolds for tissue engineering. Here we investigated the influence of electrospun hydroxyapatite fibers (HA) on macrophages and osteoclasts. A mouse macrophage cell line (RAW 264.7) and human bone marrow derived primary osteoclasts (hOC) were cultured with electrospun HA fibers embedded in Matrigel. Cell morphology and the secretion of pro-inflammatory cytokines (IL-6 and TNF-α) were analyzed using macrophages. Both fluorescent microscopy and scanning electron microscopy indicated that the cell morphology differed on the various materials (HA fibers on Matrigel, pure Matrigel and a glass control). Control macrophages were activated with bacterial lipopolysaccharide (LPS) but electrospun HA did not provoke an inflammatory response. Cytokine secretion detected with enzyme-linked immunosorbent assay (ELISA) also supported this observation. LPS, but not HA fibers, stimulated TNF-α and IL-6 secretion by macrophages at the 2 day time point. After 4 days in culture there was an increasing trend in cytokine secretion in the HA fiber samples. Human bone marrow myeloid precursor cells were able to fuse and differentiate on the fibrous mineral scaffold to form functional multinuclear osteoclasts that were able to resorb the HA nanofibers. This indicates that osteoclasts do not necessarily need a continuous bone surface but osteoclast ruffled border membranes can form a resorption interface with a fibrous mineral scaffold. PMID:26342323

  19. Synthesis and Antimicrobial Activity of Silver-Doped Hydroxyapatite Nanoparticles

    PubMed Central

    Ciobanu, Carmen Steluta; Iconaru, Simona Liliana; Chifiriuc, Mariana Carmen; Costescu, Adrian; Le Coustumer, Philippe; Predoi, Daniela

    2013-01-01

    The synthesis of nanosized particles of Ag-doped hydroxyapatite with antibacterial properties is of great interest for the development of new biomedical applications. The aim of this study was the evaluation of Ca10−xAgx(PO4)6(OH)2 nanoparticles (Ag:HAp-NPs) for their antibacterial and antifungal activity. Resistance to antimicrobial agents by pathogenic bacteria has emerged in the recent years and became a major health problem. Here, we report a method for synthesizing Ag doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionised water. Also, in this paper Ag:HAp-NPs are evaluated for their antimicrobial activity against Gram-positive and Gram-negative bacteria and fungal strains. The specific antimicrobial activity revealed by the qualitative assay is demonstrating that our compounds are interacting differently with the microbial targets, probably due to the differences in the microbial wall structures. PMID:23509801

  20. Fabrication, Properties and Applications of Dense Hydroxyapatite: A Review

    PubMed Central

    Prakasam, Mythili; Locs, Janis; Salma-Ancane, Kristine; Loca, Dagnija; Largeteau, Alain; Berzina-Cimdina, Liga

    2015-01-01

    In the last five decades, there have been vast advances in the field of biomaterials, including ceramics, glasses, glass-ceramics and metal alloys. Dense and porous ceramics have been widely used for various biomedical applications. Current applications of bioceramics include bone grafts, spinal fusion, bone repairs, bone fillers, maxillofacial reconstruction, etc. Amongst the various calcium phosphate compositions, hydroxyapatite, which has a composition similar to human bone, has attracted wide interest. Much emphasis is given to tissue engineering, both in porous and dense ceramic forms. The current review focusses on the various applications of dense hydroxyapatite and other dense biomaterials on the aspects of transparency and the mechanical and electrical behavior. Prospective future applications, established along the aforesaid applications of hydroxyapatite, appear to be promising regarding bone bonding, advanced medical treatment methods, improvement of the mechanical strength of artificial bone grafts and better in vitro/in vivo methodologies to afford more particular outcomes. PMID:26703750

  1. Recent Advances in Hydroxyapatite Scaffolds Containing Mesenchymal Stem Cells

    PubMed Central

    Michel, John; Penna, Matthew; Kochen, Juan; Cheung, Herman

    2015-01-01

    Modern day tissue engineering and cellular therapies have gravitated toward using stem cells with scaffolds as a dynamic modality to aid in differentiation and tissue regeneration. Mesenchymal stem cells (MSCs) are one of the most studied stem cells used in combination with scaffolds. These cells differentiate along the osteogenic lineage when seeded on hydroxyapatite containing scaffolds and can be used as a therapeutic option to regenerate various tissues. In recent years, the combination of hydroxyapatite and natural or synthetic polymers has been studied extensively. Due to the interest in these scaffolds, this review will cover the wide range of hydroxyapatite containing scaffolds used with MSCs for in vitro and in vivo experiments. Further, in order to maintain a progressive scope of the field this review article will only focus on literature utilizing adult human derived MSCs (hMSCs) published in the last three years. PMID:26106425

  2. Study of thermal effects of silicate-containing hydroxyapatites

    NASA Astrophysics Data System (ADS)

    Golovanova, O. A.; Zaits, A. V.; Berdinskaya, N. V.; Mylnikova, T. S.

