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Sample records for ag-doped nanocrystalline hydroxyapatite

  1. 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

  2. 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

  3. Photocatalytic characteristics for the nanocrystalline TiO2 on the Ag-doped CaAl2O4:(Eu,Nd) phosphor

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Sik; Sung, Hyun-Je; Kim, Bum-Joon

    2015-04-01

    This study investigated the photocatalytic behavior of nanocrystalline TiO2 deposited on Ag-doped long-lasting phosphor (CaAl2O4:Eu2+,Nd3+). The CaAl2O4:Eu2+,Nd3+ phosphor powders were prepared via conventional sintering using CaCO3, Al2O3, Eu2O3, and Nd2O3 as raw materials according to the appropriate molar ratios. Silver nanoparticles were loaded on the phosphor by mixing with an aqueous Ag-dispersion solution. Nanocrystalline TiO2 was deposited on Ag-doped CaAl2O4:Eu2+,Nd3+ powders via low-pressure chemical vapor deposition (LPCVD). The TiO2 coated on the phosphor was actively photo-reactive under irradiation with visible light and showed much faster benzene degradation than pure TiO2, which is almost non-reactive. The coupling of TiO2 with phosphor may result in an energy band bending in the junction region, which then induces the TiO2 crystal at the interface to be photo-reactive under irradiation with visible light. In addition, the intermetallic compound of CaTiO3 that formed at the interface between TiO2 and the CaAl2O4:(Eu2+,Nd3+) phosphor results in the formation of oxygen vacancies and additional electrons that promote the photodecomposition of benzene gas. The addition of Ag nanoparticles enhanced the photocatalytic reactivity of the TiO2/CaAl2O4:Eu2+,Nd3+ phosphor. TiO2 on the Ag-doped phosphor presented a higher benzene gas decomposition rate than the TiO2 did on the phosphor without Ag-doping under both irradiation with ultraviolet and visible light.

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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

  9. Nanocrystalline hydroxyapatite prepared under various pH conditions

    NASA Astrophysics Data System (ADS)

    Palanivelu, R.; Mary Saral, A.; Ruban Kumar, A.

    2014-10-01

    Hydroxyapatite (HAP) has sovereign biomedical application due to its excellent biocompatibility, chemical and crystallographic similitude with natural human bone. In this present work, we discussed about the role of pH in the synthesis of calcium phosphate compound using calcium nitrate tetrahydrate and di-ammonium hydrogen phosphate as starting materials by chemical precipitation method assisted with ultrasonic irradiation technique. 5% polyethylene glycol (PEG600) is added along with the precursors under various pH condition of 7, 9 and 11 respectively. The functional group analysis, crystallized size and fraction of crystallized size are confirmed using Fourier Transformation Infra-Red spectroscopy and X-ray diffraction pattern. Morphological observations are done by scanning electron microscope. The results revealed the presence of nanocrystalline hydroxyapatite at pH above 9.

  10. Nanocrystalline hydroxyapatite coatings on titanium: a new fast biomimetic method.

    PubMed

    Bigi, Adriana; Boanini, Elisa; Bracci, Barbara; Facchini, Alessandro; Panzavolta, Silvia; Segatti, Francesco; Sturba, Luigina

    2005-07-01

    We obtained a fast biomimetic deposition of hydroxyapatite (HA) coatings on Ti6Al4V substrates using a slightly supersaturated Ca/P solution, with an ionic composition simpler than that of simulated body fluid (SBF). At variance with other fast deposition methods, which produce amorphous calcium phosphate coatings, the new proposed composition allows one to obtain nanocrystalline HA. Soaking in supersaturated Ca/P solution results in the deposition of a uniform coating in a few hours, whereas SBF, or even 1.5SBF, requires 14 days to deposit a homogeneous coating on the same substrates. The coating consists of HA globular aggregates, which exhibit a finer lamellar structure than those deposited from SBF. The extent of deposition increases on increasing the immersion time. Transmission electron microscope (TEM) images recorded on the material detached from the coating show that the deposition is constituted of thin nanocrystals. Electron diffraction (ED) patterns recorded from most of the crystals exhibit the presence of rings, which can be indexed as reflections characteristic of HA. Furthermore, several HA single-crystal spot ED images were obtained from individual crystals. PMID:15664635

  11. Nanocrystalline hydroxyapatite doped with selenium oxyanions: a new material for potential biomedical applications.

    PubMed

    Kolmas, Joanna; Oledzka, Ewa; Sobczak, Marcin; Nałęcz-Jawecki, Grzegorz

    2014-06-01

    Selenium-substituted hydroxyapatites containing selenate SeO4(2-) or selenite SeO3(2-) ions were synthesized using a wet precipitation method. The selenium content was determined by atomic absorbance spectrometry. The raw, unsintered powders were also characterized using powder X-ray diffraction, middle-range FT-IR spectroscopy and transmission electron microscopy with energy-dispersive X-ray spectroscopic microanalysis. The synthesized apatites were found to be pure and nanocrystalline with a crystal size similar to that in bone mineral. The incorporation of selenium oxyanions into the crystal lattice was confirmed. The toxicity of hydroxyapatites containing selenite or selenate ions was evaluated with a protozoan assay and bacterial luminescence test. PMID:24863209

  12. Structural and microstructural characterizations of nanocrystalline hydroxyapatite synthesized by mechanical alloying.

    PubMed

    Lala, S; Satpati, B; Kar, T; Pradhan, S K

    2013-07-01

    Single phase nanocrystalline hydroxyapatite (HAp) powder has been synthesized by mechanical alloying the stoichiometric mixture of CaCO3 and CaHPO4 powders in open air at room temperature, for the first time, within 2 h of milling. Nanocrystalline hexagonal single crystals are obtained by sintering of 2h milled sample at 500 °C. Structural and microstructural properties of as-milled and sintered powders are revealed from both the X-ray line profile analysis and transmission electron microscopy. Shape and lattice strain of nanocrystalline HAp particles are found to be anisotropic in nature. Particle size of HAp powder remains almost invariant up to 10h of milling and there is no significant growth of nanocrystalline HAp particles after sintering at 500 °C for 3 h. Changes in lattice volume and some primary bond lengths of as-milled and sintered are critically measured, which indicate that lattice imperfections introduced into the HAp lattice during ball milling have been reduced partially after sintering the powder at elevated temperatures. We could achieve ~96.7% of theoretical density of HAp within 3h by sintering the pellet of nanocrystalline powder at a lower temperature of 1000 °C. Vickers microhardness (VHN) of the uni-axially pressed (6.86 MPa) pellet of nanocrystalline HAp is 4.5 GPa at 100 gm load which is close to the VHN of bulk HAp sintered at higher temperature. The strain-hardening index (n) of the sintered pellet is found to be >2, indicating a further increase in microhardness value at higher load. PMID:23623111

  13. A Solid-State NMR Study of Selenium Substitution into Nanocrystalline Hydroxyapatite

    PubMed Central

    Kolmas, Joanna; Kuras, Marzena; Oledzka, Ewa; Sobczak, Marcin

    2015-01-01

    The substitution of selenium oxyanions in the hydroxyapatite structure was examined using multinuclear solid-state resonance spectroscopy (ssNMR). The study was supported by powder X-ray diffractometry (PXRD) and wavelength dispersion X-ray fluorescence (WD-XRF). Samples of pure hydroxyapatite (HA300) and selenate (HA300-1.2SeO4) or selenite (HA300-1.2SeO3) substituted hydroxyapatites were synthesized using the standard wet method and heated at 300 °C to remove loosely bonded water. PXRD data showed that all samples are single-phase, nanocrystalline hydroxyapatite. The incorporation of selenite and selenate ions affected the lattice constants. In selenium-containing samples the concentration of Se was very similar and amounted to 9.55% and 9.64%, for HA300-1.2SeO4 and HA300-1.2SeO3, respectively. PXRD and ssNMR data showed that the selenite doping significantly decreases the crystallite size and crystallinity degree. 31P and 1H NMR experiments demonstrated the developed surface hydrated layer in all samples, especially in HA300-1.2SeO3. 1H NMR studies showed the dehydroxylation of HA during the selenium oxyanions substitution and the existence of hydrogen bonding in structural hydroxyl group channels. 1H→77Se cross polarization NMR experiments indicated that selenites and selenates are located in the crystal lattice and on the crystal surface. PMID:25997001

  14. Synthesis and sintering of nanocrystalline hydroxyapatite powders by citric acid sol-gel combustion method

    SciTech Connect

    Han Yingchao; Li Shipu; Wang Xinyu; Chen Xiaoming

    2004-01-03

    The citric acid sol-gel combustion method has been used for the synthesis of nanocrystalline hydroxyapatite (HAP) powder from calcium nitrate, diammonium hydrogen phosphate and citric acid. The phase composition of HAP powder was characterized by X-ray powder diffraction analysis (XRD). The morphology of HAP powder was observed by transmission electron microscope (TEM). The HAP powder has been sintered into microporous ceramic in air at 1200 deg. C with 3 h soaking time. The microstructure and phase composition of the resulting HAP ceramic were characterized by scanning electron microscope (SEM) and XRD, respectively. The physical characterization of open porosity and flexural strength have also been carried out.

  15. Nanocrystalline Hydroxyapatite/Si Coating by Mechanical Alloying Technique

    PubMed Central

    Hannora, Ahmed E.; Mukasyan, Alexander S.; Mansurov, Zulkhair A.

    2012-01-01

    A novel approach for depositing hydroxyapatite (HA) films on titanium substrates by using mechanical alloying (MA) technique has been developed. However, it was shown that one-hour heat treatment at 800°C of such mechanically coated HA layer leads to partial transformation of desired HA phase to beta-tri-calcium phosphate (β-TCP) phase. It appears that the grain boundary and interface defects formed during MA promote this transformation. It was discovered that doping HA by silicon results in hindering this phase transformation process. The Si-doped HA does not show phase transition to β-TCP or decomposition after heat treatment even at 900°C. PMID:22312324

  16. Electric field-assisted sintering of nanocrystalline hydroxyapatite for biomedical applications

    NASA Astrophysics Data System (ADS)

    Tran, Tien Bich

    As the main inorganic component of bone, hydroxyapatite (HA, Ca 10(PO4)6(OH)2) should be an ideal candidate in biomaterials selection. When grain sizes are in the nanometric regime, protein adsorption and cell adhesion are enhanced, while strength, hardness, and wear resistance are improved. Unfortunately, low phase stability, poor sinterability, and a tendency towards exaggerated grain coarsening challenge full densification of nanocrystalline hydroxyapatite by conventional sintering methods. The field-assisted sintering technique (FAST) has successfully consolidated a variety of nanocrystalline metals and ceramics in dramatically reduced times. The sintering enhancements observed during FAST can be attributed to thermal and athermal effects. The rapid heating rates (up to ˜1000ºC/min) afforded by FAST contribute a significant thermal effect. Since fast heating rates reduce powder exposure to sub-sintering temperatures, non-densifying surface diffusion is limited. The athermal effects of FAST are less well understood and can include plasma generation, dielectric breakdown, particle surface cleaning, grain boundary pinning, and space charge effects. Applying the field-assisted sintering technique to nanocrystalline hydroxyapatite yielded surprising results. Deviations from conventional densification behavior were observed, with dehydroxylation identified as the most deleterious process to densification as well as mechanical and biological performance. Since hydroxyapatite is not a stable phase at high temperatures and low water partial pressure atmospheres, desintering due to dehydroxylation-related pore formation became apparent during Stage III sintering. In fact, the degree of desintering and pore formation increased with the extent of Stage III sintering and grain growth. The atomic rearrangements taking place during grain boundary migration are believed to favor the formation of more-stable oxyapatite through hydroxyapatite dehydroxylation. This behavior was

  17. Biomineralization of hydroxyapatite in silver ion-exchanged nanocrystalline ZSM-5 zeolite using simulated body fluid.

    PubMed

    Kaur, Balwinder; Srivastava, Rajendra; Satpati, Biswarup; Kondepudi, Kanthi Kiran; Bishnoi, Mahendra

    2015-11-01

    Silver ion-exchanged nanocrystalline zeolite (Ag-Nano-ZSM-5) and silver ion-exchanged conventional zeolite (Ag-ZSM-5) were synthesized. Zeolites were incubated in simulated body fluid at 310K for different time periods to grow hydroxyapatite in their matrixes. Significant large amount of hydroxyapatite was grown in Ag-Nano-ZSM-5 matrix after incubation in simulated body fluid when compared to Ag-ZSM-5. The resultant material was characterized using X-ray diffraction, N2-adsorption, scanning/transmission electron microscopy, energy dispersive X-ray, and inductively coupled plasma analysis. Mechanical properties such as compressive modulus, compressive strength, and strain at failure of the parent materials were evaluated. Biocompatibility assays suggested that Ag-Nano-ZSM-5 and hydroxyapatite grown in Ag-Nano-ZSM-5 were compatible and did not impose any toxicity to RAW 264.7 cells macrophase and Caco2 cells suggesting considerable potential for biomedical applications such as bone implants. PMID:26255163

  18. Synthesis of nano-crystalline hydroxyapatite and ammonium sulfate from phosphogypsum waste

    SciTech Connect

    Mousa, Sahar; Hanna, Adly

    2013-02-15

    Graphical abstract: TEM micrograph of dried HAP at 800 °C. -- Abstract: Phosphogypsum (PG) waste which is derived from phosphoric acid manufacture by using wet method was converted into hydroxyapatite (HAP) and ammonium sulfate. Very simple method was applied by reacting PG with phosphoric acid in alkaline medium with adjusting pH using ammonia solution. The obtained nano-HAP was dried at 80 °C and calcined at 600 °C and 900 °C for 2 h. Both of HAP and ammonium sulfate were characterized by X-ray diffraction (XRD) and infrared spectroscopy (IR) to study the structural evolution. The thermal behavior of nano-HAP was studied; the particle size and morphology were estimated by using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). All the results showed that HAP nano-crystalline and ammonium sulfate can successfully be produced from phosphogypsum waste.

  19. Green synthesis of magnesium ion incorporated nanocrystalline hydroxyapatite and their mechanical, dielectric and photoluminescence properties

    SciTech Connect

    Arul, K. Thanigai; Kolanthai, Elayaraja; Manikandan, E.; Bhalerao, G.M.; Chandra, V. Sarath; Ramya, J. Ramana; Mudali, U. Kamachi; Nair, K.G.M.; Kalkura, S.Narayana

    2015-07-15

    Highlights: • Rapid technique to synthesize nanorods of magnesium ion incorporated hydroxyapatite. • Enhanced electrical and mechanical properties. • Improved photoluminescence and wettability on magnesium incorporation. • Increased in vitro bioactivity. - Abstract: Nanocrystalline hydroxyapatite (HAp-Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2,} 35 nm) and magnesium (Mg{sup 2+}) ion incorporated HAp were synthesized by microwave technique. XRD (X-ray diffraction), FTIR (Fourier transform infrared spectroscopy), FE-HRTEM (Field emission high resolution transmission electron microscopy), DLS (dynamic light scattering), EDXRF (energy dispersive X-ray fluorescence spectrometry), microhardness, permittivity and alternating current (ac) conductivity, besides the PL (photoluminescence), wettability and in vitro bioactivity of the samples were analysed. EDXRF revealed the Mg{sup 2+} ion incorporation in HAp. The Mg{sup 2+} ion incorporation did not alter the phase but drastically reduced the crystallite size and particle size respectively by 48% and 32%. There was enhanced microhardness (24%) at low level (<13%) and decreased zeta potential of Mg{sup 2+} ion incorporation. The permittivity, ac conductivity, PL, wettability and in vitro bioactivity were enhanced on Mg{sup 2+} ion incorporation. These properties enable them to be a promising candidate for wound healing, bone replacement applications and also as a biosensor.

  20. Biocompatible nanocrystalline natural bonelike carbonated hydroxyapatite synthesized by mechanical alloying in a record minimum time.

    PubMed

    Lala, S; Brahmachari, S; Das, P K; Das, D; Kar, T; Pradhan, S K

    2014-09-01

    Single phase nanocrystalline biocompatible A-type carbonated hydroxyapatite (A-cHAp) powder has been synthesized by mechanical alloying the stoichiometric mixture of CaCO3 and CaHPO4.2H2O powders in open air at room temperature within 2h of milling. The A-type carbonation in HAp is confirmed by FTIR analysis. Structural and microstructure parameters of as-milled powders are obtained from both Rietveld's powder structure refinement analysis and transmission electron microscopy. Size and lattice strain of nanocrystalline HAp particles are found to be anisotropic in nature. Mechanical alloying causes amorphization of a part of crystalline A-cHAp which is analogous to native bone mineral. Some primary bond lengths of as-milled samples are critically measured. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay test reveals high percentage of cell viability and hence confirms the biocompatibility of the sample. The overall results indicate that the processed A-cHAp has a chemical composition very close to that of biological apatite. PMID:25063165

  1. Preparation and bioactive properties of nanocrystalline hydroxyapatite thin films obtained by conversion of atomic layer deposited calcium carbonate.

    PubMed

    Holopainen, Jani; Kauppinen, Kyösti; Mizohata, Kenichiro; Santala, Eero; Mikkola, Esa; Heikkilä, Mikko; Kokkonen, Hanna; Leskelä, Markku; Lehenkari, Petri; Tuukkanen, Juha; Ritala, Mikko

    2014-09-01

    Nanocrystalline hydroxyapatite thin films were fabricated on silicon and titanium by atomic layer deposition (ALD) of CaCO3 and its subsequent conversion to hydroxyapatite by diammonium hydrogen phosphate (DAP) solution. The effects of conversion process parameters to crystallinity and morphology of the films were examined. DAP concentration was found to be critical in controlling the crystal size and homogeneity of the films. The hydroxyapatite phase was identified by XRD. ToF-elastic recoil detection analysis studies revealed that the films are calcium deficient in relation to hydroxyapatite with a Ca/P ratio of 1.39 for films converted with 0.2 M DAP at 95 °C. The coatings prepared on titanium conformally follow the rough surface topography of the substrate, verifying that the good step coverage of the ALD method was maintained in the conversion process. The dissolution tests revealed that the coating was nondissolvable in the cell culture medium. Annealing the coated sample at 700 °C for 1 h seemed to enhance its bonding properties to the substrate. Also, the biocompatibility of the coatings was confirmed by human bone marrow derived cells in vitro. The developed method provides a new possibility to produce thin film coatings on titanium implants with bone-type hydroxyapatite that is biocompatible with human osteoblasts and osteoclasts. PMID:25280849

  2. Similar healthy osteoclast and osteoblast activity on nanocrystalline hydroxyapatite and nanoparticles of tri-calcium phosphate compared to natural bone

    PubMed Central

    MacMillan, Adam K; Lamberti, Francis V; Moulton, Julia N; Geilich, Benjamin M; Webster, Thomas J

    2014-01-01

    While there have been numerous studies to determine osteoblast (bone forming cell) functions on nanocrystalline compared to micron crystalline ceramics, there have been few studies which have examined osteoclast activity (including tartrate-resistant acid phosphatase, formation of resorption pits, size of resorption pits, and receptor activator of nuclear factor κB [RANK]). This is despite the fact that osteoclasts are an important part of maintaining healthy bone since they resorb bone during the bone remodeling process. Moreover, while it is now well documented that bone formation is enhanced on nanoceramics compared to micron ceramics, some have pondered whether osteoblast functions (such as osteoprotegerin and RANK ligand [RANKL]) are normal (ie, non-diseased) on such materials compared to natural bone. For these reasons, the objective of the present in vitro study was to determine various functions of osteoclasts and osteoblasts on nanocrystalline and micron crystalline hydroxyapatite as well as tri-calcium phosphate materials and compare such results to cortical and cancellous bone. Results showed for the first time similar osteoclast activity (including tartrate-resistant acid phosphatase, formation of resorption pits, size of resorption pits, and RANK) and osteoblast activity (osteoprotegerin and RANKL) on nanocrystalline hydroxyapatite compared to natural bone, whereas osteoclast and osteoblast functions on micron crystalline versions of these ceramics were much different than natural bone. In this manner, this study provides additional evidence that nanocrystalline calcium phosphates can serve as suitable synthetic analogs to natural bone to improve numerous orthopedic applications. It also provides the first data of healthy osteoclast and osteoblast functions on nanocrystalline calcium phosphates compared to natural bone. PMID:25506216

  3. [Hydroxyapatite bone substitute (Ostim) in sinus floor elevation. Maxillary sinus floor augmentation: bone regeneration by means of a nanocrystalline in-phase hydroxyapatite (Ostim)].

    PubMed

    Smeets, Ralf; Grosjean, Maurice B; Jelitte, Gerd; Heiland, Max; Kasaj, Adrian; Riediger, Dieter; Yildirim, Murat; Spiekermann, Hubertus; Maciejewski, Oliver

    2008-01-01

    The range of bone regeneration materials suitable for maxillar bone augmentation has increased steadily in the past few years and there is now a wide variety of materials being used. In the present case report, we analyzed the state of bone regeneration after sinus floor augmentation using a nanocrystalline in-phase synthetic anorganic hydroxyapatite bone grafting material (Ostim). A 60-year-old female patient underwent maxillary sinus floor elevation and the cavity was filled with Ostim three years before. Actually, she presented herself with loosening of the dental implant at position 17, as a result of parafunction. At the time of the insertion of a second implant at position 17, bone samples were taken by using a trepan drilling device from the previously augmented area. These samples were analyzed histologically to determine the extent of bone remodeling around the deposits of Ostim. We found that the Ostim deposits were surrounded largely by woven bone and, in parts, by lamellar bone and had facilitated osteoconductive bone regeneration. The adjacent implant, at position 16, which beared a crown exposed to proper biting forces without parafunction, showed proper clinical and radiological characteristics of complete and firm integration into the area which was also filled with Ostim three years ago. We conclude that the use of the nanocrystalline hydroxyapatite Ostim with its stable volume properties appears to be suitable for maxillary sinus floor augmentation. Furthermore, we even found osteoconductive bone regeneration under Ostim near the site of the loosened implant. PMID:18422056

  4. Effects of nanocrystalline calcium deficient hydroxyapatite incorporation in glass ionomer cements.

    PubMed

    Goenka, Sumit; Balu, Rajkamal; Sampath Kumar, T S

    2012-03-01

    Glass ionomer cements (GICs) are clinically attractive filling materials often employed in the field of dentistry as restorative and luting materials. The present work aims to formulate bioactive nanocrystalline calcium deficient hydroxyapatite (nCDHA)-GIC composite cements with improved mechanical and resorption properties of the set cement than GICs. The nCDHA was synthesized via an accelerated microwave process and characterized by X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) methods. The synthesized nCDHA was mixed with GIC in different compositions (5, 10 and 15 wt%) maintaining the powder to liquid ratio. Cylinders of dimensions 8 mm height and 4 mm diameter were formed using a Teflon mold following a conventional cement forming technique. The XRD and FT-IR of the cylinders showed increased intensity and characteristic bands of CDHA with increase in nCDHA content. The surface cracks and the elemental composition of the set cements were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). Decreased surface hardness was observed for composite cements with increase in nCDHA addition. The cement cylinders were tested for ionic release in Millipore water (pH=7) via inductive coupled plasma (ICP) spectroscopy and in demineralization solution of pH=5 to find out the weight loss in an acidic environment at 37 °C performed periodically for 5 weeks. The ionic release percentage, weight loss and compressive strength were observed to increase with an increase in nCDHA addition. PMID:22340686

  5. Effect of Nanocrystalline Hydroxyapatite Socket Preservation on Orthodontically Induced Inflammatory Root Resorption

    PubMed Central

    Seifi, Massoud; Arayesh, Ali; Shamloo, Nafise; Hamedi, Roya

    2015-01-01

    Objective Orthodontically induced inflammatory root resorption (OIIRR) is considered to be an important sequel associated with orthodontic tooth movement (OTM). OTM after Socket preservation enhances the periodontal condition before orthodontic space closure. The purpose of this study is to investigate the histologic effects of NanoBone®, a new highly nonsintered porous nano-crystalline hydroxyapatite bone on root resorption following OTM. Materials and Methods This experimental study was conducted on four male dogs. In each dog, four defects were created at the mesial aspects of the maxillary and mandibular first premolars. The defects were filled with NanoBone®. We used the NiTi closed coil for mesial movement of the first premolar tooth. When the experimental teeth moved approximately halfway into the defects, after two months, the animals were sacrificed and we harvested the area of interest. The first premolar root and adjacent tissues were histologically evaluated. The three-way ANOVA statistical test was used for comparison. Results The mean root resorption in the synthetic bone substitute group was 22.87 ± 11.25×10-4mm2 in the maxilla and 21.41 ± 11.25×10-4mm2 in the mandible. Statistically, there was no significant difference compared to the control group (p>0.05). Conclusion The use of a substitution graft in the nano particle has some positive effects in accessing healthy periodontal tissue following orthodontic procedures without significant influence on root resorption (RR). Histological evaluation in the present study showed osteoblastic activity and remodeling environment of nanoparticles in NanoBone®. PMID:25685742

  6. First histological observations on the incorporation of a novel nanocrystalline hydroxyapatite paste OSTIM® in human cancellous bone

    PubMed Central

    Huber, Franz-Xaver; Belyaev, Orlin; Hillmeier, Joachim; Kock, Hans-Juergen; Huber, Colette; Meeder, Peter-Juergen; Berger, Irina

    2006-01-01

    Background: A commercially available nanocrystalline hydroxyapatite paste Ostim® has been reported in few recent studies to surpass other synthetic bone substitutes with respect to the observed clinical results. However, the integration of this implantable material has been histologically evaluated only in animal experimental models up to now. This study aimed to evaluate the tissue incorporation of Ostim® in human cancellous bone after reconstructive bone surgery for trauma. Methods: Biopsy specimens from 6 adult patients with a total of 7 tibial, calcaneal or distal radial fractures were obtained at the time of osteosynthesis removal. The median interval from initial operation to tissue sampling was 13 (range 3–15) months. Samples were stained with Masson-Goldner, von Kossa, and toluidine blue. Osteoid volume, trabecular width and bone volume, and cortical porosity were analyzed. Samples were immunolabeled with antibodies against CD68, CD56 and human prolyl 4-hydroxylase to detect macrophages, osteoblasts, and fibroblasts, respectively. TRAP stainings were used to identify osteoclasts. Results: Histomorphometric data indicated good regeneration with normal bone turnover: mean osteoid volume was 1.93% of the trabecular bone mass, trabecular bone volume – 28.4%, trabecular width – 225.12 μm, and porosity index – 2.6%. Cortical and spongious bone tissue were well structured. Neither inflammatory reaction, nor osteofibrosis or osteonecrosis were observed. The implanted material was widely absorbed. Conclusion: The studied nanocrystalline hydroxyapatite paste showed good tissue incorporation. It is highly biocompatible and appears to be a suitable bone substitute for juxtaarticular comminuted fractures in combination with a stable screw-plate osteosynthesis. PMID:16762071

  7. Nanocrystalline hydroxyapatite enriched in selenite and manganese ions: physicochemical and antibacterial properties.

    PubMed

    Kolmas, Joanna; Groszyk, Ewa; Piotrowska, Urszula

    2015-12-01

    In this work, we used the co-precipitation method to synthesize hydroxyapatite (Mn-SeO3-HA) containing both selenium IV (approximately 3.60 wt.%) and manganese II (approximately 0.29 wt.%). Pure hydroxyapatite (HA), hydroxyapatite-containing manganese (II) ions (Mn-HA), and hydroxyapatite-containing selenite ions alone (SeO3-HA), prepared with the same method, were used as reference materials. The structures and physicochemical properties of all the obtained samples were investigated. PXRD studies showed that the obtained materials were homogeneous and consisted of apatite phase. Introducing selenites into the hydroxyapatite crystals considerably affects the size and degree of ordering. Experiments with transmission electron microscopy (TEM) showed that Mn-SeO3-HA crystals are very small, needle-like, and tend to form agglomerates. Fourier transform infrared spectroscopy (FT-IR) and solid-state nuclear magnetic resonance (ssNMR) were used to analyze the structure of the obtained material. Preliminary microbiological tests showed that the material demonstrated antibacterial activity against Staphylococcus aureus, yet such properties were not confirmed regarding Escherichia coli. PACS codes: 61, 76, 81. PMID:26138453

  8. Nanocrystalline hydroxyapatite enriched in selenite and manganese ions: physicochemical and antibacterial properties

    NASA Astrophysics Data System (ADS)

    Kolmas, Joanna; Groszyk, Ewa; Piotrowska, Urszula

    2015-07-01

    In this work, we used the co-precipitation method to synthesize hydroxyapatite (Mn-SeO3-HA) containing both selenium IV (approximately 3.60 wt.%) and manganese II (approximately 0.29 wt.%). Pure hydroxyapatite (HA), hydroxyapatite-containing manganese (II) ions (Mn-HA), and hydroxyapatite-containing selenite ions alone (SeO3-HA), prepared with the same method, were used as reference materials. The structures and physicochemical properties of all the obtained samples were investigated. PXRD studies showed that the obtained materials were homogeneous and consisted of apatite phase. Introducing selenites into the hydroxyapatite crystals considerably affects the size and degree of ordering. Experiments with transmission electron microscopy (TEM) showed that Mn-SeO3-HA crystals are very small, needle-like, and tend to form agglomerates. Fourier transform infrared spectroscopy (FT-IR) and solid-state nuclear magnetic resonance (ssNMR) were used to analyze the structure of the obtained material. Preliminary microbiological tests showed that the material demonstrated antibacterial activity against Staphylococcus aureus, yet such properties were not confirmed regarding Escherichia coli. PACS codes: 61, 76, 81

  9. Determination of Microstructural Parameters of Nanocrystalline Hydroxyapatite Prepared by Mechanical Alloying Method

    NASA Astrophysics Data System (ADS)

    Joughehdoust, Sedigheh; Manafi, Sahebali

    2011-12-01

    Hydroxyapatite [HA, Ca10(PO4)6(OH)2] is chemically similar to the mineral component of bones and hard tissues. HA can support bone ingrowth and osseointegration when used in orthopaedic, dental and maxillofacial applications. In this research, HA nanostructure was synthesized by mechanical alloying method. Phase development, particle size and morphology of HA were investigated by X-ray diffraction (XRD) pattern, zetasizer instrument, scanning electron microscopy (SEM), respectively. XRD pattern has been used to determination of the microstructural parameters (crystallite size, lattice parameters and crystallinity percent) by Williamson-Hall equation, Nelson-Riley method and calculating the areas under the peaks, respectively. The crystallite size and particle size of HA powders were in nanometric scales. SEM images showed that some parts of HA particles have agglomerates. The ratio of lattice parameters of synthetic hydroxyapatite (c/a = 0.73) was determined in this study is the same as natural hydroxyapatite structure.

  10. Optical and biological properties of transparent nanocrystalline hydroxyapatite obtained through spark plasma sintering.

    PubMed

    Li, Zhong; Thompson, Brianna C; Dong, Zhili; Khor, Khiam Aik

    2016-12-01

    Transparent bioceramics have attracted a large amount of research interest as they facilitate direct observation of biointerfacial reactions. Thus far, attempts to achieve transparent hydroxyapatite have been focused on augmenting the sintering pressure and/or extending the sintering duration. This study aims at fabricating transparent HA using a direct and fast spark plasma sintering process with appropriate starting powder and moderate sintering pressure. Three types of raw powder, namely micro-spheres, nano-rods and nano-spheres, were sintered to investigate the optical and biological properties of the compacted pellets. It was found that in terms of transparency, the micro-sphere pellet sintered at 1000°C stood out with an in-line transmittance as high as 84% achieved at 1300nm for a 2mm thick sample. In addition, pellets fabricated from micro-spheres demonstrated the highest cell viability in in vitro biological tests with L929 cells. Living cells cultured on a transparent micro-sphere pellet could be directly and clearly observed by light microscopy. It is thus concluded that the micro-sphere powder is the most desirable raw material to manufacture transparent hydroxyapatite because it could enable dense pellets with notably high transparency and outstanding in vitro biocompatibility to be readily obtained. PMID:27612791

  11. X-ray peak broadening studies of nanocrystalline hydroxyapatite by Williamson-Hall analysis

    NASA Astrophysics Data System (ADS)

    Venkateswarlu, K.; Chandra Bose, A.; Rameshbabu, N.

    2010-10-01

    Hydroxyapatite (HA) nanoparticles were prepared by microwave synthesis method and the obtained powder is annealed at 800 °C for 2 h. The annealed HA particles were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy methods. The HA size and morphology were examined using a transmission electron microscope (TEM). The XRD results reveal that the diffraction peaks of the annealed HA were of well crystalline and correspond to the hexagonal crystal structure. The XRD and FTIR results confirm the absence of secondary phases such as β-tricalcium phosphate (β-TCP) and calcium oxide in annealed HA particles. The TEM result confirms the hexagonal structure of annealed HA and the particles were observed to be of ellipsoid-like shaped morphology with less agglomeration. The lattice strain, crystallite size, lattice deformation stress and deformation energy density for annealed (800 °C) HA nanoparticles were estimated by Williamson-Hall-isotropic strain model ( W- H-ISM), W-H-anisotropic strain model ( W- H-ASM) and W-H-energy density model ( W- H-EDM) based on Williamson-Hall ( W- H) plot from powder X-ray diffraction data. The results of estimated average crystallite size of annealed HA by Scherrer and W- H plot methods were compared with TEM results. It is found that the average crystallite size measured by W- H plot methods is in good agreement with TEM results.

  12. 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

  13. Modification of gellan gum with nanocrystalline hydroxyapatite facilitates cell expansion and spontaneous osteogenesis.

    PubMed

    Jamshidi, Parastoo; Chouhan, Gurpreet; Williams, Richard L; Cox, Sophie C; Grover, Liam M

    2016-07-01

    Nanocomposites composed of hydrogels and calcium phosphates are of great interest in the development of bone graft replacements since they may have a structural and compositional resemblance to bone. Culture beads formed from such materials could be used in stirred tank culture and thereby enable cell expansion in a sufficiently efficient manner to allow for the generation of enough large number of cells for large-scale bone reconstruction. Although combinations of materials such as alginate, collagens, and various calcium phosphates have been investigated as culture beads, these materials are unsuitable for application since they have been shown to rapidly degrade in physiological conditions and enable relatively little tailoring of mechanical properties. In this study, gellan gum-nano sized hydroxyapatite (nHA) composites, which have been shown to be resistant to degradation and easily modified with respect to modulus, were formulated and characterized as regards their ability to enable cell attachment and proliferation. It was shown that the addition of 5 wt% of nHA to the culture beads enabled cell attachment and that an increase in nHA concentration to up to 25 wt% enhanced the rate of cell proliferation. Most importantly, it was demonstrated that the addition of nHA to the cell culture beads enabled the formation of nodules in culture of MC3T3-E1 cells and strikingly stimulated the osteogenic differentiation of bone marrow stromal cells in the absence of osteogenic media when compared with tissue culture plastic (TCP) with the same condition. Biotechnol. Bioeng. 2016;113: 1568-1576. © 2016 Wiley Periodicals, Inc. PMID:26704737

  14. Mode of heparin attachment to nanocrystalline hydroxyapatite affects its interaction with bone morphogenetic protein-2.

    PubMed

    Goonasekera, Chandhi S; Jack, Kevin S; Bhakta, Gajadhar; Rai, Bina; Luong-Van, Emma; Nurcombe, Victor; Cool, Simon M; Cooper-White, Justin J; Grøndahl, Lisbeth

    2015-01-01

    Heparin has a high affinity for bone morphogenetic protein-2 (BMP-2), which is a key growth factor in bone regeneration. The aim of this study was to investigate how the rate of release of BMP-2 was affected when adsorbed to nanosized hydroxyapatite (HAP) particles functionalized with heparin by different methods. Heparin was attached to the surface of HAP, either via adsorption or covalent coupling, via a 3-aminopropyltriethoxysilane (APTES) layer. The chemical composition of the particles was evaluated using X-ray photoelectron spectroscopy and elemental microanalysis, revealing that the heparin grafting densities achieved were dependent on the curing temperature used in the fabrication of APTES-modified HAP. Comparable amounts of heparin were attached via both covalent coupling and adsorption to the APTES-modified particles, but characterization of the particle surfaces by zeta potential and Brunauer-Emmett-Teller measurements indicated that the conformation of the heparin on the surface was dependent on the method of attachment, which in turn affected the stability of heparin on the surface. The release of BMP-2 from the particles after 7 days in phosphate-buffered saline found that 31% of the loaded BMP-2 was released from the APTES-modified particles with heparin covalently attached, compared to 16% from the APTES-modified particles with the heparin adsorbed. Moreover, when heparin was adsorbed onto pure HAP, it was found that the BMP-2 released after 7 days was 5% (similar to that from unmodified HAP). This illustrates that by altering the mode of attachment of heparin to HAP the release profile and total release of BMP-2 can be manipulated. Importantly, the BMP-2 released from all the heparin particle types was found by the SMAD 1/5/8 phosphorylation assay to be biologically active. PMID:26474791

  15. 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

  16. 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

  17. The Synthesis of Ag-Doped Mesoporous TiO2

    SciTech Connect

    Li, Xiaohong S.; Fryxell, Glen E.; Wang, Chong M.; Engelhard, Mark H.

    2008-04-15

    Ag-doped mesoporous titanium oxide was prepared using non-ionic surfactants and easily handled titanium precursors, under mild reaction conditions. In contrast to the stabilizing effect of Cd-doping on mesoporous TiO2, Ag-doping was found to significantly destabilize the mesoporous structure.

  18. Effect of Ag doping and annealing on thermoelectric properties of PbTe

    SciTech Connect

    Bala, Manju Tripathi, T. S.; Avasthi, D. K.; Asokan, K.; Gupta, Srashti

    2015-06-24

    The present study reveals that annealing Ag doped PbTe thin films enhance thermoelectric properties. Phase formation was identified by using X-ray diffraction measurement. Annealing increases the crystallinity of both undoped and Ag doped PbTe. Electrical resistivity and thermoelectric power measurements are done using four probe and bridge method respectively. The increase in thermoelectric power of Ag doped PbTe is 29 % in comparison to undoped PbTe and it further increases to 34 % after annealing at 250{sup o} C for 1 hour whereas thermoelectric power increases by 14 % on annealing undoped PbTe thin films at same temperature.

  19. Clinical and radiographic evaluation of Nano-crystalline hydroxyapatite bone graft (Sybograf®) in combination with bioresorbable collagen membrane (Periocol®) in periodontal intrabony defects

    PubMed Central

    Singh, Vijendra P.; Nayak, Dilip G.; Uppoor, Ashita S.; Shah, Dipen

    2012-01-01

    Background: Nanosized ceramics may represent a promising class of bone graft substitutes due to their improved osseointegrative properties. Nanocrystalline Hydroxyapatite (NcHA) bind to bone and stimulate bone healing by stimulation of osteoblast activity. The present study aims to explore the clinical and radiographical outcome of NcHA bonegraft (Sybograf®) with collagen membrane (Periocol®), in comparison with open flap debridement (OFD), in the treatment of intrabony periodontal defects. Materials and Methods: A parallel-group, randomized, controlled clinical trial was designed to conduct the study. Eighteen intrabony defects in 14 systemically healthy patients aged between 25 to 65 years were randomly assigned to test and control group. The plaque index, gingival index, probing pocket depth (PPD), clinical attachment level (CAL), and gingival recession (REC) were recorded at baseline, and were reevaluated at 6 months. In addition to this, radiographic bone fill was assessed using digital software. At the test site, NcHA bone graft and collagen membrane was placed, whereas at the control site, only OFD was done. Recall appointments were made at 7 days, 30 days, and then at 3 months and 6 months. Results: The data were subjected to statistical analysis using the Mann-Whitney ‘U’ Test and Wilcoxon signed rank sum test. In the control group, the mean reduction of PPD was 3.22±1.09 mm (P=0.007) and CAL gain was 2.77±1.09 mm (P=0.007). In the test group, the mean PPD reduction of 4.33±0.5 mm (P=0.006) and mean gain in CAL was 3.77±0.66 mm (P=0.006) at 6 months. The mean increase in REC was 0.55±0.72 mm (P=0.025) in test, and 0.44±0.52 mm (P=0.046) in control group. The mean gain in radiographic defect fill was 2.07±0.67 mm (P=0.008) in test and 0.91±0.21 mm (P=0.007) in control group. Conclusion: The nanocrystalline hydroxyapatite bone graft in combination with collagen membrane demonstrated clinical advantages beyond that achieved by OFD alone. PMID

  20. Nanocrystalline spin coated sol-gel hydroxyapatite thin films on Ti substrate: Towards potential applications for implants

    NASA Astrophysics Data System (ADS)

    Carradò, Adele; Viart, Nathalie

    2010-07-01

    Sol-gel spin coating is a promising process to obtain hydroxyapatite (HA) thin films. It is an alternative route to the hydroxyapatite deposition techniques usually employed to cover orthopaedic or dental titanium implant surfaces. The sol-gel (SG) parameters leading to a pure and crystalline HA coatings on Ti substrate were determined. They allow to reach a stoichiometric hydroxyapatite composition (ideal Ca/P atomic ratio 1.67) and a control of the growth of the crystalline phases. The samples, when observed by Scanning Electron Microscopy (SEM), exhibit grains of ca. 200 nm, well adapted for cell proliferation. The crystallisation of the HA films was thoroughly studied by X-Ray diffraction (XRD). The aim of this paper is to validate the sol-gel method as a processing method allowing the control of the mechanical state of the films and, in particular, of the residual stresses (RS) at metal-ceramic interfaces. These stresses were determined on titanium substrates. While the uncoated Ti substrates were in a compressive residual state, the coated ones were in a low tensile state. These results suggest that the sol-gel process is indeed a processing route to obtain HA coated Ti implants.