    2016-02-01

    The possibility of modifications of hydroxyapatite silicate ions, from the extracellular fluid prototype solution under near-physiological conditions has been studied. Formation of silicon-structured hydroxyapatite with different extent of substitution of phosphate groups in the silicate group has been established through chemical and X-ray diffraction analyses, FTIR spectroscopy and optical microscopy. The results obtained are in agreement and suggest the possibility of substitution of phosphate groups for silicate groups in the hydroxyapatite structure when introducing different sources of silica, tetraethoxysilane and sodium silicate, in the reaction mixture. Growth in the amount of silicon in Si-HA results in the increase in the thermal stability of the samples. The greatest mass loss occurs at temperatures in the range of 25-400 0C that is caused by the removal of the crystallization and adsorption water and volatile impurities. It is shown that the modified apatites are of imperfect structure and crystallize in a nanocrystalline state.

  3. Investigations on hydroxyapatite powder obtained by wet precipitation

    NASA Astrophysics Data System (ADS)

    Poinescu, Aurora Anca; Ion, Rodica Mariana; van Staden, Raluca-Ioana; van Staden, Jacobus Frederick; Ghiurea, Marius

    2010-11-01

    It is well-known that hydroxyapatite have multiple applications in tissue engineering due to compositional similarities with bone tissue. In this work, hydroxyapatite powders obtained by modified chemical precipitation route, has been investigated by AMF and SEM analysis grain size, X-ray diffraction and infra-red spectroscopy. The particle size of hydroxyapatite was observed to be very fine, uniform, around 50 -60 nm. SEM observation of the HA coatings showed the presence of nano-sized needles, with a significant level of agglomeration. The infrared analysis show the characteristic peaks of absorbed water, hydroxyl, phosphate and carbonate species. The XRD pattern clearly indicated the crystallites responsible for the Bragg reflection of the (002) and (003) planes are useful for size determination by Sherrer relationship (around 68 nm).

  4. Fabrication, Properties and Applications of Dense Hydroxyapatite: A Review.

    PubMed

    Prakasam, Mythili; Locs, Janis; Salma-Ancane, Kristine; Loca, Dagnija; Largeteau, Alain; Berzina-Cimdina, Liga

    2015-01-01

    In the last five decades, there have been vast advances in the field of biomaterials, including ceramics, glasses, glass-ceramics and metal alloys. Dense and porous ceramics have been widely used for various biomedical applications. Current applications of bioceramics include bone grafts, spinal fusion, bone repairs, bone fillers, maxillofacial reconstruction, etc. Amongst the various calcium phosphate compositions, hydroxyapatite, which has a composition similar to human bone, has attracted wide interest. Much emphasis is given to tissue engineering, both in porous and dense ceramic forms. The current review focusses on the various applications of dense hydroxyapatite and other dense biomaterials on the aspects of transparency and the mechanical and electrical behavior. Prospective future applications, established along the aforesaid applications of hydroxyapatite, appear to be promising regarding bone bonding, advanced medical treatment methods, improvement of the mechanical strength of artificial bone grafts and better in vitro/in vivo methodologies to afford more particular outcomes. PMID:26703750

  5. Hydroxyapatite Growth Inhibition Effect of Pellicle Statherin Peptides.

    PubMed

    Xiao, Y; Karttunen, M; Jalkanen, J; Mussi, M C M; Liao, Y; Grohe, B; Lagugné-Labarthet, F; Siqueira, W L

    2015-08-01

    In our recent studies, we have shown that in vivo-acquired enamel pellicle is a sophisticated biological structure containing a significant portion of naturally occurring salivary peptides. From a functional aspect, the identification of peptides in the acquired enamel pellicle is of interest because many salivary proteins exhibit functional domains that maintain the activities of the native protein. Among the in vivo-acquired enamel pellicle peptides that have been newly identified, 5 peptides are derived from statherin. Here, we assessed the ability of these statherin pellicle peptides to inhibit hydroxyapatite crystal growth. In addition, atomistic molecular dynamics (MD) simulations were performed to better understand the underlying physical mechanisms of hydroxyapatite growth inhibition. A microplate colorimetric assay was used to quantify hydroxyapatite growth. Statherin protein, 5 statherin-derived peptides, and a peptide lacking phosphate at residues 2 and 3 were analyzed. Statherin peptide phosphorylated on residues 2 and 3 indicated a significant inhibitory effect when compared with the 5 other peptides (P < 0.05). MD simulations showed a strong affinity and fast adsorption to hydroxyapatite for phosphopeptides, whereas unphosphorylated peptides interacted weakly with the hydroxyapatite. Our data suggest that the presence of a covalently linked phosphate group (at residues 2 and 3) in statherin peptides modulates the effect of hydroxyapatite growth inhibition. This study provides a mechanism to account for the composition and function of acquired enamel pellicle statherin peptides that will contribute as a base for the development of biologically stable and functional synthetic peptides for therapeutic use against dental caries and/or periodontal disease. PMID:26116492

  6. Plasticizer Effect on Rheological Behaviour of Screen Printing Pastes Based on Barium Titanate Nanopowder

    NASA Astrophysics Data System (ADS)

    Dulina, I.; Umerova, S.; Ragulya, A.

    2015-04-01

    The dependence of rheological behaviour of pastes based on BaTiO3 nanopowder vs. plasticizer content has been investigated. All pastes prepared for research can be divided into groups by structure types and viscosity. Such a grouping has been explained by different interaction between nanoparticles and binder in the pastes. Particles with molecules of binder form clusters - the representative units in the volume of paste where particles are uniformly distributed. Plasticizer adding effects on binder molecule conformation and change clusters size. Bond strength between clusters can be specified with rheopexy in the area of low shear stress and low strain rates. Rheopexy degree increasing authenticates interaction intensification between clusters. Rheopexy structure destruction leads to separate clusters formation and initiation of the pseudoplastic flow stage. The end of pseudoplastic flow corresponds to structure with clusters assembled into separated layers. Further shear stress increasing leads to inter-clusters bonds appear which can be deformed elastically and the temporary local linkage is possible. Such a phenomenon fully discloses the features of thixotropic structure destruction in plasticized pastes.

  7. Temperature dependence of Er3+ ionoluminescence and photoluminescence in Gd2O3:Bi nanopowder

    NASA Astrophysics Data System (ADS)

    Boruc, Zuzanna; Gawlik, Grzegorz; Fetliński, Bartosz; Kaczkan, Marcin; Malinowski, Michał

    2014-06-01

    Ionoluminescence (IL) and photoluminescence (PL) of trivalent erbium ions (Er3+) in Gd2O3 nanopowder host activated with Bi3+ ions has been studied in order to establish the link between changes in luminescent spectra and temperature of the sample material. IL measurements have been performed with H2+ 100 keV ion beam bombarding the target material for a few seconds, while PL spectra have been collected for temperatures ranging from 20 °C to 700 °C. The PL data was used as a reference in determining the temperature corresponding to IL spectra. The collected data enabled the definition of empirical formula based on the Boltzmann distribution, which allows the temperature to be determined with a maximum sensitivity of 9.7 × 10-3 °C-1. The analysis of the Er3+ energy level structure in terms of tendency of the system to stay in thermal equilibrium, explained different behaviors of the line intensities. This work led to the conclusion that temperature changes during ion excitation can be easily defined with separately collected PL spectra. The final result, which is empirical formula describing dependence of fluorescence intensity ratio on temperature, raises the idea of an application of method in temperature control, during processes like ion implantation and some nuclear applications.

  8. When Halides Come to Lithium Niobate Nanopowders Purity and Morphology Assistance.

    PubMed

    Lamouroux, Emmanuel; Badie, Laurent; Miska, Patrice; Fort, Yves

    2016-03-01

    The preparation of pure lithium niobate nanopowders was carried out by a matrix-mediated synthesis approach. Lithium hydroxide and niobium pentachloride were used as precursors. The influence of the chemical environment was studied by adding lithium halide (LiCl or LiBr). After thermal treatment of the precursor mixture at 550 °C for 30 min, the morphology of the products was obtained from transmission electron microscopy and dynamic light scattering, whereas the crystallinity and phase purity were characterized by X-ray diffraction and UV-visible and Raman spectroscopies. Our results point out that the chemical environment during lithium niobate formation at 550 °C influences the final morphology. Moreover, direct and indirect band-gap energies have been determined from UV-visible spectroscopy. Their values for the direct-band-gap energies range from 3.97 to 4.36 eV with a slight dependence on the Li/Nb ratio, whereas for the indirect-band-gap energies, the value appears to be independent of this ratio and is 3.64 eV. No dependence of the band-gap energies on the average crystallite and nanoparticle sizes is observed. PMID:26859157

  9. One-pot synthesis and characterization of Nb2O5 nanopowder.

    PubMed

    Athar, Taimur; Hashmi, Ameed; Al-Hajry, Ali; Ansari, Z A; Ansari, S G

    2012-10-01

    Nanosized niobium oxide powders were synthesized with a yield of approximately 87% using a simple and facile soft-chemical process. Niobium pentachloride (Nb2Cl5) was used as the precursor which was first converted into niobium ethoxide and then hydrolysed with water to synthesize niobia nanopowder. The synthesized powder was calcined at 500 degrees C for phase conversion to end-centered monoclinic as confirmed by diffraction studies and elemental analysis with a chemical composition in the ratio of Nb:O as 1:2.5. The molecular framework of Nb-O-Nb stretching and asymmetric frequency was confirmed by FT-IR, UV-visible and Raman spectroscopic studies. The size, shape and surface morphology of the powders were observed by SEM and TEM which indicated particle sizes of approximately 20 nm. The surface area of 20 m2/g, pore volume of 0.0538 cm2/g and the average pore size of 6.5 nm2 for the calcined sample were obtained with the help of nitrogen adsorption/desorption method using the Barrett-Joyner-Halenda (BJH) method which indicates that the synthesized powder can be used for catalysis and other surface sensitive applications. PMID:23421157

  10. Proton beam effects on phenolic-based composites reinforced with nanopowders

    NASA Astrophysics Data System (ADS)

    Chhay, B.; Minamisawa, R.; Zheng, B.; Budak, S.; Ila, D.

    2007-08-01

    We have introduced various nanopowders in the precursor of glassy polymeric carbon (GPC) and studied the electrical properties as well as the chemical structure. In general the GPC ware produced at Alabama A&M University (AAMU) is used for making crucibles, heat exchangers and for prosthetic devices because of its biocompatibility and inertness. GPC ware at AAMU is synthesized from a phenolic resin solution from Georgia Pacific in a pyrolyzer system at temperatures between 100 °C and 2800 °C. The heat treatment includes several stages: gelling, curing, postcuring, precarbonization and carbonization. The fabrication of GPC is complicated because of the high production rate of gaseous products in critical temperature ranges where out-diffusion is relatively slow. Special care should be taken in temperature programming to avoid kilning faults and misshapen or porous GPC end results [H. Maleki, L.R. Holland, G.M. Jenkins, et al., Carbon 35 (1997) 227]. In this work we have introduced 1 wt% of SiC, carbon nanotubes (CNT) and Al2O3 to the precursor, pyrolyzed composites to 1000 °C and studied the effect of 1 MeV and 3 MeV proton bombardment on the final products.