  1. Mechanical preparation of nanocrystalline biocompatible single-phase Mn-doped A-type carbonated hydroxyapatite (A-cHAp): effect of Mn doping on microstructure.

    PubMed

    Lala, S; Ghosh, M; Das, P K; Kar, T; Pradhan, S K

    2015-12-14

    Nanocrystalline biocompatible single-phase Mn-doped A-type carbonated hydroxyapatite (A-cHAp) powder has been synthesized by mechanical alloying of a stoichiometric mixture of CaCO3, CaHPO4·2H2O and MnO powder for 10 h at room temperature under open air. The A-type carbonation in HAp (substitution of CO3(2-) for OH(-)) is confirmed by FTIR analysis. Microstructure characterization in terms of lattice imperfections and phase quantification of ball milled samples are made by analyzing XRD patterns employing the Rietveld structure refinement method. Rietveld analysis of XRD patterns recorded from Mn-doped HAp samples has been used to locate Mn(2+) cations in HAp. The Ca2 vacancy site is found to be more favorable for Mn substitution. Microstructure characterization by HRTEM corroborates the findings of the X-ray analysis where the presence of a significant amount of amorphous phase of HAp analogous to indigenous bone mineral is clearly found. MTT assay shows sufficiently high percentage cell viability confirming the cytocompatibility of the sample. PMID:26530783

  2. Comparative Study on the Efficacy of Anorganic Bovine Bone (Bio-Oss) and Nanocrystalline Hydroxyapatite (Ostim) in Maxillary Sinus Floor Augmentation

    PubMed Central

    Shirmohammadi, Adileh; Roshangar, Leila; Chitsazi, Mohammad Taghi; Pourabbas, Reza; Faramarzie, Masoumeh; Rahmanpour, Nasrin

    2014-01-01

    Purpose. The aim of this study was to evaluate the efficacy of anorganic bovine bone (Bio-Oss) in comparison with nanocrystalline hydroxyapatite (Ostim) in sinus floor augmentation. Methods. Ten patients aged 40–80 were selected. All the patients needed sinus floor augmentation due to insufficient bone for simultaneous implant placement. The patients underwent panoramic radiography and cone beam computed tomography (CBCT) prior to surgical procedure. After lifting the sinus membrane, Bio-Oss and Ostim are randomly grafted at one of the two sides. Biopsies were obtained from areas identified 5 months after the surgery and before implant placement and then were prepared for histological analysis. Statistical analysis was performed with nonparametric Wilcoxon signed-rank test for comparison of histological and radiological parameters between the two groups. Results. Histological findings revealed a significant increase in percentages of new bone in the Ostim group (P = 0.015). Furthermore, new bone density was greater with Ostim compared to Bio-Oss (P = 0.038); however, the difference in height increase after surgery did not reach statistical significance (P = 0.191). Conclusion. Despite the limitations of this trial, Ostim and Bio-Oss are useful biomaterials in sinus augmentation and Ostim seems to be even more effective in new bone formation.

  3. Comparative Study on the Efficacy of Anorganic Bovine Bone (Bio-Oss) and Nanocrystalline Hydroxyapatite (Ostim) in Maxillary Sinus Floor Augmentation.

    PubMed

    Shirmohammadi, Adileh; Roshangar, Leila; Chitsazi, Mohammad Taghi; Pourabbas, Reza; Faramarzie, Masoumeh; Rahmanpour, Nasrin

    2014-01-01

    Purpose. The aim of this study was to evaluate the efficacy of anorganic bovine bone (Bio-Oss) in comparison with nanocrystalline hydroxyapatite (Ostim) in sinus floor augmentation. Methods. Ten patients aged 40-80 were selected. All the patients needed sinus floor augmentation due to insufficient bone for simultaneous implant placement. The patients underwent panoramic radiography and cone beam computed tomography (CBCT) prior to surgical procedure. After lifting the sinus membrane, Bio-Oss and Ostim are randomly grafted at one of the two sides. Biopsies were obtained from areas identified 5 months after the surgery and before implant placement and then were prepared for histological analysis. Statistical analysis was performed with nonparametric Wilcoxon signed-rank test for comparison of histological and radiological parameters between the two groups. Results. Histological findings revealed a significant increase in percentages of new bone in the Ostim group (P = 0.015). Furthermore, new bone density was greater with Ostim compared to Bio-Oss (P = 0.038); however, the difference in height increase after surgery did not reach statistical significance (P = 0.191). Conclusion. Despite the limitations of this trial, Ostim and Bio-Oss are useful biomaterials in sinus augmentation and Ostim seems to be even more effective in new bone formation. PMID:27382621

  4. Structural, morphological, optical and photocatalytic investigation of Ag-doped TiO2

    NASA Astrophysics Data System (ADS)

    Kundu, Virender Singh; Singh, Davender; Maan, A. S.; Tanwar, Amit

    2016-05-01

    The pure and Ag-doped TiO2 nanoparticles were prepared by using Titanium isoproxide (TTIP), silver nitrate sodium hydroxide and sodium hydroxide. The calcined nanoparticles at 400°C were characterized by means of X-ray diffraction (XRD). XRD analyses reveal that the nanoparticles of various doping concentration were having anatase phase. The particle size was calculated by Scherrer formula and was found 11.08 nm for pure TiO2 and 8.86 nm for 6 mol % Ag doped TiO2. The morphology and nature of nanoparticles was analyzed by using scanning electron microscope (SEM), the optical absorption spectra of pure TiO2 and Ag-doped TiO2 nanoparticles showed that absorption edge increases towards longer wavelength from 390 nm (pure) to 450 nm (doped), also band gap energy calculated from Tauc's plot decrease from 3.20eV to 2.92eV with increase in doing. The measurement of photocatalytic properties of pure TiO2 and Ag-doped TiO2 nanoparticles showed that Ag-doped TiO2 degrades MB dye more efficiently than pure TiO2.

  5. Nano-crystalline hydroxyapatite bone graft combined with bioresorbable collagen membrane in the treatment of periodontal intrabony defects: A randomized controlled clinical trial

    PubMed Central

    Singh, Vijendra P.; Nayak, Dilip G.; Uppoor, Ashita S.; Shah, Dipen

    2012-01-01

    Aim: To evaluate the clinical outcome of nanocrystalline hydroxyapatite (NcHA) bonegraft (Sybograf®) in combination with collagen membrane (PerioCol®) compared with open flap debridement (OFD) only in the treatment of intrabony periodontal defects. Materials and Methods: Eighteen intrabony defects in 16 systemically healthy patients aged between 25-65 years, were randomly assigned to test and control groups. The Plaque index, gingival index, probing pocket depth (PPD), clinical attachment level (CAL), and gingival recession were recorded at baseline, and were reevaluated at 6 months. In addition to this, radiographic bone fill was assessed using digital software. At the test site NcHA bone graft and collagen membrane was placed, whereas at the control site only, OFD was done. Recall appointments were made at 7th day, 1st month, 3rd month, and 6th month. Results: The data were subjected to statistical analysis using the Mann-Whitney ‘U’ Test and Wilcoxon signed rank sum test. In the control group, the mean reduction of PPD was 3.22±1.09 mm and CAL gain was 2.78±1.09 mm. In the test group, the mean PPD reduction of 4.33±0.5 mm and mean gain in CAL was 3.78±0.66 mm at 6 months. The mean increase in gingival recession was 0.55±0.72 mm in test and 0.44±0.52 mm in control group. Conclusion: The NcHA bone graft in combination with collagen membrane demonstrated better clinical outcomes compared with OFD alone. PMID:23493628

  6. Antibacterial activity of silver-doped hydroxyapatite nanoparticles against gram-positive and gram-negative bacteria

    NASA Astrophysics Data System (ADS)

    Ciobanu, Carmen Steluta; Iconaru, Simona Liliana; Le Coustumer, Phillippe; Constantin, Liliana Violeta; Predoi, Daniela

    2012-06-01

    Ag-doped nanocrystalline hydroxyapatite nanoparticles (Ag:HAp-NPs) (Ca10- x Ag x (PO4)6(OH)2, x Ag = 0.05, 0.2, and 0.3) with antibacterial properties are of great interest in the development of new products. Coprecipitation method is a promising route for obtaining nanocrystalline Ag:HAp with antibacterial properties. X-ray diffraction identified HAp as an unique crystalline phase in each sample. The calculated lattice constants of a = b = 9.435 Å, c = 6.876 Å for x Ag = 0.05, a = b = 9.443 Å, c = 6.875 Å for x Ag = 0.2, and a = b = 9.445 Å, c = 6.877 Å for x Ag = 0.3 are in good agreement with the standard of a = b = 9.418 Å, c = 6.884 Å (space group P63/m). The Fourier transform infrared and Raman spectra of the sintered HAp show the absorption bands characteristic to hydroxyapatite. The Ag:HAp nanoparticles are evaluated for their antibacterial activity against Staphylococcus aureus, Klebsiella pneumoniae, Providencia stuartii, Citrobacter freundii and Serratia marcescens. The results showed that the antibacterial activity of these materials, regardless of the sample types, was greatest against S. aureus, K. pneumoniae, P. stuartii, and C. freundii. The results of qualitative antibacterial tests revealed that the tested Ag:HAp-NPs had an important inhibitory activity on P. stuartii and C. freundii. The absorbance values measured at 490 nm of the P. stuartii and C. freundii in the presence of Ag:HAp-NPs decreased compared with those of organic solvent used (DMSO) for all the samples ( x Ag = 0.05, 0.2, and 0.3). Antibacterial activity increased with the increase of x Ag in the samples. The Ag:HAp-NP concentration had little influence on the bacterial growth ( P. stuartii).

  7. Maxillary sinus floor augmentation using a nano-crystalline hydroxyapatite silica gel: case series and 3-month preliminary histological results.

    PubMed

    Canullo, Luigi; Dellavia, Claudia; Heinemann, Friedhelm

    2012-03-20

    The aim of this case series is to histologically examine a new hydroxyapatite in sinus lift procedure after 3 months. Ten 2-stage sinus lifts were performed in 10 healthy patients having initial bone height of 1-2mm and bone width of 5mm, asking for a fixed implant-supported rehabilitation. After graft material augmentation, a rough-surfaced mini-implant was inserted to maintain stability of the sinus widow. A bioptical core containing a mini-implant was retrieved 3 months after maxillary sinus augmentation with NanoBone(®) and processed for undecalcified histology. From the histomorphometric analysis, NanoBone(®) residuals accounted for the 38.26% ± 8.07% of the bioptical volume, marrow spaces for the 29.23% ± 5.18% and bone for the 32.51% ± 4.96% (new bone: 20.64% ± 2.96%, native bone: 11.87% ± 3.27%). Well-mineralized regenerated bone with lamellar parallel-fibred structure and Haversian systems surrounded the residual NanoBone(®) particles. The measured bone-to-implant contact amounted to 26.02% ± 5.46%. No connective tissue was observed at the implant boundary surface. In conclusion, the tested material showed good histological outcomes also 3 months after surgery. In such critical conditions, the use of a rough-surfaced mini-implant showed BIC values supposed to be effective also in case of functional loading. Although longer follow-up and a wider patient size are needed, these preliminary results encourage further research on this biomaterial for implant load also under early stage and critical conditions. PMID:21640571

  8. On the impact of Ag doping on performance and reliability of GeS2-based conductive bridge memories

    NASA Astrophysics Data System (ADS)

    Longnos, F.; Vianello, E.; Cagli, C.; Molas, G.; Souchier, E.; Blaise, P.; Carabasse, C.; Rodriguez, G.; Jousseaume, V.; De Salvo, B.; Dahmani, F.; Verrier, P.; Bretegnier, D.; Liebault, J.

    2013-06-01

    In this work, we study the impact of Ag doping on GeS2-based CBRAM devices employing Ag as active electrode. Several devices with Ag doping varying between 10% and 24% are extensively analyzed. First, we assess switching voltages and time-to-set as a function of Ag concentration in the electrolyte layer. Subsequently, we evaluate the two most important reliability aspects of RRAM devices: endurance and data retention at different temperatures. The results show that an increase of Ag doping in the GeS2 layer yields a strong improvement to both endurance and data retention performances. The extrapolated temperature allowing for 10 years data retention increases from 75 °C for the 10% Ag-doped sample to 109 °C for the 24% Ag-doped one.

  9. An asymmetric Zn//Ag doped polyaniline microparticle suspension flow battery with high discharge capacity

    NASA Astrophysics Data System (ADS)

    Wu, Sen; Zhao, Yongfu; Li, Degeng; Xia, Yang; Si, Shihui

    2015-02-01

    In this study, the effect of oxygen on the potential of reduced polyaniline (PANI) was investigated. In order to enhance the air oxidation of reduced PANI, several composites of PANI doped with co-catalysts were prepared, and a reasonable flow Zn//PANI suspension cell system was designed to investigate the discharge capacity of obtained PANI composite microparticle suspension cathodes. Compared with PANI doped with Cu2+, La+, Mn2+ and zinc protoporphyrin, Ag doped PANI composite at 0.90 weight percent doping of Ag gave the highest value of discharge capacity for the half-cell potential from the initial value to -0.20 V (vs. SCE). A comparison study on the electrochemical properties of both PANI and Ag doped PANI microparticle suspension was done by using cyclic voltammetry, AC Impedance. Due to partial utilization of Zn//air fuel cell, the discharge capacity for Ag doped PANI reached 470 mA h g-1 at the current density of 20 mA cm-2. At 15 mA cm-2, the discharge capacity even reached up to 1650 mA h g-1 after 220 h constant current discharge at the final discharge voltage of 0.65 V. This work demonstrates an effective and feasible approach toward obtaining high energy and power densities by a Zn//Ag-doped PANI suspension flow battery system combined with Zn//air fuel cell.

  10. Synthesis of highly efficient antibacterial agent Ag doped ZnO nanorods: Structural, Raman and optical properties

    SciTech Connect

    Jan, Tariq; Iqbal, Javed; Ismail, Muhammad; Mahmood, Arshad

    2014-04-21

    Here, synthesis, structural, morphological, Raman, optical properties and antibacterial activity of undoped and Ag doped ZnO nanorods by chemical co-precipitation technique have been reported. Structural analysis has revealed that Ag doping cannot deteriorate the structure of ZnO and wurtzite phase is maintained. Lattice constants are found to be decreased with the Ag doping. Fourier transform infrared and Raman spectroscopy also confirm the X-ray diffraction results. Scanning electron microscopy results have demonstrated the formation of ZnO nanorods with average diameter and length of 96 nm and 700 nm, respectively. Raman spectroscopy results suggest that the Ag doping enhances the number of defects in ZnO crystal. It has been found from optical study that Ag doping results in positional shift of band edge absorption peak. This is attributed to the successful incorporation of Ag dopant into ZnO host matrix. The antibacterial activity of prepared nanorods has been determined by two different methods and compared to that of undoped ZnO nanorods. Ag doped ZnO nanorods exhibit excellent antibacterial activity as compared to that of undoped ZnO nanorods. This excellent antibacterial activity may be attributed to the presence of oxygen vacancies and Zn{sup 2+} interstitial defects. Our preliminary findings suggest that Ag doped ZnO nanorods can be used externally to control the spreading of infections related with tested bacterial strains.

  11. Bone formation and degradation behavior of nanocrystalline hydroxyapatite with or without collagen-type 1 in osteoporotic bone defects - an experimental study in osteoporotic goats.

    PubMed

    Alt, Volker; Cheung, Wing Hoi; Chow, Simon K H; Thormann, Ulrich; Cheung, Edmond N M; Lips, Katrin S; Schnettler, Reinhard; Leung, Kwok-Sui

    2016-06-01

    The intention of the current work is to assess new bone formation and degradation behavior of nanocrystalline hydroxyapatite with (HA/col-1) or without collagen-type I (HA) in osteoporotic metaphyseal bone defects in goats. After ovariectomy and special low-calcium diet for three months, 3 drill hole defects in the vertebrae of L3, L4, L5, 4 drill hole defects in the right and left iliac crest and 1 drill hole defect at the distal femur were created in three Chinese mountain goats with a total of 24 defects. The defects were either filled with one of the biomaterials or left empty (empty defect control group). After 42 days, the animals were euthanized and the samples were assessed for new bone formation using high-resolution peripheral quantitative computed tomography (HR-pQCT) and histomorphometry with 2 regions of interest. Detail histology, enzymehistochemistry and immunohistochemistry as well as connexin-43 in situ hybridization and transmission electron microscopy were carried out for evaluation of degradation behavior of the materials and cellular responses of the surrounding tissue in respect to the implants. HR-pQCT showed the highest BV/TV ratio (p = 0.008) and smallest trabecular spacing (p = 0.005) for HA compared to the other groups in the region of interest at the interface with 1mm distance to the initially created defect. The HA/col-1 yielded the highest connectivity density (Conn.D) (p = 0.034) and the highest number of trabeculae (Tb.N) (p = 0.002) compared to the HA and the control group. Histomorphometric analysis for the core region of the initially created defect revealed a statistically higher new bone formation in the HA (p = 0.001) and HA/col-1 group (p = 0.001) compared to the empty defect group including all defect sites. This result was confirmed for site specific analysis with significant higher new bone formation for the HA group for vertebral defects compared to the empty defect group (p = 0.029). For the interface region, no

  12. Photoluminescence of Ag-doped ZnSe nanowires synthesized by metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhang, X. T.; Ip, K. M.; Li, Quan; Hark, S. K.

    2005-05-01

    Photoluminescence of Ag-doped ZnSe nanowires synthesized by metalorganic chemical vapor deposition is investigated in the temperature range from 10to300K. Ag impurities were introduced into the ZnSe nanowires during the growing process. Some dominating Ag-related centers are found. Especially, the strong zero-phonon bound exciton luminescence with energy near 2.747eV is attributed to a neutral AgZn acceptor complex. This is because the emission peak at the same energy is observed only in the photoluminescence spectrum of the Ag-doped bulk ZnSe. A new luminescence peak at 2.842eV is attributed to the recombination of excitons bound to ionized acceptors (I2h) in the hexagonal phase of ZnSe nanowires. The physical origins of the emissions are briefly discussed.

  13. Structural and nonlinear optical behavior of Ag-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Tan, Ming-Yue; Yao, Cheng-Bao; Yan, Xiao-Yan; Li, Jin; Qu, Shu-Yang; Hu, Jun-Yan; Sun, Wen-Jun; Li, Qiang-Hua; Yang, Shou-Bin

    2016-01-01

    We present the structural and nonlinear optical behavior of Ag-doped ZnO (AZO) films prepared by magnetron sputtering. The structural of AZO films are systematically investigated by X-ray diffraction (XRD) and scanning electronic microscopy (SEM), respectively. The results show that AZO films can still retain a wurtzite structure, although the c-axis as preferred orientation is decreased by Ag doping. As the amounts of the Ag dopant were increased, the crystallinity as well as the absorptivity and optical band gap were increased. Moreover, the nonlinear optical characterized of the AZO films was studied using Z-scan technique. These samples show self-defocusing nonlinearity and good nonlinear absorption behavior which increases with increasing Ag volume fraction. AZO is a potential nanocomposite material for the development of nonlinear optical devices with a relatively small limiting threshold.

  14. Transport and pinning properties of Ag-doped FeSe0.94

    NASA Astrophysics Data System (ADS)

    Nazarova, E.; Balchev, N.; Nenkov, K.; Buchkov, K.; Kovacheva, D.; Zahariev, A.; Fuchs, G.

    2015-02-01

    We investigated the superconducting transition and the pinning properties of undoped and Ag-doped FeSe0.94 at magnetic fields up to 14 T. We established that, due to Ag addition, the hexagonal phase formation in melted FeSe0.94 samples is suppressed and the grain connectivity is strongly improved. The obtained superconducting zero-field transition becomes sharp, with a transition width below 1 K. Tc and the upper critical field were found to increase, while the normal-state resistivity was significantly reduced, becoming comparable with that of FeSe single crystals. In addition, a considerable magnetoresistance was observed due to Ag doping. The resistive transition of undoped and Ag-doped FeSe0.94 is dominated by a thermally activated flux flow. From the activation energy U versus H dependence, we found a crossover from single-vortex pinning to a collective-creep pinning behavior by increasing the magnetic field.

  15. Ag-doped carbon aerogels for removing halide ions in water treatment.

    PubMed

    Sánchez-Polo, M; Rivera-Utrilla, J; Salhi, E; von Gunten, U

    2007-03-01

    The objective of this study was to analyze the efficiency of silver(Ag)-doped carbon aerogels for the removal of bromide (Br(-)) and iodide (I(-)) from drinking waters. Textural characterization of Ag-doped aerogels showed that an increase in the Ag dose added during the preparation process produced: (i) a reduction in the surface area (S(BET)) and (ii) an increase in mesopore (V(2)) and macropore (V(3)) volumes. Chemical characterization of the materials revealed an acidic surface (pH of point of zero charge, pH(PZC)=4.5, O(surface)=20%). The oxidation state of Ag was +1 and the surface concentration of this element ranged from 4% to 10%. The adsorption capacity (X(m)) and affinity of adsorbent (BX(m)) increased with a reduction in the radius of the halogenide. Furthermore, an increase in the adsorption capacity was observed with higher Ag concentrations on the aerogel surface. The high adsorption capacity of the aerogel may be due to the presence of Ag(I) on its surface, with the formation of the corresponding Ag halides. Our observations indicate that the halogenides adsorption on commercial activated carbon (Sorbo-Norit) is much lower than that of the Ag-doped carbon aerogels. The presence of chloride and natural organic matter (NOM) in the medium reduced the adsorption capacity of Br(-) and I(-) on Ag carbon aerogels. PMID:16970974

  16. Synthesis, structural characterisation and antibacterial activity of Ag+-doped fluorapatite nanomaterials prepared by neutralization method

    NASA Astrophysics Data System (ADS)

    Stanić, Vojislav; Radosavljević-Mihajlović, Ana S.; Živković-Radovanović, Vukosava; Nastasijević, Branislav; Marinović-Cincović, Milena; Marković, Jelena P.; Budimir, Milica D.

    2015-05-01

    Silver doped fluorapatite nanopowders were synthesised by neutralization method, which consists of dissolving Ag2O in solution of HF and H3PO4 and addition to suspension of Ca(OH)2. The powder XRD, SEM and FTIR studies indicated the formation of a fluorapatite nanomaterials with average length of the particles is about 80 nm and a width of about 15 nm. The FTIR studies show that carbonate content in samples is very small and carbonte ions substitute both phosphate and hydroxyl groups in the crystal structure of samples, forming AB-type fluorapatite. Antibacterial studies have demonstrated that all Ag+-doped fluorapatite samples exhibit bactericidal effect against pathogens: Staphylococcus aureus, Micrococcus luteus and Kllebsiela pneumoniae. Antibacterial activity increased with the increase of Ag+ in the samples. The atomic force microscopy studies revealed extensive damage to the bacterial cell envelops in the presence of Ag+-doped fluorapatite particles which may lead to their death. The synthesized Ag+-doped fluorapatite nanomaterials are promising as antibacterial biomaterials in orthopedics and dentistry.

  17. Evaluation of Ag containing hydroxyapatite coatings to the Candida albicans infection.

    PubMed

    Ciuca, S; Badea, M; Pozna, E; Pana, I; Kiss, A; Floroian, L; Semenescu, A; Cotrut, C M; Moga, M; Vladescu, A

    2016-06-01

    In this research work, the synthesis of Ag doped hydroxyapatite coatings for dental or orthopedic implants was performed. The main goal was to determine the influence of Ag content on the roughness and antimicrobial performance of the prepared thin films. The films were deposited on Ti6Al4V alloy by means of RF magnetron sputtering. Those coatings were characterized by X-ray diffraction (XRD) and 3D surface profilometry. The antifungal activity after 1 and 7days of culture was evaluated in the presence of Candida albicans (ATCC - 10231). The increase of Ag content increased roughness and reduced the antifungal activity. The results showed that the Ag doped hydroxyapatite coatings can be a potential solution for the improvement of the antifungal activities of Ti based alloy. PMID:27021660

  18. Evaluation of Bone Healing on Sandblasted and Acid Etched Implants Coated with Nanocrystalline Hydroxyapatite: An In Vivo Study in Rabbit Femur

    PubMed Central

    Melin Svanborg, Lory; Meirelles, Luiz; Franke Stenport, Victoria; Currie, Fredrik; Andersson, Martin

    2014-01-01

    This study aimed at investigating if a coating of hydroxyapatite nanocrystals would enhance bone healing over time in trabecular bone. Sandblasted and acid etched titanium implants with and without a submicron thick coat of hydroxyapatite nanocrystals (nano-HA) were implanted in rabbit femur with healing times of 2, 4, and 9 weeks. Removal torque analyses and histological evaluations were performed. The torque analysis did not show any significant differences between the implants at any healing time. The control implant showed a tendency of more newly formed bone after 4 weeks of healing and significantly higher bone area values after 9 weeks of healing. According to the results from this present study, both control and nano-HA surfaces were biocompatible and osteoconductive. A submicron thick coating of hydroxyapatite nanocrystals deposited onto blasted and acid etched screw shaped titanium implants did not enhance bone healing, as compared to blasted and etched control implants when placed in trabecular bone. PMID:24723952

  19. Control of Ag nanoparticle distribution influencing bioactive and antibacterial properties of Ag-doped mesoporous bioactive glass particles prepared by spray pyrolysis.

    PubMed

    Shih, Shao-Ju; Tzeng, Wei-Lung; Jatnika, Rifqi; Shih, Chi-Jen; Borisenko, Konstantin B

    2015-05-01

    Mesoporous bioactive glasses (MBGs) have become important bone implant materials because of their high specific surface area resulting in high bioactivity. Doping MBGs with Ag removes one of the remaining challenges to their applications, namely their lack of intrinsic antibacterial properties. In present work we demonstrate that Ag-doped MBGs can be prepared in one-step spray pyrolysis (SP) process. The SP preparation method offers the advantages of short processing times and continuous production over the sol-gel method previously used to prepare MBGs. Using scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction we demonstrate that the synthesized MBG particles have amorphous structure with nanocrystalline Ag inclusions. The scanning transmission electron microscopy-X-ray energy dispersive spectrometry of cross-sectional samples shows that the distribution of the Ag dopant nanoparticles within MBGs can be controlled by using the appropriate formulation of the precursors. The distribution of the Ag dopant nanoparticles within the MBG particles was found to affect their surface areas, bioactivities and antibacterial properties. Based on the observations, we propose a mechanism describing MBG particle formation and controlling dopant distribution. PMID:25171327

  20. Synthesis and Characterization of Varying Concentrations of Ag-doped ZnO Thin Films

    NASA Astrophysics Data System (ADS)

    Hachlica, Justin; Wadie-Ibrahim, Patrick; Sahiner, M. Alper

    Silver doped ZnO is a promising compound for photovoltaic solar cell use. Doping this compound with varying amounts of silver will theoretically make this type of thin film more efficient by reducing the overall resistance and increasing the voltage and current output. The extent of this promise is being tested experimentally, by analysis of both the electrical and the surface roughness properties of the cells. Ag-doped Zinc Oxide is deposited by method of Pulsed Laser Deposition (PLD) onto Indium Tin Oxide (ITO) coated Glass. Annealing effects were also observed by varying the temperature at which the annealing occurred after synthesis of the sample. Thickness is confirmed by use of Ellipsometery. X-Ray Diffraction (XRD) measurements confirmed a ZnO crystal structure on the thin films. The active dopant carrier concentrations were determined using a Hall Effect Measuring System. Finally, the photovoltaic properties of the film are recorded by using a Keithley Source Meter. The structural characterization and electrical results of the effect of Ag doping on ZnO will then be discussed.

  1. Effect of Ag doping and insulator buffer layer on the memory mechanism of polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Kaur, Ramneek; Kaur, Jagdish; Tripathi, S. K.

    2015-07-01

    Resistive memory devices based on nanocomposites have attracted great potential for future applications in electronic and optoelectronic devices. The successful synthesis of aqueous CdSe nanoparticles has been provided with UV-Vis and Photoluminescence spectroscopy. The two terminal planar devices of CdSe nanocomposite have been fabricated. The effect of Ag doping and additional dielectric buffer layers on the memory devices have been studied by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The devices show hysteresis loops in both positive and negative bias directions. The memory window has been found to be increased with both Ag doping and PVA layer addition. The charge carrier transport mechanism in the memory devices has been studied by fitting the I-V characteristics with the theoretical model, Space charge conduction model (SCLC). C-V hysteresis loop in both positive and negative bias directions indicate that both the electrons and holes are responsible for memory mechanism of the devices. The switching mechanism of the memory devices has been explained by charge trapping/detrapping model. The retention characteristics show good stability and reliability of the devices.

  2. Antibacterial activity of silver-doped hydroxyapatite nanoparticles against gram-positive and gram-negative bacteria

    PubMed Central

    2012-01-01

    Ag-doped nanocrystalline hydroxyapatite nanoparticles (Ag:HAp-NPs) (Ca10-xAgx(PO4)6(OH)2, xAg = 0.05, 0.2, and 0.3) with antibacterial properties are of great interest in the development of new products. Coprecipitation method is a promising route for obtaining nanocrystalline Ag:HAp with antibacterial properties. X-ray diffraction identified HAp as an unique crystalline phase in each sample. The calculated lattice constants of a = b = 9.435 Å, c = 6.876 Å for xAg = 0.05, a = b = 9.443 Å, c = 6.875 Å for xAg = 0.2, and a = b = 9.445 Å, c = 6.877 Å for xAg = 0.3 are in good agreement with the standard of a = b = 9.418 Å, c = 6.884 Å (space group P63/m). The Fourier transform infrared and Raman spectra of the sintered HAp show the absorption bands characteristic to hydroxyapatite. The Ag:HAp nanoparticles are evaluated for their antibacterial activity against Staphylococcus aureus, Klebsiella pneumoniae, Providencia stuartii, Citrobacter freundii and Serratia marcescens. The results showed that the antibacterial activity of these materials, regardless of the sample types, was greatest against S. aureus, K. pneumoniae, P. stuartii, and C. freundii. The results of qualitative antibacterial tests revealed that the tested Ag:HAp-NPs had an important inhibitory activity on P. stuartii and C. freundii. The absorbance values measured at 490 nm of the P. stuartii and C. freundii in the presence of Ag:HAp-NPs decreased compared with those of organic solvent used (DMSO) for all the samples (xAg = 0.05, 0.2, and 0.3). Antibacterial activity increased with the increase of xAg in the samples. The Ag:HAp-NP concentration had little influence on the bacterial growth (P. stuartii). PMID:22721352

  3. Ag-doped FeSe0.94 polycrystalline samples obtained through hot isostatic pressing with improved grain connectivity

    NASA Astrophysics Data System (ADS)

    Gajda, G.; Morawski, A.; Rogacki, K.; Cetner, T.; Zaleski, A. J.; Buchkov, K.; Nazarova, E.; Balchev, N.; Hossain, M. S. A.; Diduszko, R.; Gruszka, K.; Przysłupski, P.; Fajfrowski, Ł.; Gajda, D.

    2016-09-01

    We evaluate the effects of high pressure during annealing on the structural and superconducting properties of Ag-doped FeSe bulks. The results obtained in this work indicate that the annealing at high pressure increases the critical temperature, upper critical field and irreversibility field due to the improved uniformity and grain connectivity.

  4. Size dependent electron-phonon coupling in N, Li, In, Ga, F and Ag doped ZnO thin films.

    PubMed

    Shinde, S S; Bhosale, C H; Rajpure, K Y

    2012-12-01

    Polarized micro-Raman measurements are performed to study the phonon modes of N, Li, In, Ga, F and Ag doped ZnO thin films, grown by spray pyrolysis on corning glass substrates. The E(2)(high) mode displays a visible asymmetric line shape. The size and dopant dependence onto coupling strength between electron and LO phonon is experimentally estimated. PMID:23010630

  5. Bromide and iodide removal from waters under dynamic conditions by Ag-doped aerogels.

    PubMed

    Sánchez-Polo, M; Rivera-Utrilla, J; von Gunten, U

    2007-02-01

    The objective of this study was to analyze the efficiency of Ag-doped aerogels in the removal of bromide and iodide from water. To test the applicability of these aerogels in water treatment, adsorption of bromide and iodide was studied under dynamic conditions using waters from Lake Zurich and a mineral water. The results obtained by using these waters showed a high breakthrough volume (V(0.02)=0.4 L) of the columns, while the height of the mass transfer zone (H(MTZ)=6.8 cm) was low, regardless of the anion under study. Bromide- and iodide-saturated columns were regenerated with NH4OH. No change in the column characteristics was observed after two regeneration treatments, regardless of the type of water considered. PMID:17109877

  6. Local order origin of thermal stability enhancement in amorphous Ag doping GeTe

    SciTech Connect

    Xu, L.; Li, Y.; Yu, N. N.; Zhong, Y. P.; Miao, X. S.

    2015-01-19

    We demonstrate the impacts of Ag doping on the local atomic structure of amorphous GeTe phase-change material. The variations of phonon vibrational modes, boding nature, and atomic structure are shown by Raman, X-ray photoelectron spectroscopy, and ab initio calculation. Combining the experiments and simulations, we observe that the number of Ge atoms in octahedral site decreases and that in tetrahedral site increases. This modification in local order of GeTe originating from the low valence element will affect the crystallization behavior of amorphous GeTe, which is verified by differential scanning calorimetry and transmission electron microscope results. This work not only gives the analysis on the structural change of GeTe with Ag dopants but also provides a method to enhance the thermal stability of amorphous phase-change materials for memory and brain-inspired computing applications.

  7. Efficient inverted organic light-emitting devices with self or intentionally Ag-doped interlayer modified cathode

    SciTech Connect

    Liu, Wenbo; Liu, Shihao; Yu, Jing; Zhang, Wei; Wen, Xuemei; Yin, Yongming; Zhang, Letian; Chen, Ping; Xie, Wenfa

    2014-03-03

    Green phosphorescent inverted organic light-emitting devices (IOLEDs) with self or intentionally Ag-doped interlayer modified cathode were demonstrated. The IOLEDs show low driving voltage and high efficiency. For example, the efficiency of inverted bottom-emitting OLED with ITO cathode is comparable with the conventional bottom-emitting OLED with ITO anode. The top-emitting IOLED with Ag cathode shows high current efficiency of 76.4 cd/A which is 2.38 times of that of the conventional bottom-emitting OLED with ITO anode. The results indicate that the electron injection from cathode was observably improved by the Ag-doped interlayer and such interlayer is cathode independent relatively.

  8. Photocatalytic performance of Ag doped SnO2 nanoparticles modified with curcumin

    NASA Astrophysics Data System (ADS)

    Vignesh, K.; Hariharan, R.; Rajarajan, M.; Suganthi, A.

    2013-07-01

    Visible light active Ag doped SnO2 nanoparticles modified with curcumin (Cur-Ag-SnO2) have been prepared by a combined precipitation and chemical impregnation route. The optical properties, phase structures and morphologies of the as-prepared nanoparticles were characterized using UV-visible diffuse reflectance spectra (UV-vis-DRS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The surface area was measured by Brunauer. Emmett. Teller (B.E.T) analysis. Compared to bare SnO2, the surface modified photocatalysts (Ag-SnO2 and Cur-Ag-SnO2) showed a red shift in the visible region. The photocatalytic activity was monitored via the degradation of rose bengal (RB) dye and the results revealed that Cur-Ag-SnO2 shows better photocatalytic activity than that of Ag-SnO2 and SnO2. The superior photocatalytic activity of Cur-Ag-SnO2 could be attributed to the effective electron-hole separation by surface modification. The effect of photocatalyst concentration, initial dye concentration and electron scavenger on the photocatalytic activity was examined in detail. Furthermore, the antifungal activity of the photocatalysts and the reusability of Cur-Ag-SnO2 were tested.

  9. Influence of oxygen partial pressure on the physical properties of Ag doped NiO thin films

    NASA Astrophysics Data System (ADS)

    Reddy, Y. Ashok Kumar; Reddy, A. Sivasankar; Reddy, P. Sreedhara

    2013-06-01

    Ag doped p-type NiO thin films were successfully deposited by DC reactive magnetron sputtering technique at different oxygen partial pressures in the range 1 × 10-4 - 9 × 10-4 mbar. The structural and morphological properties of the films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). All the deposited films were of polycrystalline nature and exhibited cubic structure with preferential growth. The morphological studies revealed that the surface roughness was increased with increasing oxygen partial pressure up to 5 × 10-4 mbar and decreased at higher oxygen partial pressures.

  10. Ag-doped ZnO nanorods coated metal wire meshes as hierarchical photocatalysts with high visible-light driven photoactivity and photostability.

    PubMed

    Hsu, Mu-Hsiang; Chang, Chi-Jung

    2014-08-15

    Ag-doped ZnO nanorods were grown on stainless-steel wire meshes to fabricate the hierarchical photocatalysts with excellent visible light driven activity and anti-photocorrosion property. Effects of Ag doping and the surface structure on the surface chemistry, surface wetting properties, absorption band shift, photoelectrochemical response, and photocatalytic decolorization properties of the hierarchical photocatalysts, together with the stability of photocatalytic activity for recycled photocatalysts were investigated. Ag doping leads to red-shift in the absorption band and increased visible light absorption. Nanorods coated wire meshes hierarchical structure not only increases the surface area of photocatalysts but also makes the surface hydrophilic. The photocatalytic activity enhancement and reduced photocorrosion can be achieved because of increased surface area, enhanced hydrophilicity, and the interaction between the metal wire/ZnO and Ag/ZnO heterostructure interface which can improve the charge separation of photogenerated charge carriers. PMID:24997260

  11. Improved performance of Ag-doped TiO2 synthesized by modified sol-gel method as photoanode of dye-sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Gupta, Arun Kumar; Srivastava, Pankaj; Bahadur, Lal

    2016-08-01

    Ag-doped TiO2 with Ag content ranging from 1 to 7 mol% was synthesized by a modified sol-gel route, and its performance as the photoanode of dye-sensitized solar cells (DSSCs) was compared with undoped TiO2 photoanode. Titanium(IV)isopropoxide was used as precursor and hexamethylenetetramine as the capping agent. XRD results show the formation of TiO2 nanoparticles with an average crystallite size of 5 nm (1 % Ag-doped TiO2) and 9 nm (undoped TiO2), respectively. The TiO2 nanopowder was used to prepare its thin film photoelectrode using doctor's blade method. Significant improvement in light-to-energy conversion efficiency was achieved when thin films of 1 % Ag-doped TiO2 were applied as photoanode in DSSC taking N719 as the sensitizer dye. As evidenced by EIS measurements, the electron lifetime of DSSC with Ag-doped TiO2 increased from 1.33 (for undoped TiO2) to 2.05 ms. The short-circuit current density ( J sc), open-circuit voltage ( V oc), fill factor (FF) and the overall energy conversion efficiency ( η) were 1.07 mA cm-2, 0.72 V, 0.73 and 0.40 %, respectively, with the use of 1 % Ag-doped TiO2 photoanode, whereas with undoped TiO2 under similar conditions, J sc = 0.63 mA cm-2, V oc = 0.70 V, fill factor 0.45 and conversion efficiency 0.14 % could be obtained. Therefore, compared with the reference DSSC containing an undoped TiO2 photoanode, the power conversion efficiency of the cell based on Ag-doped TiO2 has been remarkably enhanced by ~70 %. The substantial improvement in the device performance is attributed to the reduced band-gap energy, retarded charge recombination and greater surface coverage of the sensitizing dye over Ag-doped TiO2, which ultimately resulted in improved IPCE, J SC and η values.