  11. Irradiation creep of nano-powder sintered silicon carbide at low neutron fluences

    NASA Astrophysics Data System (ADS)

    Koyanagi, T.; Shimoda, K.; Kondo, S.; Hinoki, T.; Ozawa, K.; Katoh, Y.

    2014-12-01

    The irradiation creep behavior of nano-powder sintered silicon carbide was investigated using the bend stress relaxation method under neutron irradiation up to 1.9 dpa. The creep deformation was observed at all temperatures ranging from 380 to 1180 °C mainly from the irradiation creep but with the increasing contributions from the thermal creep at higher temperatures. The apparent stress exponent of the irradiation creep slightly exceeded unity, and instantaneous creep coefficient at 380-790 °C was estimated to be ∼1 × 10-5 [MPa-1 dpa-1] at ∼0.1 dpa and 1 × 10-7 to 1 × 10-6 [MPa-1 dpa-1] at ∼1 dpa. The irradiation creep strain appeared greater than that for the high purity SiC. Microstructural observation and data analysis indicated that the grain-boundary sliding associated with the secondary phases contributes to the irradiation creep at 380-790 °C to 0.01-0.11 dpa.

  12. TiO 2 nanopowders doped with boron and nitrogen for photocatalytic applications

    NASA Astrophysics Data System (ADS)

    Gombac, V.; De Rogatis, L.; Gasparotto, A.; Vicario, G.; Montini, T.; Barreca, D.; Balducci, G.; Fornasiero, P.; Tondello, E.; Graziani, M.

    2007-10-01

    TiO 2-based systems have attracted an increasing interest for their potential use as photocatalysts under visible-light irradiation. In this context, the present work was dedicated to the tailored synthesis of TiO 2 nanopowders doped with boron, nitrogen or both species for the photocatalytic degradation of organic dyes. In particular, the systems were synthesized by a sol-gel route starting from titanium(IV) butoxide as a Ti source and thoroughly characterized by the combined use of N 2 physisorption, X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), UV-Vis reflectance spectroscopy and temperature-programmed oxidation (TPO). Finally, the photocatalytic performances in the decomposition of the azo-dye methyl orange (MO) were investigated. The obtained results suggest that both dopants promote the photocatalytic activity with respect to pure TiO 2 systems. Nevertheless, while our surface N-doping does not appreciably modify the titania structure and texture, B incorporation inhibits the TiO 2 crystallite growth and induces an increase in the surface area. As regards the codoped systems, a remarkable reactivity improvement was observed only when B is present in excess with respect to N. A rational interpretation of the observed behaviour was attempted by calculations based on the density functional theory (DFT). We suggest that the presence of B in molar excess with respect to N generates reactive Ti(III) sites, which, in turn, might induce the formation of reactive superoxide species.

  13. Flame-driven aerosol synthesis of copper-nickel nanopowders and conductive nanoparticle films.

    PubMed

    Sharma, Munish K; Qi, Di; Buchner, Raymond D; Scharmach, William J; Papavassiliou, Vasilis; Swihart, Mark T

    2014-08-27

    We report the continuous one-step synthesis of bimetallic copper-nickel nanostructured coatings by deposition and sintering of metal nanoparticles produced as an aerosol using a flame driven high temperature reducing jet (HTRJ) process. The HTRJ process allows gas-phase (aerosol) formation of metal nanoparticles from low-cost metal salt precursors. These can be collected as discrete powders for subsequent use in formulating conductive inks or for other applications. However, direct deposition of nanoparticles to form coatings allows measurements of electrical conductivity of films of deposited nanoparticles as a function of composition and sintering temperature, without actually formulating and printing inks. This is the approach taken here for the purpose of screening nanoparticle compositions quickly. We characterized the microstructure and composition of both nanopowders and films and found that their composition consistently matched the ratio of metals in the precursor solution. The electrical conductivity was highest (∼10(4) S/m) for films with 60:40 and 40:60 copper-to-nickel mass ratios. These films maintained their conductivity during extended storage (1 month) under ambient conditions. The oxidation resistance and high conductivity observed here suggest that 60:40 and 40:60 Cu:Ni nanoparticles have promise as lower cost replacements for silver nanoparticles in conductive ink formulations. PMID:25075968

  14. Magnetic structure, magnetoelastic coupling, and thermal properties of EuCrO3 nanopowders

    NASA Astrophysics Data System (ADS)

    Taheri, M.; Razavi, F. S.; Yamani, Z.; Flacau, R.; Reuvekamp, P. G.; Schulz, A.; Kremer, R. K.

    2016-03-01

    We carried out detailed studies of the magnetic structure, magnetoelastic coupling, and thermal properties of EuCrO3 nanopowders from room temperature to liquid helium temperature. Our neutron powder diffraction and x-ray powder diffraction measurements provide precise atomic positions of all atoms in the cell, especially for the light oxygen atoms. The low-temperature neutron powder diffraction data revealed extra Bragg peaks of magnetic origin, which can be attributed to a Gx antiferromagnetic structure with an ordered moment of ˜2.4 μB consistent with the 3 d3 electronic configuration of the Cr3 + cations. Apart from previously reported antiferromagnetic and ferromagnetic transitions in EuCrO3 at low temperatures, we also observed an anomaly at about 100 K. This anomaly was observed in the temperature dependence of the sample's, lattice parameters, thermal expansion, Raman spectroscopy, permittivity, and conductance measurements. This anomaly is attributed to the magnetoelastic distortion in the EuCrO3 crystal.

  15. Structure, nanohardness and photoluminescence of ZnO ceramics based on nanopowders

    NASA Astrophysics Data System (ADS)

    Muktepavela, Faina; Grigorjeva, Larisa; Kundzins, Karlis; Gorokhova, Elena; Rodnyi, Piotr

    2015-09-01

    ZnO ceramics obtained from grained powders with different grain size by hot pressing and ceramics from tetrapods nanopowders obtained by press-less sintering have been investigated under identical conditions. Ceramics obtained by hot pressing were optically transparent but were composed of large inhomogeneous grains (d = 8-35 μm) exhibiting a substructure. Decreased values of elastic modulus within a grain and a wide defect-associated (‘green’) photoluminescence (PL) band at 2.2-2.8 eV in conjunction with a weak excitonic band indicate a high concentration of residual point defects in hot pressed ZnO ceramics. Utilization of more small-grained powders contributes to the formation of more uniform microstructure (d = 5-15 μm) and extraction of point defects. This reflects as a substantially decreased defect PL band and increased excitonic band. Ceramics obtained by press-less sintering from tetrapods had fine-grained structure (d = 1-4 μm) with no signs of a substructure. PL spectrum has a narrow excitonic band with phonon replicas (1LO_ExD0), whereas the defect ‘green’ luminescence is negligible. The effects of powders morphologies have been explained in terms of a hereditary influence of interaction processes between initial particles on the formation of a microstructure and kinetic of defect distribution on the grain growth stages during the sintering of ZnO ceramics.

  16. Plasma column and nano-powder generation from solid titanium by localized microwaves in air

    SciTech Connect

    Popescu, Simona; Jerby, Eli Meir, Yehuda; Ashkenazi, Dana; Barkay, Zahava; Mitchell, J. Brian A.; Le Garrec, Jean-Luc; Narayanan, Theyencheri

    2015-07-14

    This paper studies the effect of a plasma column ejected from solid titanium by localized microwaves in an ambient air atmosphere. Nanoparticles of titanium dioxide (titania) are found to be directly synthesized in this plasma column maintained by the microwave energy in the cavity. The process is initiated by a hotspot induced by localized microwaves, which melts the titanium substrate locally. The molten hotspot emits ionized titanium vapors continuously into the stable plasma column, which may last for more than a minute duration. The characterization of the dusty plasma obtained is performed in-situ by small-angle X-ray scattering (SAXS), optical spectroscopy, and microwave reflection analyses. The deposited titania nanoparticles are structurally and morphologically analyzed by ex-situ optical and scanning-electron microscope observations, and also by X-ray diffraction. Using the Boltzmann plot method combined with the SAXS results, the electron temperature and density in the dusty plasma are estimated as ∼0.4 eV and ∼10{sup 19 }m{sup −3}, respectively. The analysis of the plasma product reveals nanoparticles of titania in crystalline phases of anatase, brookite, and rutile. These are spatially arranged in various spherical, cubic, lamellar, and network forms. Several applications are considered for this process of titania nano-powder production.

  17. Synthesis and magnetic properties of NiFe2-xSmxO4 nanopowder

    NASA Astrophysics Data System (ADS)

    Hassanzadeh-Tabrizi, S. A.; Behbahanian, Shahrzad; Amighian, Jamshid

    2016-07-01

    NiFe2-xSmxO4 (x=0.00, 0.05, 0.10 and 0.15) nanopowders were synthesized via a sol-gel combustion route. The structural studies were carried out by X-ray diffractometer, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The XRD results confirmed the formation of single-phase spinel cubic structure. The crystallite size decreased with an increase of samarium ion concentration, while lattice parameter and lattice strain increased with samarium substitution. TEM micrographs showed that agglomerated nanoparticles with particle sizes ranging from 35 to 90 nm were obtained. The magnetic studies were carried out using vibrating sample magnetometer. Magnetic measurements revealed that the saturation magnetization (Ms) of NiFe2-xSmxO4 nanoparticles decreases with increasing Sm3+substitution. The reduction of saturation magnetization is attributed to the dilution of the magnetic interaction. The coercivity (Hc) of samples increases by adding samarium.

  18. Non-isothermal oxidation of aluminum nanopowder coated by hydrocarbons and fluorohydrocarbons

    NASA Astrophysics Data System (ADS)

    Sossi, A.; Duranti, E.; Paravan, C.; DeLuca, L. T.; Vorozhtsov, A. B.; Gromov, A. A.; Pautova, Yu. I.; Lerner, M. I.; Rodkevich, N. G.