  12. Photocatalytic activity of undoped and Ag-doped TiO{sub 2}-supported zeolite for humic acid degradation and mineralization

    SciTech Connect

    Lazau, C.; Ratiu, C.; Orha, C.; Pode, R.; Manea, F.

    2011-11-15

    Highlights: {yields} Hybrid materials based on natural zeolite and TiO{sub 2} obtained by solid-state reaction. {yields} XRD proved the presence of anatase form of undoped and Ag-doped TiO{sub 2} onto zeolite. {yields} FT-IR spectra evidenced the presence on TiO{sub 2} bounded at the zeolite network. {yields} Ag-doped TiO{sub 2} onto zeolitic matrix exhibited an enhanced photocatalytic activity. -- Abstract: The hybrid materials based on natural zeolite and undoped and Ag-doped TiO{sub 2}, i.e., Z-Na-TiO{sub 2} and Z-Na-TiO{sub 2}-Ag, were successfully synthesized by solid-state reaction in microwave-assisted hydrothermal conditions. Undoped TiO{sub 2} and Ag-doped TiO{sub 2} nanocrystals were previously synthesized by sol-gel method. The surface characterization of undoped TiO{sub 2}/Ag-doped TiO{sub 2} and natural zeolite hybrid materials has been investigated by X-ray diffraction, DRUV-VIS spectroscopy, FT-IR spectroscopy, BET analysis, SEM microscopy and EDX analysis. The results indicated that anatase TiO{sub 2} is the dominant crystalline type as spherical form onto zeolitic matrix. The presence of Ag into Z-Na-TiO{sub 2}-Ag was confirmed by EDX analysis. The DRUV-VIS spectra showed that Z-Na-TiO{sub 2}-Ag exhibited absorption within the range of 400-500 nm in comparison with Z-Na-TiO{sub 2} catalyst. The enhanced photocatalytic activity of Z-Na-TiO{sub 2}-Ag catalyst is proved through the degradation and mineralization of humic acid under ultraviolet and visible irradiation.

  13. 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.

  14. Thermally induced effect on sub-band gap absorption in Ag doped CdSe thin films

    NASA Astrophysics Data System (ADS)

    Kaur, Jagdish; Sharma, Kriti; Bharti, Shivani; Tripathi, S. K.

    2015-05-01

    Thin films of Ag doped CdSe have been prepared by thermal evaporation using inert gas condensation (IGC) method taking Argon as inert gas. The prepared thin films are annealed at 363 K for one hour. The sub-band gap absorption spectra in the as deposited and annealed thin films have been studied using constant photocurrent method (CPM). The absorption coefficient in the sub-band gap region is described by an Urbach tail in both as deposited and annealed thin films. The value of Urbach energy and number density of trap states have been calculated from the absorption coefficient in the sub-band gap region which have been found to increase after annealing treatment indicating increase in disorderness in the lattice. The energy distribution of the occupied density of states below Fermi level has also been studied using derivative procedure of absorption coefficient.

  15. Influence of Ag doping concentration on structural and optical properties of CdS thin film

    SciTech Connect

    Kumar, Pragati; Saxena, Nupur; Gupta, Vinay; Agarwal, Avinash

    2015-05-15

    This work shows the influence of Ag concentration on structural properties of pulsed laser deposited nanocrystalline CdS thin film. X-ray photoelectron spectroscopy (XPS) studies confirm the dopant concentration in CdS films and atomic concentration of elements. XPS studies show that the samples are slightly sulfur deficient. GAXRD scan reveals the structural phase transformation from cubic to hexagonal phase of CdS without appearance of any phase of CdO, Ag{sub 2}O or Ag{sub 2}S suggesting the substitutional doping of Ag ions. Photoluminescence studies illustrate that emission intensity increases with increase in dopant concentration upto 5% and then decreases for higher dopant concentration.

  16. Synthesis and characterization of hierarchical multilayered flower-like assemblies of Ag doped Bi2WO6 and their photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Dumrongrojthanath, Phattharanit; Thongtem, Titipun; Phuruangrat, Anukorn; Thongtem, Somchai

    2013-12-01

    In this research, 0-3 mol% Ag doped Bi2WO6 hierarchical multilayered flower-like assemblies were successfully synthesized by a simple hydrothermal method at 180 °C for 24 h. The XRD, FE-SEM, FTIR and Raman analyses revealed the presence of flower-like Russellite Bi2WO6 structures which were constructed from a large number of orderly arranged 2D layers of interconnected nanoplates. Their photocatalytic activities were evaluated by photodegradation of rhodamine B (RhB) under Xe visible light irradiation (λ > 420 nm). The 3 mol% Ag doped Bi2WO6 showed the highest photocatalytic activities of 98.20% within 180 min.

  17. Synthesis, characterizations and anti-bacterial activities of pure and Ag doped CdO nanoparticles by chemical precipitation method

    NASA Astrophysics Data System (ADS)

    Sivakumar, S.; Venkatesan, A.; Soundhirarajan, P.; Khatiwada, Chandra Prasad

    2015-02-01

    In the present study, synthesized pure and Ag (1%, 2%, and 3%) doped Cadmium Oxide (CdO) nanoparticles by chemical precipitation method. Then, the synthesized products were characterized by thermo gravimetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD) analysis, Fourier transform infrared (FT-IR) spectroscopy, Ultra violet-Vis diffused reflectance spectroscopy (UV-Vis-DRS), Scanning electron microscopy (SEM), Energy dispersive X-rays (EDX) spectroscopy, and anti-bacterial activities, respectively. The transition temperatures and phase transitions of Cd(OH)2 to CdO at 400 °C was confirmed by TG-DTA analysis. The XRD patterns show the cubic shape and average particle sizes are 21, 40, 34, and 37 nm, respectively for pure and Ag doped samples. FT-IR study confirmed the presence of CdO and Ag at 677 and 459 cm-1, respectively. UV-Vis-DRS study shows the variation on direct and indirect band gaps. The surface morphologies and elemental analysis have been confirmed from SEM and with EDX. In addition, the synthesized products have been characterized by antibacterial activities against Gram-positive and negative bacteria. Further, the present investigation suggests that CdO nanoparticles have the great potential applications on various industrial and medical fields of research.

  18. Attempt of Deposition of Ag-Doped Amorphous Carbon Film by Ag-Cathode DC Plasma with CH4 Flow.

    PubMed

    Tsubota, Toshiki; Kuratsu, Kazuhiro; Murakami, Naoya; Ohno, Teruhisa

    2015-06-01

    A simple DC plasma apparatus having large Ag cathode with CH4 flow was used for the attempt to prepare Ag-doped amorphous carbon film. As the gaseous source, CH4 and the additive (N2 or Ar) were used for the plasma process. When N2 was the additive, the substrate surfaces after the plasma process were electrical conductor although high electrical resistance. The growth rate of the deposits decreased with increasing the amount of N2, and the deposits contained nitrogen. Although the small amount of silver was detected by XPS, the peak for Ag may not be in the carbon deposit but be in interlayer formed at Ar etching process. When Ar was the additive, the substrate surfaces after the plasma process were also electrical conductor although high electrical resistance. The growth rate of the deposits was almost independent of the amount of Ar, and the deposits contained no argon. The small XPS peaks for Ag may not be in the carbon deposit but be in interlayer formed at Ar etching process. Both the prepared samples had high antibiotic property. The method of this study could be used for the surface reforming with amorphous carbon coating having electrical conductivity and antibiotic property. PMID:26369089

  19. Tuning of Ag doped core-shell ZnO NWs/Cu2O grown by electrochemical deposition

    NASA Astrophysics Data System (ADS)

    Makhlouf, Houssin; Messaoudi, Olfa; Souissi, Ahmed; Ben Assaker, Ibtissem; Oueslati, Mihrez; Bechelany, Mikhael; Chtourou, Radhouane

    2015-09-01

    ZnO nanowires (NWs)/Cu2O-Ag core-shell nanostructures (NSs) have been synthesized by electrochemical deposition method on ITO-coated glass substrates in order to improve the efficiency of the type-II transition of core-shell ZnO NWs/Cu2O-Ag NSs. The morphologies of the obtained NSs were studied by scanning electron microscopy confirming the presence of core-shell NSs. The crystalline proprieties were analyzed by x-ray diffraction and micro-Raman measurement: wurtzite ZnO and cuprit Cu2O phase were founded. The presence of Ag content in core-shell NS was detected by EDX. Optical measurement reveals an additional contribution δE at about 1.72 eV attributed to the type-II interfacial transition between the valance band of cuprit-Cu2O and the conduction band of W-ZnO. The effect of the Ag doping into the type-II transition was investigated. A red shift of the type-II transition was detected according to the Ag concentration. These materials could have potential applications in photocatalytic and photovoltaic fields.

  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. Photocatalytic comparison of Cu- and Ag-doped TiO2/GF for bioaerosol disinfection under visible light

    NASA Astrophysics Data System (ADS)

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2015-12-01

    Photocatalysts, TiO2/glass fiber (TiO2/GF), Cu-doped TiO2/glass fiber (Cu-TiO2/GF) and Ag-doped TiO2/glass fiber (Ag-TiO2/GF), were synthesized by a sol-gel method. They were then used to disinfect Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in bioaerosols under visible light irradiation. TiO2/GF did not show any significant disinfection effect. Both Cu and Ag acted as intermediate agents to enhance separation efficiency of electron-hole pairs of TiO2, leading to improved photocatalytic activity of Cu-TiO2/GF and Ag-TiO2/GF under visible light. Cu in Cu-TiO2/GF acted as a defective agent, increasing the internal quantum efficiency of TiO2, while Ag in Ag-TiO2/GF acted as a sensitive agent, enhancing the transfer efficiency of the electrons generated. The highest disinfection efficiencies of E. coli and S. aureus by Cu-TiO2/GF were 84.85% and 65.21%, respectively. The highest disinfection efficiencies of E. coli and S. aureus by Ag-TiO2/GF were 94.46% and 73.12%, respectively. Among three humidity conditions - 40±5% (dry), 60±5% (moderate), and 80±5% (humid) - the moderate humidity condition showed the highest disinfection efficiency for both E. coli and S. aureus. This study also showed that a Gram-negative bacterium (E. coli) were more readily disinfected by the photocatalysts than a Gram-positive bacterium (S. aureus).

  2. Visible-Light-Responsive Photocatalysis: Ag-Doped TiO2 Catalyst Development and Reactor Design Testing

    NASA Technical Reports Server (NTRS)

    Coutts, Janelle L.; Hintze, Paul E.; Meier, Anne; Shah, Malay G.; Devor, Robert W.; Surma, Jan M.; Maloney, Phillip R.; Bauer, Brint M.; Mazyck, David W.

    2016-01-01

    In recent years, the alteration of titanium dioxide to become visible-light-responsive (VLR) has been a major focus in the field of photocatalysis. Currently, bare titanium dioxide requires ultraviolet light for activation due to its band gap energy of 3.2 eV. Hg-vapor fluorescent light sources are used in photocatalytic oxidation (PCO) reactors to provide adequate levels of ultraviolet light for catalyst activation; these mercury-containing lamps, however, hinder the use of this PCO technology in a spaceflight environment due to concerns over crew Hg exposure. VLR-TiO2 would allow for use of ambient visible solar radiation or highly efficient visible wavelength LEDs, both of which would make PCO approaches more efficient, flexible, economical, and safe. Over the past three years, Kennedy Space Center has developed a VLR Ag-doped TiO2 catalyst with a band gap of 2.72 eV and promising photocatalytic activity. Catalyst immobilization techniques, including incorporation of the catalyst into a sorbent material, were examined. Extensive modeling of a reactor test bed mimicking air duct work with throughput similar to that seen on the International Space Station was completed to determine optimal reactor design. A bench-scale reactor with the novel catalyst and high-efficiency blue LEDs was challenged with several common volatile organic compounds (VOCs) found in ISS cabin air to evaluate the system's ability to perform high-throughput trace contaminant removal. The ultimate goal for this testing was to determine if the unit would be useful in pre-heat exchanger operations to lessen condensed VOCs in recovered water thus lowering the burden of VOC removal for water purification systems.

  3. Ag doped hollow TiO2 nanoparticles as an effective green fungicide against Fusarium solani and Venturia inaequalis phytopathogens.

    PubMed

    Boxi, Siddhartha Sankar; Mukherjee, Khushi; Paria, Santanu

    2016-02-26

    Chemical-based pesticides are widely used in agriculture to protect crops from insect infestation and diseases. However, the excessive use of highly toxic pesticides causes several human health (neurological, tumor, cancer) and environmental problems. Therefore nanoparticle-based green pesticides have become of special importance in recent years. The antifungal activities of pure and Ag doped (solid and hollow) TiO2 nanoparticles are studied against two potent phytopathogens, Fusarium solani (which causes Fusarium wilt disease in potato, tomato, etc) and Venturia inaequalis (which causes apple scab disease) and it is found that hollow nanoparticles are more effective than the other two. The antifungal activities of the nanoparticles were further enhanced against these two phytopathogens under visible light exposure. The fungicidal effect of the nanoparticles depends on different parameters, such as particle concentration and the intensity of visible light. The minimum inhibitory dose of the nanoparticles for V. inaequalis and F. solani are 0.75 and 0.43 mg/plate. The presence of Ag as a dopant helps in the formation of stable Ag-S and disulfide bonds (R-S-S-R) in cellular protein, which leads to cell damage. During photocatalysis generated (•)OH radicals loosen the cell wall structure and this finally leads to cell death. The mechanisms of the fungicidal effect of nanoparticles against these two phytopathogens are supported by biuret and triphenyl tetrazolium chloride analyses and field emission electron microscopy. Apart from the fungicidal effect, at a very low dose (0.015 mg/plate) the nanoparticles are successful in arresting production of toxic napthoquinone pigment for F. solani which is related to the fungal pathogenecity. The nanoparticles are found to be effective in protecting potatoes affected by F. solani or other fungi from spoiling. PMID:26808118

  4. Ag doped hollow TiO2 nanoparticles as an effective green fungicide against Fusarium solani and Venturia inaequalis phytopathogens

    NASA Astrophysics Data System (ADS)

    Sankar Boxi, Siddhartha; Mukherjee, Khushi; Paria, Santanu

    2016-02-01

    Chemical-based pesticides are widely used in agriculture to protect crops from insect infestation and diseases. However, the excessive use of highly toxic pesticides causes several human health (neurological, tumor, cancer) and environmental problems. Therefore nanoparticle-based green pesticides have become of special importance in recent years. The antifungal activities of pure and Ag doped (solid and hollow) TiO2 nanoparticles are studied against two potent phytopathogens, Fusarium solani (which causes Fusarium wilt disease in potato, tomato, etc) and Venturia inaequalis (which causes apple scab disease) and it is found that hollow nanoparticles are more effective than the other two. The antifungal activities of the nanoparticles were further enhanced against these two phytopathogens under visible light exposure. The fungicidal effect of the nanoparticles depends on different parameters, such as particle concentration and the intensity of visible light. The minimum inhibitory dose of the nanoparticles for V. inaequalis and F. solani are 0.75 and 0.43 mg/plate. The presence of Ag as a dopant helps in the formation of stable Ag-S and disulfide bonds (R-S-S-R) in cellular protein, which leads to cell damage. During photocatalysis generated •OH radicals loosen the cell wall structure and this finally leads to cell death. The mechanisms of the fungicidal effect of nanoparticles against these two phytopathogens are supported by biuret and triphenyl tetrazolium chloride analyses and field emission electron microscopy. Apart from the fungicidal effect, at a very low dose (0.015 mg/plate) the nanoparticles are successful in arresting production of toxic napthoquinone pigment for F. solani which is related to the fungal pathogenecity. The nanoparticles are found to be effective in protecting potatoes affected by F. solani or other fungi from spoiling.

  5. Nanocrystalline ceramic materials

    DOEpatents

    Siegel, Richard W.; Nieman, G. William; Weertman, Julia R.

    1994-01-01

    A method for preparing a treated nanocrystalline metallic material. The method of preparation includes providing a starting nanocrystalline metallic material with a grain size less than about 35 nm, compacting the starting nanocrystalline metallic material in an inert atmosphere and annealing the compacted metallic material at a temperature less than about one-half the melting point of the metallic material.

  6. Hardness and microplasticity of nanocrystalline and amorphous calcium phosphate coatings

    NASA Astrophysics Data System (ADS)

    Ievlev, V. M.; Kostyuchenko, A. V.; Darinskii, B. M.; Barinov, S. M.

    2014-02-01

    The hardness of thin (1.0-4.0 μm) hydroxyapatite coatings with different structures (nanocrystalline, amorphous-crystalline, and amorphous) grown by rf magnetron sputtering on Ti and Si plates has been studied using the nanoindentation method. All the grown structures are characterized by the strain which has reversible and irreversible components. The hardness of nanocrystalline coatings (about 10 GPa) corresponds to the average hardness of hydroxyapatite single crystals. The structure of nanocrystalline coatings in the indentation zone and outside it has been investigated and changes in the structure under the indenter have been revealed using high-resolution transmission electron microscopy. From a comparison of the hardnesses of coatings with different structures and based on an analysis of the intragranular structure, it has been assumed that the plastic deformation occurs according to a dislocation-free mechanism. The plastic deformation is interpreted in terms of the cluster representation of the hydroxyapatite structure and amorphous calcium phosphates of the same elemental composition and cluster-boundary sliding during the deformation.

  7. 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.

  8. Structural and optical properties of Ag-doped copper oxide thin films on polyethylene napthalate substrate prepared by low temperature microwave annealing

    SciTech Connect

    Das, Sayantan; Alford, T. L.

    2013-06-28

    Silver doped cupric oxide thin films are prepared on polyethylene naphthalate (flexible polymer) substrates. Thin films Ag-doped CuO are deposited on the substrate by co-sputtering followed by microwave assisted oxidation of the metal films. The low temperature tolerance of the polymer substrates led to the search for innovative low temperature processing techniques. Cupric oxide is a p-type semiconductor with an indirect band gap and is used as selective absorption layer solar cells. X-ray diffraction identifies the CuO phases. Rutherford backscattering spectrometry measurements confirm the stoichiometry of each copper oxide formed. The surface morphology is determined by atomic force microscopy. The microstructural properties such as crystallite size and the microstrain for (-111) and (111) planes are calculated and discussed. Incorporation of Ag led to the lowering of band gap in CuO. Consequently, it is determined that Ag addition has a strong effect on the structural, morphological, surface, and optical properties of CuO grown on flexible substrates by microwave annealing. Tauc's plot is used to determine the optical band gap of CuO and Ag doped CuO films. The values of the indirect and direct band gap for CuO are found to be 2.02 eV and 3.19 eV, respectively.

  9. Ag Doping Effects on Y0.5Gd0.5Ba2Cu3O7-δ multilayers derived by low-fluorine metalorganic solution deposition

    NASA Astrophysics Data System (ADS)

    Sun, M. J.; Yang, W. T.; Liu, Z. Y.; Bai, C. Y.; Guo, Y. Q.; Lu, Y. M.; Lu, Q.; Cai, C. B.

    2015-09-01

    Various artificial multilayers consisting of Y0.5Gd0.5Ba2Cu3O7-δ (YGdBCO) superconducting films were built up on an oxide buffered Hastelloy substrate using the low-fluorine metallorganic deposition method (MOD). Microscopic and superconducting performances are studied on composite YGdBCO multilayer films with and without alternate ultrathin layers of Ag, which comparatively demonstrates the Ag doping effects in such architectures. X-ray diffraction and scanning electron microscopy imply that the growth thermodynamic parameters of the YGdBCO are modified, resulting in a better c-axis orientation and a higher in-plane texture, as well as a superior surface, and finally give rise to great improvement of superconducting performance. To understand the above Ag doping effects further, the critical Gibbs free energy ΔG*(r) on nucleation of MOD-YGdBCO films on the biaxially textured buffer layers is analyzed with respect to the additions of Ag, which shows the competition between a-axis and c-axis growths subject to supersaturation. As a consequence, Ag additions may reduce the supersaturation at the growth interfaces, and hence give rise to a wider window of c-axis nucleation.

  10. Nanophase hydroxyapatite coatings for dental and orthopedic applications

    NASA Astrophysics Data System (ADS)

    Sato, Michiko

    In order to improve dental and orthopedic implant performance, the objective of this study was to synthesize nanocrystalline hydroxyapatite (HA) powders to coat metals (specifically, titanium and tantalum). Precipitated HA powders were either sintered in order to produce UltraCaP HA (or microcrystalline size HA) or were treated hydrothermally to produce nanocrystalline HA. Some of the UltraCaP and nanocrystalline HA powders were doped with yttrium (Y) since previous in vitro studies demonstrated that Y-doped HA in bulk improved osteoblast (or bone-forming cell) function over undoped HA. The nanocrystalline HA powders were also mixed with nanophase titania powders because previous studies demonstrated that titania/HA composite coatings increased coating adhesive strength and HA nucleation. These powders were then deposited onto titanium by a novel room-temperature process, called IonTiteT(TM). The results demonstrated that the chemical properties and crystallite size of the original HA powders were maintained in the coatings. More importantly, in vitro studies showed increased osteoblast (bone-forming cell) adhesion on the single phase nanocrystalline HA and nano-titania/HA coatings compared to traditionally used plasma-sprayed HA coatings and uncoated metals. Results further demonstrated greater amounts of calcium deposition by osteoblasts cultured on nanocrystalline HA coatings compared to UltraCaP coatings and conventionally used plasma-sprayed HA coatings. To elucidate mechanisms that influenced osteoblast functions on the HA coatings, the amount of proteins (fibronectin and vitronectin) onto the HA powders and the adsorbed fibronectin conformation were investigated. Exposure of cell integrin binding domains (in fibronectin III10 segments) was greater in fibronectin adsorbed onto 1.2 mole% Y-doped UltraCaP HA coatings compared to nanocrystalline HA coatings tested. However, 1.2 mole% Y-doped UltraCaP HA coatings did not increase mineralization by osteoblasts

  11. Room-temperature NH3 gas sensors based on Ag-doped γ-Fe2O3/SiO2 composite films with sub-ppm detection ability.

    PubMed

    Tang, Yongliang; Li, Zhijie; Zu, Xiaotao; Ma, Jinyi; Wang, Lu; Yang, Jing; Du, Bo; Yu, Qingkai

    2015-11-15

    In this report, NH3 gas sensors based on Ag-doped γ-Fe2O3/SiO2 composite films are investigated. The composite films were prepared with a sol-gel process, and the films' electrical resistance responded to the change of NH3 concentration in the environment. The SEM and AFM investigations showed that the films had a porous structure, and the XRD investigation indicated that the size of Ag particles changed with the modification of Ag loading content. Through a comparative gas sensing study among the Ag-doped composite films, undoped composite film, γ-Fe2O3 film, and SiO2 film, the Ag-doped composite films were found to be much more sensitive than the sensors based on the undoped composite film and γ-Fe2O3 film at room temperature, indicating the significant influences of the SiO2 and Ag on the sensing property. Moreover, the sensor based on Ag-doped (4%) γ-Fe2O3/SiO2 composite film was able to detect the NH3 gas at ppb level. Conversely, the responses of the sensor to other test gases (C2H5OH, CO, H2, CH4 and H2S) were all markedly low, suggesting excellent selectivity. PMID:26057440

  12. Nanocrystalline ceramic materials

    DOEpatents

    Siegel, R.W.; Nieman, G.W.; Weertman, J.R.

    1994-06-14

    A method is disclosed for preparing a treated nanocrystalline metallic material. The method of preparation includes providing a starting nanocrystalline metallic material with a grain size less than about 35 nm, compacting the starting nanocrystalline metallic material in an inert atmosphere and annealing the compacted metallic material at a temperature less than about one-half the melting point of the metallic material. 19 figs.

  13. 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

  14. 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.

  15. High-Pressure Synthesis and Superconductivity of Ag-Doped Topological Crystalline Insulator SnTe (Sn1-xAgxTe with x = 0-0.5)

    NASA Astrophysics Data System (ADS)

    Mizuguchi, Yoshikazu; Miura, Osuke

    2016-05-01

    We have synthesized single-phase polycrystalline samples of Sn1-xAgxTe, i.e., the Ag-doped topological crystalline insulator SnTe, with a range of x ≤ 0.5 by a high-pressure synthesis method. The crystal structure of Sn1-xAgxTe at room temperature is a cubic NaCl type structure, which does not vary upon Ag substitution. Bulk superconductivity with a transition temperature of 2.4 K was observed for x = 0.15-0.25, and the optimal Ag content was x = 0.2. The Sn1-xAgxTe superconducting phase will be useful for understanding the superconductive nature and mechanisms of the carrier-doped SnTe system.

  16. Deposition, structure, physical and invitro characteristics of Ag-doped β-Ca3(PO4)2/chitosan hybrid composite coatings on Titanium metal.

    PubMed

    Singh, Ram Kishore; Awasthi, Sharad; Dhayalan, Arunkumar; Ferreira, J M F; Kannan, S

    2016-05-01

    Pure and five silver-doped (0-5Ag) β-tricalcium phosphate [β-TCP, β-Ca3(PO4)2]/chitosan composite coatings were deposited on Titanium (Ti) substrates and their properties that are relevant for applications in hard tissue replacements were assessed. Silver, β-TCP and chitosan were combined to profit from their salient and complementary antibacterial and biocompatible features.The β-Ca3(PO4)2 powders were synthesized by co-precipitation. The characterization results confirmed the Ag(+) occupancy at the crystal lattice of β-Ca3(PO4)2. The Ag-dopedβ-Ca3(PO4)2/chitosan composite coatings deposited by electrophoresis showed good antibacterial activity and exhibited negative cytotoxic effects towards the human osteosarcoma cell line MG-63. The morphology of the coatings was observed by SEM and their efficiency against corrosion of metallic substrates was determined through potentiodynamic polarization tests. PMID:26952474

  17. One-pot synthesis of Ag+ doped BiVO4 microspheres with enhanced photocatalytic activity via a facile hydrothermal method

    NASA Astrophysics Data System (ADS)

    Zhu, Shiwen; Li, Quanguo; Li, Feng; Cao, Wei; Li, Taohai

    2016-05-01

    The Ag+/BiVO4 photocatalyst was fabricated through a facile hydrothermal method by using K6V10O28·9H2O as the vanadium source. The impact of Ag+ on the product's structure and morphology was studied. It was shown that the amount of Ag+ has no effect on the product's crystal phases but plays an important role on the morphology of the nanoparticles that construct the shell of BiVO4 microspheres. In addition, the Ag+-doped photocatalysts have much higher photocatalytic activities in removing RhB and MB under the UV light illumination than the pure BiVO4. A possible photocatalytic mechanism was proposed in photoexcitation of the BiVO4 electrons which subsequently captured by the dopant. The present work may offer a novel route to reach higher photocatalytic activity by doping the Ag+ in the semiconductor catalysts.

  18. Low-Temperature Preparation of Ag-Doped ZnO Nanowire Arrays, DFT Study, and Application to Light-Emitting Diode.

    PubMed

    Pauporté, Thierry; Lupan, Oleg; Zhang, Jie; Tugsuz, Tugba; Ciofini, Ilaria; Labat, Frédéric; Viana, Bruno

    2015-06-10

    Doping ZnO nanowires (NWs) by group IB elements is an important challenge for integrating nanostructures into functional devices with better and tuned performances. The growth of Ag-doped ZnO NWs by electrodeposition at 90 °C using a chloride bath and molecular oxygen precursor is reported. Ag acts as an electrocatalyst for the deposition and influences the nucleation and growth of the structures. The silver atomic concentration in the wires is controlled by the additive concentration in the deposition bath and a content up to 3.7 atomic % is reported. XRD analysis shows that the integration of silver enlarges the lattice parameters of ZnO. The optical measurements also show that the direct optical bandgap of ZnO is reduced by silver doping. The bandgap shift and lattice expansion are explained by first principle calculations using the density functional theory (DFT) on the silver impurity integration as an interstitial (Ag(i)) and as a substitute of zinc atom (Ag(Zn)) in the crystal lattice. They notably indicate that Ag(Zn) doping forms an impurity band because of Ag 4d and O 2p orbital interactions, shifting the Fermi level toward the valence band. At least, Ag-doped ZnO vertically aligned nanowire arrays have been epitaxially grown on GaN(001) substrate. The heterostructure has been inserted in a light emitting device. UV-blue light emission has been achieved with a low emission threshold of 5 V and a tunable red-shifted emission spectrum related to the bandgap reduction induced by silver doping of the ZnO emitter material. PMID:25990263

  19. Synthesis of Ag-doped TiO2 nanoparticles by combining laser decomposition of titanium isopropoxide and ablation of Ag for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Al-Kamal, Ahmed Kamal

    Nanostructured powders of TiO2 and Ag-doped TiO2 are synthesized by a novel pulsed-laser process that combines laser ablation of a silver (Ag) disc with laser decomposition of a titanium tetra-isopropoxide (TTIP) solution. Nanoparticles are formed by rapid condensation of vaporized species in the plasma plume generated by the high power laser, resulting in the formation of rapidly quenched Ag-doped TiO2 nanoparticles that have far-from-equilibrium or metastable structures. The uniqueness of the new ablation process is that it is a one-step process, in contrast to the two-step process developed by previous researchers in the field. Moreover, its ability to synthesize an extended-solid solution phase of Ag in TiO 2 may also be unique. The present work implies that other oxide phases, such as Al2O3, MgO and MgAl2O4, can be doped with normally insoluble metals, such as Pt and Ir, thus opening new opportunities for catalytic applications. Again, there is the prospect of being able to synthesize nanopowders of diamond, c-BN, and mixtures thereof, which are of interest for applications in machine tools, rock-drill bits, and lightweight armor. A wet-chemistry method is also investigated, which has much in common with that adopted by previous workers in the field. However, photo-voltaic properties do not measure up to expectations based on published data. A possible explanation is that the selected Ag concentrations are too high, so that recombination of holes and electrons occurs via a quantum-tunneling mechanism reduces photo-activity. Future work, therefore, will investigate lower concentrations of Ag dopant in TiO2, while also examining the effects of metastable states, including extended solid solution, amorphous, and semi-crystalline structures.

  20. Creating bulk nanocrystalline metal.

    SciTech Connect

    Fredenburg, D. Anthony; Saldana, Christopher J.; Gill, David D.; Hall, Aaron Christopher; Roemer, Timothy John; Vogler, Tracy John; Yang, Pin

    2008-10-01

    Nanocrystalline and nanostructured materials offer unique microstructure-dependent properties that are superior to coarse-grained materials. These materials have been shown to have very high hardness, strength, and wear resistance. However, most current methods of producing nanostructured materials in weapons-relevant materials create powdered metal that must be consolidated into bulk form to be useful. Conventional consolidation methods are not appropriate due to the need to maintain the nanocrystalline structure. This research investigated new ways of creating nanocrystalline material, new methods of consolidating nanocrystalline material, and an analysis of these different methods of creation and consolidation to evaluate their applicability to mesoscale weapons applications where part features are often under 100 {micro}m wide and the material's microstructure must be very small to give homogeneous properties across the feature.

  1. Microstructure and temperature dependence of microwave penetration depth of Ag doped Y 1Ba 2Cu 3O 7- x thin films

    NASA Astrophysics Data System (ADS)

    Kaur, Davinder; Pai, S. P.; Jesudasan, J.; Pinto, R.

    2004-06-01

    We report the measurements of magnetic penetration depth λ( T) of Ag-doped YBa 2Cu 3O 7- δ (YBCO) thin films in the thickness range 1500-4000 A and temperature range 18-88 K. The films are in situ grown by laser ablation on <1 0 0> LaAlO 3 substrates. The penetration depth measurements are performed by microstrip resonator technique. A correlation of λ( T) with the film microstructure observed with atomic force microscopy has shown that λ( T) depends critically on the film microstructure. Temperature dependence of magnetic penetration depth has also been studied for best quality films. The experimental results are discussed in terms of BCS theory (s-wave pairing) and d-wave Pairing with and without unitary scattering. The results are found to be best fitted to the d-wave model with unitary scattering limit. Near Tc, we have also compare the (3D) XY critical regime and the Ginzburg-Landau (GL) behaviour.

  2. Fluorometric sensing of ultralow As(III) concentrations using Ag doped hollow CdS/ZnS bi-layer nanoparticles.

    PubMed

    Boxi, Siddhartha Sankar; Paria, Santanu

    2015-12-21

    Arsenic poisoning from drinking water has been an important global issue in recent years. Because of the high level toxicity of arsenic to human health, an easy, inexpensive, low level and highly selective detection technique is of great importance to take any early precautions. This study reports the synthesis of Ag doped hollow CdS/ZnS bi-layer (Ag-h-CdS/ZnS) nanoparticles for the easy fluorometric determination of As(iii) ions in the aqueous phase. The hollow bi-layer structures were synthesized by a sacrificial core method using AgBr as the sacrificial core and the core was removed by dissolution in an ammonium hydroxide solution. The synthesized nanoparticles were characterized using different instrumental techniques. A good linear relationship was obtained between fluorescence quenching intensity and As(iii) concentration in the range of 0.75-22.5 μg L(-1) at neutral pH with a limit of detection as low as 0.226 μg L(-1). PMID:26541652

  3. 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.

  4. Biological and bactericidal properties of Ag-doped bioactive glass in a natural extracellular matrix hydrogel with potential application in dentistry.

    PubMed

    Wang, Y-Y; Chatzistavrou, X; Faulk, D; Badylak, S; Zheng, L; Papagerakis, S; Ge, L; Liu, H; Papagerakis, P

    2015-01-01

    The aim of this study was the fabrication and evaluation of a novel bioactive and bactericidal material, which could have applications in dentistry by supporting tissue regeneration and killing oral bacteria. Our hypothesis was that a new scaffold for pulp-dentin tissue engineering with enhanced antibacterial activity could be obtained by associating extracellular matrix derived from porcine bladder with an antibacterial bioactive glass. Our study combines in vitro approaches and ectopic implantation in scid mice. The novel material was fabricated by incorporating a sol-gel derived silver (Ag)-doped bioactive glass (BG) in a natural extracellular matrix (ECM) hydrogel in ratio 1:1 in weight % (Ag-BG/ECM). The biological properties of the Ag-BG/ECM were evaluated in culture with dental pulp stem cells (DPSCs). In particular, cell proliferation, cell apoptosis, stem cells markers profile, and cell differentiation potential were studied. Furthermore, the antibacterial activity against Streptococcus mutans and Lactobacillus casei was measured. Moreover, the capability of the material to enhance pulp/dentin regeneration in vivo was also evaluated. Our data show that Ag-BG/ECM significantly enhances DPSCs' proliferation, it does not affect cell morphology and stem cells markers profile, protects cells from apoptosis, and enhances in vitro cell differentiation and mineralisation potential as well as in vivo dentin formation. Furthermore, Ag-BG/ECM strongly inhibits S. mutans and L. casei growth suggesting that the new material has also anti-bacterial properties. This study provides foundation for future clinical applications in dentistry. It could potentially advance the currently available options of dental regenerative materials. PMID:26091732

  5. Nanocrystalline Heterojunction Materials

    DOEpatents

    Elder, Scott H.; Su, Yali; Gao, Yufei; Heald, Steve M.

    2004-02-03

    Mesoporous nanocrystalline titanium dioxide heterojunction materials and methods of making the same are disclosed. In one disclosed embodiment, materials comprising a core of titanium dioxide and a shell of a molybdenum oxide exhibit a decrease in their photoadsorption energy as the size of the titanium dioxide core decreases.

  6. Nanocrystalline heterojunction materials

    DOEpatents

    Elder, Scott H.; Su, Yali; Gao, Yufei; Heald, Steve M.

    2003-07-15

    Mesoporous nanocrystalline titanium dioxide heterojunction materials are disclosed. In one disclosed embodiment, materials comprising a core of titanium dioxide and a shell of a molybdenum oxide exhibit a decrease in their photoadsorption energy as the size of the titanium dioxide core decreases.

  7. Mechanical, In Vitro Antimicrobial and Biological Properties of Plasma Sprayed Silver-Doped Hydroxyapatite Coating

    PubMed Central

    Roy, Mangal; Fielding, Gary A.; Beyenal, Haluk; Bandyopadhyay, Amit; Bose, Susmita

    2012-01-01

    Implant related infection is one of the key concerns in total joint hip arthroplasties. In order to reduce bacterial adhesion, silver (Ag) / silver oxide (Ag2O) doping was used in plasma sprayed hydroxyapatite (HA) coating on titanium substrate. HA powder was doped with 2.0, 4.0 and 6.0 wt% Ag, heat treated at 800 °C and used for plasma spray coating using a 30 kW plasma spray system, equipped with supersonic nozzle. Application of supersonic plasma nozzle significantly reduced phase decomposition and amorphous phase formation in the HA coatings as evident by X-ray diffraction (XRD) study and Fourier transformed infrared spectroscopic (FTIR) analysis. Adhesive bond strength of more than 15 MPa ensured the mechanical integrity of the coatings. Resistance against bacterial adhesion of the coatings was determined by challenging them against Pseudomonas Aeruginosa (PAO1). Live/Dead staining of the adherent bacteria on the coating surfaces indicated a significant reduction in bacterial adhesion due to the presence of Ag. In vitro cell-material interactions and alkaline phosphatase (ALP) protein expressions were evaluated by culturing human fetal osteoblast cells (hFOB). Present results suggest that the plasma sprayed HA coatings doped with an optimum amount of Ag can have excellent antimicrobial property without altering mechanical property of the Ag doped HA coatings. PMID:22313742

  8. Mechanical, in vitro antimicrobial, and biological properties of plasma-sprayed silver-doped hydroxyapatite coating.

    PubMed

    Roy, Mangal; Fielding, Gary A; Beyenal, Haluk; Bandyopadhyay, Amit; Bose, Susmita

    2012-03-01

    Implant-related infection is one of the key concerns in total joint hip arthroplasties. To reduce bacterial adhesion, we used silver (Ag)/silver oxide (Ag(2)O) doping in plasma sprayed hydroxyapatite (HA) coating on titanium substrate. HA powder was doped with 2.0, 4.0, and 6.0 wt % Ag, heat-treated at 800 °C and used for plasma spray coating using a 30 kW plasma spray system, equipped with supersonic nozzle. Application of supersonic plasma nozzle significantly reduced phase decomposition and amorphous phase formation in the HA coatings as evident by X-ray diffraction (XRD) study and Fourier transformed infrared spectroscopic (FTIR) analysis. Adhesive bond strength of more than 15 MPa ensured the mechanical integrity of the coatings. Resistance against bacterial adhesion of the coatings was determined by challenging them against Pseudomonas aeruginosa (PAO1). Live/dead staining of the adherent bacteria on the coating surfaces indicated a significant reduction in bacterial adhesion due to the presence of Ag. In vitro cell-material interactions and alkaline phosphatase (ALP) protein expressions were evaluated by culturing human fetal osteoblast cells (hFOB). Our results suggest that the plasma-sprayed HA coatings doped with an optimum amount of Ag can have excellent antimicrobial property without altering mechanical property of the Ag-doped HA coatings. PMID:22313742

  9. Mechanical properties of nanocrystalline cobalt

    NASA Astrophysics Data System (ADS)

    Karimpoor, Amir A.; Erb, Uwe

    2006-05-01

    Due to their excellent wear and corrosion properties, nanocrystalline cobalt and several cobalt alloys made by electrodeposition are currently being developed as environmentally benign replacement coatings for hard chromium electrodeposits. The focus of this study is on the mechanical properties of nanocrystalline cobalt, which are currently not well understood. A comparison is presented for hardness, tensile properties, Charpy impact properties and fracture surface analysis of both nanocrystalline (grain size: 12 nm) and conventional polycrystalline (grain size: 4.8 m) cobalt. It is shown that the hardness and tensile strength of nanocrystalline cobalt is 2-3 times higher than for polycrystalline cobalt. However, in contrast to other nanocrystalline materials tested previously, nanocrystalline cobalt retains considerable ductility with elongation to fracture values up to 7%.