    2013-04-01

    Aluminum nanopowder (nAl) obtained by electrical explosion of wires and passivated/coated with hydrocarbons and fluorohydrocarbons is comprehensively characterized. Coatings of different natures (octadecanoic and hexadecanoic acid, (1,1,11) trihydroperfluoro-undecan-1-ol, Fluorel™ + ester from esterification of (1,1,11) trihydroperfluoro-undecan-1-ol with furan-2,5-dione) were applied on the particle surface. The powders were studied by TEM, SEM, DSC-TGA, and BET specific surface area. The active aluminum content was determined by volumetric analyses. Coated nAl particles were compared to non-coated powder by the corresponding reactivity parameters obtained from DSC-TGA. It was found that while fatty acids have a weak effect on the non-isothermal oxidation behavior, fluoroelastomers shift the oxidation onset of nAl to higher temperatures by ˜20 °C for the first oxidation stage and by ˜100 °C for the second oxidation stage.

  19. Microwave sintering of nanopowder ZnNb2O6: Densification, microstructure and microwave dielectric properties

    NASA Astrophysics Data System (ADS)

    Bafrooei, H. Barzegar; Nassaj, E. Taheri; Hu, C. F.; Huang, Q.; Ebadzadeh, T.

    2014-12-01

    High density ZnNb2O6 ceramics were successfully fabricated by microwave sintering of ZnO-Nb2O5 and ZnNb2O6 nanopowders. Phase formation, microstructure and microwave electrical properties of the microwave sintered (MS) and microwave reaction sintered (MRS) specimens were examined using X-ray diffraction, field emission scanning electron microscopy and microwave dielectric properties measurement. Specimens were sintered in a temperature range from 950 to 1075 °C for 30 min at an interval of 25 °C using a microwave furnace operated at 2.45 GHz frequency, 3 kW power. XRD pattern revealed the formation of pure columbite phase of ZnNb2O6. The SEM micrographs show grain growth and reduction in porosity of specimens with the increase in sintering temperature. Good combination of microwave dielectric properties (εr~23.6, Qf~64,300 GHz and τf~-66 ppm/°C and εr~24, Qf~75,800 GHz and τf~-64 ppm/°C) was obtained for MS- and MRS-prepared samples at 1000 °C and 1050 °C for 30 min, respectively.

  20. Enhanced osteoblast and osteoclast responses to a thin film sputtered hydroxyapatite coating.

    PubMed

    Hao, J; Kuroda, S; Ohya, K; Bartakova, S; Aoki, H; Kasugai, S

    2011-06-01

    A sputtering technique followed by a low temperature hydrothermal treatment has been demonstrated to produce a dense-and-bioactive hydroxyapatite thin film coating. The purpose of the present study was to investigate osteoblast and osteoclast responses to the hydroxyapatite coated plates and titanium plates with similar roughness. Rat bone marrow stromal cells were cultured on these plates to induce osteoblasts. The cells showed a significantly enhanced proliferation on the hydroxyapatite surface, accompanied by increase of osteoblastic phenotypes. The co-cultured osteoclasts exhibited the significantly different cell number and morphology between the hydroxyapatite and the titanium surfaces. A series of osteoclast marker genes were more stimulated on the hydroxyapatite and thirty two percent of the hydroxyapatite surface area could be resorbed by osteoclasts. The thin film sputtered hydroxyapatite could provide a favorable surface for both osteoblast and osteoclast formation and their function, indicating its good osteoconductivity and biodegradability. PMID:21567286

  1. Aminosilane as an effective binder for hydroxyapatite-gelatin nanocomposites.

    PubMed

    Luo, Tzy-Jiun M; Ko, Ching-Chang; Chiu, Chi-Kai; Llyod, Jacob; Huh, Uk

    2010-02-01

    Aminosilane has been explored as an alternative chemical linker to facilitate the binding and solidification of hydroxyapatite-gelatin nanocomposite at room temperature, which was synthesized using co-precipitation method in the presence of gelatin. This aminosilane treatment was found effective at low concentration (~25 μL/mL) and the solidification and dehydration of hydroxyapatite-gelatin slurry completes within hours depending on the amount of aminosilane. The resulting sample exhibits compressive strength of 133 MPa, about 40% higher than glutaraldehyde treated samples, and shows good biocompatibility based on cell adhesion, proliferation, alkaline phosphate synthesis, and mineralization studies. PMID:23833395

  2. Aminosilane as an effective binder for hydroxyapatite-gelatin nanocomposites

    PubMed Central

    Luo, Tzy-Jiun M.; Ko, Ching-Chang; Chiu, Chi-Kai; Llyod, Jacob; Huh, Uk

    2013-01-01

    Aminosilane has been explored as an alternative chemical linker to facilitate the binding and solidification of hydroxyapatite-gelatin nanocomposite at room temperature, which was synthesized using co-precipitation method in the presence of gelatin. This aminosilane treatment was found effective at low concentration (~25 μL/mL) and the solidification and dehydration of hydroxyapatite-gelatin slurry completes within hours depending on the amount of aminosilane. The resulting sample exhibits compressive strength of 133 MPa, about 40% higher than glutaraldehyde treated samples, and shows good biocompatibility based on cell adhesion, proliferation, alkaline phosphate synthesis, and mineralization studies. PMID:23833395

  3. Femur bone repair in ovariectomized rats under the local action of alendronate, hydroxyapatite and the association of alendronate and hydroxyapatite

    PubMed Central

    Canettieri, Antonio Carlos Victor; Colombo, Carlos Eduardo Dias; Chin, Chung Man; Faig-Leite, Horácio