  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. Nano-hydroxyapatite and its applications in preventive, restorative and regenerative dentistry: a review of literature

    PubMed Central

    Pepla, Erlind; Besharat, Lait Kostantinos; Palaia, Gaspare; Tenore, Gianluca; Migliau, Guido

    2014-01-01

    Summary This study aims to critically summarize the literature about nano-hydroxyapatite. The purpose of this work is to analyze the benefits of using nano-hydroxyapatite in dentistry, especially for its preventive, restorative and regenerative applications. We also provide an overview of new dental materials, still experimental, which contain the nano-hydroxyapatite in its nano-crystalline form. Hydroxyapatite is one of the most studied biomaterials in the medical field for its proven biocompatibility and for being the main constituent of the mineral part of bone and teeth. In terms of restorative and preventive dentistry, nano-hydroxyapatite has significant remineralizing effects on initial enamel lesions, certainly superior to conventional fluoride, and good results on the sensitivity of the teeth. The nano-HA has also been used as an additive material, in order to improve already existing and widely used dental materials, in the restorative field (experimental addition to conventional glass ionomer cements, that has led to significant improvements in their mechanical properties). Because of its unique properties, such as the ability to chemically bond to bone, to not induce toxicity or inflammation and to stimulate bone growth through a direct action on osteoblasts, nano-HA has been widely used in periodontology and in oral and maxillofacial surgery. Its use in oral implantology, however, is a widely used practice established for years, as this substance has excellent osteoinductive capacity and improves bone-to-implant integration. PMID:25506416

  12. 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.

  13. 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.

  14. 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.

  15. Processing of nanocrystalline ceramics

    SciTech Connect

    Ciftcioglu, M. . Center for Micro-Engineered Ceramics); Mayo, M.J. )

    1990-01-01

    Methods of preparing non-agglomerated powders for three systems -- yttria, titania, and yttria-stabilized zirconia -- are reviewed. The non-agglomerated nature of these powders should make it possible to sinter them into dense ceramic bodies with nanocrystalline grain sizes. Experiments with yttria-stabilized zirconia have shown that this is indeed the case, with mean linear intercept grain sizes of 60 nm resulting from original powder particle diameters of 13 nm. This ultrafine-grained zirconia is shown, in turn, to have superplastic forming rates 34 times faster than a 0.3 {mu}m-grained commercial zirconia of the same composition. 7 refs., 9 figs.

  16. Osteocalcin enhances bone remodeling around hydroxyapatite/collagen composites.

    PubMed

    Rammelt, Stefan; Neumann, Mirjam; Hanisch, Uwe; Reinstorf, Antje; Pompe, Wolfgang; Zwipp, Hans; Biewener, Achim

    2005-06-01

    The effect of osteocalcin (OC), an extracellular bone matrix protein, on bone healing around hydroxyapatite/collagen composites was investigated. Cylindrical nanocrystalline hydroxyapatite implants of 2.5-mm diameter containing 2.5% biomimetically mineralized collagen type I were inserted press-fit into the tibial head of adult Wistar rats. To one implant group, 10 mug/g OC was added. Six specimens per group were analyzed at 2, 7, 14, 28, and 56 days. After 14 days, newly formed woven bone had reached the implant surface of the OC implants whereas a broad fibrous interface could still be observed around controls. Woven bone was formed directly around both implant groups after 28 days and had been replaced partially by lamellar bone around the OC implants only. No significant differences in total bone contact were seen between both groups after 56 days. The higher number of phagocytosing cells and osteoclasts characterized immunohistochemically with ED1, cathepsin D, and tartate-resistant alkaline phosphatase around the OC implants at the early stages of bone healing suggests an earlier onset of bone remodeling. The earlier and increased expression of bone-specific matrix proteins and multifunctional adhesion proteins (osteopontin, bone sialoprotein, CD44) at the interface around the OC implants indicates that OC may accelerate bone formation and regeneration. This study supports the observations from in vitro studies that OC activates both osteoclasts and osteoblasts during early bone formation. PMID:15800855

  17. 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.

  18. 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

  19. Thermally deposited Ag-doped CdS thin film transistors with high-k rare-earth oxide Nd{sub 2}O{sub 3} as gate dielectric

    SciTech Connect

    Gogoi, P.

    2013-03-15

    The performance of thermally deposited CdS thin film transistors doped with Ag has been reported. Ag-doped CdS thin films have been prepared using chemical method. High dielectric constant rare earth oxide Nd{sub 2}O{sub 3} has been used as gate insulator. The thin film trasistors are fabricated in coplanar electrode structure on ultrasonically cleaned glass substrates with a channel length of 50 {mu}m. The thin film transistors exhibit a high mobility of 4.3 cm{sup 2} V{sup -1} s{sup -1} and low threshold voltage of 1 V. The ON-OFF ratio of the thin film transistors is found as 10{sup 5}. The TFTs also exhibit good transconductance and gain band-width product of 1.15 Multiplication-Sign 10{sup -3} mho and 71 kHz respectively.

  20. Preparation of nanocrystalline bredigite powders with apatite-forming ability by a simple combustion method

    SciTech Connect

    Huang Xianghui; Chang Jiang

    2008-06-03

    Nanocrystalline bredigite (Ca{sub 7}MgSi{sub 4}O{sub 16}) powders were synthesized by a simple solution combustion method. Phase pure bredigite powders with particle sizes ranging from 234 to 463 nm could be obtained at a relatively low temperature of 650 deg. C. The apatite-forming ability of the bredigite powders was examined by soaking them in a stimulated body fluid. The compositional and morphological changes of the powders before and after soaking were analyzed by X-ray diffraction and scanning electron microscopy and the results showed that hydroxyapatite was formed after soaking for 4 days.

  1. Processing and Characterization of Functionally Graded Hydroxyapatite Coatings for Biomedical Implants

    NASA Astrophysics Data System (ADS)

    Bai, Xiao

    the region near coating top surface is mostly amorphous. TEM/STEM observation of FGHA coating with incorporated Ag has also demonstrated that the metallic silver particles in size of 10 ˜ 50 nm distribute at the coating cross section throughout the coating thickness. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis have shown that coatings consist of HA and various calcium phosphate compounds. The pull off tests have shown that the average adhesion strength of FGHA coatings (both with and without Ag) to substrate are in the range of 83.44 +/- 5.71 ˜ 89.36 +/- 5.13 MPa. Further optical observation of pull off area of coating shows that no coating delamination is observed and epoxy failure is dominant, indicating a well-boned interface and a strong coating itself. It has been concluded that the high adhesion strength of coating to substrate is attributed to the atomic intermixed interface and dense structure of coating, which is resulted from the increased mobility of coating atoms at high substrate temperature under bombardment of assisted ion beam. Culture tests have shown a distinct increase in osteoblast cell attachment to FGHA surface after 24 hours culture test when compared to blank Ti controls. Both calcium and silver release tests of Ag-doped FGHA coatings have shown the release rate is high at the initial stage and it steadily decreases, which is the expected performance of FGHA coatings. Antibacterial test using S. aureus has revealed that Ag doped FGHA coatings show an inhibitory effect when compared to coating without Ag and blank Ti. In particular, with higher amounts of Ag in coatings, the inhibition of S. aureus is stronger. Cytotoxicity test indicates that the FGHA coating with the highest amounts of Ag shows a negative effect on the osteoblast response.

  2. 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

  3. 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.

  4. Dislocation dynamics in nanocrystalline nickel.

    PubMed

    Shan, Z W; Wiezorek, J M K; Stach, E A; Follstaedt, D M; Knapp, J A; Mao, S X

    2007-03-01

    It is believed that the dynamics of dislocation processes during the deformation of nanocrystalline materials can only be visualized by computational simulations. Here we demonstrate that observations of dislocation processes during the deformation of nanocrystalline Ni with grain sizes as small as 10 nm can be achieved by using a combination of in situ tensile straining and high-resolution transmission electron microscopy. Trapped unit lattice dislocations are observed in strained grains as small as 5 nm, but subsequent relaxation leads to dislocation recombination. PMID:17359167

  5. 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.

  6. LASER COMPRESSION OF NANOCRYSTALLINE METALS

    SciTech Connect

    Meyers, M. A.; Jarmakani, H. N.; Bringa, E. M.; Earhart, P.; Remington, B. A.; Vo, N. Q.; Wang, Y. M.

    2009-12-28

    Shock compression in nanocrystalline nickel is simulated over a range of pressures (10-80 GPa) and compared with experimental results. Laser compression carried out at Omega and Janus yields new information on the deformation mechanisms of nanocrystalline Ni. Although conventional deformation does not produce hardening, the extreme regime imparted by laser compression generates an increase in hardness, attributed to the residual dislocations observed in the structure by TEM. An analytical model is applied to predict the critical pressure for the onset of twinning in nanocrystalline nickel. The slip-twinning transition pressure is shifted from 20 GPa, for polycrystalline Ni, to 80 GPa, for Ni with g. s. of 10 nm. Contributions to the net strain from the different mechanisms of plastic deformation (partials, perfect dislocations, twinning, and grain boundary shear) were quantified in the nanocrystalline samples through MD calculations. The effect of release, a phenomenon often neglected in MD simulations, on dislocation behavior was established. A large fraction of the dislocations generated at the front are annihilated.

  7. In vitro and in vivo anticancer activity of surface modified paclitaxel attached hydroxyapatite and titanium dioxide nanoparticles.

    PubMed

    Venkatasubbu, G Devanand; Ramasamy, S; Reddy, G Pramod; Kumar, J

    2013-08-01

    Targeted drug delivery using nanocrystalline materials delivers the drug at the diseased site. This increases the efficacy of the drug in killing the cancer cells. Surface modifications were done to target the drug to a particular receptor on the cell surface. This paper reports synthesis of hydroxyapatite and titanium dioxide nanoparticles and modification of their surface with polyethylene glycol (PEG) followed by folic acid (FA). Paclitaxel, an anticancer drug, is attached to functionalized hydroxyapatite and titanium dioxide nanoparticles. The pure and functionalised nanoparticles are characterised with XRD, TEM and UV spectroscopy. Anticancer analysis was carried out in DEN induced hepatocarcinoma animals. Biochemical, hematological and histopathological analysis show that the surface modified paclitaxel attached nanoparticles have an higher anticancer activity than the pure paclitaxel and surface modified nanoparticles without paclitaxel. This is due to the targeting of the drug to the folate receptor in the cancer cells. PMID:23615724

  8. Thermal spraying of nanocrystalline materials

    NASA Astrophysics Data System (ADS)

    Lau, Maggy L.

    The present research addresses the fundamental synergism between thermal spray synthesis, microstructural evolution and mechanical behavior of Ni, Inconel 718 and Fe based 316-stainless steel nanocrystalline materials. Nanocrystalline Ni powders produced by mechanical milling in liquid nitrogen were investigated under isothermal and non-isothermal conditions. Significant grain growth occurred in the case of cryomilled Ni powders even when annealing at lower temperatures (equivalent to about 0.17 Tm), indicating the poor thermal stability of these powders. The activation energy for grain growth was calculated to be 146.2 kJ/mol. The values of the time exponent, n, were very close to 4.0, implying that grain growth was controlled by grain boundary diffusion mechanism. The grain growth behavior of the nanocrystalline Ni powders under non-isothermal annealing conditions showed good correspondence between the experimental results and the theoretical simulation. The grain growth behavior of the milled Inconel 718 powders and coatings, under isothermal annealing indicated that the nanocrystalline powders and coatings exhibited thermal stability against grain growth up to 1073 K (0.67Tm). The average grain sizes of methanol milled powders after annealing at 1273 K for 1 hr, cryomilled powders, HVOF coating of the methanol milled powders and HVOF coatings of the cryomilled Inconel 718 powders were 91, 84, 137 and 102 nm, respectively. In the present study, Zener pinning of nanoscale oxides of (Cr,Fe) contributed to the stability against grain growth during thermal annealing of the nanocrystalline Inconel 718 powders and coatings. (Abstract shortened by UMI.)

  9. Electronic structure and thermoelectric properties of p-type Ag-doped Mg₂Sn and Mg₂Sn{sub 1-x}Si{sub x} (x=0.05, 0.1)

    SciTech Connect

    Kim, Sunphil; Jin, Hyungyu; Wiendlocha, Bartlomiej; Tobola, Janusz; Heremans, Joseph P.

    2014-10-21

    An experimental and theoretical study of p-type Ag-doped Mg₂Sn and Mg₂Sn{sub 1-x}Si{sub x} (x=0.05, 0.1) is presented. Band structure calculations show that behavior of Ag in Mg₂Sn depends on the site it occupies. Based on Bloch spectral functions and density of states calculations, we show that if Ag substitutes for Sn, it is likely to form a resonant level; if it substitutes for Mg, a rigid-band-like behavior is observed. In both cases, the doped system should exhibit p-type conductivity. Experimentally, thermoelectric, thermomagnetic, and galvanomagnetic properties are investigated of p-type Mg₂Sn{sub 1–x}Si{sub x} (x=0, 0.05, 0.1) samples synthesized by a co-melting method in sealed crucibles. Ag effectively dopes the samples p-type, and thermoelectric power factors in excess of 20μW cm⁻¹K⁻² are observed in optimally doped samples. From the measured Seebeck coefficient, Nernst coefficient, and mobility, we find that the combination of acoustic phonon scattering, optical phonon scattering and defect scattering results in an energy-independent scattering rate. No resonant-like increase in thermopower is observed, which correlates well with electronic structure calculations assuming the location of Ag on Mg site.

  10. 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

  11. 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.

  12. 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

  13. Synthesis and characterization of silver doped hydroxyapatite nanocomposite coatings and evaluation of their antibacterial and corrosion resistance properties in simulated body fluid.

    PubMed

    Mirzaee, Majid; Vaezi, Mohammadreza; Palizdar, Yahya

    2016-12-01

    Silver-doped hydroxyapatite (Ca10-xAgx(PO4)6(OH)2-x) films were synthesized and deposited on anodized titanium (Ti) using electrophoretic. The influence of different silver-dopant contents (X=0, 0.02, 0.05, 0.08 and 0.1) on the phase formation and microstructure of the powders were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscope (XPS), and Fourier transform infrared spectrum analysis (FT-IR). XRD analysis confirmed the formation of Hexagonal structure of hydroxyapatite (HAp) annealed at 600°C with a small shift in the major peak position toward lower angles with adding silver. FT-IR spectroscopy disclosed the presence of the different vibrational modes matching to phosphates and hydroxyl groups and the absence of any band characteristics to silver. XPS analysis showed that 75% and 23% of silver was in the chemical states of Ag(2+) and Ag(+), respectively. However, only about 2% of silver was in the Ag(0) state, resulting in the high quality of nanocomposite films. The anodization treatment improves the bond strength between the Ag doped HAp deposited layers on TiO2. HAp and silver doped HAp (X=0.05) are regarded to be hydrophilic due to a large number of -OH groups on the surface. The sample with content of silver (x=0.05) also showed excellent antimicrobial efficacy (>99% reduction in viable cells). Electrochemical reveals the passive current densities of the HAp coated anodized Ti are lower than those of silver doped HAp coated anodized Ti, leading to a slightly lower corrosion resistance. PMID:27612761

  14. 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.

  15. Method of making nanocrystalline alpha alumina

    DOEpatents

    Siegel, Richard W.; Hahn, Horst; Eastman, Jeffrey A.

    1992-01-01

    Method of making selected phases of nanocrystalline ceramic materials. Various methods of controlling the production of nanocrystalline alpha alumina and titanium oxygen phases are described. Control of the gas atmosphere and use of particular oxidation treatments give rise to the ability to control the particular phases provided in the aluminum/oxygen and titanium/oxygen system.

  16. Facile and controllable synthesis of hydroxyapatite/graphene hybrid materials with enhanced sensing performance towards ammonia.

    PubMed

    Zhang, Qing; Liu, Yong; Zhang, Ying; Li, Huixia; Tan, Yanni; Luo, Lanlan; Duan, Junhao; Li, Kaiyang; Banks, Craig E

    2015-08-01

    In this work, needle-like and micro-spherical agglomerates of nanocrystalline hydroxyapatite (HA) were successfully assembled on the surface of graphene sheets with the aid of dopamine having two roles, as a template and a reductant for graphite oxide during the process of self-polymerization. The crystalline structure and micromorphology of HA can be conveniently regulated by controlling the mineralization route either with a precipitation (cHA/GR) or biomimetic methodology (bHA/GR). Both the composites exhibit improvements of ∼150% and ∼250% in sensitivity towards the sensing of ammonia at room temperature, compared with that of bare graphene. The combination of the multi-adsorption capability of HA and the electric conductivity of graphene is proposed to be the major reason for the observed enhancements. Gas sensing tests demonstrated that the HA/GR composites exhibit excellent selectivity, high sensitivity and repeatable stability towards the analytical sensing of ammonia. PMID:26066071

  17. 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

  18. Structural and Magnetic Studies on Nano-crystalline Biocompatible Glass/Glass-ceramic

    NASA Astrophysics Data System (ADS)

    Kothiyal, G. P.; Sharma, K.; Dixit, A.; Srinivasan, A.

    2010-12-01

    Ferrimagnetic glass-ceramics have been derived from bulk CaO-P2O5-SiO2-Fe2O3 glass system containing different additives like MgO, ZnO etc. by controlled crystallization. Phase formation and magnetic behaviour of glass-ceramics samples have been studied using XRD and SQUID magnetometer. The microstructure as seen by scanning electron microscopy exhibits nano sized particles. Nanocrystalline hematite and magnetite along with bone mineral phases constitute the major crystalline phases. Saturation magnetization increases with increase in amount of iron oxide since the volume fraction of magnetite has also increased. Addition of ZnO leads to increase in the saturation magnetization. In vitro response in simulated body fluid shows the formation of hydroxyapatite like layer implying the bioactive nature of the samples.

  19. 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.

  20. Multifunctionality of nanocrystalline lanthanum ferrite

    NASA Astrophysics Data System (ADS)

    Rai, Atma; Thakur, Awalendra K.

    2016-05-01

    Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ˜42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ˜3.45 m2/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanum ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO3.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.

  1. Thermal stability of nanocrystalline microstructures

    NASA Astrophysics Data System (ADS)

    Darling, Kris Allen

    The objective of the proposed research is to develop the experimental data and scientific basis that can optimize the thermodynamic stabilization of a nanoscale microstructure during consolidation of Fe powder particles through select solute diffusion to grain boundaries. Fe based alloys were high energy ball milled to produce supersaturated solid solutions with a nominal grain size of ˜10nm. Solutes such as Y, W, Ta, Ni and Zr were selected based on their propensity to grain boundary segregated in Fe. Based on preliminary heat treatments Zr was selected as the solute of choice. Upon further heat treating experiments and microstructural analysis it was found that Zr solute additions of <4at% could stabilize a nanocrystalline microstructure of <100nm at temperatures in excess of 900°C. This is in stark comparison to pure nanocrystalline Fe which shows coarsening to the micron scale after annealing above 600°C. Reduction in grain boundary energy due to Zr segregation and solute drag are proposed as mechanism responsible for the observed thermal stability. In addition to the work presented on Fe based Zr alloys supplementary research is presented on the following systems: Fe based Ni alloys, Pd 20at%Zr, Cu3Ge and CuGeO3. The addition of Ni to Fe was selected as a control. Since Ni and Fe have similar atomic radii, the elastic enthalpy of segregation of Ni in Fe is low (+1kJ/mol) and at high temperatures Ni has complete solid solubility in Fe; it is suggested that Ni will have a negligible influence in the thermal stability of nanocrystalline Fe. It was shown that at 700°C the addition of 1at% Ni produce a bimodal microstructure consisting of ˜70% abnormally grown grains and ˜30% nanocrystalline grains of 100-200nm. While these results are interesting extensive work is still needed to understand the mechanisms governing the thermal stability in this system. A presentation of the collected data is given. Pd 20 at% Zr was high energy ball milled to produce an

  2. 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.

  3. Three-dimensional printed PCL-hydroxyapatite scaffolds filled with CNTs for bone cell growth stimulation.

    PubMed

    Gonçalves, Elsa M; Oliveira, Filipe J; Silva, Rui F; Neto, Miguel A; Fernandes, M Helena; Amaral, Margarida; Vallet-Regí, María; Vila, Mercedes

    2016-08-01

    A three-phase [nanocrystalline hydroxyapatite (HA), carbon nanotubes (CNT), mixed in a polymeric matrix of polycaprolactone (PCL)] composite scaffold produced by 3D printing is presented. The CNT content varied between 0 and 10 wt % in a 50 wt % PCL matrix, with HA being the balance. With the combination of three well-known materials, these scaffolds aimed at bringing together the properties of all into a unique material to be used in tissue engineering as support for cell growth. The 3D printing technique allows producing composite scaffolds having an interconnected network of square pores in the range of 450-700 μm. The 2 wt % CNT scaffold offers the best combination of mechanical behaviour and electrical conductivity. Its compressive strength of ∼4 MPa is compatible with the trabecular bone. The composites show typical hydroxyapatite bioactivity, good cell adhesion and spreading at the scaffolds surface, this combination of properties indicating that the produced 3D, three-phase, scaffolds are promising materials in the field of bone regenerative medicine. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1210-1219, 2016. PMID:26089195

  4. 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

  5. Biodegradation and cytotoxicity of ciprofloxacin-loaded hydroxyapatite-polycaprolactone nanocomposite film for sustainable bone implants

    PubMed Central

    Nithya, Rajendran; Meenakshi Sundaram, Nachiappan

    2015-01-01

    Introduction In recent years there has been a steep increase in the number of orthopedic patients for many reasons. One major reason is osteomyelitis, caused by pyrogenic bacteria, with progressive infection of the bone or bone marrow and surrounding tissues. So antibiotics must be introduced during bone implantation to avoid prolonged infection. Aim The objective of the study reported here was to prepare a composite film of nanocrystalline hydroxyapatite (HAp) and polycaprolactone (PCL) polymer loaded with ciprofloxacin, a frequently used antibiotic agent for bone infections. Methods Nanocrystalline HAp was synthesized by precipitation method using the precursor obtained from eggshell. The nanocomposite film (HAp-PCL-ciprofloxacin) was prepared by solvent evaporation. Drug-release and biodegradation studies were undertaken by immersing the composite film in phosphate-buffered saline solution, while a cytotoxicity test was performed using the fibroblast cell line NIH-3T3 and osteoblast cell line MG-63. Results The pure PCL film had quite a low dissolution rate after an initial sharp weight loss, whereas the ciprofloxacin-loaded HAp-PCL nanocomposite film had a large weight loss due to its fast drug release. The composite film had higher water absorption than the pure PCL, and increasing the concentration of the HAp increased the water absorption. The in vitro cell-line study showed a good biocompatibility and bioactivity of the developed nanocomposite film. Conclusion The prepared film will act as a sustainable bone implant in addition to controlled drug delivery. PMID:26491313

  6. Nanocrystalline silicon based thin film solar cells

    NASA Astrophysics Data System (ADS)

    Ray, Swati

    2012-06-01

    Amorphous silicon solar cells and panels on glass and flexible substrate are commercially available. Since last few years nanocrystalline silicon thin film has attracted remarkable attention due to its stability under light and ability to absorb longer wavelength portion of solar spectrum. For amorphous silicon/ nanocrystalline silicon double junction solar cell 14.7% efficiency has been achieved in small area and 13.5% for large area modules internationally. The device quality nanocrystalline silicon films have been fabricated by RF and VHF PECVD methods at IACS. Detailed characterizations of the materials have been done. Nanocrystalline films with low defect density and high stability have been developed and used as absorber layer of solar cells.

  7. Micromechanics Modeling of Fracture in Nanocrystalline Metals

    NASA Technical Reports Server (NTRS)

    Glaessgen, E. H.; Piascik, R. S.; Raju, I. S.; Harris, C. E.

    2002-01-01

    Nanocrystalline metals have very high theoretical strength, but suffer from a lack of ductility and toughness. Therefore, it is critical to understand the mechanisms of deformation and fracture of these materials before their full potential can be achieved. Because classical fracture mechanics is based on the comparison of computed fracture parameters, such as stress intlmsity factors, to their empirically determined critical values, it does not adequately describe the fundamental physics of fracture required to predict the behavior of nanocrystalline metals. Thus, micromechanics-based techniques must be considered to quanti@ the physical processes of deformation and fracture within nanocrystalline metals. This paper discusses hndamental physicsbased modeling strategies that may be useful for the prediction Iof deformation, crack formation and crack growth within nanocrystalline metals.

  8. Nanocrystalline diamond synthesized from C60

    SciTech Connect

    Dubrovinskaia, N.; Dubrovinsky, L.; Langehorst, F.; Jacobsen, S.; Liebske, C.

    2010-11-30

    A bulk sample of nanocrystalline cubic diamond with crystallite sizes of 5-12 nm was synthesized from fullerene C{sub 60} at 20(1) GPa and 2000 C using a multi-anvil apparatus. The new material is at least as hard as single crystal diamond. It was found that nanocrystalline diamond at high temperature and ambient pressure kinetically is more stable with respect to graphitization than usual diamonds.

  9. Development of functionalized hydroxyapatite/poly(vinyl alcohol) composites

    NASA Astrophysics Data System (ADS)

    Stipniece, Liga; Salma-Ancane, Kristine; Rjabovs, Vitalijs; Juhnevica, Inna; Turks, Maris; Narkevica, Inga; Berzina-Cimdina, Liga

    2016-06-01

    Based on the well-known pharmaceutical excipient potential of poly(vinyl alcohol) (PVA) and clinical success of hydroxyapatite (HAp), the objective of this work was to fabricate functionalized composite microgranules. PVA was modified with succinic anhydride to introduce carboxyl groups (-COOH), respectively, by reaction between the -OH groups of PVA and succinic anhydride, for attachment of drug molecules. For the first time, the functionalized composite microgranules containing HAp/PVA in the ratio of 1:1 were prepared through in situ precipitation of HAp in modified PVA aqueous solutions followed by spray drying of obtained suspensions. The microgranules were characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and differential scanning calorimetry (DSC). The presence of -COOH groups was verified by FT-IR, and the amount of functional groups added to PVA molecules (averaging 15 mol%) was determined by nuclear magnetic resonance spectroscopy (NMR). DSC results showed that modification with -COOH groups slightly decreased the thermal stability of PVA. FT-IR and XRD analysis confirmed that the resulting composites contain mainly nanocrystalline HAp and PVA. Moreover, the images taken by FE-SEM revealed that the microgranules consisted of nanosized HAp crystallites homogenously embedded in the PVA matrix. DSC measurements indicated that decomposition mechanism of the HAp/PVA differs from that of pure PVA and occurs at lower temperatures. However, the presence of HAp had minor influence on the thermal decomposition of the PVA modified with succinic anhydride. The investigation of composite microgranules confirmed interaction and integration between the HAp and PVA.

  10. Ag-doped titanium dioxide gas sensor

    NASA Astrophysics Data System (ADS)

    Alaei Sheini, Navid; Rohani, Mahsa

    2016-03-01

    Titanium dioxide has been utilized for the fabrication of oxygen sensitive ceramic bodies. In this work, disk-shaped TiO2 pellets are fabricated by the sintering of the press- formed anatase powder at 1000°C. Two silver contacts are printed on one of the top base of each sample. Silver wire segments are connected to the printed electrodes. It is shown that the gradual diffusion of silver into titanium dioxide from the electrodes profoundly affects the resistive properties of the ceramic samples. SEM, XRD and EDAX analyses are carried out to determine the position of the silver diffused in the structure. At 35°C, before silver diffusion, the electrical resistance of the device decreases ten times in response to the presence of 3000 ppm ethanol contamination. Sensitivity (Rair/Rgas) to reducing gases is severely affected by the silver doping level in the titanium dioxide. The progress of silver diffusion continuously decreases the sensitivity till it become less than one. Further progress in silver diffusion brings the devices to the condition at which the resistance increases at the presents of reducing gases. In this condition, inverse sensitivities (Rgas/Rair) as large as 103 are demonstrated.

  11. Nanocrystalline cellulose from coir fiber: preparation, properties, and applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nanocrystalline cellulose derived from various botanical sources offers unique and potentially useful characteristics. In principle, any cellulosic material can be considered as a potential source of a nanocrystalline material, including crops, crop residues, and agroindustrial wastes. Because of t...

  12. 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

  13. 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

  14. 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

  15. Structural and biological evaluation of lignin addition to simple and silver-doped hydroxyapatite thin films synthesized by matrix-assisted pulsed laser evaporation.

    PubMed

    Janković, A; Eraković, S; Ristoscu, C; Mihailescu Serban, N; Duta, L; Visan, A; Stan, G E; Popa, A C; Husanu, M A; Luculescu, C R; Srdić, V V; Janaćković, Dj; Mišković-Stanković, V; Bleotu, C; Chifiriuc, M C; Mihailescu, I N

    2015-01-01

    We report on thin film deposition by matrix-assisted pulsed laser evaporation of simple hydroxyapatite (HA) or silver (Ag) doped HA combined with the natural biopolymer organosolv lignin (Lig) (Ag:HA-Lig). Solid cryogenic target of aqueous dispersions of Ag:HA-Lig composite and its counterpart without silver (HA-Lig) were prepared for evaporation using a KrF* excimer laser source. The expulsed material was assembled onto TiO2/Ti substrata or silicon wafers and subjected to physical-chemical investigations. Smooth, uniform films adherent to substratum were observed. The chemical analyses confirmed the presence of the HA components, but also evidenced traces of Ag and Lig. Deposited HA was Ca deficient, which is indicative of a film with increased solubility. Recorded X-ray Diffraction patterns were characteristic for amorphous films. Lig presence in thin films was undoubtedly proved by both X-ray Photoelectron and Fourier Transform Infra-Red Spectroscopy analyses. The microbiological evaluation showed that the newly assembled surfaces exhibited an inhibitory activity both on the initial steps of biofilm forming, and on mature bacterial and fungal biofilm development. The intensity of the anti-biofilm activity was positively influenced by the presence of the Lig and/or Ag, in the case of Staphylococcus aureus, Pseudomonas aeruginosa and Candida famata biofilms. The obtained surfaces exhibited a low cytotoxicity toward human mesenchymal stem cells, being therefore promising candidates for fabricating implantable biomaterials with increased biocompatibility and resistance to microbial colonization and further biofilm development. PMID:25578691

  16. 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.

  17. Stacking fault and twinning in nanocrystalline metals.

    SciTech Connect

    Liao, Xiaozhou; Zhao, Y.; Srivilliputhur, S. G.; Zhou, F.; Lavernia, E. J.; Baskes, M. I.; Zhu, Y. T.; Xu, H. F.

    2004-01-01

    Nanocrystalline Al processed by cryogenic ball-milling and nanocrystalline Cu processed by high-pressure torsion at a very low strain rate and at room temperature were investigated using high-resolution transmission electron microscopy. For nanocrystalline Al, we observed partial dislocation emission from grain boundaries, which consequently resulted in deformation stacking faults and twinning. We also observed deformation twins formed via two other mechanisms recently predicted by molecular dynamic simulations. These results are surprising because (1) partial dislocation emission from grain boundaries has not been experimentally observed although it has been predicted by simulations and (2) deformation stacking faults and twinning have not been reported in Al due to its high stacking fault energy. For nanocrystalline Cu, we found that twinning becomes a major deformation mechanism, which contrasts with the literature reports that deformation twinning in coarse-grained Cu occurs only under high strain rate and/or low temperature conditions and that reducing grain sizes suppresses deformation twinning. The investigation of the twinning morphology suggests that twins and stacking faults in nanocrystalline Cu were formed through partial dislocation emissions from grain boundaries. This mechanism differs from the pole mechanism operating in coarse-grained Cu.

  18. Rapid phase synthesis of nanocrystalline cobalt ferrite

    SciTech Connect

    Shanmugavel, T.; Raj, S. Gokul; Rajarajan, G.; Kumar, G. Ramesh

    2014-04-24

    Synthesis of single phase nanocrystalline Cobalt Ferrite (CoFe{sub 2}O{sub 4}) was achieved by single step autocombustion technique with the use of citric acid as a chelating agent in mono proportion with metal. Specimens prepared with this method showed significantly higher initial permeability's than with the conventional process. Single phase nanocrystalline cobalt ferrites were formed at very low temperature. Surface morphology identification were carried out by transmission electron microscopy (TEM) analysis. The average grain size and density at low temperature increased gradually with increasing the temperature. The single phase formation is confirmed through powder X-ray diffraction analysis. Magnetization measurements were obtained at room temperature by using a vibrating sample magnetometer (VSM), which showed that the calcined samples exhibited typical magnetic behaviors. Temperature dependent magnetization results showed improved behavior for the nanocrystalline form of cobalt ferrite when compared to the bulk nature of materials synthesized by other methods.

  19. 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.

  20. 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

  1. Direct Coating of Nanocrystalline Diamond on Steel

    NASA Astrophysics Data System (ADS)

    Tsugawa, Kazuo; Kawaki, Shyunsuke; Ishihara, Masatou; Hasegawa, Masataka

    2012-09-01

    Nanocrystalline diamond films have been successfully deposited on stainless steel substrates without any substrate pretreatments to promote diamond nucleation, including the formation of interlayers. A low-temperature growth technique, 400 °C or lower, in microwave plasma chemical vapor deposition using a surface-wave plasma has cleared up problems in diamond growth on ferrous materials, such as the surface graphitization, long incubation time, substrate softening, and poor adhesion. The deposited nanocrystalline diamond films on stainless steel exhibit good adhesion and tribological properties, such as a high wear resistance, a low friction coefficient, and a low aggression strength, at room temperature in air without lubrication.

  2. Synthesis of nanocrystalline tungsten carbide (WC) powder

    NASA Astrophysics Data System (ADS)

    Singla, Gourav; Singh, K.; Pandey, O. P.

    2013-06-01

    Nanocrystalline tungsten carbide (WC) has been obtained from bulk WO3 by in situ reduction and carbonization reactions at low temperature (˜ 600 °C) by taking Mg as reductant and acetone C3H6O as carbon source. It was aimed to elucidate carburization behavior of WO3 powder and to establish optimal conditions for the synthesis of nanocrystalline WC. The role of reaction time on the synthesis of WC has been investigated and discussed. The synthesized powders were characterized by X-ray powder diffraction, differential thermal analyzer (DTA), thermo gravimetric analysis (TGA).

  3. Deformation of nanocrystalline materials at ultrahigh strain rates - microstructure perspective in nanocrystalline nickel

    SciTech Connect

    Wang, Y; Bringa, E; Victoria, M; Caro, A; McNaney, J; Smith, R; Remington, B

    2006-04-10

    Nanocrystalline materials with grain sizes smaller than 100 nm have attracted extensive research in the past decade. Due to their high strength, these materials are good candidates for high pressure shock loading experiments. In this paper, we investigated the microstructural evolutions of nanocrystalline nickel with grain sizes of 10-50 nm, shock-loaded in a range of pressures (20-70 GPa). A laser-driven isentropic compression process was applied to achieve high shock-pressures in a timescale of nanoseconds and thus the high-strain-rate deformation of nanocrystalline nickel. Postmortem transmission electron microscopy (TEM) examinations reveal that the nanocrystalline structures survive the shock deformation and that dislocation activity is the prevalent deformation mechanism when the grain sizes are larger than 30 nm, without any twinning activity at twice the stress threshold for twin formation in micrometer-sized polycrystals. However, deformation twinning becomes an important deformation mode for 10-20 nm grain-sized samples.

  4. Platelet-rich fibrin combined with synthetic nanocrystalline hydroxy apatite granules in the management of radicular cyst.

    PubMed

    Pradeep, K; Kudva, Adarsh; Narayanamoorthy, Vidya; Cariappa, K M; Saraswathi, M Vidya

    2016-01-01

    Radicular cysts are inflammatory jaw cysts confined to the apices of teeth with infected and necrotic pulp. They arise from the epithelial residues in the periodontal ligament as a result of inflammation, following the death of pulp. The treatment of such lesions vary with regard to their sizes; the small cystic lesions heal after an endodontic therapy, but larger lesions, may require additional treatment. Apical surgery for radicular cysts generally involves apical root resection and sealing with endodontic material. This case report, describes the treatment of a cyst related to the maxillary central and lateral incisors using platelet rich fibrin along with synthetic nanocrystalline hydroxyapatite granules for the regeneration of lost tissues. A follow-up evaluation at 6 months and 1-year revealed a significant radiographic bone fill with satisfactory healing at the surgical site. PMID:27538563

  5. [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

  6. 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.

  7. Facile preparation of nanocrystalline gallium antimonide

    SciTech Connect

    Baldwin, R.A.; Foos, E.E.; Wells, R.L.

    1997-02-01

    The 1:1 reaction of GaCl3 with Sb(SiMe{sub 3}){sub 3} in pentane solution affords an intermediate material which, upon thermolysis, yields nanocrystalline GaSb with an approximate average particle size of 12 nm. The product was characterized through powder X-ray diffraction, elemental analysis, and HRTEM.

  8. 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

  9. Corrosion and hydrogen embrittlement of nanocrystalline nickel

    NASA Astrophysics Data System (ADS)

    Desai, Tapas

    Nanocrystalline (nc) materials have attracted the interest of the scientific community because of their unique physical and mechanical properties. However, limited research has been performed to analyze their electrochemical behavior. The majority of research in the field of electrochemical and corrosion behavior exists for electrodeposited nanocrystalline metals. This research studies the behavior of sputter-deposited nc Nickel films in corrosive and hydrogen environment by potentiodynamic polarization and microindentation. The surface morphology and composition of the samples was examined by Scanning Electron Microscopy and Energy Dispersive X-Ray spectroscopy. Bulk Ni samples exhibit mild passivation in 3.5 % NaCl solution. The surface reveals a fine distribution of small pits and numerous large pits. However, nc Ni films show a higher corrosion potential, but lower corrosion rate. This can be attributed to the rapid formation of a passive film to resist the corrosion, and better purity of sputtered films. A very uniform and periodic corrosion pattern is observed on the surface, without any pitting. In 0.1 N H2 SO4 solution, active dissolution of Ni was observed in both bulk and nanocrystalline samples. This is due to the absence of passivation for Ni in this environment. Nc Ni shows a higher corrosion rate and higher anodic corrosion potential. This behavior is attributed to a higher density of grain boundaries that act as a catalyst to the hydrogen reduction reaction and increase the corrosion rate. Effect of electrochemically charged hydrogen was observed for bulk and nanocrystalline Nickel. Bulk Ni displayed a slight increase in hardness and signs of hydrogen induced plastic deformation. On the other hand, the nanocrystalline Ni shows brittle failure by buckling and spalling. This is attributed to its limited ductility and the high density that act as preferred sites for hydrogen adsorption and subsequently enhance hydrogen diffusion, leading to

  10. Synthesis and characterization of nanocrystalline silicide compounds

    SciTech Connect

    Karen, B.

    1992-01-03

    This thesis involves the investigation into the production of nanocrystalline silicide compounds by radio frequency inductively coupled plasma (RF-ICP) and mechanical milling. A system constructed which utilized a RF-ICP, a powder feed system and a condensation / collection chamber to produce nanocrystalline materials. Several silicides, such as Ti{sub 5}Si{sub 3}, Cr{sub 3}Si and MoSi{sub 2}, were fed into the plasma were they vaporized. The vaporized material then passed into a connecting chamber, where it condensed out of the vapor phase and the resulting powder was collected. Much of the work conducted was in designing and building of the systems components. This was followed by establishing the plasmas operating parameters. The material collected from the ICP chamber was then compared to material produced by mechanical milling. The material produced by both methods were characterized by x-ray diffraction, scanning and transmission-electron microscopy, and energy dispersive spectroscopy. The results indicate that it is possible to produce nanocrystalline material by mechanical milling; however, there is a significant amount of contamination from the milling ball and milling container. The results also show that the Ti{sub 5}Si{sub 3} and Cr{sub 3}Si compounds can be produced in nanocrystalline form by the ICP method. The resultant material collected from the ICP chamber following the MoSi{sub 2} run consisted of nanocrystalline Si and crystalline, Mo rich Si compound. Inductively coupled plasma - atomic emission spectroscopy (ICP-AES) was also used to observe the powders as they passed through the plasma. The resulting data indicates that each compound was vaporized and dissociated in the plasma. The following thesis describes the apparatus and experimental procedure used in producing nanocrystals.

  11. 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

  12. 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

  13. 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

  14. 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.

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. Synthesis and in-depth analysis of highly ordered yttrium doped hydroxyapatite nanorods prepared by hydrothermal method and its mechanical analysis

    SciTech Connect

    Nathanael, A. Joseph; Mangalaraj, D.; Hong, S.I.; Masuda, Y.

    2011-12-15

    In this study, undoped and yttrium (Y) doped nanocrystalline hydroxyapatite crystals were synthesized by the hydrothermal method at 180 Degree-Sign C for 24 h. Highly ordered and oriented hydroxyapatite (HAp) nanorods were prepared by yttrium doping and their nanostructure and physical properties were compared with those of undoped HAp rods. FESEM images showed that the doping with Y ions reduced the diameter (from 25 nm to 15 nm) and increased the length (from 95 nm to 115 nm) of the synthesized rods. The aspect ratio of the undoped and Y-doped nanorods were calculated to be 4.303 (SD = 0.0959) and 7.61 (SD = 0.0355), respectively. Specific surface area (SSA) analysis showed that SSA also increased from 66.74 m{sup 2}/g to 68.57 m{sup 2}/g with the addition of yttrium. Y-doped HAp nanorod reinforced HMWPE composites displayed the better mechanical performance than those reinforced with pure HAp nanorods. The possible strengthening of nanorods and the increase of SSA due to the reduction in the size of nanorods in the presence of yttrium may have contributed to the strengthening of Y-doped HAp/HMWPE composites. - Graphical Abstract: Highly ordered and oriented yttrium doped hydroxyapatite (HAp) nanorods were prepared by hydrothermal method. For undoped HAp the average length of the nanorod is 95 nm with mean diameter of 24 nm and for a Y doped nanorod the average length is {approx} 115 nm and the mean diameter is 15 nm. Mechanical analysis was carried out by polymer/nanoparticle composite method. Highlights: Black-Right-Pointing-Pointer Yttrium doped hydroxyapatite nanorods were prepared by hydrothermal method. Black-Right-Pointing-Pointer The nanorods have highly uniform size distribution. Black-Right-Pointing-Pointer Yttrium substitution and nanostructure formation was confirmed by careful analysis. Black-Right-Pointing-Pointer Mechanical strength was analyzed by polymer nanoparticle reinforcement method.

  1. Microemulsion-based synthesis of nanocrystalline materials.

    PubMed

    Ganguli, Ashok K; Ganguly, Aparna; Vaidya, Sonalika

    2010-02-01

    Microemulsion-based synthesis is found to be a versatile route to synthesize a variety of nanomaterials. The manipulation of various components involved in the formation of a microemulsion enables one to synthesize nanomaterials with varied size and shape. In this tutorial review several aspects of microemulsion based synthesis of nanocrystalline materials have been discussed which would be of interest to a cross-section of researchers working on colloids, physical chemistry, nanoscience and materials chemistry. The review focuses on the recent developments in the above area with current understanding on the various factors that control the structure and dynamics of microemulsions which can be effectively used to manipulate the size and shape of nanocrystalline materials. PMID:20111772

  2. Nanosecond magnetization reversal in nanocrystalline magnetic films

    NASA Astrophysics Data System (ADS)

    Rahman, I. Z.; Gandhi, A. A.; Khaddem-Mousavi, M. V.; Lynch, T. F.; Rahman, M. A.

    2007-03-01

    This paper reports on the investigation of dynamic magnetization reversal process in electrodeposited nanocrystalline Ni and Ni80Fe20 films by employing nanosecond magnetic pulse technique. The surface morphology has been investigated using SEM, EDAX, XRD and AFM analyses and static magnetic properties of the films are characterized by vibrating sample magnetometer (VSM). Two different techniques are designed and employed to study the nanosecond magnetization reversal process in nanocrystalline thin films: Magneto-Optical Kerr Effect (MOKE) and nanosecond pulsed field magnetometer. Results of dynamical behavior as a function of several variables such as magnitude of applied bias magnetic field, amplitude and width of the pulsed magnetic field are analyzed in detail using both techniques. A computer simulation package called Object Oriented Micro-Magnetic Framework (OOMMF) has been used to simulate the magnetic domain patterns of the samples.

  3. Nanocrystalline cobalt oxides for carbon nanotube growth

    NASA Astrophysics Data System (ADS)

    Guo, Kun; Jayatissa, Ahalapitiya H.; Jayasuriya, Ambalangodage C.

    2007-09-01

    Thin Films of nanocrystalline cobalt oxide were formed by sol-gel method. Structure, optical properties and surface properties of these films were investigated by numerous characterization techniques. These films were successfully fabricated on glass substrates below 500°C. . Micropatterns of cobalt oxide thin films were also fabricated on glass and silicon substrates by employing a lift-off method. Crystal size of these nanocrystalline cobalt films could be successfully controllable by varying the amount of cobalt precursors and number of layers. These films were used as the seeding layers for carbon nanotube growth in a CVD process By changing the concentration of monomer precursors in the solgel coating solutions, different size nanoclusters hence different size carbon nanotubes could be synthesized in CVD process. This method can be used for controlled growth of carbon nanotubes for many different applications. In this paper, detail of these experimental results will be presented.

  4. DNA attachment to nanocrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Wenmackers, S.; Christiaens, P.; Daenen, M.; Haenen, K.; Nesládek, M.; van Deven, M.; Vermeeren, V.; Michiels, L.; Ameloot, M.; Wagner, P.

    2005-09-01

    A biochemical method to immobilize DNA on synthetic diamond for biosensor applications is developed. Nanocrystalline diamond is grown using microwave plasma-enhanced chemical vapour deposition. On the hydrogen-terminated surface 10-undecenoic acid is tethered photochemically under 254 nm illumination, followed by 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide crosslinker-mediated attachment of amino modified DNA. The attachment is functionally confirmed by comparison of supernatant fluorescence and gel electrophoresis. The linking procedure allowed for 35 denaturation and rehybridisation steps.

  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. In-vivo behavior of Si-hydroxyapatite/polycaprolactone/DMB scaffolds fabricated by 3D printing.

    PubMed

    Meseguer-Olmo, Luis; Vicente-Ortega, Vicente; Alcaraz-Baños, Miguel; Calvo-Guirado, José Luis; Vallet-Regí, María; Arcos, Daniel; Baeza, Alejandro

    2013-07-01

    Scaffolds made of polycaprolactone and nanocrystalline silicon-substituted hydroxyapatite have been fabricated by 3D printing rapid prototyping technique. To asses that the scaffolds fulfill the requirements to be considered for bone grafting applications, they were implanted in New Zealand rabbits. Histological and radiological studies have demonstrated that the scaffolds implanted in bone exhibited an excellent osteointegration without the interposition of fibrous tissue between bone and implants and without immune response after 4 months of implantation. In addition, we have evaluated the possibility of improving the scaffolds efficiency by incorporating demineralized bone matrix during the preparation by 3D printing. When demineralized bone matrix (DBM) is incorporated, the efficacy of the scaffolds is enhanced, as new bone formation occurs not only in the peripheral portions of the scaffolds but also within its pores after 4 months of implantation. This enhanced performance can be explained in terms of the osteoinductive properties of the DBM in the scaffolds, which have been assessed through the new bone tissue formation when the scaffolds are ectopically implanted. PMID:23255259

  7. 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

  8. 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.

  9. 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.

  10. 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

  11. Solid state consolidation nanocrystalline copper-tungsten using cold spray

    SciTech Connect

    Hall, Aaron Christopher; Sarobol, Pylin; Argibay, Nicolas; Clark, Blythe; Diantonio, Christopher

    2015-09-01

    It is well known that nanostructured metals can exhibit significantly improved properties compared to metals with conventional grain size. Unfortunately, nanocrystalline metals typically are not thermodynamically stable and exhibit rapid grain growth at moderate temperatures. This severely limits their processing and use, making them impractical for most engineering applications. Recent work has shown that a number of thermodynamically stable nanocrystalline metal alloys exist. These alloys have been prepared as powders using severe plastic deformation (e.g. ball milling) processes. Consolidation of these powders without compromise of their nanocrystalline microstructure is a critical step to enabling their use as engineering materials. We demonstrate solid-state consolidation of ball milled copper-tantalum nanocrystalline metal powder using cold spray. Unfortunately, the nanocrystalline copper-tantalum powder that was consolidated did not contain the thermodynamically stable copper-tantalum nanostructure. Nevertheless, this does this demonstrates a pathway to preparation of bulk thermodynamically stable nanocrystalline copper-tantalum. Furthermore, it demonstrates a pathway to additive manufacturing (3D printing) of nanocrystalline copper-tantalum. Additive manufacturing of thermodynamically stable nanocrystalline metals is attractive because it enables maximum flexibility and efficiency in the use of these unique materials.

  12. 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

  13. 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.

  14. Spectroscopic characterization of nanocrystalline chromium nitride (CrN).

    PubMed

    Mangamma, G; Sairam, T N; Dash, S; Rajalakshmi, M; Kamruddin, M; Mittal, V K; Narasimhan, S V; Arora, A K; Sundar, C S; Tyagi, A K; Raj, Baldev

    2007-03-01

    Nanocrystalline chromiuim nitride has been synthesised by direct gas phase nitridation of nanocrystalline chromia at 1100 degrees C in ammonia-atmosphere. XRD of this material showed formation of single phase CrN with particle size around 20 nm. AFM studies showed particle distribution along with some soft agglomerated nanostructures. Nanocrystalline Cr2O3 and partially-as well as fully--converted nanocrystalline CrN were also investigated using various spectroscopic techniques like XPS, FT-IR, and Raman for gaining insight into the conversion pathways. Spectroscopic investigations of these materials clearly indicate that complete conversion of CrN occurs by nitriding at 1100 degrees C for 4 hrs. The salient spectroscopic features of these nanocrystalline materials with respect to their microcrystalline counterparts are discussed. PMID:17450861

  15. 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}.

  16. 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

  17. Energy level alignments at the interface of N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1‧-biphenyl-4,4‧-diamine (NPB)/Ag-doped In2O3 and NPB/Sn-doped In2O3

    NASA Astrophysics Data System (ADS)

    Jung, Kwanwook; Park, Soohyung; Lee, Younjoo; Youn, Yungsik; Shin, Hae-In; Kim, Han-Ki; Lee, Hyunbok; Yi, Yeonjin

    2016-11-01

    The electronic structures of Ag-doped In2O3 (IAgO) and its energy level alignments with a N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1‧-biphenyl-4,4‧-diamine (NPB) hole transport layer (HTL) were investigated using in situ ultraviolet and X-ray photoelectron spectroscopies (UPS and XPS). As compared to the conventional Sn-doped In2O3 (ITO), IAgO has less oxygen vacancies leading to a higher work function (WF). The lower hole injection barrier (Φh) from IAgO to a NPB HTL is observed, which is attributed mainly to its higher WF and interface dipoles. The UPS measurements reveal that the Φh is 0.87 eV at NPB/IAgO while 1.11 eV is at NPB/ITO. Therefore, IAgO could be an alternative transparent anode in organic optoelectronics.

  18. Advances in amorphous and nanocrystalline materials

    NASA Astrophysics Data System (ADS)

    Hasegawa, Ryusuke

    2012-10-01

    A new amorphous alloy has been recently introduced which shows a saturation magnetic induction Bs of 1.64 T which is compared with Bs=1.57 T for a currently available Fe-based amorphous alloy and decreased magnetic losses. Such a combination is rare but can be explained in terms of induced magnetic anisotropy being reduced by the alloy's chemistry and its heat treatment. It has been found that the region of magnetization rotation in the new alloy is considerably narrowed, resulting in reduced exciting power in the magnetic devices utilizing the material. Efforts to increase Bs also have been made for nanocrystalline alloys. For example, a nanocrystalline alloy having a composition of Fe80.5Cu1.5Si4B14 shows Bs exceeding 1.8 T. The iron loss at 50 Hz and at 1.6 T induction in a toroidal core of this material is 0.46 W/kg which is 2/3 that of a grain-oriented silicon steel. At 20 kHz/0.2 T excitation, the iron loss is about 60% of that in an Fe-based amorphous alloy which is widely used in power electronics. Another example is a Fe85Si2B8P4Cu1 nanocrystalline alloy with a Bs of 1.8 T, which is reported to exhibit a magnetic core loss of about 0.2 W/kg at 50 Hz and at 1.5 T induction. This article is a review of these new developments and their impacts on energy efficient magnetic devices.

  19. LIGHT-WEIGHT NANOCRYSTALLINE HYDROGEN STORAGE MATERIALS

    SciTech Connect

    S. G. Sankar; B. Zande; R.T. Obermyer; S. Simizu

    2005-11-21

    During Phase I of this SBIR Program, Advanced Materials Corporation has addressed two key issues concerning hydrogen storage: 1. We have conducted preliminary studies on the effect of certain catalysts in modifying the hydrogen absorption characteristics of nanocrystalline magnesium. 2. We have also conducted proof-of-concept design and construction of a prototype instrument that would rapidly screen materials for hydrogen storage employing chemical combinatorial technique in combination with a Pressure-Composition Isotherm Measurement (PCI) instrument. 3. Preliminary results obtained in this study approach are described in this report.

  20. 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.

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. 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

  6. 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

  7. 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

  8. 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.

  9. Cathodic electrodeposition of nanocrystalline titanium dioxide thin films

    SciTech Connect

    Natarajan, C.; Nogami, G.

    1996-05-01

    A new technique for depositing nanocrystalline titanium dioxide thin films on electronically conducting glass was developed. This technique is a two-stage process: (i) cathodic electrodeposition of titanium oxyhydroxide gel film from aqueous solution containing a Ti precursor and (ii) subsequent heat-treatment of this gel film results in the formation of titanium dioxide film. The deposition potential may have a considerable effect on the formation of nanocrystalline film. The nanocrystalline titanium dioxide film shows reversible electrochromism in lithium-ion-containing organic electrolyte. The coloration and bleaching throughout the visible and near-IR range can be switched on and off within a few seconds.

  10. Nanocrystalline cerium oxide materials for solid fuel cell systems

    DOEpatents

    Brinkman, Kyle S

    2015-05-05

    Disclosed are solid fuel cells, including solid oxide fuel cells and PEM fuel cells that include nanocrystalline cerium oxide materials as a component of the fuel cells. A solid oxide fuel cell can include nanocrystalline cerium oxide as a cathode component and microcrystalline cerium oxide as an electrolyte component, which can prevent mechanical failure and interdiffusion common in other fuel cells. A solid oxide fuel cell can also include nanocrystalline cerium oxide in the anode. A PEM fuel cell can include cerium oxide as a catalyst support in the cathode and optionally also in the anode.

  11. Formation of Surface Corrosion-Resistant Nanocrystalline Structures on Steel

    NASA Astrophysics Data System (ADS)

    Nykyforchyn, Hryhoriy; Kyryliv, Volodymyr; Maksymiv, Olha; Slobodyan, Zvenomyra; Tsyrulnyk, Oleksandr

    2016-02-01

    Engineering materials with nanocrystalline structure could be exploited under simultaneous action of mechanical loading and corrosion environments; therefore, their corrosion resistance is important. Surface nanocrystalline structure was generated on middle carbon steels by severe plastic deformation using the method of mechanical pulse friction treatment. This treatment additionally includes high temperature phase transformation and alloying. Using a complex of the corrosive, electrochemical and physical investigations, it was established that nanocrystalline structures can be characterized by lower or increased corrosion resistance in comparison with the reference material. It is caused by the action of two confronting factors: arising energy level and anticorrosive alloying of the surface layer.

  12. On the hardening and softening of nanocrystalline materials

    SciTech Connect

    Fougere, G.E.; Weertman, J.R. . Dept. of Materials Science and Engineering); Siegel, R.W. . Materials Science Div.)

    1993-04-01

    Nanocrystalline Pd and Cu samples have been thermally treated to determine whether the relation between hardness and grain size depend on the method used to vary the grain sizes. Previous reports indicate that hardening with decreasing grain size resulted from data obtained using individual samples, while softening with decreasing grain size resulted from data from a given sample that had been thermally treated. Hardening and softening regimes were evident for the nanocrystalline cu, and the hardness improvements over the original as-consolidated state were maintained throughout the thermal treatments. This review examines our hardness results for Cu and Pd and those for other nanocrystalline materials.

  13. Formation of Surface Corrosion-Resistant Nanocrystalline Structures on Steel.

    PubMed

    Nykyforchyn, Hryhoriy; Kyryliv, Volodymyr; Maksymiv, Olha; Slobodyan, Zvenomyra; Tsyrulnyk, Oleksandr

    2016-12-01

    Engineering materials with nanocrystalline structure could be exploited under simultaneous action of mechanical loading and corrosion environments; therefore, their corrosion resistance is important. Surface nanocrystalline structure was generated on middle carbon steels by severe plastic deformation using the method of mechanical pulse friction treatment. This treatment additionally includes high temperature phase transformation and alloying. Using a complex of the corrosive, electrochemical and physical investigations, it was established that nanocrystalline structures can be characterized by lower or increased corrosion resistance in comparison with the reference material. It is caused by the action of two confronting factors: arising energy level and anticorrosive alloying of the surface layer. PMID:26831689

  14. Functionalized squaraine donors for nanocrystalline organic photovoltaics.

    PubMed

    Wei, Guodan; Xiao, Xin; Wang, Siyi; Sun, Kai; Bergemann, Kevin J; Thompson, Mark E; Forrest, Stephen R

    2012-01-24

    We study a family of functionalized squaraine (fSQ) donors for absorbing in the near-infrared (NIR) and green spectral regions. The NIR-absorbing materials are the symmetric molecules 2,4-bis[4-(N-phenyl-1-naphthylamino)-2,6-dihydroxyphenyl]squaraine (1-NPSQ), 2,4-bis[4-(N,N-diphenylamino)-2,6 dihydroxyphenyl]squaraine, and 2,4-bis[4-(N,N-dipropylamino)-2,6-dihydroxyphenyl]squaraine. The green light absorbing donors are asymmetric squaraines, namely, 2,4-bis[4-(N,N-diphenylamino)-2,6-dihydroxyphenyl]squaraine and 2-[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl]-4-diphenylamino]squaraine. Substitution of the arylamine groups enhances intermolecular packing, thereby increasing hole transport and the possibility of forming extended nanocrystalline junctions when annealed. Nanocrystalline solar cells based on fSQ and a C(60) acceptor have V(oc) = 1.0 V and fill factors 0.73 ± 0.01. Solar cells incorporating annealed 1-NPSQ films result in a power conversion efficiency of 5.7 ± 0.6% at 1 sun, AM1.5G illumination. PMID:22196154

  15. 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

  16. 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

  17. [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

  18. 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.

  19. 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...

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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

  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. 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

  9. 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

  10. 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

  11. 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.

  12. 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

  13. Preliminary exploration of the interfacial structure of nanocrystalline materials

    SciTech Connect

    Guo, W.Q.; Liu, X.D.; Ding, B.Z.

    1995-12-31

    The present intense interest in exploration on nanostructured materials stems from the studies of interfacial structures of nanocrystalline materials. Up to now, there are two different results of the exploration on interfacial structure of nanocrystalline materials. The first one supposed by Gleiter et al. is a so-called {open_quotes}gas-like{close_quotes} structure. They reported that the interfaces of nanocrystalline materials represent a novel type of solid structure without any long or short range order, corresponding structurally to a {open_quotes}gas-like{close_quotes} solid. This structure can be verified with X-ray diffraction, Mossbauer spectroscopy, positron lifetime spectroscopy and extended X-ray absorption fine structure (EXFAS). The second result obtained by Siegel et al. with high resolution electron microscopy, raman scattering and small angle X-ray and neutron diffraction is that the interfacial structures of nanocrystalline materials are rather similar to those in conventional coarse-grained polycrystals.

  14. Corrosion properties of nanocrystalline cobalt and cobalt-phosphorus alloys

    NASA Astrophysics Data System (ADS)

    Jung, Hundal

    In this thesis, the corrosion properties of electrodeposited nanocrystalline Co and Co-1.1 and 2.1 wt% P alloys (7 to 20 nm grain size) were investigated in a wide range of solution pH by using polarization and electrochemical impedance spectroscopy techniques along with scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy analysis. In 0.1 M H2SO 4 and 0.5 M Na2SO4 solutions (pH 1 and 3, respectively), nanocrystalline Co showed higher anodic and cathodic reaction rates and reduced localized corrosion attack compared to coarse grained Co counterparts. An enhanced electrochemical reaction rate of nanocrystalline Co was correlated to a significant increase in grain boundaries and triple junctions. For pure Co, a catalytic mechanism has been suggested to rationalize a more favorable route for their anodic dissolution reaction. An addition of P leads to a significant increase of corrosion resistance of nanocrystalline Co-P due to the increased elemental P concentration on the corroded surface at Eoc following an initial selective dissolution of Co. However, at higher anodic overpotential, the superior corrosion resistance of nanocrystalline Co-P did not last due to the formation of a porous and defective surface film. The excellent corrosion resistance of nanocrystalline Co-P deteriorated from heat treatment at 350°C and 800°C due to higher chemical heterogeneity. In a 3.56% NaCl solution at pH 6.2, nanocrystalline Co-P showed a higher anodic dissolution rate than that of nanocrystalline Co due to a reduced adsorption area of chloride ions. However, the corrosion rate of nanocrystalline Co-P decreased in comparison to nanocrystalline Co due to a much smaller cathodic exchange current density for oxygen reduction on nanocrystalline Co-P. A physical model was elaborated to explain the different response of annealed nanocrystalline Co-P by considering the different adsorption properties

  15. High Temperature Stable Nanocrystalline SiGe Thermoelectric Material

    NASA Technical Reports Server (NTRS)

    Yang, Sherwin (Inventor); Matejczyk, Daniel Edward (Inventor); Determan, William (Inventor)

    2013-01-01

    A method of forming a nanocomposite thermoelectric material having microstructural stability at temperatures greater than 1000 C. The method includes creating nanocrystalline powder by cryomilling. The method is particularly useful in forming SiGe alloy powder.

  16. 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).

  17. Application of nanocrystalline metals in microsystem fabrication

    NASA Astrophysics Data System (ADS)

    Baghbanan, Mohammadreza

    This research addresses the issues of performance variability and reliability concerns frequently encountered with conventional metallic microsystem components (e.g. MEMS) produced by electrodeposition methods such as LIGA. Previous studies have demonstrated that microsystem components produced by conventional electrodeposition approaches show relatively low overall hardness and considerable variations in Young's modulus and hardness throughout the cross-section of the components. In this work, this undesirable property variability has been traced back to microstructural and scaling effects. It has been shown that the microstructure of conventional deposits exhibits grain size gradients resulting from a fine grained to columnar structure transition with increasing component thickness. In addition, the overall component size is often comparable to the relatively large grain size in these deposits. In past efforts, both post-deposition recrystallization annealing and texture control during the electroplating process have been used in efforts to alleviate these concerns, however only with some limited success. In this research, a new approach is used which essentially involves the application of an electrodeposition process that produces fully dense nanostructured deposits throughout the entire cross-section of the component without the transition from fine to large grained columnar structure. The cross-sectional microstructures and mechanical properties (i.e. hardness and Young's modulus) are presented for electrodeposited nickel and cobalt foils with conventional polycrystalline and nanocrystalline structures as well as nanocrystalline nickel plated in molds with non-conductive side-walls prepared by the UV-photolithography molding process. Microstructural characterization was performed on these materials using scanning electron microscopy (SEM), optical microscopy, back scattered electron imaging (BSEI), and transmission electron microscopy (TEM) as well as

  18. Supra- and nanocrystallinities: a new scientific adventure.

    PubMed

    Pileni, M P

    2011-12-21

    Nanomaterials exist in the interstellar medium, in biology, in art and also metallurgy. Assemblies of nanomaterials were observed in the early solar system as well as silicate particle opals. The latter exhibits unusual optical properties directly dependent on particle ordering in 3D superlattices.The optical properties of noble metal nanoparticles (Ag, Au and Cu) change with the ordering of atoms in the nanocrystals, called nanocrystallinity. The vibrational properties related to nanocrystallinity markedly differ with the vibrational modes studied. Hence, a drastic effect on nanocrystallinity is observed on the confined acoustic vibrational property of the fundamental quadrupolar modes whereas the breathing acoustic modes remain quasi-unchanged. The mechanical properties characterized by the Young's modulus of multiply twinned particle (MTP) films are markedly lower than those of single nanocrystals.Two fcc supracrystal growth mechanisms, supported by simulation, of Au nanocrystals are proposed: heterogeneous and homogeneous growth processes. The final morphology of nanocrystal assemblies, with either films by layer-by-layer growth characterized by their plastic deformation or well-defined shapes grown in solution, depends on the solvent used to disperse the nanocrystals before the evaporation process.At thermodynamic equilibrium, two simultaneous supracrystal growth processes of Au nanocrystals take place in solution and at the air-liquid interface. These growth processes are rationalized by simulation. They involve, on the one hand, van der Waals interactions and, on the other hand, the attractive interaction between nanocrystals and the interface.Ag nanocrystals (5 nm) self-order in colloidal crystals with various arrangements called supracrystallinities. As in bulk materials, phase diagrams of supracrystals with structural transitions from face-centered-cubic (fcc) to hexagonal-close-packed (hcp) and body-centered-cubic (bcc) structures are observed. They

  19. Supra- and nanocrystallinities: a new scientific adventure

    NASA Astrophysics Data System (ADS)

    Pileni, M. P.

    2011-12-01

    Nanomaterials exist in the interstellar medium, in biology, in art and also metallurgy. Assemblies of nanomaterials were observed in the early solar system as well as silicate particle opals. The latter exhibits unusual optical properties directly dependent on particle ordering in 3D superlattices. The optical properties of noble metal nanoparticles (Ag, Au and Cu) change with the ordering of atoms in the nanocrystals, called nanocrystallinity. The vibrational properties related to nanocrystallinity markedly differ with the vibrational modes studied. Hence, a drastic effect on nanocrystallinity is observed on the confined acoustic vibrational property of the fundamental quadrupolar modes whereas the breathing acoustic modes remain quasi-unchanged. The mechanical properties characterized by the Young’s modulus of multiply twinned particle (MTP) films are markedly lower than those of single nanocrystals. Two fcc supracrystal growth mechanisms, supported by simulation, of Au nanocrystals are proposed: heterogeneous and homogeneous growth processes. The final morphology of nanocrystal assemblies, with either films by layer-by-layer growth characterized by their plastic deformation or well-defined shapes grown in solution, depends on the solvent used to disperse the nanocrystals before the evaporation process. At thermodynamic equilibrium, two simultaneous supracrystal growth processes of Au nanocrystals take place in solution and at the air-liquid interface. These growth processes are rationalized by simulation. They involve, on the one hand, van der Waals interactions and, on the other hand, the attractive interaction between nanocrystals and the interface. Ag nanocrystals (5 nm) self-order in colloidal crystals with various arrangements called supracrystallinities. As in bulk materials, phase diagrams of supracrystals with structural transitions from face-centered-cubic (fcc) to hexagonal-close-packed (hcp) and body-centered-cubic (bcc) structures are observed

  20. Luminescence and related properties of nanocrystalline porous silicon

    NASA Astrophysics Data System (ADS)

    Koshida, N.

    This document is part of subvolume C3 'Optical Properties' of volume 34 'Semiconductor quantum structures' of Landolt-Börnstein, Group III, Condensed Matter, on the optical properties of quantum structures based on group IV semiconductors. It discusses luminescence and related properties of nanocrystalline porous silicon. Topics include an overview of nanostructured silicon, its fabrication technology, and properties of nanocrystalline porous silicon such as confinement effects, photoluminescence, electroluminesce, carrier charging effects, ballistic transport and emission, and thermally induced acoustic emission.

  1. High temperature deformation behavior of a nanocrystalline titanium aluminide

    SciTech Connect

    Mishra, R.S.; Mukherjee, A.K.; Mukhopadhyay, D.K.; Suryanarayana, C.; Froes, F.H.

    1996-06-01

    Gamma titanium intermetallic alloys are potentially attractive for elevated temperature applications. The room temperature ductility and fracture toughness have been improved considerably by the addition of ternary and quaternary elements. The synthesis of nanocrystalline materials has provided further avenues for possible improvement in the mechanical properties. The exciting prospect of low temperature superplasticity in nanocrystalline materials has been discussed. Recently, nanocrystalline {gamma}-TiAl alloys have been synthesized by hot isostatic pressing (HIP) of mechanically alloyed (MA) Ti-47.5 Al-3 Cr (at.%) powders. The purpose of this study was to evaluate the possibility of observing low temperature superplasticity in this nanocrystalline alloy. By determining the stress exponent for flow, it should be possible to comment on the micromechanism of deformation in a nanocrystalline intermetallic alloy. A number of studies have shown that superplasticity is possible in {gamma}-TiAl alloys and it is important to establish whether the scaling law extends to nanocrystalline {gamma}-TiAl regime or the flow behavior changes.

  2. Toughness and strength of nanocrystalline graphene.

    PubMed

    Shekhawat, Ashivni; Ritchie, Robert O

    2016-01-01

    Pristine monocrystalline graphene is claimed to be the strongest material known with remarkable mechanical and electrical properties. However, graphene made with scalable fabrication techniques is polycrystalline and contains inherent nanoscale line and point defects--grain boundaries and grain-boundary triple junctions--that lead to significant statistical fluctuations in toughness and strength. These fluctuations become particularly pronounced for nanocrystalline graphene where the density of defects is high. Here we use large-scale simulation and continuum modelling to show that the statistical variation in toughness and strength can be understood with 'weakest-link' statistics. We develop the first statistical theory of toughness in polycrystalline graphene, and elucidate the nanoscale origins of the grain-size dependence of its strength and toughness. Our results should lead to more reliable graphene device design, and provide a framework to interpret experimental results in a broad class of two-dimensional materials. PMID:26817712

  3. Microstructural characterization in nanocrystalline ceramic thin films

    NASA Astrophysics Data System (ADS)

    Kim, Hakkwan

    The primary objective of this research is to investigate the effects of process variables on microstructure in several fluoride and oxide thin films prepared by vapor deposition, in order to predict the properties and behaviors of nanocrystalline thin film materials. There are three distinct stages of this research. The first stage focuses on measuring of the porosity in polycrystalline thin films of a variety of fluorides as a function of the substrate temperature during deposition, and discussing the mechanism by which the porosity varies as a function of the process variables. We have measured the porosity in thin films of lithium fluoride (LiF), magnesium fluoride (MgF2), barium fluoride (BaF 2) and calcium fluoride (CaF2) using an atomic force microscope (AFM) and a quartz crystal thickness monitor. The porosity is very sensitive to the substrate temperature and decreases as the substrate temperature increases. Consistent behavior is observed among all of the materials in this study. The second stage is to understand the film microstructure including grain growth and texture development, because these factors are known to influence the behavior and stability of polycrystalline thin films. This study focuses on grain growth and texture development in polycrystalline lithium fluoride thin films using dark field (DF) transmission electron microscopy (TEM). It is demonstrated that we can isolate the size distribution of <111> surface normal grains from the overall size distribution, based on simple and plausible assumptions about the texture. The {111} texture formation and surface morphology were also observed by x-ray diffraction (XRD) and AFM, respectively. The grain size distributions become clearly bimodal as the annealing time increases, and we deduce that the short-time size distributions are also a sum of two overlapping peaks. The smaller grain-size peak in the distribution corresponds to the {111}-oriented grains which do not grow significantly, while

  4. Stabilizing Nanocrystalline Grains in Ceramic-Oxides

    SciTech Connect

    Aidhy, Dilpuneet S; Zhang, Yanwen; Weber, William J

    2013-01-01

    Nanocrystalline ceramic-oxides are prone to grain growth rendering their highly attractive properties practically unusable. Using atomistic simulations ofon ceria as a model material system, we elucidate a framework to design dopant-pinned grain boundaries that prevent this grain growth. While in metallic systems it has been shown that a large mismatch between host and dopant atomic size prevents grain growth, in ceramic-oxides we find that this concept is not applicable. Instead, we find that dopant-oxygen vacancy interaction, i.e., dopant migration energy in the presence of oxygen vacancy, and dopant-oxygen vacancy binding energy are the controlling factors in grain growth. Our prediction agrees with and explains previous experimental observations.

  5. Toughness and strength of nanocrystalline graphene

    DOE PAGESBeta

    Shekhawat, Ashivni; Ritchie, Robert O.

    2016-01-28

    Pristine monocrystalline graphene is claimed to be the strongest material known with remarkable mechanical and electrical properties. However, graphene made with scalable fabrication techniques is polycrystalline and contains inherent nanoscale line and point defects—grain boundaries and grain-boundary triple junctions—that lead to significant statistical fluctuations in toughness and strength. These fluctuations become particularly pronounced for nanocrystalline graphene where the density of defects is high. Here we use large-scale simulation and continuum modelling to show that the statistical variation in toughness and strength can be understood with ‘weakest-link’ statistics. We develop the first statistical theory of toughness in polycrystalline graphene, and elucidatemore » the nanoscale origins of the grain-size dependence of its strength and toughness. Lastly, our results should lead to more reliable graphene device design, and provide a framework to interpret experimental results in a broad class of two-dimensional materials.« less

  6. Nanocrystalline silicon thin films for thermoelectric applications

    NASA Astrophysics Data System (ADS)

    Queen, Daniel; Jugdersuren, Battogtokh; Culberston, Jim; Wang, Qi; Nemeth, William; Metcalf, Tom; Liu, Xiao

    2014-03-01

    Recent advances in thermoelectric materials have come from reductions in thermal conductivity by manipulating both chemical composition and nanostructure to limit the phonon mean free path. However, wide spread applications for some of these materials may be limited due to high raw material and integration costs. In this talk we will discuss our recent results on nanocrystalline silicon thin films deposited by both hot-wire and plasma enhanced chemical vapor deposition where the nanocrystal size and crystalline volume fraction are varied by dilution of the silane precursor gas with hydrogen. Nanocyrstalline silicon is an established material technology used in multijunction amorphous silicon solar cells and has the potential to be a low cost and scalable material for use in thermoelectric devices. This work supported by the Office of Naval Research and the National Research Council.

  7. Toughness and strength of nanocrystalline graphene

    PubMed Central

    Shekhawat, Ashivni; Ritchie, Robert O.

    2016-01-01

    Pristine monocrystalline graphene is claimed to be the strongest material known with remarkable mechanical and electrical properties. However, graphene made with scalable fabrication techniques is polycrystalline and contains inherent nanoscale line and point defects—grain boundaries and grain-boundary triple junctions—that lead to significant statistical fluctuations in toughness and strength. These fluctuations become particularly pronounced for nanocrystalline graphene where the density of defects is high. Here we use large-scale simulation and continuum modelling to show that the statistical variation in toughness and strength can be understood with ‘weakest-link' statistics. We develop the first statistical theory of toughness in polycrystalline graphene, and elucidate the nanoscale origins of the grain-size dependence of its strength and toughness. Our results should lead to more reliable graphene device design, and provide a framework to interpret experimental results in a broad class of two-dimensional materials. PMID:26817712

  8. Nanocrystalline diamond coatings for mechanical seals applications.

    PubMed

    Santos, J A; Neto, V F; Ruch, D; Grácio, J

    2012-08-01

    A mechanical seal is a type of seal used in rotating equipment, such as pumps and compressors. It consists of a mechanism that assists the connection of the rotating shaft to the housings of the equipments, preventing leakage or avoiding contamination. A common cause of failure of these devices is end face wear out, thus the use of a hard, smooth and wear resistant coating such as nanocrystalline diamond would be of great importance to improve their working performance and increase their lifetime. In this paper, different diamond coatings were deposited by the HFCVD process, using different deposition conditions. Additionally, the as-grown films were characterized for, quality, morphology and microstructure using scanning electron microscopy (SEM) and Raman spectroscopy. The topography and the roughness of the films were characterized by atomic force microscopy (AFM). PMID:22962831

  9. Thermal Conductivity in Nanocrystalline Ceria Thin Films

    SciTech Connect

    Marat Khafizov; In-Wook Park; Aleksandr Chernatynskiy; Lingfeng He; Jianliang Lin; John J. Moore; David Swank; Thomas Lillo; Simon R. Phillpot; Anter El-Azab; David H. Hurley

    2014-02-01

    The thermal conductivity of nanocrystalline ceria films grown by unbalanced magnetron sputtering is determined as a function of temperature using laser-based modulated thermoreflectance. The films exhibit significantly reduced conductivity compared with stoichiometric bulk CeO2. A variety of microstructure imaging techniques including X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron analysis, and electron energy loss spectroscopy indicate that the thermal conductivity is influenced by grain boundaries, dislocations, and oxygen vacancies. The temperature dependence of the thermal conductivity is analyzed using an analytical solution of the Boltzmann transport equation. The conclusion of this study is that oxygen vacancies pose a smaller impediment to thermal transport when they segregate along grain boundaries.

  10. Toughness and strength of nanocrystalline graphene

    NASA Astrophysics Data System (ADS)

    Shekhawat, Ashivni; Ritchie, Robert O.

    2016-01-01

    Pristine monocrystalline graphene is claimed to be the strongest material known with remarkable mechanical and electrical properties. However, graphene made with scalable fabrication techniques is polycrystalline and contains inherent nanoscale line and point defects--grain boundaries and grain-boundary triple junctions--that lead to significant statistical fluctuations in toughness and strength. These fluctuations become particularly pronounced for nanocrystalline graphene where the density of defects is high. Here we use large-scale simulation and continuum modelling to show that the statistical variation in toughness and strength can be understood with `weakest-link' statistics. We develop the first statistical theory of toughness in polycrystalline graphene, and elucidate the nanoscale origins of the grain-size dependence of its strength and toughness. Our results should lead to more reliable graphene device design, and provide a framework to interpret experimental results in a broad class of two-dimensional materials.

  11. Hydrogenated nanocrystalline silicon germanium thin films

    NASA Astrophysics Data System (ADS)

    Yusoff, A. R. M.; Syahrul, M. N.; Henkel, K.

    2007-08-01

    Hydrogenated nanocrystalline silicon germanium thin films (nc-SiGe:H) is an interesting alternative material to replace hydrogenated nanocrystalline silicon (nc-Si:H) as the narrow bandgap absorber in an a-Si/a-SiGe/nc-SiGe(nc-Si) triple-junction solar cell due to its higher optical absorption in the wavelength range of interest. In this paper, we present results of optical, structural investigations and electrical characterization of nc-SiGe:H thin films made by hot-wire chemical vapor deposition (HWCVD) with a coil-shaped tungsten filament and with a disilane/germane/hydrogen gas mixture. The optical band gaps of a-SiGe:H and nc-SiGe:H thin-films, which are deposited with the same disilane/germane/hydrogen gas mixture ratio of 3.4:1.7:7, are about 1.58 eV and 2.1 eV, respectively. The nc-SiGe:H thin film exhibits a larger optical absorption coefficient of about 2-4 in the 600-900 nm range when compared to nc-Si:H thin film. Therefore, a thinner nc-SiGe:H layer of sim500 nm thickness may be sufficient for the narrow bandgap absorber in an a-Si based multiple-junction solar cell. We enhanced the transport properties as measured by the photoconductivity frequency mixing technique. These improved alloys do not necessarily show an improvement in the degree of structural heterogeneity on the nanometer scale as measured by small-angle X-ray scattering. Decreasing both the filament temperature and substrate temperature produced a film with relatively low structural heterogeneity while photoluminescence showed an order of magnitude increase in defect density for a similar change in the process.

  12. 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

  13. 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

  14. Bone integration capability of nanopolymorphic crystalline hydroxyapatite coated on titanium implants

    PubMed Central

    Yamada, Masahiro; Ueno, Takeshi; Tsukimura, Naoki; Ikeda, Takayuki; Nakagawa, Kaori; Hori, Norio; Suzuki, Takeo; Ogawa, Takahiro

    2012-01-01

    The mechanism by which hydroxyapatite (HA)-coated titanium promotes bone–implant integration is largely unknown. Furthermore, refining the fabrication of nano-structured HA to the level applicable to the mass production process for titanium implants is challenging. This study reports successful creation of nanopolymorphic crystalline HA on microroughened titanium surfaces using a combination of flame spray and low-temperature calcination and tests its biological capability to enhance bone–implant integration. Sandblasted microroughened titanium implants and sandblasted + HA-coated titanium implants were subjected to biomechanical and histomorphometric analyses in a rat model. The HA was 55% crystallized and consisted of nanoscale needle-like architectures developed in various diameters, lengths, and orientations, which resulted in a 70% increase in surface area compared to noncoated microroughened surfaces. The HA was free from impurity contaminants, with a calcium/phosphorus ratio of 1.66 being equivalent to that of stoichiometric HA. As compared to microroughened implants, HA-coated implants increased the strength of bone–implant integration consistently at both early and late stages of healing. HA-coated implants showed an increased percentage of bone–implant contact and bone volume within 50 μm proximity of the implant surface, as well as a remarkably reduced percentage of soft tissue intervention between bone and the implant surface. In contrast, bone volume outside the 50 μm border was lower around HA-coated implants. Thus, this study demonstrated that the addition of pure nanopolymorphic crystalline HA to microroughened titanium not only accelerates but also enhances the level of bone–implant integration and identified the specific tissue morphogenesis parameters modulated by HA coating. In particular, the nanocrystalline HA was proven to be drastic in increasing osteoconductivity and inhibiting soft tissue infiltration, but the effect was

  15. An Unusual Low-Density Supernova Graphite Grain with a Nanocrystalline Core

    NASA Astrophysics Data System (ADS)

    Groopman, E.; Bernatowicz, T.; Zinner, E.