    2009-01-01

    An evaluation was made of the local action of alendronate sodium (A), hydroxyapatite (HA) and the association of both substances (A + HA), in different molar concentrations, on the femur bone repair of ovariectomized rats. Ninety-eight animals were divided into seven groups: control (C), starch (S), alendronate 1 mol (A1), alendronate 2 mols (A2), hydroxyapatite 1 mol (HA1), hydroxyapatite 2 mols (HA2) and the association of alendronate + hydroxyapatite (A + HA). Rats weighing about 250 g were ovariectomized and 2.5-mm diameter bone defects were made on the left femur 30 days later. Each experimental group had defects filled with appropriate material, except for group C (control). The animals were killed 7 and 21 days after surgery. Histological, histomorphometric and statistical analyses of bone neoformation in the bone defect site were performed. From the histological standpoint, the major differences occurred after 21 days. All specimens in groups C, S, HA1 and HA2 presented linear closure of the bone defect, and most animals in groups A1, A2 and A + HA showed no bone neoformation in the central area of the defect. No statistically significant difference was found among the experimental groups after 7 days; after 21 days, group HA2 presented the highest amount of neoformed bone. There was no significant difference among groups A1, A2 and A + HA in the two study periods. It was concluded that alendronate, either isolated or in association with hydroxyapatite, had an adverse effect on bone repair in this experimental model. Moreover, the hydroxyapatite used here proved to be biocompatible and osteoconductive, with group HA2 showing the best results. PMID:19765106

  4. Luminous and tunable white-light upconversion for YAG (Yb3Al5O12) and (Yb,Y)2O3 nanopowders.

    PubMed

    Wang, Jiwei; Hao, Jian Hua; Tanner, Peter A

    2010-12-01

    We report on multiphoton white-light upconversion in vacuum for Pechini synthesis Yb(3)Al(5)O(12) (YbAG) and combustion synthesis (Yb,Y(2))O(3) nanopowders under IR excitation. Their intense white-light upconversion is attributed to charge transfer luminescence superimposed upon a broadband emission. Unlike common nanoscale phosphors, which show low luminescence efficiency, the intensity of white-light upconversion for nanopowders is similar to that of their bulk counterparts. The luminary efficacy of the upconversion is estimated to be 10-15 lm W(-1), and the Commission Internationale d'Eclairage (CIE) coordinates can be widely tuned by the excitation power, pressure, and codoping ratio. The nano-YbAG sample exhibits a longer buildup time for emission, a higher excitation threshold, and a wider CIE range than the oxide nanopowders. PMID:21124566

  5. Inhibition of hydroxyapatite formation by osteopontin phosphopeptides.

    PubMed Central

    Pampena, David A; Robertson, Karen A; Litvinova, Olga; Lajoie, Gilles; Goldberg, Harvey A; Hunter, Graeme K

    2004-01-01

    Osteopontin (OPN) is an acidic phosphoglycoprotein that is believed to function in the prevention of soft tissue calcification. In vitro studies have shown that OPN can inhibit the formation of hydroxyapatite (HA) and other biologically relevant crystal phases, and that this inhibitory activity requires phosphorylation of the protein; however, it is not known which phosphorylated residues are involved. We have synthesized peptides corresponding to four phosphoserine-containing sequences in rat OPN: OPN7-17, containing phosphoserines 10 and 11; OPN41-52, containing phosphoserines 46 and 47; OPN248-264, containing phosphoserines 250, 257 and 262; and OPN290-301, containing phosphoserines 295-297. The abilities of these peptides to inhibit de novo HA formation were determined using a constant-composition autotitration assay. All four OPN phosphopeptides caused a dose-dependent increase in nucleation lag time, but did not significantly affect subsequent formation of the crystals. However, OPN41-52 (inhibitory constant 73.5 min/microM) and OPN290-301 (72.2 min/microM) were approx. 4 times more potent inhibitors than OPN7-17 (19.7 min/microM) and OPN247-264 (16.3 min/microM). 'Scrambling' the amino acid sequence of OPN290-301 resulted in decreased potency (45.6 min/microM), whereas omission of the phosphate groups from this peptide caused a greater decrease (5.20 min/microM). These findings have identified phosphorylated sequences that are important for the ability of rat bone OPN to inhibit HA crystal formation, and suggest that negative-charge density is an important factor in this activity. PMID:14678013

  6. Biomechanical analysis of hydroxyapatite cement cranioplasty.

    PubMed

    Matic, Damir B; Manson, Paul N

    2004-05-01

    A recent review of the authors' experience with hydroxyapatite (HA) cement cranioplasties revealed a high infection rate. During removal of these implants, all were loose and fractured. Forty percent of these patients had a history of minor trauma at the site of cranioplasty before experiencing infection. Minor trauma may fracture HA cranioplasties and result in infection. The purpose of this study is to determine the force to fracture full- and partial-thickness cranial defects reconstructed with HA cement and to compare peak loads of differing HA cement cranioplasty techniques. Standardized craniotomy defects were created in five fresh cadaver heads. Full-thickness defects were reconstructed with either rigid or flexible titanium mesh and then covered with HA cement. Partial-thickness defects were reconstructed with HA alone. After setting, a uniaxial impact was delivered to each of the defects. Peak loads were recorded, and defects were examined for evidence of fracture.Predictable fractures of the HA cranioplasties occurred at 1200 N in all full-thickness defects reconstructed with mesh and a thin layer of HA. Implant loosening and chipping was similar to what was seen clinically in the authors' patients with infections. Full-thickness defects in which titanium mesh was shaped like a cup and filled with a thick layer of HA resist fracture at 1200 N. Partial-thickness defects reconstructed with HA alone also do not fracture at this peak load. Patient selection, defect characteristics, and reconstructive techniques are factors that need to be considered before using HA cement for cranioplasty purposes. PMID:15111799

  7. Structural study and phase transition investigation in a simple synthesis of porous architected-ZnO nanopowder

    SciTech Connect

    Shang, C.; Barnabé, A.