    2013-09-01

    We have discovered a unique supernova graphite grain containing a nanocrystalline core. Electron diffraction studies of the core show evidence for stacked graphene sheets, previously unobserved in other nanocrystalline cores.

  16. 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.

  17. 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

  18. 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

  19. 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.

  20. 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

  1. Hydroxyapatite coating on biodegradable AZ31 and Mg-Ca alloys prepared by RF-magnetron sputtering

    SciTech Connect

    Mukhametkaliyev, T. Surmeneva, M. Surmenev, R.; Mathan, B. K.

    2015-11-17

    A thin film of hydroxyapatite (HA) was deposited on AZ31 and Mg-Ca alloys by using radio frequency (RF) magnetron sputtering. The thickness of the HA coating was determined to be 750 nm. The phase composition, microstructure, and surface morphology of the HA coatings were investigated using X-ray diffraction and scanning electron microscopy. In vitro degradation behaviour of the HA coated alloys was evaluated in simulated body fluid (SBF) and 3.5wt.% NaCl solution using electrochemical method. The coatings homogeneously covered the entire surface of the substrates. The coating structure corresponded to a nanostructured HA. The ultrathin coating significantly improved the degradation resistance of the alloy. Nanocrystalline HA coating significantly improved the corrosion resistance of the Mg-Ca and AZ31 magnesium alloys. The polarization resistance (Rp) of the coated Mg-Ca alloy was more than two-order of magnitude higher and the corrosion current density I{sub corr} reduced by ∼ 98% as compared to the base alloy.

  2. Fabrication of hydroxyapatite on pure titanium by micro-arc oxidation coupled with microwave-hydrothermal treatment.

    PubMed

    Zhao, Quan-ming; Yang, Hui-lin; Liu, Zhong-tang; Gu, Xiao-feng; Li, Cheng; Feng, De-hong

    2015-02-01

    Porous hydroxyapatite (HA)-containing composite films were prepared by a novel method consisting of micro-arc oxidation (MAO) combined with microwave-hydrothermal (M-H) treatment. The morphology, composition and phase composition of the bioactive films were investigated with scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffraction. MTT assay was carried out to investigate the in vitro effects of the different surfaces on bone integration properties. The prepared MAO films consisted mainly of anatase, rutile and tricalcium phosphate along with amorphous calcium (Ca) and phosphorus (P) phases. The M-H-treated composite films were composed primarily of anatase, rutile and HA. As the time and temperature of the M-H treatment increased, the number of HA crystals gradually increased. Using the M-H method, HA was obtained at a lower temperature and in a shorter period of time compared to the conventional hydrothermal method. The results suggest that the M-H method significantly decreases the hydrothermal reaction temperature and also greatly shortens the reaction time. Due to the nanocrystallinity and porosity of the prepared composite films, the method presented here shows promise for the formation of bioactive materials for medical applications. PMID:25649513

  3. Hydroxyapatite coating on biodegradable AZ31 and Mg-Ca alloys prepared by RF-magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Mukhametkaliyev, T.; Surmeneva, M.; Surmenev, R.; Mathan, B. K.

    2015-11-01

    A thin film of hydroxyapatite (HA) was deposited on AZ31 and Mg-Ca alloys by using radio frequency (RF) magnetron sputtering. The thickness of the HA coating was determined to be 750 nm. The phase composition, microstructure, and surface morphology of the HA coatings were investigated using X-ray diffraction and scanning electron microscopy. In vitro degradation behaviour of the HA coated alloys was evaluated in simulated body fluid (SBF) and 3.5wt.% NaCl solution using electrochemical method. The coatings homogeneously covered the entire surface of the substrates. The coating structure corresponded to a nanostructured HA. The ultrathin coating significantly improved the degradation resistance of the alloy. Nanocrystalline HA coating significantly improved the corrosion resistance of the Mg-Ca and AZ31 magnesium alloys. The polarization resistance (Rp) of the coated Mg-Ca alloy was more than two-order of magnitude higher and the corrosion current density Icorr reduced by ˜ 98% as compared to the base alloy.

  4. Surfactant free rapid synthesis of hydroxyapatite nanorods by a microwave irradiation method for the treatment of bone infection

    NASA Astrophysics Data System (ADS)

    Vani, R.; Bharathi Raja, Subramaniya; Sridevi, T. S.; Savithri, K.; Niranjali Devaraj, S.; Girija, E. K.; Thamizhavel, A.; Narayana Kalkura, S.

    2011-07-01

    Mesoporous nanocrystalline hydroxyapatite (nHAp) rods of size 40-75 nm long and 25 nm wide (resembling bone mineral) were synthesized under microwave irradiation without using any surfactants or modifiers. The surface area and average pore size of the nHAp were found to be 32 m2 g - 1 and 4 nm, respectively. Rifampicin (RIF) and ciprofloxacin (CPF) loaded nHAp displayed an initial burst followed by controlled release (zero order kinetics). Combination of CPF and RIF loaded nHAp showed enhanced bacterial growth inhibition against Staphylococcus aureus (S aureus), Staphylococcus epidermidis (S epidermidis) and Escherichia coli (E coli) compared to individual agent loaded nHAp and pure nHAp. In addition, decreased bacterial adhesion (90%) was observed on the surface of CPF plus RIF loaded nHAp. The biocompatibility test toward MG63 cells infected with micro-organisms showed better cell viability and alkaline phosphatase activity (ALP) for the combination of CPF and RIF loaded nHAp. The influence on cell viability of infected MG63 cells was attributed to the simultaneous and controlled release of CPF and RIF from nHAp, which prevented the emergence of subpopulations that were resistant to each other. Hence, apart from the issue of the rapid synthesis of nHAp without surfactants or modifiers, the simultaneous and controlled release of dual drugs from nHAp would be a simple, non-toxic and cost-effective method to treat bone infections.

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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).

  15. Synergistic strengthening effect of nanocrystalline copper reinforced with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Hu; Zhang, Zhao-Hui; Hu, Zheng-Yang; Wang, Fu-Chi; Li, Sheng-Lin; Korznikov, Elena; Zhao, Xiu-Chen; Liu, Ying; Liu, Zhen-Feng; Kang, Zhe

    2016-05-01

    In this study, a novel multi-walled carbon nanotubes reinforced nanocrystalline copper matrix composite with super high strength and moderate plasticity was synthesized. We successfully overcome the agglomeration problem of the carbon nanotubes and the grain growth problem of the nanocrystalline copper matrix by combined use of the electroless deposition and spark plasma sintering methods. The yield strength of the composite reach up to 692 MPa, which is increased by 2 and 5 times comparing with those of the nanocrystalline and coarse copper, respectively. Simultaneously, the plasticity of the composite was also significantly increased in contrast with that of the nanocrystalline copper. The increase of the density of the carbon nanotubes after coating, the isolation effect caused by the copper coating, and the improvement of the compatibility between the reinforcements and matrix as well as the effective control of the grain growth of the copper matrix all contribute to improving the mechanical properties of the composite. In addition, a new strengthening mechanism, i.e., the series-connection effect of the nanocrystalline copper grains introduced by carbon nanotubes, is proposed to further explain the mechanical behavior of the nanocomposite.

  16. Synergistic strengthening effect of nanocrystalline copper reinforced with carbon nanotubes.

    PubMed

    Wang, Hu; Zhang, Zhao-Hui; Hu, Zheng-Yang; Wang, Fu-Chi; Li, Sheng-Lin; Korznikov, Elena; Zhao, Xiu-Chen; Liu, Ying; Liu, Zhen-Feng; Kang, Zhe

    2016-01-01

    In this study, a novel multi-walled carbon nanotubes reinforced nanocrystalline copper matrix composite with super high strength and moderate plasticity was synthesized. We successfully overcome the agglomeration problem of the carbon nanotubes and the grain growth problem of the nanocrystalline copper matrix by combined use of the electroless deposition and spark plasma sintering methods. The yield strength of the composite reach up to 692 MPa, which is increased by 2 and 5 times comparing with those of the nanocrystalline and coarse copper, respectively. Simultaneously, the plasticity of the composite was also significantly increased in contrast with that of the nanocrystalline copper. The increase of the density of the carbon nanotubes after coating, the isolation effect caused by the copper coating, and the improvement of the compatibility between the reinforcements and matrix as well as the effective control of the grain growth of the copper matrix all contribute to improving the mechanical properties of the composite. In addition, a new strengthening mechanism, i.e., the series-connection effect of the nanocrystalline copper grains introduced by carbon nanotubes, is proposed to further explain the mechanical behavior of the nanocomposite. PMID:27185503

  17. Synergistic strengthening effect of nanocrystalline copper reinforced with carbon nanotubes

    PubMed Central

    Wang, Hu; Zhang, Zhao-Hui; Hu, Zheng-Yang; Wang, Fu-Chi; Li, Sheng-Lin; Korznikov, Elena; Zhao, Xiu-Chen; Liu, Ying; Liu, Zhen-Feng; Kang, Zhe

    2016-01-01

    In this study, a novel multi-walled carbon nanotubes reinforced nanocrystalline copper matrix composite with super high strength and moderate plasticity was synthesized. We successfully overcome the agglomeration problem of the carbon nanotubes and the grain growth problem of the nanocrystalline copper matrix by combined use of the electroless deposition and spark plasma sintering methods. The yield strength of the composite reach up to 692 MPa, which is increased by 2 and 5 times comparing with those of the nanocrystalline and coarse copper, respectively. Simultaneously, the plasticity of the composite was also significantly increased in contrast with that of the nanocrystalline copper. The increase of the density of the carbon nanotubes after coating, the isolation effect caused by the copper coating, and the improvement of the compatibility between the reinforcements and matrix as well as the effective control of the grain growth of the copper matrix all contribute to improving the mechanical properties of the composite. In addition, a new strengthening mechanism, i.e., the series-connection effect of the nanocrystalline copper grains introduced by carbon nanotubes, is proposed to further explain the mechanical behavior of the nanocomposite. PMID:27185503

  18. 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

  19. 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

  20. 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

  1. 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

  2. A nearly pure monoclinic nanocrystalline zirconia

    SciTech Connect

    Guo Gongyi . E-mail: guo_gongyi@hotmail.com; Chen Yuli

    2005-05-15

    Generally, monoclinic zirconia is considered to be much more difficult to prepare at low temperatures and particularly in a pure state. The present work is the first example that shows that the hydrous zirconia formed by precipitation can yield a nearly pure nanocrystalline monoclinic zirconia at a temperature as low as 320 deg. C. The crystallite size of the monoclinic zirconia produced in the present work is around 15nm, and it does not change appreciably as calcination temperature is increased from 320 to or above 400 deg. C. Such a small monoclinic crystallite arises from some of the chemical and physical factors built into the solution-gelation-xerogel process such as acidic preparation-pH, rapid precipitation, and moderate aging time and drying temperature, which result in a structure different from those of the existing zirconium hydroxides. In addition, the hydrous zirconia exhibits a unique thermal behavior in two respects: first, a sudden weight drop in the region of exothermic peak of the thermogravimetric curve is seen, suggesting that the main decomposition of the hydrous zirconia occurs in this region; second, there is an endothermic peak at high temperature in the differential thermal analysis curve, indicating the presence of coordinated water in the hydrous zirconia.

  3. Nanocrystalline films for gas-reactive applications

    DOEpatents

    Eastman, Jeffrey A.; Thompson, Loren J.

    2004-02-17

    A gas sensor for detection of oxidizing and reducing gases, including O.sub.2, CO.sub.2, CO, and H.sub.2, monitors the partial pressure of a gas to be detected by measuring the temperature rise of an oxide-thin-film-coated metallic line in response to an applied electrical current. For a fixed input power, the temperature rise of the metallic line is inversely proportional to the thermal conductivity of the oxide coating. The oxide coating contains multi-valent cation species that change their valence, and hence the oxygen stoichiometry of the coating, in response to changes in the partial pressure of the detected gas. Since the thermal conductivity of the coating is dependent on its oxygen stoichiometry, the temperature rise of the metallic line depends on the partial pressure of the detected gas. Nanocrystalline (<100 nm grain size) oxide coatings yield faster sensor response times than conventional larger-grained coatings due to faster oxygen diffusion along grain boundaries rather than through grain interiors.

  4. Rare earths in nanocrystalline glass ceramics

    NASA Astrophysics Data System (ADS)

    Lahoz, F.; Martín, I. R.; Rodríguez-Mendoza, U. R.; Iparraguirre, I.; Azkargorta, J.; Mendioroz, A.; Balda, R.; Fernández, J.; Lavín, V.

    2005-10-01

    The optical spectroscopic analysis of rare earth ions in transparent oxyfluoride glass-ceramics obtained from SiO2-Al2O3-PbF2-CdF2 based precursor glasses is presented. The oscillator strengths of the optical transitions were measured from the absorption spectra of glasses and glass-ceramics doped with rare earth ions. The results were analysed in the framework of the Judd-Ofelt theory giving the values of the three Ω2, Ω4 and Ω6 intensity parameters over the rare earth series. On the other hand, high efficient infrared-to-blue upconversion has been observed in Tm3+-Yb3+ codoped glass and glass-ceramic compared to the Tm3+ single doped matrices. The contributions to the upconversion process of the rare earth ions in the nanocrystalline and in the vitreous phase of the glass-ceramics have been distinguished. Finally, laser action in Nd3+-doped glass-ceramic has been studied. Losses due to UV and visible upconverted emissions inside the laser cavity have been also estimated.

  5. Functionalization of nanocrystalline diamond films with phthalocyanines

    NASA Astrophysics Data System (ADS)

    Petkov, Christo; Reintanz, Philipp M.; Kulisch, Wilhelm; Degenhardt, Anna Katharina; Weidner, Tobias; Baio, Joe E.; Merz, Rolf; Kopnarski, Michael; Siemeling, Ulrich; Reithmaier, Johann Peter; Popov, Cyril

    2016-08-01

    Phthalocyanine (Pc) derivatives containing different central metal atoms (Mn, Cu, Ti) and different peripheral chains were synthesized and comprehensively characterized. Their interaction with nanocrystalline diamond (NCD) films, as-grown by hot-filament chemical vapor deposition or after their modification with oxygen plasma to exchange the hydrogen termination with oxygen-containing groups, was studied by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The elemental composition as determined by XPS showed that the Pc were grafted on both as-grown and O-terminated NCD. Mn, Cu and Ti were detected together with N stemming from the Pc ring and S in case of the Ti-Pc from the peripheral ligands. The results for the elemental surface composition and the detailed study of the N 1s, S 2p and O 1s core spectra revealed that Ti-Pc grafted better on as-grown NCD but Cu-Pc and Mn-Pc on O-terminated films. Samples of Mn-Pc on as-grown and O-terminated NCD were further investigated by NEXAFS spectroscopy. The results showed ordering of the grafted molecules, laying flat on the H-terminated NCD surface while only the macrocycles were oriented parallel to the O-terminated surface with the peripheral chains perpendicular to it.

  6. Nanocrystalline cellulose for covert optical encryption

    NASA Astrophysics Data System (ADS)

    Zhang, Yu Ping; Chodavarapu, Vamsy P.; Kirk, Andrew G.; Andrews, Mark P.

    2012-02-01

    Nanocrystalline cellulose solid films derived from spruce pulp exhibit iridescence when cast from chiral nematic aqueous phase suspensions of the nanocrystals. Iridescence is a color travel phenomenon that might have potential for overt encryption as an anti-counterfeiting measure. The iridescent phase also offers an intrinsic level of covert encryption by virtue of the fact that films of NCC reflect left-circularly polarized light. Addition of TINOPAL, an optical brightening agent (OBA), adds a third level of (covert) encryption potential since the chromophore exhibits strong fluorescence when excited at ultra-violet wavelengths. The overall result is a selectively polarizing fluorescent iridescent film. We study the impact of additions of OBA on NCC iridescence, optical activity, and physical structure variation with polarized optical microscopy, circular dichroism spectropolarimetry and zeta potential analysis. Increasing OBA additions increase the chiral nematic pitch of NCC films, and this in turn alters chiral nematic domain structure in the solid film. Under low concentration conditions defined by our experiments, OBA yields intense UV fluorescence, without compromising the visible light iridescent properties of the film. The potential security offered by NCC and its optical responses can be authenticated using a UV light source such as is commonly used for banknote verification, a circular polarizer in conjunction with an iridescent feature which can be verified by the eye or by chiral spectrometry.

  7. Deuterium storage in nanocrystalline magnesium thin films

    NASA Astrophysics Data System (ADS)

    Checchetto, R.; Bazzanella, N.; Miotello, A.; Brusa, R. S.; Zecca, A.; Mengucci, A.

    2004-02-01

    Nanocrystalline magnesium deuteride thin films with the β-MgD2 structure were prepared by vacuum evaporation of hexagonal magnesium (h-Mg) samples and thermal annealing in 0.15 MPa D2 atmosphere at 373 K. Thermal desorption spectroscopy analysis indicated that the rate-limiting step in the deuterium desorption was given by the thermal decomposition of the deuteride phase. The activation energy Δg of the β-MgD2→h-Mg+D2 reaction scaled from 1.13±0.03 eV in 650-nm-thick films to 1.01±0.02 eV in 75-nm-thick films most likely as consequence of different stress and defect level. Positron annihilation spectroscopy analysis of the thin-film samples submitted to deuterium absorption and desorption cycles reveal the presence of a high concentration of void-like defects in the h-Mg layers after the very first decomposition of the β-MgD2 phase, the presence of these open volume defects reduces the D2 absorption capacity of the h-Mg thin film.

  8. Films prepared from electrosterically stabilized nanocrystalline cellulose.

    PubMed

    Yang, Han; Tejado, Alvaro; Alam, Nur; Antal, Miro; van de Ven, Theo G M

    2012-05-22

    Electrosterically stabilized nanocrystalline cellulose (ENCC) was modified in three ways: (1) the hydroxyl groups on C2 and C3 of glucose repeat units of ENCC were converted to aldehyde groups by periodate oxidation to various extents; (2) the carboxyl groups in the sodium form on ENCC were converted to the acid form by treating them with an acid-type ion-exchange resin; and (3) ENCC was cross-linked in two different ways by employing adipic dihydrazide as a cross-linker and water-soluble 1-ethyl-3-[3-(dimethylaminopropyl)] carbodiimide as a carboxyl-activating agent. Films were prepared from these modified ENCC suspensions by vacuum filtration. The effects of these three modifications on the properties of films were investigated by a variety of techniques, including UV-visible spectroscopy, a tensile test, thermogravimetric analysis (TGA), the water vapor transmission rate (WVTR), and contact angle (CA) studies. On the basis of the results from UV spectra, the transmittance of these films was as high as 87%, which shows them to be highly transparent. The tensile strength of these films was increased with increasing aldehyde content. From TGA and WVTR experiments, cross-linked films showed much higher thermal stability and lower water permeability. Furthermore, although the original cellulose is hydrophilic, these films also exhibited a certain hydrophobic behavior. Films treated by trichloromethylsilane become superhydrophobic. The unique characteristics of these transparent films are very promising for potential applications in flexible packaging and other high-technology products. PMID:22482733

  9. Dispersibility in water of dried nanocrystalline cellulose.

    PubMed

    Beck, Stephanie; Bouchard, Jean; Berry, Richard

    2012-05-14

    Dispersibility is important for nanocrystalline cellulose (NCC) because recovering the unique suspension and particle properties is essential after the product has been dried for storage or transport. It is our goal to produce dried NCC that redisperses in water to yield colloidal suspensions without the use of additives or a large energy input. In contrast with the as-prepared acidic form of NCC (H-NCC), suspensions of neutral sodium-form NCC (Na-NCC) dried by evaporation, lyophilization, or spray-drying are readily dispersible in water. Suspension properties and NCC particle size determined by light scattering were used as indicators of dispersion quality. The neutral counterion content, drying technique, freezing action, drying and redispersion concentrations, and moisture content in the dried NCC were all found to influence dispersibility. When a minimum of 94% of the H(+) counterion is exchanged for Na(+), the neutral salt form is fully dispersible in water even when fully dried. Mild sonication is generally sufficient to recover measured particle sizes identical to those in the never-dried Na-NCC sample. A threshold moisture content of 4 wt % was found, above which dried H-NCC is fully dispersible in water. PMID:22482888

  10. Nanocrystalline diamond nanoelectrode arrays and ensembles.

    PubMed

    Hees, Jakob; Hoffmann, René; Kriele, Armin; Smirnov, Waldemar; Obloh, Harald; Glorer, Karlheinz; Raynor, Brian; Driad, Rachid; Yang, Nianjun; Williams, Oliver A; Nebel, Christoph E

    2011-04-26

    In this report, the fabrication of all-nanocrystalline diamond (NCD) nanoelectrode arrays (NEAs) by e-beam lithography as well as of all-diamond nanoelectrode ensembles (NEEs) using nanosphere lithography is presented. In this way, nanostructuring techniques are combined with the excellent properties of diamond that are desirable for electrochemical sensor devices. Arrays and ensembles of recessed disk electrodes with radii ranging from 150 to 250 nm and a spacing of 10 μm have been fabricated. Electrochemical impedance spectroscopy as well as cyclic voltammetry was conducted to characterize arrays and ensembles with respect to different diffusion regimes. One outstanding advantage of diamond as an electrode material is the stability of specific surface terminations influencing the electron transfer kinetics. On changing the termination from hydrogen- to oxygen-terminated diamond electrode surface, we observe a dependence of the electron transfer rate constant on the charge of the analyte molecule. Ru(NH(3))(6)(+2/+3) shows faster electron transfer on oxygen than on hydrogen-terminated surfaces, while the anion IrCl(6)(-2/-3) exhibits faster electron transfer on hydrogen-terminated surfaces correlating with the surface dipole layer. This effect cannot be observed on macroscopic planar diamond electrodes and emphasizes the sensitivity of the all-diamond NEAs and NEEs. Thus, the NEAs and NEEs in combination with the efficiency and suitability of the selective electrochemical surface termination offer a new versatile system for electrochemical sensing. PMID:21413786

  11. Resputtering Effect on Nanocrystalline Ni-Ti Alloy Films

    NASA Astrophysics Data System (ADS)

    Priydarshini, B. Geetha; Esakkiraja, N.; Aich, Shampa; Chakraborty, M.

    2016-04-01

    We report on the effect of resputtering on the properties of nanocrystalline Ni-Ti alloy thin films deposited using co-sputtering of Ni and Ti targets. In order to facilitate the formation of nanocrystalline phases, films were deposited at room temperature and 573 K (300 °C) with substrate bias voltage of -100 V. The influence of substrate material on the composition, surface topography microstructure, and phase formations of nanocrystalline Ni-Ti thin films was also systematically investigated. The preferential resputtering of Ti adatoms was lesser for Ni-Ti films deposited on quartz substrate owing to high surface roughness of 4.87 nm compared to roughness value of 1.27 nm for Si(100) substrate.

  12. Kinetic constants of abnormal grain growth in nanocrystalline nickel

    NASA Astrophysics Data System (ADS)

    Aleshin, A. N.

    2016-02-01

    The grain growth in nanocrystalline nickel with a purity of 99.5 at % during non-isothermal annealing was experimentally investigated using differential scanning calorimetry and transmission electron microscopy. Nanocrystalline nickel was prepared by electrodeposition and had an average grain size of approximately 20 nm. It was shown that, at a temperature corresponding to the calorimetric signal peak, abnormal grain growth occurs with the formation of a bimodal grain microstructure. Calorimeters signals were processed within the Johnson-Mehl-Avrami formalism. This made it possible to determine the exponent of the corresponding equation, the frequency factor, and the activation energy of the grain growth, which was found to be equal to the activation energy of the vacancy migration. The reasons for the abnormal grain growth in nanocrystalline nickel were discussed.

  13. Structural, optical and magnetic behaviour of nanocrystalline Volborthite

    NASA Astrophysics Data System (ADS)

    Arvind, Hemant K.; Kalal, Sangeeta; Punjabi, P. B.; Choudhary, B. L.; Dolia, S. N.; Kumar, Sudhish

    2016-05-01

    Nanocrystalline sample of Volborthite (Copper Pyrovanadate: Cu3V2 (OH)2O7.2H2O) has been synthesized using wet chemical route and characterized by XRD, SEM, FTIR, UV-Vis-NIR spectroscopic and magnetization measurements. Room temperature X-ray diffraction analysis confirms the single phase monoclinic structure and nanocrystalline nature of Volborthite. The UV-Visible optical absorption spectrum displays two broad absorption peaks in the range of 200-350 nm and 400-1000 nm. The direct band gap is found to be Eg= ˜2.74 eV. Bulk Volborthite was reported to be a natural frustrated antiferromagnet, however our nanocrystalline Volborthite display week ferromagnetic hysteresis loop with very small coercivity and retentivity at room temperature.

  14. Tuning the Properties of Nanocrystalline CdS Thin Films

    NASA Astrophysics Data System (ADS)

    Ikhmayies, Shadia J.

    2014-01-01

    Tuning the properties of nanocrystalline cadmium sulfide (CdS) thin films is very important in the technology of photonics, detectors, and computing devices. This can be achieved through the appropriate selection of the synthesis techniques, types and concentrations of the chemicals, deposition parameters, and postdeposition heat treatments. In addition, control of the properties can be achieved by controlling the size, structure type, and surface states of the nanocrystallites without altering the chemical composition of the films. A review of the experimental methods for tuning the properties of nanocrystalline CdS thin films is performed. Although control of these variables is a complicated process, high-quality nanocrystalline CdS thin films with optimum structural, morphological, and optical properties have been produced by different authors.

  15. Nanocrystalline Pd alloy films coated by electroless deposition.

    PubMed

    Strukov, G V; Strukova, G K; Batov, I E; Sakharov, M K; Kudrenko, E A; Mazilkin, A A

    2011-10-01

    The structures of palladium and palladium alloys thin films deposited from organic electrolytes onto metallic substrates by electroless plating method have been investigated. The coatings are dense, pore-free 0.005-1 microm thick films with high adhesive strength to the substrate surface. EDX, XRD, SEM and TEM methods were used to determine the composition and structure of alloy coatings of the following binary systems: Pd-Au, Pd-Ag, Pd-Ni, Pd-Pb, and ternary system Pd-Au-Ni. The coatings of Pd-Au, Pd-Ag and Pd-Ni have a solid solution structure, whereas Pd-Pb is intermetallic compound. It has been found that the deposited films consist of nanocrystalline grains with sizes in the range of 11-35 nm. Scanning and transmission electron microscopy investigations reveal the existence of clusters formed by nanocrystalline grains. The origin for the formation of nanocrystalline structures of coating films is discussed. PMID:22400291

  16. 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

  17. 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

  18. 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

  19. Diffraction studies of the thermal properties of nanocrystalline Pd and Cr

    SciTech Connect

    Eastman, J.A.; Thompson, L.J. ); Fitzsimmons, M.R.; Lawson, A.C.; Robinson, R.A. )

    1992-09-01

    Quantitative X-ray and neutron diffraction measurements were made on nanocrystalline and coarse-grained samples of Pd and Cr. For both materials, Debye-Waller parameter comparisons over a temperature range of approximately 20-300 K indicate that the nanocrystalline materials have increased static displacements of atoms from their equilibrium sites compared to coarse-grained material. No grain-size-correlated differences in thermal vibrational amplitude, lattice parameter, or thermal expansion coefficients were observed in either material. In contrast to earlier results on nanocrystalline Pd, significantly more non-peak intensity is observed from a nanocrystalline Cr sample than from a coarse-grained Cr sample. Impurities may account for the increased background intensity from nanocrystalline Cr. These results indicate that there is no significant grain boundary excess volume in nanocrystalline Pd, and therefore the reduced density typically observed in nanocrystalline Pd samples must be due to porosity.

  20. Fabrication of heterostructures based on layered nanocrystalline silicon carbide polytypes

    SciTech Connect

    Semenov, A. V. Lopin, A. V.; Puzikov, V. M.; Baumer, V. N.; Dmitruk, I. N.

    2010-06-15

    The study demonstrates the possibility of forming heterostructures consisting of nanocrystalline SiC layers of the cubic 3C polytype (the lower layer on the substrate) and the rhombohedral 21R polytype (the upper layer) by direction deposition of nanocrystalline SiC layers onto a substrate subjected to gradient heating. The structure and order of arrangement of the SiC layers are analyzed in detail by X-ray diffraction studies, femtosecond photoluminescence measurements, and optical spectroscopy. The nature of the peaks observed in the photoluminescence, optical reflectance, and absorption spectra is discussed.

  1. Synthesis, characterization and mechanical properties of nanocrystalline NiAl

    SciTech Connect

    Choudry, M. |; Eastman, J.A.; DiMelfi, R.J.; Dollar, M.

    1996-11-01

    Nanocrystalline NiAl was produced from pre-cast alloys using an electron beam inert gas condensation system. In-situ compaction was carried out at 100-300 C under vacuum conditions. Energy dispersive spectroscopy was used to determine chemical composition and homogeneity. Average grain sizes in the range 4-10 nm were found from TEM dark field analyses. A compression-cage fixture was designed to perform disk bend tests. These tests revealed substantial room temperature ductility in nanocrystalline NiAl, while coarse grained NiAl showed no measurable room temperature ductility.

  2. Low temperature nanocrystalline zinc oxide for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Greulich-Weber, S.; Arceiz Casas, S.; Weber, N.

    2015-04-01

    Nanocrystalline ZnO was synthesized by a low temperature sol-gel route. The ZnOnanocrystals were investigated by X-ray diffraction (XRD), electron paramagnetic resonance (EPR), photoluminescence (PL), and conductivity measurements. The goal was the development of nanocrystalline ZnO as a transparent conductive oxide blocking ultraviolet (uv) light and using a defect photoluminescence band for down-shifting uvlight into the visible range, where organic photoactive polymers have their absorption maximum. The resulting defects and physical properties are discussed with respect to the conductivity of ZnO nanocrystals.

  3. Strengthening and softening of nanocrystalline nickel during multistep nanoindentation

    SciTech Connect

    Nieh, Tai-Gang; Pan, D; Chen, Ming-Wei

    2006-04-01

    Multistep load-unload nanoindentation was employed to address the effect of deformation-induced microstructural evolution on mechanical behavior of nanocrystalline Ni. Deformation discontinuity was deliberately introduced by unloading-reloading during nanoindentation testing, which allows us to examine the influence of microstructural evolution on the successive deformation. Strain strengthening/softening of nanocrystalline nickel, associated with the transition of deformation behavior from dislocation activity at high loading rates to a grain-boundary-mediated process at low loading rates, was uncovered by means of this experimental methodology.

  4. TRACKING SOLUTE ATOMS DURING BAINITE REACTION IN A NANOCRYSTALLINE STEEL

    SciTech Connect

    Caballero, Francesca G.; Miller, Michael K; Garcia-Mateo, C.

    2010-01-01

    The extremely slow transformation kinetics of a nanocrystalline bainitic steel makes this novel structure the perfect candidate to determine the carbon content of the bainitic ferrite away from any carbon enriched regions, such as dislocations and boundaries, as the bainite transformation progresses at extremely low temperatures. The purpose of this atom probe tomography study was to systematically track atom distributions during the bainite reaction in a nanocrystalline steel. The results will provide new experimental evidence on the explanation for the incomplete reaction phenomenon and the carbon supersaturation of the bainitic ferrite during transformation, subjects critically relevant to understanding the atomic mechanism controlling bainitic ferrite growth.

  5. Nanocrystalline glass ceramics: Structural, physical and optical properties

    NASA Astrophysics Data System (ADS)

    Singh, Satwinder; Singh, K.

    2015-02-01

    Four different transition metals contained nanocrystalline glass ceramics are synthesized by melting and quenching technique. The transition metal oxides play as former, modifier or both the roles depending on their oxidation states, field strength and covalent characteristics. The optical band gaps are observed in the range of 3.2-5.5 eV. The presence of nano-crystalline phases dominates the optical band gap. The softening temperature (Ts) is mainly affected by the residual glass in glass ceramics. These glass ceramics can be used as shielding materials for nuclear waste.

  6. Deformation mechanism crossover and mechanical behaviour in nanocrystalline materials.

    SciTech Connect

    Yamakov, V.; Wolf, D.; Phillpot, S. R.; Mukherjee, A. K.; Gleiter, H.; Materials Science Division; Univ. of California-Davis; Forschungszentrum Karlsruhe

    2003-06-01

    We use molecular dynamics simulations to elucidate the transition with decreasing grain size from a dislocation- to a grain-boundary-based deformation mechanism in nanocrystalline fcc metals. Our simulations reveal that this crossover is accompanied by a pronounced transition in the mechanical behaviour of the material; namely, at the grain size where the crossover occurs (the 'strongest size'), the strain rate under tensile elongation goes through a minimum. This simultaneous transition in both the deformation mechanism and the corresponding mechanical behaviour offers an explanation for the experimentally observed crossover in the yield strength of nanocrystalline materials, from Hall-Petch hardening to 'inverse Hall-Petch' softening.

  7. Coarse Graining and Localized Plasticity between Sliding Nanocrystalline Metals

    NASA Astrophysics Data System (ADS)

    Romero, Pedro A.; Järvi, Tommi T.; Beckmann, Nils; Mrovec, Matous; Moseler, Michael

    2014-07-01

    Tribological shearing of polycrystalline metals typically leads to grain refinement at the sliding interface. This study, however, shows that nanocrystalline metals exhibit qualitatively different behavior. Using large-scale atomistic simulations, we demonstrate that during sliding, contact interface nanocrystalline grains self-organize through extensive grain coarsening and lattice rotation until the optimal plastic slip orientation is established. Subsequently, plastic deformation is frequently confined to localized nanoshear bands aligned with the shearing direction and emanating from voids and other defects in the vicinity of the sliding interface.

  8. A mild reduction phosphidation approach to nanocrystalline GaP

    NASA Astrophysics Data System (ADS)

    Chen, Luyang; Luo, Tao; Huang, Mingxing; Gu, Yunle; Shi, Liang; Qian, Yitai

    2004-12-01

    Nanocrystalline gallium phosphide (GaP) has been prepared through a reduction-phosphidation by using Ga, PCl 3 as gallium and phosphorus sources and metallic sodium as reductant at 350 °C. The XRD pattern can be indexed as cublic GaP with the lattice constant of a=5.446 Å. The TEM image shows particle-like polycrystals and flake-like single crystals. The PL spectrum exhibits one peak at 330 nm for the as-prepared nanocrystalline GaP.

  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.

  11. Electrophoretic deposition of zinc-substituted hydroxyapatite coatings.

    PubMed

    Sun, Guangfei; Ma, Jun; Zhang, Shengmin

    2014-06-01

    Zinc-substituted hydroxyapatite nanoparticles synthesized by the co-precipitation method were used to coat stainless steel plates by electrophoretic deposition in n-butanol with triethanolamine as a dispersant. The effect of zinc concentration in the synthesis on the morphology and microstructure of coatings was investigated. It is found that the deposition current densities significantly increase with the increasing zinc concentration. The zinc-substituted hydroxyapatite coatings were analyzed by X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. It is inferred that hydroxyapatite and triethanolamine predominate in the chemical composition of coatings. With the increasing Zn/Ca ratios, the contents of triethanolamine decrease in the final products. The triethanolamine can be burnt out by heat treatment. The tests of adhesive strength have confirmed good adhesion between the coatings and substrates. The formation of new apatite layer on the coatings has been observed after 7days of immersion in a simulated body fluid. In summary, the results show that dense, uniform zinc-substituted hydroxyapatite coatings are obtained by electrophoretic deposition when the Zn/Ca ratio reaches 5%. PMID:24863199

  12. 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

  13. Periodontal regeneration with stem cells-seeded collagen-hydroxyapatite scaffold.

    PubMed

    Liu, Zeping; Yin, Xing; Ye, Qingsong; He, Wulin; Ge, Mengke; Zhou, Xiaofu; Hu, Jing; Zou, Shujuan

    2016-07-01

    Re-establishing compromised periodontium to its original structure, properties and function is demanding, but also challenging, for successful orthodontic treatment. In this study, the periodontal regeneration capability of collagen-hydroxyapatite scaffolds, seeded with bone marrow stem cells, was investigated in a canine labial alveolar bone defect model. Bone marrow stem cells were isolated, expanded and characterized. Porous collagen-hydroxyapatite scaffold and cross-linked collagen-hydroxyapatite scaffold were prepared. Attachment, migration, proliferation and morphology of bone marrow stem cells, co-cultured with porous collagen-hydroxyapatite or cross-linked collagen-hydroxyapatite, were evaluated in vitro. The periodontal regeneration capability of collagen-hydroxyapatite scaffold with or without bone marrow stem cells was tested in six beagle dogs, with each dog carrying one sham-operated site as healthy control, and three labial alveolar bone defects untreated to allow natural healing, treated with bone marrow stem cells - collagen-hydroxyapatite scaffold implant or collagen-hydroxyapatite scaffold implant, respectively. Animals were euthanized at 3 and 6 months (3 animals per group) after implantation and the resected maxillary and mandibular segments were examined using micro-computed tomography scan, H&E staining, Masson's staining and histometric evaluation. Bone marrow stem cells were successfully isolated and demonstrated self-renewal and multi-potency in vitro. The porous collagen-hydroxyapatite and cross-linked collagen-hydroxyapatite had average pore sizes of 415 ± 20 µm and 203 ± 18 µm and porosity of 69 ± 0.5% and 50 ± 0.2%, respectively. The attachment, proliferation and migration of bone marrow stem cells were satisfactory on both porous collagen-hydroxyapatite and cross-linked collagen-hydroxyapatite scaffolds. Implantation of bone marrow stem cells - collagen-hydroxyapatite or collagen-hydroxyapatite scaffold in

  14. Alternative designs for nanocrystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Madhavan, Atul

    Nanocrystalline silicon is an attractive material for solar cells. It has very small grains, about 20 nm, and yet its electronic properties are very similar to those of crystalline silicon. The material exhibits smaller mobilities than crystalline Silicon, but the minority carrier lifetimes are reasonable. It is known that the properties of the material depend critically upon deposition parameters, in particular, the degree of grain boundary passivation achieved during growth and grain size. Previous work has shown that as the material grows, the grains tend to agglomerate into a cluster, and the development of this cluster leads to poorer electronic properties. The traditional method for overcoming such clustering has been to change the hydrogen to silane dilution ratio as the material grows, keeping the material near its crystalline to amorphous transition zone. However, this method is dependent upon the precise growth chemistry and is not suitable for mass production. In this project, we develop a new device design, a superlattice comprising alternating layers of amorphous and nanocrystalline silicon, which allows one to precisely control the agglomeration of grains without having to resort to hydrogen profiling techniques. We study structural properties such as grain size and the degree of crystallnity, and electronic properties such as carrier diffusion lengths and defect densities. We show that an appropriate design of the superlattice allows one to minimize defect densities and maximize carrier diffusion lengths. We also study how to reduce series resistance in solar cells, and show that an appropriate combination of superlattice and contacts can lead to devices with high fill factors and good solar cell efficiencies. We also report on a new discovery, namely that the optical absorption itself depends critically upon grain size. Larger grain sizes, up to 50 nm, lead to increased optical absorption, a totally unexpected and very useful discovery for devices

  15. Copper removal using electrosterically stabilized nanocrystalline cellulose.

    PubMed

    Sheikhi, Amir; Safari, Salman; Yang, Han; van de Ven, Theo G M

    2015-06-01

    Removal of heavy metal ions such as copper using an efficient and low-cost method with low ecological footprint is a critical process in wastewater treatment, which can be achieved in a liquid phase using nanoadsorbents such as inorganic nanoparticles. Recently, attention has turned toward developing sustainable and environmentally friendly nanoadsorbents to remove heavy metal ions from aqueous media. Electrosterically stabilized nanocrystalline cellulose (ENCC), which can be prepared from wood fibers through periodate/chlorite oxidation, has been shown to have a high charge content and colloidal stability. Here, we show that ENCC scavenges copper ions by different mechanisms depending on the ion concentration. When the Cu(II) concentration is low (C0≲200 ppm), agglomerates of starlike ENCC particles appear, which are broken into individual starlike entities by shear and Brownian motion, as evidenced by photometric dispersion analysis, dynamic light scattering, and transmission electron microscopy. On the other hand, at higher copper concentrations, the aggregate morphology changes from starlike to raftlike, which is probably due to the collapse of protruding dicarboxylic cellulose (DCC) chains and ENCC charge neutralization by copper adsorption. Such raftlike structures result from head-to-head and lateral aggregation of neutralized ENCCs as confirmed by transmission electron microscopy. As opposed to starlike aggregates, the raftlike structures grow gradually and are prone to sedimentation at copper concentrations C0≳500 ppm, which eliminates a costly separation step in wastewater treatment processes. Moreover, a copper removal capacity of ∼185 mg g(-1) was achieved thanks to the highly charged DCC polyanions protruding from ENCC. These properties along with the biorenewability make ENCC a promising candidate for wastewater treatment, in which fast, facile, and low-cost removal of heavy metal ions is desired most. PMID:25950624

  16. The inhibition of lamellar hydroxyapatite and lamellar magnetic hydroxyapatite on the migration and adhesion of breast cancer cells.