    2013-12-15

    In this work, zinc oxide powder with a rectangular-shaped porous architecture, made of numerous spherical nanometric particles, was obtained. A simple precipitation/decomposition procedure was used comprising a zinc oxalate intermediate, obtained from zinc sulfate and oxalic acid without any additives. Detailed studies on zinc oxalate dehydration, decomposition and zinc oxide formation, were carried out using in-situ temperature X-ray diffraction and thermogravimetric analysis. During the investigation, the temperature dependence of particle sizes, lattice parameters and crystal structures of ZnC{sub 2}O{sub 4}·2H{sub 2}O, ZnC{sub 2}O{sub 4} and ZnO nanopowders were analyzed from room temperature to 450 °C. Structural transitions were also discussed. The structure and morphology of the as-prepared ZnO nanopowder were investigated by electron microscopy and compared to the crystalline rectangular shape of ZnC{sub 2}O{sub 4}·2H{sub 2}O. The calcination temperature, counter ion and precipitate agent were found to be related to the product's shape and diameter. Spherical ZnO nanoparticles with diameters of less than 20 nm and a maximum specific surface of 53 m{sup 2}/g were obtained using this method. Highlights: • ZnO nanopowders with porous architecture were synthesized by a simple method. • Spherical ZnO nanoparticles confined in submicronic rectangular shape are obtained. • Crystal structures are determined temperature in-situ XRD up to 450 °C. • Structural transitions were analyzed.

  8. Accelerated Nucleation of Hydroxyapatite Using an Engineered Hydrophobin Fusion Protein.

    PubMed

    Melcher, Melanie; Facey, Sandra J; Henkes, Thorsten M; Subkowski, Thomas; Hauer, Bernhard

    2016-05-01

    Calcium phosphate mineralization is of particular interest in dental repair. A biomimetic approach using proteins or peptides is a highly promising way to reconstruct eroded teeth. In this study, the screening of several proteins is described for their binding and nucleating activities toward hydroxyapatite. Out of 27 tested candidates, only two hydrophobin fusion proteins showed binding abilities to hydroxyapatite in a mouthwash formulation and an increased nucleation in artificial saliva. Using a semirational approach, one of the two candidates (DEWA_5), a fusion protein consisting of a truncated section of the Bacillus subtilis synthase YaaD, the Aspergillus nidulans hydrophobin DEWA, and the rationally designed peptide P11-4 described in the literature, could be further engineered toward a faster mineral formation. The variants DEWA_5a (40aaYaaD-SDSDSD-DEWA) and DEWA_5b (40aaYaaD-RDRDRD-DEWA) were able to enhance the nucleation activity without losing the ability to form hydroxyapatite. In the case of variant DEWA_5b, an additional increase in the binding toward hydroxyapatite could be achieved. Especially with the variant DEWA_5a, the protein engineering of the rationally designed peptide sequence resulted in a resemblance of an amino acid motif that is found in nature. The engineered peptide resembles the amino acid motif in dentin phosphoprotein, one of the major proteins involved in dentinogenesis. PMID:27010648

  9. Facilitated transport of copper with hydroxyapatite nanoparticles in saturated sand

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Saturated packed column experiments were conducted to investigate the facilitated transport of Cu with hydroxyapatite nanoparticles (nHAP) at different pore water velocities (0.22-2.2 cm min–1), solution pH (6.2-9.0), and fraction of Fe oxide coating on grain surfaces (', 0-0.36). The facilitated tr...

  10. Peculiarities of hydroxyapatite/nanodiamond composites as novel implants

    NASA Astrophysics Data System (ADS)

    Pramatarova, L.; Dimitrova, R.; Pecheva, E.; Spassov, T.; Dimitrova, M.

    2007-12-01

    Hydroxyapatite/detonation nanodiamond composites are created on silica glass and cover glass by simple soaking process in an open deposition type set-up. The supersaturated solution (simulated body fluid, SBF) is prepared in a way to resemble the composition of human blood plasma. The composite growth is carried out through the addition of detonation nanodiamond particles to the SBF. Scanning electron microscopy, X-ray diffraction and FTIR spectroscopy are used to determine the surface morphology and the structure of the hydroxyapatite /detonation nanodiamond composite layers. The applied methods provide evidence that the nanodiamond surface functional groups interact strongly with the biological solution. The detonation nanodiamond surface is chemically multifunctional (surface OH, C-O-H, C = C, C-O-C and C = O groups exist), so that the hydroxyapatite is grown both by physical adsorption and chemical interaction. The OH- groups are regarded to play an important role in the hydroxyapatite growth on a diamond's surface from SBF, as they charge it negatively and attract Ca2+ ions, which in turn attract PO43- ions, thus forming apatite nuclei.