    PubMed

    Jin, Jun; Zuo, Guifu; Xiong, Guangyao; Luo, Honglin; Li, Qiuping; Ma, Chunying; Li, Deying; Gu, Feng; Ma, Yongjie; Wan, Yizao

    2014-04-01

    Hydroxyapatite nanoparticles have been reported to exhibit potent anti-tumor effects in some cancer cells. In our previous study, we have successfully synthesized two types of hydroxyapatite nanoparticles, laminated hydroxyapatite (L-HAp) and laminated magnetic hydroxyapatite (LM-HAp). In this study, we wanted to investigate the effects of L-HAp and LM-HAp with various concentrations on human breast cancer MDA-MB-231 cells. Cell proliferation was assessed with a MTT colorimetric assay. Scratch and adhesion assays were used to detect the effects of these two materials on migration and adhesion. The expressions of integrin β1 and Akt were measured by Western blotting. Our results showed that L-HAp and LM-HAp had little cell cytotoxicity and significantly reduced cell mobility and adhesion. LM-HAp showed greater inhibitor ability on migration and adhesion of MDA-MB-231 cells. Moreover, results from western blotting showed that L-HAp and LM-HAp impacted the phosphorylation of integrin β1, but showed no regular impact on Akt. This study suggests that L-HAp and LM-HAp may be potential anti-tumor and delivery system for breast cancer therapy. PMID:24363068

  17. New route to the fabrication of nanocrystalline diamond films

    SciTech Connect

    Varshney, Deepak Morell, Gerardo; Palomino, Javier; Resto, Oscar; Gil, Jennifer; Weiner, Brad R.

    2014-02-07

    Nanocrystalline diamond (NCD) thin films offer applications in various fields, but the existing synthetic approaches are cumbersome and destructive. A major breakthrough has been achieved by our group in the direction of a non-destructive, scalable, and economic process of NCD thin-film fabrication. Here, we report a cheap precursor for the growth of nanocrystalline diamond in the form of paraffin wax. We show that NCD thin films can be fabricated on a copper support by using simple, commonplace paraffin wax under reaction conditions of Hot Filament Chemical Vapor Deposition (HFCVD). Surprisingly, even the presence of any catalyst or seeding that has been conventionally used in the state-of-the-art is not required. The structure of the obtained films was analyzed by scanning electron microscopy and transmission electron microscopy. Raman spectroscopy and electron energy-loss spectroscopy recorded at the carbon K-edge region confirm the presence of nanocrystalline diamond. The process is a significant step towards cost-effective and non-cumbersome fabrication of nanocrystalline diamond thin films for commercial production.

  18. Development of Bulk Nanocrystalline Cemented Tungsten Carbide for Industrial Applicaitons

    SciTech Connect

    Z. Zak Fang, H. Y. Sohn

    2009-03-10

    This report contains detailed information of the research program entitled "Development of Bulk Nanocrystalline Cemented Tungsten Carbide Materials for Industrial Applications". The report include the processes that were developed for producing nanosized WC/Co composite powders, and an ultrahigh pressure rapid hot consolidation process for sintering of nanosized powders. The mechanical properties of consolidated materials using the nanosized powders are also reported.

  19. Synthesis and characterization of nanocrystalline and mesoporous zeolites

    NASA Astrophysics Data System (ADS)

    Petushkov, Anton

    2011-12-01

    Mesoporous aggregates of nanocrystalline zeolites with MFI and BEA frameworks have been synthesized using a one-pot and single structure directing agent. The effect of different reaction conditions, such as temperature, time, pH and water content, on the particle size, surface area and mesopore volume has been studied. Nanocrystalline and mesoporous ZSM-5, beta and Y zeolites were modified with different transition metals and the resulting single- and double metal containing catalyst materials were characterized. Nanocrystalline Silicalite-1 zeolite samples with varying particle size were functionalized with different organosilane groups and the cytotoxic activity of the zeolite nanocrystals was studied as a function of particle size, concentration, organic functional group type, as well as the type of cell line. Framework stability of nanocrystalline NaY zeolite was tested under different pH conditions. The synthesized zeolites used in this work were characterized using a variety of physico-chemical methods, including powder X-ray diffraction, Solid State NMR, nitrogen sorption, electron microscopy, Inductively Coupled Plasma -- Optical Emission Spectroscopy and X-ray Photoelectron Spectroscopy.

  20. Synthesis of Nano-Crystalline Gamma-TiAl Materials

    NASA Technical Reports Server (NTRS)

    Hales, Stephen J.; Vasquez, Peter

    2003-01-01

    One of the principal problems with nano-crystalline materials is producing them in quantities and sizes large enough for valid mechanical property evaluation. The purpose of this study was to explore an innovative method for producing nano-crystalline gamma-TiAl bulk materials using high energy ball milling and brief secondary processes. Nano-crystalline powder feedstock was produced using a Fritsch P4(TM) vario-planetary ball mill recently installed at NASA-LaRC. The high energy ball milling process employed tungsten carbide tooling (vials and balls) and no process control agents to minimize contamination. In a collaborative effort, two approaches were investigated, namely mechanical alloying of elemental powders and attrition milling of pre-alloyed powders. The objective was to subsequently use RF plasma spray deposition and short cycle vacuum hot pressing in order to effect consolidation while retaining nano-crystalline structure in bulk material. Results and discussion of the work performed to date are presented.

  1. Light emission, light detection and strain sensing with nanocrystalline graphene

    NASA Astrophysics Data System (ADS)

    Riaz, Adnan; Pyatkov, Feliks; Alam, Asiful; Dehm, Simone; Felten, Alexandre; Chakravadhanula, Venkata S. K.; Flavel, Benjamin S.; Kübel, Christian; Lemmer, Uli; Krupke, Ralph

    2015-08-01

    Graphene is of increasing interest for optoelectronic applications exploiting light detection, light emission and light modulation. Intrinsically, the light-matter interaction in graphene is of a broadband type. However, by integrating graphene into optical micro-cavities narrow-band light emitters and detectors have also been demonstrated. These devices benefit from the transparency, conductivity and processability of the atomically thin material. To this end, we explore in this work the feasibility of replacing graphene with nanocrystalline graphene, a material which can be grown on dielectric surfaces without catalyst by graphitization of polymeric films. We have studied the formation of nanocrystalline graphene on various substrates and under different graphitization conditions. The samples were characterized by resistance, optical transmission, Raman and x-ray photoelectron spectroscopy, atomic force microscopy and electron microscopy measurements. The conducting and transparent wafer-scale material with nanometer grain size was also patterned and integrated into devices for studying light-matter interaction. The measurements show that nanocrystalline graphene can be exploited as an incandescent emitter and bolometric detector similar to crystalline graphene. Moreover the material exhibits piezoresistive behavior which makes nanocrystalline graphene interesting for transparent strain sensors.

  2. Fatigue stress concentration and notch sensitivity in nanocrystalline metals

    DOE PAGESBeta

    Furnish, Timothy A.; Boyce, Brad L.; Sharon, John A.; O’Brien, Christopher J.; Clark, Blythe G.; Arrington, Christian L.; Pillars, Jamin R.

    2016-03-11

    Recent studies have shown the potential for nanocrystalline metals to possess excellent fatigue resistance compared to their coarse-grained counterparts. Although the mechanical properties of nanocrystalline metals are believed to be particularly susceptible to material defects, a systematic study of the effects of geometric discontinuities on their fatigue performance has not yet been performed. In the present work, nanocrystalline Ni–40 wt%Fe containing both intrinsic and extrinsic defects were tested in tension–tension fatigue. The defects were found to dramatically reduce the fatigue resistance, which was attributed to the relatively high notch sensitivity in the nanocrystalline material. Microstructural analysis within the crack-initiation zonesmore » underneath the defects revealed cyclically-induced abnormal grain growth (AGG) as a predominant deformation and crack initiation mechanism during high-cycle fatigue. Furthermore, the onset of AGG and the ensuing fracture is likely accelerated by the stress concentrations, resulting in the reduced fatigue resistance compared to the relatively defect-free counterparts.« less

  3. Light emission, light detection and strain sensing with nanocrystalline graphene.

    PubMed

    Riaz, Adnan; Pyatkov, Feliks; Alam, Asiful; Dehm, Simone; Felten, Alexandre; Chakravadhanula, Venkata S K; Flavel, Benjamin S; Kübel, Christian; Lemmer, Uli; Krupke, Ralph

    2015-08-14

    Graphene is of increasing interest for optoelectronic applications exploiting light detection, light emission and light modulation. Intrinsically, the light-matter interaction in graphene is of a broadband type. However, by integrating graphene into optical micro-cavities narrow-band light emitters and detectors have also been demonstrated. These devices benefit from the transparency, conductivity and processability of the atomically thin material. To this end, we explore in this work the feasibility of replacing graphene with nanocrystalline graphene, a material which can be grown on dielectric surfaces without catalyst by graphitization of polymeric films. We have studied the formation of nanocrystalline graphene on various substrates and under different graphitization conditions. The samples were characterized by resistance, optical transmission, Raman and x-ray photoelectron spectroscopy, atomic force microscopy and electron microscopy measurements. The conducting and transparent wafer-scale material with nanometer grain size was also patterned and integrated into devices for studying light-matter interaction. The measurements show that nanocrystalline graphene can be exploited as an incandescent emitter and bolometric detector similar to crystalline graphene. Moreover the material exhibits piezoresistive behavior which makes nanocrystalline graphene interesting for transparent strain sensors. PMID:26207014

  4. Ag doped silicon nitride nanocomposites for embedded plasmonics

    NASA Astrophysics Data System (ADS)

    Bayle, M.; Bonafos, C.; Benzo, P.; Benassayag, G.; Pécassou, B.; Khomenkova, L.; Gourbilleau, F.; Carles, R.

    2015-09-01

    The localized surface plasmon-polariton resonance (LSPR) of noble metal nanoparticles (NPs) is widely exploited for enhanced optical spectroscopies of molecules, nonlinear optics, photothermal therapy, photovoltaics, or more recently in plasmoelectronics and photocatalysis. The LSPR frequency depends not only of the noble metal NP material, shape, and size but also of its environment, i.e., of the embedding matrix. In this paper, Ag-NPs have been fabricated by low energy ion beam synthesis in silicon nitride (SiNx) matrices. By coupling the high refractive index of SiNx to the relevant choice of dielectric thickness in a SiNx/Si bilayer for an optimum antireflective effect, a very sharp plasmonic optical interference is obtained in mid-range of the visible spectrum (2.6 eV). The diffusion barrier property of the host SiNx matrix allows for the introduction of a high amount of Ag and the formation of a high density of Ag-NPs that nucleate during the implantation process. Under specific implantation conditions, in-plane self-organization effects are obtained in this matrix that could be the result of a metastable coarsening regime.

  5. Ag doped silicon nitride nanocomposites for embedded plasmonics

    SciTech Connect

    Bayle, M.; Bonafos, C. Benzo, P.; Benassayag, G.; Pécassou, B.; Carles, R.; Khomenkova, L.; Gourbilleau, F.

    2015-09-07

    The localized surface plasmon-polariton resonance (LSPR) of noble metal nanoparticles (NPs) is widely exploited for enhanced optical spectroscopies of molecules, nonlinear optics, photothermal therapy, photovoltaics, or more recently in plasmoelectronics and photocatalysis. The LSPR frequency depends not only of the noble metal NP material, shape, and size but also of its environment, i.e., of the embedding matrix. In this paper, Ag-NPs have been fabricated by low energy ion beam synthesis in silicon nitride (SiN{sub x}) matrices. By coupling the high refractive index of SiN{sub x} to the relevant choice of dielectric thickness in a SiN{sub x}/Si bilayer for an optimum antireflective effect, a very sharp plasmonic optical interference is obtained in mid-range of the visible spectrum (2.6 eV). The diffusion barrier property of the host SiN{sub x} matrix allows for the introduction of a high amount of Ag and the formation of a high density of Ag-NPs that nucleate during the implantation process. Under specific implantation conditions, in-plane self-organization effects are obtained in this matrix that could be the result of a metastable coarsening regime.

  6. Hot Superplastic Powder Forging for Transparent nanocrystalline Ceramics

    SciTech Connect

    Cannon, W. Roger

    2006-05-22

    The program explored a completely new, economical method of manufacturing nanocrystalline ceramics, Hot Superplastic Powder Forging (HSPF). The goal of the work was the development of nanocrystalline/low porosity optically transparent zirconia/alumina. The high optical transparency should result from lack of grain boundary scattering since grains will be smaller than one tenth the wavelength of light and from elimination of porosity. An important technological potential for this process is manufacturing of envelopes for high-pressure sodium vapor lamps. The technique for fabricating monolithic nanocrystalline material does not begin with powder whose particle diameter is <100 nm as is commonly done. Instead it begins with powder whose particle diameter is on the order of 10-100 microns but contains nanocrystalline crystallites <<100 nm. Spherical particles are quenched from a melt and heat treated to achieve the desired microstructure. Under a moderate pressure within a die or a mold at temperatures of 1100C to 1300C densification is by plastic flow of superplastic particles. A nanocrystalline microstructure results, though some features are greater than 100nm. It was found, for instance, that in the fully dense Al2O3-ZrO2 eutectic specimens that a bicontinuous microstructure exists containing <100 nm ZrO2 particles in a matrix of Al2O3 grains extending over 1-2 microns. Crystallization, growth, phase development and creep during hot pressing and forging were studied for several compositions and so provided some details on development of polycrystalline microstructure from heating quenched ceramics.

  7. Biomolecule-mediated synthesis of nanocrystalline semiconductors

    NASA Astrophysics Data System (ADS)

    Bae, Weon

    CdS and ZnS nanocrystalline semiconductors (NCs) were prepared by titrating inorganic sulfide into preformed Cd(II)- or Zn(II)-complexes of phytochelatins, glutathione or cysteine. This strategy resulted in the formation NCs capped by the chosen biomolecule. The range of sizes and their distributions depended primarily on the quantity of sulfide titrated and the biomolecule chosen for the initial metallo-complex. The processes of NC formation were studied by absorption and fluorescence spectrophotometry. The size distribution was analyzed by gel permeation chromatography. Ethanol precipitation of NCs under aqueous conditions was used to isolate nanoparticles within a very narrow size-range. Reduction of selected dyes was also studied on the surfaces of NCs. Glutathione-capped CdS nanoparticles exhibited significant size heterogeneity even at a single sulfide titration. In contrast, phytochelatins showed much less dispersion in size at a given sulfide titration. Phytochelatins could replace glutathione without changing the size of glutathione-capped CdS nanoparticles. Cysteine appeared to be intermediate between glutathione and phytochelatins in the formation of CdS nanoparticles. The calculated radii, using an effective mass approximation method, were 10.8-17.3, 10.6-11.8, and 13.5-15.5A for glutathione-, phytochelatin-, and cysteine-capped CdS nanoparticles, respectively. Cysteine-capped ZnS showed narrower size distribution than glutathione-capped ZnS. However, elevated temperatures were necessary to accomplish optimal yields of cysteine-capped ZnS NCs. An additional control over the size distribution of NCs was achieved by size-selective precipitation with ethanol. These procedures led to the isolation of nanoparticles that were more uniform in size and chemical compositions as determined by spectroscopic and chemical analyses of size-fractionated samples. Precipitation also allowed preparation of large quantities of powdered nanoparticles that could be

  8. A new injectable biphasic hydrogel based on partially hydrolyzed polyacrylamide and nano hydroxyapatite, crosslinked with chromium acetate, as scaffold for cartilage regeneration

    NASA Astrophysics Data System (ADS)

    Koushki, N.; Tavassoli, H.; Katbab, A. A.; Katbab, P.; Bonakdar, S.

    2015-05-01

    Polymer scaffolds are applied in the field of tissue engineering as three dimensional structures to organize cells and present stimuli to direct generation of a desired damaged tissue. In situ gelling scaffolds have attracted great attentions, as they are structurally similar to the extra cellular matrix (ECM). In the present work, attempts have been made to design and fabricate a new injectable and crosslinkable biphasic hydrogel based on partially hydrolyzed polyacrylamide (HPAM), chromium acetate as crosslink agent and nanocrystalline hydroxyapatite (nHAp) as reinforcing and bioactive agent for repair and regeneration of damaged cartilage. The distinct characteristic of HPAM is the presence of carboxylate anion groups on its backbone which allows to engineer the structure of the hydrogel for the desired bioactivity with appropriate cells differentiation towards both soft and hard (bone) tissues. The synthesized hydrogel exhibited bifunctional behavior which was derived by its biphasic structure in which one phase was loaded with nano hydroxyapatite to provide integration capability by subchondral bones and fix the hydrogel at cartilage defect without a need for suturing. The other phase differentiates the rabbit adipogenic mesenchymal stem cells (MSCs) towards soft tissue. Rheomechanical spectrometry (RMS) was employed to study the kinetic of the gelation including induction time and rate, as well as to measure the ultimate elastic modulus of the optimum crosslinked hydrogel. Surface tension measurement was also performed to tailor the surface characteristics of the gels. In vitro culturing of the cells inside the crosslinked hydrogel revealed high viability and high differentiation of the encapsulated rabbit stem cells, providing that the chromium acetate level was kept below 0.2 wt%. Based on the obtained results, the designed and fabricated biphasic hydrogel exhibited high potential as carrier for the stem cells for cartilage tissue engineering application

  9. Electrochemically assisted deposition of hydroxyapatite on Ti6Al4V substrates covered by CVD diamond films - Coating characterization and first cell biological results.

    PubMed

    Strąkowska, Paulina; Beutner, René; Gnyba, Marcin; Zielinski, Andrzej; Scharnweber, Dieter

    2016-02-01

    Although titanium and its alloys are widely used as implant material for orthopedic and dental applications they show only limited corrosion stability and osseointegration in different cases. The aim of the presented research was to develop and characterize a novel surface modification system from a thin diamond base layer and a hydroxyapatite (HAp) top coating deposited on the alloy Ti6Al4V widely used for implants in contact with bone. This coating system is expected to improve both the long-term corrosion behavior and the biocompatibility and bioactivity of respective surfaces. The diamond base films were obtained by Microwave Plasma Assisted Chemical Vapor Deposition (MW-PACVD); the HAp coatings were formed in aqueous solutions by electrochemically assisted deposition (ECAD) at varying polarization parameters. Scanning electron microscopy (SEM), Raman microscopy, and electrical conductivity measurements were applied to characterize the generated surface states; the calcium phosphate coatings were additionally chemically analyzed for their composition. The biological properties of the coating system were assessed using hMSC cells analyzing for cell adhesion, proliferation, and osteogenic differentiation. Varying MW-PACVD process conditions resulted in composite coatings containing microcrystalline diamond (MCD/Ti-C), nanocrystalline diamond (NCD), and boron-doped nanocrystalline diamond (B-NCD) with the NCD coatings being dense and homogeneous and the B-NCD coatings showing increased electrical conductivity. The ECAD process resulted in calcium phosphate coatings from stoichiometric and non-stoichiometric HAp. The deposition of HAp on the B-NCD films run at lower cathodic potentials and resulted both in the highest coating mass and the most homogenous appearance. Initial cell biological investigations showed an improved cell adhesion in the order B-NCD>HAp/B-NCD>uncoated substrate. Cell proliferation was improved for both investigated coatings whereas ALP

  10. Bone integration capability of a series of strontium-containing hydroxyapatite coatings formed by micro-arc oxidation.

    PubMed

    Yan, Jun; Sun, Ji-Feng; Chu, Paul K; Han, Yong; Zhang, Yu-Mei

    2013-09-01

    Strontium-containing hydroxyapatites (Sr-HA) combine the desirable bone regenerative properties of hydroxyapatites (HA) with anabolic and anti-catabolic effects of strontium cations. In the present work, a series of Sr(y)HA [Sr(y)Ca(10-y)(PO4)6(OH)2; y = 0, 0.5, 1, 2] coatings on titanium are produced by micro-arc oxidation (MAO), and the effects of the in vivo osseointegration ability of the coatings are investigated by using a rabbit model. All samples are subjected to biomechanical, surface elemental, micro-CT and histological analysis after 4 and 12 weeks of healing. The obtained results show that the MAO-formed coatings exhibit a microporous network structure composed of Sr(y)HA/Sr(y)HA-Sr(x)Ca(1-x)TiO3/Sr(x)Ca(1-x)TiO3-TiO2 multilayers, in which the outer Sr(y)HA and intermediate Sr(y)HA-Sr(x)Ca(1-x)TiO3 layers have a nanocrystalline structure. All Sr-HA coated implants induce marked improvements in the behavior of bone formation, quantity and quality of bone tissue around the implants than the control HA implant and in particular, the 20%Sr-HA coating promotes early bone formation as identified by polyfluorochrome sequential labeling. The bone-to-implant contact is increased by 46% (p < 0.05) and the pull-out strength is increased by 103% over the HA group (p < 0.01). Extensive areas of mineralized tissue densely deposit on the 20%Sr-HA coating after biomechanical testing, and the greatest improvement of bone microarchitecture are observed around the 20%Sr-HA implant. The identified biological parameters successfully demonstrate the osteoconductivity of 20%Sr-HA surfaces, which results not only in an acceleration but also an improvement of bone-implant integration. The study demonstrates the immense potential of 20%Sr-HA coatings in dental and orthopedic applications. PMID:23348908

  11. Outcomes following ossicular chain reconstruction with composite prostheses: hydroxyapatite-polyethylene vs. hydroxyapatite-titanium.

    PubMed

    Hahn, Yoav; Bojrab, Dennis I

    2013-06-01

    We conducted a retrospective study to compare the results of ossicular chain reconstruction (OCR) with two types of composite prosthesis: a hydroxyapatite-polyethylene (HAPEX) implant and a hydroxyapatite-titanium (HATi) prosthesis. We reviewed the records of 222 patients-104 males and 118 females, aged 8 to 79 years (mean: 39.7)-who had undergone OCR for ossicular chain dysfunction and who met our eligibility criteria. In addition to demographic data and the type of prosthesis, we compiled information on pre- and postoperative audiometric findings, the underlying diagnosis, the timing of surgery (primary, planned, or revision), the type of surgery (tympanoplasty alone, tympanoplasty with antrotomy, intact-canal-wall tympanomastoidectomy, or canal-wall-down tympanomastoidectomy), the extent of reconstruction (partial or total), the use of the malleus, the use of a tragal cartilage graft, and evidence of extrusion. Of the 222 patients, 46 had undergone insertion of either a partial (n = 36) or total (n = 10) ossicular replacement prosthesis (PORP and TORP, respectively) made with HAPEX, and 176 had received a PORP (n = 101) or TORP (n = 75) made with HATi. Postoperatively, the mean air-bone gap (ABG) was 14.0 dB in the HAPEX group and 14.7 dB in the HATi group, which was not a significant difference (p = 0.61). Postoperative success (ABG ≤20 dB) with PORP was obtained in 30 of the 36 patients in the HAPEX group (83.3%) and in 87 of the 101 patients in the HATi group (86.1%), while success with TORP was achieved in 7 of 10 HAPEX patients (70.0%) and 56 of 75 HATi patients (74.7%); there was no significant difference in either PORP or TORP success rates between the HAPEX and HATi groups (p = 0.32). A significantly better hearing result was obtained when the malleus was used in reconstruction (p = 0.035), but the use of tragal cartilage led to a significantly worse outcome (p = 0.026). Revision surgery was associated with a significantly worse postoperative result (p

  12. Production and thermal stability of pure and Cr3+ -doped hydroxyapatite

    NASA Astrophysics Data System (ADS)

    de Araujo, T. S.; de Souza, S. O.; de Sousa, E. M. B.; Araújo, M. S.

    2010-11-01

    Hydroxyapatite (HAP) have been used as starting material for biomedical applications. The pure and Cr3+ -doped hydroxyapatite were prepared by chemical precipitation reactions at 100, 500 e 800 °C in order to investigate the thermal stability of these materials. The characterization of the thermal behavior of this phosphate, especially on the structural changes with heating, is very important for production of sunscreens The powders were characterized using chemical analysis: X-ray diffraction (XRD) and thermal analysis. The present study was successful in the preparation of pure hydroxyapatite and chromium substituted hydroxyapatites with good thermal stability and nanoparticles formation.

  13. Structure of Biocompatible Coatings Produced from Hydroxyapatite Nanoparticles by Detonation Spraying

    NASA Astrophysics Data System (ADS)

    Nosenko, Valentyna; Strutynska, Nataliia; Vorona, Igor; Zatovsky, Igor; Dzhagan, Volodymyr; Lemishko, Sergiy; Epple, Matthias; Prymak, Oleg; Baran, Nikolai; Ishchenko, Stanislav; Slobodyanik, Nikolai; Prylutskyy, Yuriy; Klyui, Nickolai; Temchenko, Volodymyr

    2015-12-01

    Detonation-produced hydroxyapatite coatings were studied by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Raman spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy. The source material for detonation spraying was a B-type carbonated hydroxyapatite powder. The coatings consisted of tetracalcium phosphate and apatite. The ratio depended slightly on the degree of crystallinity of the initial powder and processing parameters of the coating preparation. The tetracalcium phosphate phase was homogeneous; the apatite phase contained defects localized on the sixfold axis and consisted of hydroxyapatite and oxyapatite. Technological factors contributing to the transformation of hydroxyapatite powder structure during coating formation by detonation spraying are discussed.

  14. Development of lattice-inserted 5-Fluorouracil-hydroxyapatite nanoparticles as a chemotherapeutic delivery system.

    PubMed

    Tseng, Ching-Li; Chen, Jung-Chih; Wu, Yu-Chun; Fang, Hsu-Wei; Lin, Feng-Huei; Tang, Tzu-Piao

    2015-10-01

    Developing an effective vehicle for cancer treatment, hydroxyapatite nanoparticles were fabricated for drug delivery. When 5-Fluorouracil, a major chemoagent, is combined with hydroxyapatite nanocarriers by interclay insertion, the modified hydroxyapatite nanoparticles have superior lysosomal degradation profiles, which could be leveraged as controlled drug release. The decomposition of the hydroxyapatite nanocarriers facilitates the release of 5-Fluorouracil into the cytoplasm causing cell death. Hydroxyapatite nanoparticles with/without 5-Fluorouracil were synthesized and analyzed in this study. Their crystallization properties and chemical composition were examined by X-ray diffraction and Fourier transforms infrared spectroscopy. The 5-Fluorouracil release rate was determined by UV spectroscopy. The biocompatibility of hydroxyapatite-5-Fluorouracil extraction solution was assessed using 3T3 cells via a WST-8 assay. The effect of hydroxyapatite-5-Fluorouracil particles which directly work on the human lung adenocarcinoma (A549) cells was evaluated by a lactate dehydrogenase assay via contact cultivation. A 5-Fluorouracil-absorbed hydroxyapatite particles were also tested. Overall, hydroxyapatite-5-Fluorouracils were prepared using a co-precipitation method wherein 5-Fluorouracil was intercalated in the hydroxyapatite lattice as determined by X-ray diffraction. Energy dispersive scanning examination showed the 5-Fluorouracil content was higher in hydroxyapatite-5-Fluorouracil than in a prepared absorption formulation. With 5-Fluorouracil insertion in the lattice, the widths of the a and c axial constants of the hydroxyapatite crystal increased. The extraction solution of hydroxyapatite-5-Fluorouracil was nontoxic to 3T3 cells, in which 5-Fluorouracil was not released in a neutral phosphate buffer solution. In contrast, at a lower pH value (2.5), 5-Fluorouracil was released by the acidic decomposition of hydroxyapatite. Finally, the results of the lactate

  15. Structure of Biocompatible Coatings Produced from Hydroxyapatite Nanoparticles by Detonation Spraying.

    PubMed

    Nosenko, Valentyna; Strutynska, Nataliia; Vorona, Igor; Zatovsky, Igor; Dzhagan, Volodymyr; Lemishko, Sergiy; Epple, Matthias; Prymak, Oleg; Baran, Nikolai; Ishchenko, Stanislav; Slobodyanik, Nikolai; Prylutskyy, Yuriy; Klyui, Nickolai; Temchenko, Volodymyr

    2015-12-01

    Detonation-produced hydroxyapatite coatings were studied by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Raman spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy. The source material for detonation spraying was a B-type carbonated hydroxyapatite powder. The coatings consisted of tetracalcium phosphate and apatite. The ratio depended slightly on the degree of crystallinity of the initial powder and processing parameters of the coating preparation. The tetracalcium phosphate phase was homogeneous; the apatite phase contained defects localized on the sixfold axis and consisted of hydroxyapatite and oxyapatite. Technological factors contributing to the transformation of hydroxyapatite powder structure during coating formation by detonation spraying are discussed. PMID:26625888

  16. On the assessment of hydroxyapatite fluoridation by means of Raman scattering

    SciTech Connect

    Campillo, M.; Valiente, M.; Lacharmoise, P. D.; Reparaz, J. S.; Goni, A. R.

    2010-06-28

    Hydroxyapatite is the main mineral component of bones and teeth. Fluorapatite, a bioceramic that can be obtained from hydroxyapatite by chemical substitution of the hydroxide ions with fluoride, exhibits lower mineral solubility and larger mechanical strength. Despite the widespread use of fluoride against caries, a reliable technique for unambiguous assessment of fluoridation in in vitro tests is still lacking. Here we present a method to probe fluorapatite formation in fluoridated hydroxyapatite by combining Raman scattering with thermal annealing. In synthetic minerals, we found that effectively fluoride substituted hydroxyapatite transforms into fluorapatite only after heat treatment, due to the high activation energy for this first order phase transition.

  17. Hydroxyapatite/poly(epsilon-caprolactone) double coating on magnesium for enhanced corrosion resistance and coating flexibility.

    PubMed

    Jo, Ji-Hoon; Li, Yuanlong; Kim, Sae-Mi; Kim, Hyoun-Ee; Koh, Young-Hag

    2013-11-01

    Hydroxyapatite was deposited on pure magnesium (Mg) with a flexible poly(ε-caprolactone) interlayer to reduce the corrosion rate of Mg and enhance coating flexibility. The poly(ε-caprolactone) interlayer was uniformly coated on Mg by a spraying method, followed by hydroxyapatite deposition on the poly(ε-caprolactone) using an aerosol deposition method. In scanning electron microscopy observations, inorganic/organic composite-like structure was observed between the hydroxyapatite and poly(ε-caprolactone) layers, resulting from the collisions of hydroxyapatite particles into the poly(ε-caprolactone) matrix at the initial stage of the aerosol deposition. The corrosion resistance of the coated Mg was examined using potentiodynamic polarization tests. The hydroxyapatite/poly(ε-caprolactone) double coating remarkably improved the corrosion resistance of Mg in Hank's solution. In the in vitro cell tests, the coated Mg showed better cell adhesion compared with the bare Mg due to the reduced corrosion rate and enhanced biocompatibility. The stability and flexibility of hydroxyapatite/poly(ε-caprolactone) double coating was investigated by scanning electron microscopy inspections after the coated Mg was deformed. The hydroxyapatite coating on the poly(ε-caprolactone) interlayer revealed enhanced coating stability and flexibility without cracking or delamination during bending and stretching compared with the hydroxyapatite single coating. These results demonstrated that the hydroxyapatite/poly(ε-caprolactone) double coating significantly improved the surface corrosion resistance of Mg and enhanced coating flexibility for use of Mg as a biodegradable implant. PMID:23241964

  18. On the assessment of hydroxyapatite fluoridation by means of Raman scattering

    NASA Astrophysics Data System (ADS)

    Campillo, M.; Lacharmoise, P. D.; Reparaz, J. S.; Goñi, A. R.; Valiente, M.

    2010-06-01

    Hydroxyapatite is the main mineral component of bones and teeth. Fluorapatite, a bioceramic that can be obtained from hydroxyapatite by chemical substitution of the hydroxide ions with fluoride, exhibits lower mineral solubility and larger mechanical strength. Despite the widespread use of fluoride against caries, a reliable technique for unambiguous assessment of fluoridation in in vitro tests is still lacking. Here we present a method to probe fluorapatite formation in fluoridated hydroxyapatite by combining Raman scattering with thermal annealing. In synthetic minerals, we found that effectively fluoride substituted hydroxyapatite transforms into fluorapatite only after heat treatment, due to the high activation energy for this first order phase transition.

  19. [FTIR and XRD analysis of hydroxyapatite from fossil human and animal teeth in Jinsha Relict, Chengdu].

    PubMed

    Huang, Cheng-min; Zhang, Qing; Bai, Song; Wang, Cheng-shan

    2007-12-01

    Diagenetic effect during burial on the hydroxyapatite in enamel and dentin from fossil human and animal teeth was examined, using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). For the enamel and dentin of all fossil teeth, XRD patterns exhibit bulge line and overlap between major reflections of hydroxyapatite, and the crystallinity of hydroxyapatite is low. For each infrared spectrum, H2O and OH(-) have distinct peaks of absorbance, and PO4(3-) and CO3(2-) ions have intensive infrared vibration modes at the fundamental wave numbers. The component of hydroxyapatite of all fossil teeth is similar to the modern biological hydroxyapatite. Furthermore, the index (PCI) which reflects the hydroxyapatite crystallinity of each sample ranges from 2.4 to 4.0 while the index (BPI) reflecting the amount of type B carbonate to phosphate indicates that the values of CO3(2-) content in hydroxyapatite are rather high, accordingly the crystallinity of all fossil hydroxyapatites are poor. It could be concluded that little alteration of hydroxyapatites from fossil human and animal teeth occurred in the process of diagenesis in Jinsha Relict, Chengdu, China. PMID:18330282

  20. Method to produce nanocrystalline powders of oxide-based phosphors for lighting applications

    DOEpatents

    Loureiro, Sergio Paulo Martins; Setlur, Anant Achyut; Williams, Darryl Stephen; Manoharan, Mohan; Srivastava, Alok Mani

    2007-12-25

    Some embodiments of the present invention are directed toward nanocrystalline oxide-based phosphor materials, and methods for making same. Typically, such methods comprise a steric entrapment route for converting precursors into such phosphor material. In some embodiments, the nanocrystalline oxide-based phosphor materials are quantum splitting phosphors. In some or other embodiments, such nanocrystalline oxide based phosphor materials provide reduced scattering, leading to greater efficiency, when used in lighting applications.

  1. Methods for preparation of nanocrystalline rare earth phosphates for lighting applications

    DOEpatents

    Comanzo, Holly Ann; Manoharan, Mohan; Martins Loureiro, Sergio Paulo; Setlur, Anant Achyut; Srivastava, Alok Mani

    2013-04-16

    Disclosed here are methods for the preparation of optionally activated nanocrystalline rare earth phosphates. The optionally activated nanocrystalline rare earth phosphates may be used as one or more of quantum-splitting phosphor, visible-light emitting phosphor, vacuum-UV absorbing phosphor, and UV-emitting phosphor. Also disclosed herein are discharge lamps comprising the optionally activated nanocrystalline rare earth phosphates provided by these methods.

  2. Osteogenesis with hematopoiesis simulating infection in a hydroxyapatite orbital implant.

    PubMed

    Jordan, David R; Belliveau, Michel J; Brownstein, Seymour; Padmore, Ruth F

    2009-01-01

    A 28-year-old woman underwent secondary orbital implant surgery with placement of a hydroxyapatite implant. Over the next 7 years she underwent 3 drilling procedures. She began having copious discharge 1 year after the last drilling procedure. She was seen on numerous occasions with socket discharge, unresponsive to a variety of topical and oral antibiotics. Clinically, with the conjunctiva diffusely inflamed, the implant tender to touch, and the presence of a pyogenic granuloma, implant infection was suspected and the implant subsequently removed. Histopathologic assessment revealed widespread lamellar bone formation, including focal areas of marrow with active extramedullary hematopoiesis. There was no evidence of an inflammatory process or infection. Postoperatively the patient's symptoms and signs resolved. Extramedullary hematopoiesis within hydroxyapatite implants is rare. Porous orbital implant infection is also rare. Osteogenesis with extramedullary hematopoiesis simulating implant infection has not previously been reported. PMID:19273939

  3. Influence of Barium Hexaferrite on Magnetic Properties of Hydroxyapatite Ceramics.

    PubMed

    Jarupoom, P; Jaita, P

    2015-11-01

    Hydroxyapatite (HA) powders was derived from natural bovine bone by sequence of thermal processes. The barium hexaferrite (BF) find magnetic powders were added into HA powders in ratio of 1-3 vol.%. The HA-BF ceramics were prepared by a solid state reaction method and sintered at 1250 degrees C for 2 h. Effects of BF additive on structural, physical and magnetic properties of HA ceramics were investigated. X-ray diffraction revealed that all HA-BF samples showed a main phase of high purity hydroxyapatite [Ca10(PO4)6(OH)2] with calcium and phosphate molar ratio of 1.67. The addition of BF into HA inhibited grain growth and caused an improvement of mechanical properties. The M-H hysteresis loops also showed an improvement in magnetic behavior for higher content of BF. Moreover, in vitro bioactivity test indicated that the 2-3 vol.% sample may be suitable for biological applications. PMID:26726671

  4. Dissolution rates of carbonated hydroxyapatite in hydrochloric acid.

    PubMed

    Hankermeyer, Christine R; Ohashi, Kevin L; Delaney, David C; Ross, John; Constantz, Brent R

    2002-02-01

    Osteoclasts have been shown to dissolve efficiently and effectively the mineral phase of bone by locally controlling the environment surrounding the cell. Although this mineral phase has been identified and well characterized as carbonated hydroxyapatite, there is little understanding of the factors that affect the dissolution properties of this mineral phase. Mimicking the mechanism by which osteoclasts dissolve the mineral phase of bone may provide insight into methods for the decalcification of atherosclerotic mineral deposits in the vascular system. Accordingly, a detailed characterization of the effects of various chemical and mechanical parameters on the dissolution of carbonated hydroxyapatite mineral was investigated in this study. Increases in the mineral dissolution rate (2-10 times) were associated with increases in dissolving solution [H+], osmolality, temperature, and flow rate. Mineral dissolution rate increases (5-8 times) were associated with greater surface area of the mineral and mechanical agitation of the dissolving solution. PMID:11771694

  5. Antimicrobial and cytotoxicity evaluation of aliovalent substituted hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Shanmugam, Sumathi; Gopal, Buvaneswari

    2014-06-01

    Aliovalent ion substituted hydroxyapatite of formulae BiNaCa3(PO4)3OH, Bi0.5M0.5Ca4(PO4)3OH (M = K, Ag) were synthesized and characterized. Antimicrobial properties of these synthesized materials were studied quantitatively by spread plate method against the microorganisms Escherichia coli (gram negative bacteria), Staphylococcus aureus (gram positive bacteria) and Candida albicans (yeast). Among the substituted hydroxyapatite compounds bismuth and silver substituted compound of formula Bi0.5Ag0.5Ca4(PO4)3OH shown excellent activity against all the three organisms. Cytotoxicity study was carried out against mouse fibroblast NIH-3T3 cell line in two different concentrations 10 μg/mL and 20 μg/mL by MTT assay method.

  6. Electrohydrodynamic coating of metal with nano-sized hydroxyapatite.

    PubMed

    Li, Xiang; Huang, Jie; Ahmad, Zeeshan; Edirisinghe, Mohan

    2007-01-01

    Electrohydrodynamic spray deposition of a hydroxyapatite (HA) suspension consisting of nano-particles has been used to create a hydroxyapatite coating comprising of nanostructured surface topography. Preliminary coating experiments were carried out on an Al substrate and 30 s was found to be the most appropriate coating time. HA coating on titanium for this duration was found to be well-bonded to the substrate after heat-treatment. A thickness of 2 mum was achieved in 30 s and formation of a bone-like apatite on the surface was detected after incubation of the heat-treated coated Ti in simulated body fluid. Therefore, we have uncovered a new procedure by which nano-biomaterials can be deposited on real orthopedic substrates to prepare bioactive thin coatings in a simple and easy manner. PMID:18032815

  7. Hydroxyapatite: Vibrational spectra and monoclinic to hexagonal phase transition

    NASA Astrophysics Data System (ADS)

    Slepko, Alexander; Demkov, Alexander A.

    2015-02-01

    Fundamental studies of biomaterials are necessary to deepen our understanding of their degradation and to develop cure for related illnesses. Biomineral hydroxyapatite Ca10(PO4)6(OH)2 is the main mineral constituent of mammal bone, and its synthetic analogues are used in biomedical applications. The mineral can be found in either hexagonal or monoclinic form. The transformation between these two phases is poorly understood, but knowing its mechanism may be critical to reversing processes in bone related to aging. Using density functional theory, we investigate the mechanisms of the phase transformation and estimate the transition temperature to be 680 K in fair agreement with the experimental temperature of 470 K. We also report the heat capacity of hydroxyapatite and a peculiarity in its phonon dispersion that might allow for non-destructive measurements of the crystal composition with applications in preventive medical screening for bone mineral loss.

  8. Strain rate sensitivity of a nanocrystalline Cu synthesized by electric brush plating

    NASA Astrophysics Data System (ADS)

    Jiang, Zhonghao; Liu, Xianli; Li, Guangyu; Jiang, Qing; Lian, Jianshe

    2006-04-01

    A method for synthesizing bulk nanocrystalline Cu by an electric brush-plating technique is reported. This brush-plated nanocrystalline Cu has a fine (26nm) and quite uniform grain structure and predominant high-angle grain boundaries. A pronounced strain rate sensitivity of the stress with an m of 0.104 and the Coble creep and a subsequent transition to the power-law creep were observed in room temperature tensile and creep tests. The dominant grain boundary deformation due to the truly nanocrystalline structure of this nanocrystalline Cu is responsible for the observed strain rate sensitivity.

  9. Gradient porous hydroxyapatite ceramics fabricated by freeze casting method

    NASA Astrophysics Data System (ADS)

    Zuo, Kai-hui; zhang, Yuan; Jiang, Dongliang; Zeng, Yu-Ping

    2011-04-01

    By controlling the cooling rates and the composition of slurries, the gradient porous hydroxyapatite ceramics are fabricated by the freeze casting method. According to the different cooling rate, the pores of HAP ceramics fabricated by gradient freeze casting are divided into three parts: one is lamellar pores, another is column pore and the last one is fine round pores. The laminated freeze casting is in favour of obtaining the gradient porous ceramics composed of different materials and the ceramics have unclear interfaces.

  10. Growth of one-dimensional single-crystalline hydroxyapatite nanorods

    NASA Astrophysics Data System (ADS)

    Ren, Fuzeng; Ding, Yonghui; Ge, Xiang; Lu, Xiong; Wang, Kefeng; Leng, Yang

    2012-06-01

    A facile, effective and template/surfactant-free hydrothermal route in the presence of sodium bicarbonate was developed to synthesize highly uniform single-crystalline hydroxyapatite (HA) nanorods with the lengths of several hundred nanometers and aspect ratio up to ˜20. One dimensional (1-D) growth and aspect ratio could be controlled by hydrothermal reaction time and temperature. The longitudinal axis, also the growth direction of the nanorods, is parallel to the [001] direction of HA hexagonal crystal structure.

  11. Advanced Microstructural Study of Suspension Plasma Sprayed Hydroxyapatite Coatings

    NASA Astrophysics Data System (ADS)

    Podlesak, Harry; Pawlowski, Lech; D'Haese, Romain; Laureyns, Jacky; Lampke, Thomas; Bellayer, Severine

    2010-03-01

    Fine, home-synthesized, hydroxyapatite powder was formulated with water and alcohol to obtain a suspension used to plasma spray coatings onto a titanium substrate. The deposition process was optimized using statistical design of 2 n experiments with two variables: spray distance and electric power input to plasma. X-ray diffraction (XRD) was used to determine quantitatively the phase composition of obtained deposits. Raman microscopy and electron probe microanalysis (EPMA) enabled localization of the phases in different positions of the coating cross sections. Transmission electron microscopic (TEM) study associated with energy-dispersive x-ray spectroscopy (EDS) enabled visualization and analysis of a two-zone microstructure. One zone contained crystals of hydroxyapatite, tetracalcium phosphate, and a phase rich in calcium oxide. This zone included lamellas, usually observed in thermally sprayed coatings. The other zone contained fine hydroxyapatite grains that correspond to nanometric and submicrometric solids from the suspension that were agglomerated and sintered in the cold regions of plasma jet and on the substrate.

  12. XANES Data on Trace Quantities of Iron in Hydroxyapatite Structures

    NASA Astrophysics Data System (ADS)

    Tabor-Morris, A.; Schaefer, B.

    2003-03-01

    Trace elements such as iron are of interest in both biologically and geologically formed apatites. They are thought to occupy substitutional sites at the concentration of about 200 ppm. Most likely metal atoms replace the calcium atom in one of two non-equivalent calcium sites. The inorganic mineral structure hydroxyapatite (which comprises 30% of human and animal bone) consists of Ca_5(OH)(PO_4)3 in a hexagonal crystal structure designated in Herman-Maugin crystallography notation as P63/m or as Number 176 in the International Tables of Crystallography (ITC). Hydroxyapatite formed under geological conditions has the same crystal structure. Hydroxyapatite can also be fabricated synthetically, but has limitations in terms of crystal growth size. The experimental technique of X-ray Absorption Near Edge Structure (XANES) and X-ray Absorption Fine-structure Spectroscopy (XAFS) were used to evaluate the oxidation state of iron. Data was taken at the X-9B line at the National Synchrotron Light Source at Brookhaven National Laboratory.

  13. XANES Data on Metal Ions in Hydroxyapatite Structures

    NASA Astrophysics Data System (ADS)

    Schaefer, Beth; Tabor-Morris, Anne; Simons, Adrian

    2004-03-01

    The experimental technique of X-ray Absorption Near Edge Structure (XANES) was used to compare the absorption edges of different oxidation states of iron, strontium, lead, copper and zinc in the inorganic mineral structure hydroxyapatite and fluoroapatite. Trace elements such as iron, copper, zinc, lead and strontium are of interest in both biologically and geologically formed apatites. They are thought to occupy substitutional sites at the concentration of about 200 ppm. These metal atoms replace the calcium atom in one of two non-equivalent calcium sites. Hydroxyapatite consists of Ca _5 (OH)(PO_4)3 in a hexagonal crystal structure. Hydroxyapatite formed under geological conditions has the same crystal structure. Data was taken at the X-9B line at the National Synchrotron Light Source at Brookhaven National Laboratory. Samples were obtained from Dr. Susan G. Sheridan, at the University of Notre Dame, Dr. Catherine Skinner from Yale University, Dr. John Rakovan at Miami University in Ohio, Dr. Richard Riman at Rutgers University.

  14. Calcium Deficient Hydroxyapatite for Medical Application Prepared by Hydrothermal Method

    NASA Astrophysics Data System (ADS)

    Ioku, Koji; Kamitakahara, Masanobu; Ikeda, Tohru

    2010-11-01

    Hydrothermal processing plays a key role in the synthesis of biomaterials with excellent biocompatibility in the physiological environment. Especially, calcium phosphates are paid to much attention for the regenerative medicine. Two kinds of porous materials of hydroxyapatite with 70% porosity were prepared. One of them is a newly developed calcium-deficient hydroxyapatite composed of rod-shaped particles of about 20 μm in length synthesized hydrothermally (HHA) and the other one is the stoichiometric hydroxyapatite (SHA) prepared by the conventional sintering method. These materials were used for animal implantation tests to compare these biological responses. In the rabbit femur, implanted HHA was slowly resorbed and then most of the implanted HHA was resorbed after 72 weeks. The implanted SHA was unresorbed throughout the experimental period. The volume of newly formed bone and the number of osteoclasts in the implanted region were significantly larger in HHA than in SHA after 24 weeks. Results in the present research suggested that the activity of osteoclasts correlated to the bone forming activity of osteoblasts. The method to synthesize biodegradable pure calcium-deficient HA is expected to provide adequate biodegradability and bone replaceability.

  15. Multifunctional hydroxyapatite nanofibers and microbelts as drug carriers.

    PubMed

    Hou, Zhiyao; Yang, Piaoping; Lian, Hongzhou; Wang, Lili; Zhang, Cuimiao; Li, Chunxia; Chai, Ruitao; Cheng, Ziyong; Lin, Jun

    2009-07-13

    Luminescent, mesoporous, and bioactive europium-doped hydroxyapatite (HAp:Eu(3+)) nanofibers and microbelts have been prepared by a combination of sol-gel and electrospinning processes with a cationic surfactant as template. The obtained multifunctional hydroxyapatite nanofibers and microbelts, which have mesoporous structure and red luminescence, were tested as drug carriers by investigating their drug-storage/release properties with ibuprofen (IBU) as model drug. X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution (HR) TEM, FTIR spectroscopy, N(2) adsorption/desorption, photoluminescence (PL) spectra, and UV/Vis spectroscopy were used to characterize the structural, morphological, textural, and optical properties of the resulting samples. The results reveal that the multifunctional hydroxyapatites exhibit irregular mesostructure, and have fiberlike and beltlike morphologies with sizes of several hundred nanometers in width and several millimeters in length. The IBU-loaded HAp:Eu(3+) system shows red luminescence of Eu(3+) ((5)D(0)-(7)F(0,1,2)) under UV irradiation and controlled release of IBU. In addition, the emission intensity of Eu(3+) in the drug carrier system varies with the released amount of IBU, and thus drug release can be easily tracked and monitored by the change in luminescence intensity. PMID:19496099

  16. Controlled synthesis and thermal stability of hydroxyapatite hierarchical microstructures

    SciTech Connect

    Sun, Ruixue; Chen, Kezheng; Liao, Zhongmiao; Meng, Nan

    2013-03-15

    Highlights: ► Hydroxyapatite hierarchical microstructures have been synthesized by a facile method. ► The morphology and size of the building units of 3D structures can be controlled. ► The hydroxyapatite with 3D structure is morphologically and structurally stable up to 800 °C. - Abstract: Hydroxyapatite (HAp) hierarchical microstructures with novel 3D morphology were prepared through a template- and surfactant-free hydrothermal homogeneous precipitation method. Field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) were used to characterize the morphology and composition of the synthesized products. Interestingly, the obtained HAp with 3D structure is composed of one-dimensional (1D) nanorods or two-dimensional (2D) nanoribbons, and the length and morphology of these building blocks can be controlled through controlling the pH of the reaction. The building blocks are single crystalline and have different preferential orientation growth under different pH conditions. At low pH values, octacalcium phosphate (OCP) phase formed first and then transformed into HAp phase due to the increased pH value caused by the decomposition of urea. The investigation on the thermal stability reveals that the prepared HAp hierarchical microstructures are morphologically and structurally stable up to 800 °C.

  17. Synthesis of fluorapatite–hydroxyapatite nanoparticles and toxicity investigations

    PubMed Central

    Montazeri, N; Jahandideh, R; Biazar, Esmaeil

    2011-01-01

    In this study, calcium phosphate nanoparticles with two phases, fluorapatite (FA; Ca10(PO4)6F2) and hydroxyapatite (HA; Ca10(PO4)6(OH)2), were prepared using the solgel method. Ethyl phosphate, hydrated calcium nitrate, and ammonium fluoride were used, respectively, as P, Ca, and F precursors with a Ca:P ratio of 1:72. Powders obtained from the sol-gel process were studied after they were dried at 80°C and heat treated at 550°C. The degree of crystallinity, particle and crystallite size, powder morphology, chemical structure, and phase analysis were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Zetasizer experiments. The results of XRD analysis and FTIR showed the presence of hydroxyapatite and fluorapatite phases. The sizes of the crystallites estimated from XRD patterns using the Scherrer equation and the crystallinity of the hydroxyapatite phase were about 20 nm and 70%, respectively. Transmission electron microscope and SEM images and Zetasizer experiments showed an average size of 100 nm. The in vitro behavior of powder was investigated with mouse fibroblast cells. The results of these experiments indicated that the powders were biocompatibile and would not cause toxic reactions. These compounds could be applied for hard-tissue engineering. PMID:21499417

  18. Synthesis of fluorapatite-hydroxyapatite nanoparticles and toxicity investigations.

    PubMed

    Montazeri, N; Jahandideh, R; Biazar, Esmaeil

    2011-01-01

    In this study, calcium phosphate nanoparticles with two phases, fluorapatite (FA; Ca(10)(PO(4))(6)F(2)) and hydroxyapatite (HA; Ca(10)(PO(4))(6)(OH)(2)), were prepared using the solgel method. Ethyl phosphate, hydrated calcium nitrate, and ammonium fluoride were used, respectively, as P, Ca, and F precursors with a Ca:P ratio of 1:72. Powders obtained from the sol-gel process were studied after they were dried at 80°C and heat treated at 550°C. The degree of crystallinity, particle and crystallite size, powder morphology, chemical structure, and phase analysis were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Zetasizer experiments. The results of XRD analysis and FTIR showed the presence of hydroxyapatite and fluorapatite phases. The sizes of the crystallites estimated from XRD patterns using the Scherrer equation and the crystallinity of the hydroxyapatite phase were about 20 nm and 70%, respectively. Transmission electron microscope and SEM images and Zetasizer experiments showed an average size of 100 nm. The in vitro behavior of powder was investigated with mouse fibroblast cells. The results of these experiments indicated that the powders were biocompatible and would not cause toxic reactions. These compounds could be applied for hard-tissue engineering. PMID:21499417

  19. Synthesis of nanogranular Fe3O4/biomimetic hydroxyapatite for potential applications in nanomedicine: structural and magnetic characterization

    NASA Astrophysics Data System (ADS)

    Del Bianco, L.; Lesci, I. G.; Fracasso, G.; Barucca, G.; Spizzo, F.; Tamisari, M.; Scotti, R.; Ciocca, L.

    2015-06-01

    We realized the synthesis of a novel nanogranular system consisting of magnetite nanoparticles embedded in biomimetic carbonate hydroxyapatite (HA), for prospective uses in bone tissue engineering. An original two-step method was implemented: in the first step, magnetite nanoparticles are prepared by refluxing an aqueous solution of Fe(SO4) and Fe2(SO4)3 in an excess of tetrabutilammonium hydroxide acting as surfactant; then, the magnetite nanoparticles are coated with a Ca(OH)2 layer, to induce the growth of HA directly on their surface, by reaction of Ca(OH)2 with HPO42-. Two nanogranular samples were collected with magnetite content ˜0.8 and ˜4 wt%. The magnetite nanoparticles and the composite material were investigated by x-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. These analyses provided information on the structure of the nanoparticles (mean size ˜6 nm) and revealed the presence of surface hydroxyl groups, which promoted the subsequent growth of the HA phase, featuring a nanocrystalline lamellar structure. The magnetic study, by a superconducting quantum interference device magnetometer, has shown that both the as-prepared and the HA-coated magnetite nanoparticles are superparamagnetic at T = 300 K, but the magnetization relaxation process is dominated by dipolar magnetic interactions of comparable strength. In the three samples, a collective frozen magnetic regime is established below T ˜ 20 K. These results indicate that the magnetite nanoparticles tend to form agglomerates in the as-prepared state, which are not substantially altered by the HA growth, coherently with the creation of electrostatic hydrogen bonds among the surface hydroxyl groups.

  20. Dislocation-mediated creep process in nanocrystalline Cu

    NASA Astrophysics Data System (ADS)

    Mu, Jun-Wei; Sun, Shi-Cheng; Jiang, Zhong-Hao; Lian, Jian-She; Jiang, Qing

    2013-03-01

    Nanocrystalline Cu with average grain sizes ranging from ~ 24.4 to 131.3 nm were prepared by the electric brush-plating technique. Nanoindentation tests were performed within a wide strain rate range, and the creep process of nanocrystalline Cu during the holding period and its relationship to dislocation and twin structures were examined. It was demonstrated that creep strain and creep strain rate are considerably significant for smaller grain sizes and higher loading strain rates, and are far higher than those predicted by the models of Cobble creep and grain boundary sliding. The analysis based on the calculations and experiments reveals that the significant creep deformation arises from the rapid absorption of high density dislocations stored in the loading regime. Our experiments imply that stored dislocations during loading are highly unstable and dislocation activity can proceed and lead to significant post-loading plasticity.

  1. Investigations of mechanically alloyed nanocrystalline materials by microacoustic techniques

    NASA Astrophysics Data System (ADS)

    Dubief, P.; Hunsinger, J. J.; Gaffet, E.

    1996-09-01

    The purpose of this work is to determine whether yes or no, there is a difference between the physico-chemical properties of the nanocrystalline and the microcrystalline materials. This paper deals with the acoustical behavior of nanocrystalline materials which were prepared by ball- milling and mechanical alloying. Based on two specific techniques (acoustic microinterferometry and acoustic microechography), some of the mechanical properties (elastic ones) may be determined, related to a materials volume of about a few micrometers 3 (for the high frequency 600 MHz apparatus). Thus the mechanically alloyed powders (typically 200 micrometers in diameter), behave as massive materials in this range of frequency. The measurements are directly obtained on the grains and do not take into account the voids induced by further sinthering process. The result of such a micromechanical approach will be given for pure ball-milled elements (Fe) and for the supersaturated solid phase Fe(Si) obtained by mechanical alloying.

  2. Enhancement of Strength and Ductility in Bulk Nanocrystalline Metals

    SciTech Connect

    Nieh, T; Schuh, C A; Caturla, M J; Hodge, A M

    2004-02-17

    The purpose of this project is to develop a robust scientific and technological framework for the design of high-strength and -ductility nanocrystalline materials for applications of technical importance to the Laboratory. The project couples theory and experiments with an emphasis on materials of macroscopic dimensions (mm to cm) that are composed of nanoscale (<100 nm) grains. There are four major tasks: (1) synthesize nanocrystalline materials with grain size in the 5- to 100-nm range; (2) conduct experimental studies to probe mechanisms of mechanical deformation and failure; (3) use large-scale simulation modeling technologies to provide insight to deformation mechanisms that may not be observable experimentally; and (4) check the results obtained from modeling, comparing experimental observations with results obtained from atomistic and dislocation-based simulations. This project supports efforts within the Stockpile Stewardship Program (SSP) to understand and predict properties of metals such as strength and ductility.

  3. Grain growth and structural relaxation of nanocrystalline Bi₂Te₃

    SciTech Connect

    Humphry-Baker, Samuel A.; Schuh, Christopher A.

    2014-10-21

    Recovery and grain growth behavior is investigated systematically for the nanocrystalline thermoelectric compound bismuth telluride, synthesized by mechanical alloying. During annealing treatments at elevated temperatures, structural evolution is tracked using x-ray diffraction, electron microscopy and calorimetry. Below a homologous temperature of about 0.6T{sub m}, grain growth occurs slowly with an activation energy of 89 kJ/mol. However above this temperature grain growth becomes more rampant with an activation energy of 242 kJ/mol. The transition is attributed to a shift from a relaxation or recovery process that includes some reordering of the grain boundary structure, to a more conventional diffusionally-limited grain growth process. By extrapolating the measured grain growth and microstrain evolution kinetics, a thermal budget map is constructed, permitting recommendations for improving the thermoelectric properties of nanocrystalline materials processed via a powder route.

  4. Grain boundary and triple junction diffusion in nanocrystalline copper

    SciTech Connect

    Wegner, M. Leuthold, J.; Peterlechner, M.; Divinski, S. V.; Song, X.; Wilde, G.

    2014-09-07

    Grain boundary and triple junction diffusion in nanocrystalline Cu samples with grain sizes, 〈d〉, of ∼35 and ∼44 nm produced by spark plasma sintering were investigated by the radiotracer method using the {sup 63}Ni isotope. The measured diffusivities, D{sub eff}, are comparable with those determined previously for Ni grain boundary diffusion in well-annealed, high purity, coarse grained, polycrystalline copper, substantiating the absence of a grain size effect on the kinetic properties of grain boundaries in a nanocrystalline material at grain sizes d ≥ 35 nm. Simultaneously, the analysis predicts that if triple junction diffusion of Ni in Cu is enhanced with respect to the corresponding grain boundary diffusion rate, it is still less than 500⋅D{sub gb} within the temperature interval from 420 K to 470 K.

  5. Nanocrystalline SiGe films: Structure and properties

    SciTech Connect

    Edelman, F.; Komem, Y.; Stoelzer, M.; Werner, P.; Butz, R.

    1996-12-31

    Amorphous (a) Si{sub 1{minus}x}Ge{sub x} films with x = 0.27--0.55 about 200--300 nm thick and highly doped with Ga (1%), were molecular-beam deposited on SiO{sub 2}/Si(001) substrates at room temperature. For crystallization at 600 to 900 C a-Si{sub 1{minus}x}Ge{sub x}/SiO{sub 2}/Si samples were annealed in vacuum at 10{sup {minus}6} Torr. X-ray diffraction and in situ TEM observations revealed a nanocrystalline structure in Si{sub 1{minus}x}Ge{sub x} films with grain size of about 5--20 nm which is 100 times smaller than undoped films. The nanocrystalline Si{sub 1{minus}x}Ge{sub x} films showed a high hole mobility (1 to 100 cm{sup 2}/Vs) and Seebeck coefficient values (5 to 110 {micro}V/K).

  6. High pressure x-ray diffraction studies on nanocrystalline materials

    NASA Astrophysics Data System (ADS)

    Palosz, B.; Stel'makh, S.; Grzanka, E.; Gierlotka, S.; Pielaszek, R.; Bismayer, U.; Werner, S.; Palosz, W.

    2004-02-01

    Application of the in situ high pressure powder diffraction technique for examination of specific structural properties of nanocrystals based on the experimental data of SiC nanocrystalline powders of 2-30 nm in diameter is presented. Limitations and capabilities of the experimental techniques themselves and methods of diffraction data elaboration applied to nanocrystals with very small dimensions (<30 nm) are discussed. It is shown that a unique value of the lattice parameter cannot be determined for such small crystals using a standard powder diffraction experiment. It is also shown that, due to the complex structure constituting a two-phase, core/surface shell system, no unique compressibility coefficient can satisfactorily describe the behaviour of nanocrystalline powders under pressure. We offer a tentative interpretation of the distribution of macro- and micro-strains in nanoparticles of different grain size.

  7. Magnons as a Bose-Einstein Condensate in Nanocrystalline Gadolinium

    SciTech Connect

    Kaul, S. N.; Mathew, S. P.

    2011-06-17

    The recent observation [S. P. Mathew et al., J. Phys. Conf. Ser. 200, 072047 (2010)] of the anomalous softening of spin-wave modes at low temperatures in nanocrystalline gadolinium is interpreted as a Bose-Einstein condensation (BEC) of magnons. A self-consistent calculation, based on the BEC picture, is shown to closely reproduce the observed temperature variations of magnetization and specific heat at constant magnetic fields.

  8. Controllable nonlinear refraction characteristics in hydrogenated nanocrystalline silicon

    SciTech Connect

    Zheng, D. Q.; Ye, Q. H.; Shen, W. Z.; Su, W. A.

    2014-02-07

    Nonlinear refraction (NLR) of hydrogenated nanocrystalline silicon (nc-Si:H) has been investigated through the close aperture Z-scan method. We demonstrate a significant NLR and a unique feature of controllable NLR characteristics between saturable and Kerr NLR with the incident photon energy. We numerically evaluate the proportion of these two mechanisms in different wavelengths by a modified NLR equation. The band tail of nc-Si:H appears to play a crucial role in such NLR responses.

  9. Method for the preparation of nanocrystalline diamond thin films

    DOEpatents

    Gruen, Dieter M.; Krauss, Alan R.

    1998-01-01

    A method and system for manufacturing nanocrystalline diamond film on a substrate such as field emission tips. The method involves forming a carbonaceous vapor, providing a gas stream of argon, hydrocarbon and possibly hydrogen, and combining the gas with the carbonaceous vapor, passing the combined carbonaceous vapor and gas carrier stream into a chamber, forming a plasma in the chamber causing fragmentation of the carbonaceous vapor and deposition of a diamond film on the field emission tip.

  10. Method for the preparation of nanocrystalline diamond thin films

    DOEpatents

    Gruen, D.M.; Krauss, A.R.

    1998-06-30

    A method and system are disclosed for manufacturing nanocrystalline diamond film on a substrate such as field emission tips. The method involves forming a carbonaceous vapor, providing a gas stream of argon, hydrocarbon and possibly hydrogen, and combining the gas with the carbonaceous vapor, passing the combined carbonaceous vapor and gas carrier stream into a chamber, forming a plasma in the chamber causing fragmentation of the carbonaceous vapor and deposition of a diamond film on the field emission tip. 40 figs.

  11. Nanoporous nanocrystalline monoclinic zirconia for luminescent oxygen sensors

    NASA Astrophysics Data System (ADS)

    Fidelus, Janusz D.; Zhou, Wuzong; Tenderenda, Tadeusz; Nasiłowski, Tomasz

    2015-09-01

    In this work we present a nanocrystalline monoclinic ZrO2 with large free volumen open towards the nanocrystals surface dedicated for optical oxygen sensors. Nanoporous zirconia nanopowder was fabricated in hydrothermal microwave-driven process followed by annealing at 800°C. Metal-coated optical fibers are proposed as a light carrier when the working temperature exceeds 500°C. The obtained results may also find application in luminescent fiber optic oxygen sensors.

  12. Magnetic irreversibility and magnetocrystalline anisotropy in nanocrystalline nickel

    NASA Astrophysics Data System (ADS)

    Prakash, P. V.; Madduri, Srinath, S.; Kaul, S. N.

    2015-06-01

    Magnetic properties of nanocrystalline Ni samples, with average grain sizes, d = 11(1) nm, 19(1) nm and 30(2) nm, synthesized by pulse electrodeposition, have been studied. We observed that (i) at low temperatures, the effective magneto-crystalline anisotropy constant, K1, increases with the crystallite size so as to reach the bulk value at d = 30 nm, and (ii) the rate of thermal decline of K1(T) slows down as the crystallite size reduces.

  13. Characterisation of amorphous and nanocrystalline molecular materials by total scattering

    SciTech Connect

    Billinge, Simon J.L.; Dykhne, Timur; Juhás, Pavol; Boin, Emil; Taylor, Ryan; Florence, Alastair J.; Shankland, Kenneth

    2010-09-17

    The use of high-energy X-ray total scattering coupled with pair distribution function analysis produces unique structural fingerprints from amorphous and nanostructured phases of the pharmaceuticals carbamazepine and indomethacin. The advantages of such facility-based experiments over laboratory-based ones are discussed and the technique is illustrated with the characterisation of a melt-quenched sample of carbamazepine as a nanocrystalline (4.5 nm domain diameter) version of form III.

  14. Model of the magnetization of nanocrystalline materials at low temperatures

    NASA Astrophysics Data System (ADS)

    Bian, Q.; Niewczas, M.

    2014-07-01

    A theoretical model incorporating the material texture has been developed to simulate the magnetic properties of nanocrystalline materials at low temperatures where the effect of thermal energy on magnetization is neglected. The method is based on Landau-Lifshitz-Gilbert (LLG) theory and it describes the magnetization dynamics of individual grains in the effective field. The modified LLG equation incorporates the intrinsic fields from the intragrain magnetocrystalline and grain boundary anisotropies and the interacting fields from intergrain dipolar and exchange couplings between the neighbouring grains. The model is applied to study magnetic properties of textured nanocrystalline Ni samples at 2K and is capable to reproduce closely the hysteresis loop behaviour at different orientations of applied magnetic field. Nanocrystalline Ni shows the grain boundary anisotropy constant K 1 s = - 6.0 × 104 J / m 3 and the intergrain exchange coupling denoted by the effective exchange constant Ap = 2.16 × 10-11 J/m. Analytical expressions to estimate the intergrain exchange energy density and the effective exchange constant have been formulated.

  15. Model for temperature-dependent magnetization of nanocrystalline materials

    SciTech Connect

    Bian, Q.; Niewczas, M.

    2015-01-07

    A magnetization model of nanocrystalline materials incorporating intragrain anisotropies, intergrain interactions, and texture effects has been extended to include the thermal fluctuations. The method relies on the stochastic Landau–Lifshitz–Gilbert theory of magnetization dynamics and permits to study the magnetic properties of nanocrystalline materials at arbitrary temperature below the Currie temperature. The model has been used to determine the intergrain exchange constant and grain boundary anisotropy constant of nanocrystalline Ni at 100 K and 298 K. It is found that the thermal fluctuations suppress the strength of the intergrain exchange coupling and also reduce the grain boundary anisotropy. In comparison with its value at 2 K, the interparticle exchange constant decreases by 16% and 42% and the grain boundary anisotropy constant decreases by 28% and 40% at 100 K and 298 K, respectively. An application of the model to study the grain size-dependent magnetization indicates that when the thermal activation energy is comparable to the free energy of grains, the decrease in the grain size leads to the decrease in the magnetic permeability and saturation magnetization. The mechanism by which the grain size influences the magnetic properties of nc–Ni is discussed.

  16. Model for temperature-dependent magnetization of nanocrystalline materials

    NASA Astrophysics Data System (ADS)

    Bian, Q.; Niewczas, M.

    2015-01-01

    A magnetization model of nanocrystalline materials incorporating intragrain anisotropies, intergrain interactions, and texture effects has been extended to include the thermal fluctuations. The method relies on the stochastic Landau-Lifshitz-Gilbert theory of magnetization dynamics and permits to study the magnetic properties of nanocrystalline materials at arbitrary temperature below the Currie temperature. The model has been used to determine the intergrain exchange constant and grain boundary anisotropy constant of nanocrystalline Ni at 100 K and 298 K. It is found that the thermal fluctuations suppress the strength of the intergrain exchange coupling and also reduce the grain boundary anisotropy. In comparison with its value at 2 K, the interparticle exchange constant decreases by 16% and 42% and the grain boundary anisotropy constant decreases by 28% and 40% at 100 K and 298 K, respectively. An application of the model to study the grain size-dependent magnetization indicates that when the thermal activation energy is comparable to the free energy of grains, the decrease in the grain size leads to the decrease in the magnetic permeability and saturation magnetization. The mechanism by which the grain size influences the magnetic properties of nc-Ni is discussed.

  17. Improve oxidation resistance at high temperature by nanocrystalline surface layer.

    PubMed

    Xia, Z X; Zhang, C; Huang, X F; Liu, W B; Yang, Z G

    2015-01-01

    An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in conventional P91 steel. The diffusivity of Cr, Fe and O is enhanced concurrently in the nanocrystalline surface layer, which causes the fast oxidation in the initial oxidation stage. The formation of (Fe,Cr)2O3 inner layer would inhabit fast diffusion of alloy elements in the nanocrystalline surface layer of P91 steel in the later oxidation stage, and it causes a decrease in the parabolic oxidation rate compared with conventional specimens. This study provides a novel approach to improve the oxidation resistance of heat resistant steel without changing its Cr content. PMID:26269034

  18. MOLECULAR DYNAMICS STUDY OF DIFFUSIONAL CREEP IN NANOCRYSTALLINE UO2

    SciTech Connect

    Tapan G. Desai; Paul C. Millett; Dieter Wolf

    2008-09-01

    We present the results of molecular dynamics (MD) simulations to study hightemperature deformation of nanocrystalline UO2. In qualitative agreement with experimental observations, the oxygen sub-lattice undergoes a structural transition at a temperature of about 2200 K (i.e., well below the melting point of 3450 K of our model system), whereas the uranium sub-lattice remains unchanged all the way up to melting. At temperatures well above this structural transition, columnar nanocrystalline model microstructures with a uniform grain size and grain shape were subjected to constantstress loading at levels low enough to avoid microcracking and dislocation nucleation from the GBs. Our simulations reveal that in the absence of grain growth, the material deforms via GB diffusion creep (also known as Coble creep). Analysis of the underlying self-diffusion behavior in undeformed nanocrystalline UO2 reveals that, on our MD time scale, the uranium ions diffuse only via the grain boundaries (GBs) whereas the much faster moving oxygen ions diffuse through both the lattice and the GBs. As expected for the Coble-creep mechanism, the creep activation energy agrees well with that for GB diffusion of the slowest moving species, i.e., of the uranium ions.

  19. Thermoluminescence characteristics of LiF: Cu nanocrystalline phosphor

    NASA Astrophysics Data System (ADS)

    Seth, Pooja; Aggarwal, Shruti

    2016-05-01

    Copper (Cu) activated LiF phosphor in nanocrystalline form has been prepared by the chemical co-precipitation method for radiation dosimetry application. The formation of nanocrystalline structure has been confirmed by X-ray diffraction and Scanning electron microscopy. Cubical shaped nanostructure with average particle size of 33nm has been formed. The sample was prepared at different concentration of Cu from 0.01mol% to 3 mol%. TL properties were investigated by studying the glow curve after irradiating the phosphor to gamma ray Co60 source with dose of 15 Gy. It has been found that nanocrystalline LiF: Cu show simple glow curve structure with a single glow peak at 404 K where as commercially available phosphors exhibits multi peak complex glow curve structure. The effect of different normality on the TL properties of phosphor has been studied. Maximum TL intensity for LiF: Cu (0.1mol %) phosphor is observed at the normality of 0.5N and annealing temperature of 200°C. The phosphor showed good linearity up to 10 KGy.

  20. Synthesis and characterization of nanocrystalline mesoporous zirconia using supercritical drying.

    PubMed

    Tyagi, Beena; Sidhpuria, Kalpesh; Shaik, Basha; Jasra, Raksh Vir

    2006-06-01

    Synthesis of nano-crystalline zirconia aerogel was done by sol-gel technique and supercritical drying using n-propanol solvent at and above supercritical temperature (235-280 degrees C) and pressure (48-52 bar) of n-propanol. Zirconia xerogel samples have also been prepared by conventional thermal drying method to compare with the super critically dried samples. Crystalline phase, crystallite size, surface area, pore volume, and pore size distribution were determined for all the samples in detail to understand the effect of gel drying methods on these properties. Supercritical drying of zirconia gel was observed to give thermally stable, nano-crystalline, tetragonal zirconia aerogels having high specific surface area and porosity with narrow and uniform pore size distribution as compared to thermally dried zirconia. With supercritical drying, zirconia samples show the formation of only mesopores whereas in thermally dried samples, substantial amount of micropores are observed along with mesopores. The samples prepared using supercritical drying yield nano-crystalline zirconia with smaller crystallite size (4-6 nm) as compared to higher crystallite size (13-20 nm) observed with thermally dried zirconia. PMID:17025056

  1. Low temperature solid-state synthesis of nanocrystalline gallium nitride

    SciTech Connect

    Wang, Liangbiao; Shi, Liang; Li, Qianwen; Si, Lulu; Zhu, Yongchun; Qian, Yitai

    2012-11-15

    Graphical abstract: Display Omitted Highlights: ► GaN nanocrystalline was prepared via a solid-state reacion at relatively low temperature. ► The sizes and crystallinities of the GaN samples obtained at the different temperatures are investigated. ► The GaN sample has oxidation resistance and good thermal stability below 1000 °C. -- Abstract: Nanocrystalline gallium nitride was synthesized by a solid-state reaction of metallic magnesium powder, gallium sesquioxide and sodium amide in a stainless steel autoclave at a relatively low temperature (400–550 °C). The structures and morphologies of the obtained products were derived from X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). XRD patterns indicated that the products were hexagonal GaN (JCPDS card no. 76-0703). The influence of reaction temperature on size of the products was studied by XRD and TEM. Furthermore, the thermal stability and oxidation resistance of the nanocrystalline GaN were also investigated. It had good thermal stability and oxidation resistance below 800 °C in air.

  2. Improve oxidation resistance at high temperature by nanocrystalline surface layer

    NASA Astrophysics Data System (ADS)

    Xia, Z. X.; Zhang, C.; Huang, X. F.; Liu, W. B.; Yang, Z. G.

    2015-08-01

    An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in conventional P91 steel. The diffusivity of Cr, Fe and O is enhanced concurrently in the nanocrystalline surface layer, which causes the fast oxidation in the initial oxidation stage. The formation of (Fe,Cr)2O3 inner layer would inhabit fast diffusion of alloy elements in the nanocrystalline surface layer of P91 steel in the later oxidation stage, and it causes a decrease in the parabolic oxidation rate compared with conventional specimens. This study provides a novel approach to improve the oxidation resistance of heat resistant steel without changing its Cr content.

  3. Improve oxidation resistance at high temperature by nanocrystalline surface layer

    PubMed Central

    Xia, Z. X.; Zhang, C.; Huang, X. F.; Liu, W. B.; Yang, Z. G.

    2015-01-01

    An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in conventional P91 steel. The diffusivity of Cr, Fe and O is enhanced concurrently in the nanocrystalline surface layer, which causes the fast oxidation in the initial oxidation stage. The formation of (Fe,Cr)2O3 inner layer would inhabit fast diffusion of alloy elements in the nanocrystalline surface layer of P91 steel in the later oxidation stage, and it causes a decrease in the parabolic oxidation rate compared with conventional specimens. This study provides a novel approach to improve the oxidation resistance of heat resistant steel without changing its Cr content. PMID:26269034

  4. Comparison of the Weibull characteristics of hydroxyapatite and strontium doped hydroxyapatite.

    PubMed

    Yatongchai, Chokchai; Wren, Anthony W; Curran, Declan J; Hornez, Jean-Christophe; Mark R, Towler

    2013-05-01

    The effects of two strontium (Sr) additions, 5% and 10% of the total calcium (Ca) content, on the phase assemblage and Weibull statistics of hydroxyapatite (HA) are investigated and compared to those of undoped HA. Sintering was carried out in the range of 900-1200 °C in steps of 1000 °C in a conventional furnace. Sr content had little effect on the mean particulate size. Decomposition of the HA phase occurred with Sr incorporation, while β-TCP stabilization was shown to occur with 10% Sr additions. Porosity in both sets of doped samples was at a comparable level to porosity in the undoped HA samples, however the 5% Sr-HA samples displayed the greatest reduction in porosity with increasing temperature while the porosity of the 10% Sr-HA samples remain relatively constant over the full sintering temperature range. The undoped HA samples displayed the greatest Weibull strengths and the porosity was determined to be the major controlling factor. However, with the introduction of decompositional phases in the Sr-HA samples, the dependence of strength on porosity is reduced and the phase assemblage becomes the more dominant factor for Weibull strength. The Weibull modulus is relatively independent of the porosity in the undoped HA samples. The 5% Sr-HA samples experience a slight increase in Weibull modulus with porosity, indicating a possible relationship between the parameters. However the 10% Sr-HA samples show the highest Weibull modulus with a value of approximately 15 across all sintering temperatures. It is postulated that this is due to the increased amount of surface and lattice diffusion that these samples undergo, which effectively smooths out flaws in the microstructure, due to a saturation of Sr content occurring in grain boundary movement. PMID:23524073

  5. Characterization and inhibitive study of gel-grown hydroxyapatite crystals at physiological temperature

    NASA Astrophysics Data System (ADS)

    Parekh, Bharat; Joshi, Mihir; Vaidya, Ashok

    2008-04-01

    Hydroxyapatite is very useful for various biomedical applications, due to its chemical similarity with mineralized bone of human. Hydroxyapatite is also responsible for arthropathy (joint disease). In the present study, the growth of hydroxyapatite crystals was carried out by using single-diffusion gel growth technique in silica hydro gel media, at physiological temperature. The growth of hydroxyapatite crystals under slow and controlled environment in gel medium can be simulated in a simple manner to the growth in human body. The crystals, formed in the Liesegang rings, were characterized by powder XRD, FTIR and dielectric study. The diffusion study is also carried out for the hydroxyapatite crystals using the moving boundary model. The inhibitive influence of various Ayurvedic medicinal plant extracts such as Boswellia serrata gum resin , Tribulus terrestris fruits, Rotula aquatica roots, Boerhaavia diffusa roots and Commiphora wightii, on the growth of hydroxyapatite was studied. Roots of R. aquatica and B. diffusa show some inhibition of the hydroxyapatite crystals in vitro. This preclinical study will be helpful to design the therapy for prevention of hydroxyapatite-based ailments.

  6. Containment of uranium in the proposed Egyptian geologic repository for radioactive waste using hydroxyapatite.

    SciTech Connect

    Moore, Robert Charles; Hasan, Ahmed Ali Mohamed; Headley, Thomas Jeffrey; Sanchez, Charles Anthony; Zhao, Hongting; Salas, Fred Manuel; Hasan, Mahmoud A.; Holt, Kathleen Caroline

    2003-08-01

    Currently, the Egyptian Atomic Energy Authority is designing a shallow-land disposal facility for low-level radioactive waste. To insure containment and prevent migration of radionuclides from the site, the use of a reactive backfill material is being considered. One material under consideration is hydroxyapatite, Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}, which has a high affinity for the sorption of many radionuclides. Hydroxyapatite has many properties that make it an ideal material for use as a backfill including low water solubility (K{sub sp} > 10{sup -40}), high stability under reducing and oxidizing conditions over a wide temperature range, availability, and low cost. However, there is often considerable variation in the properties of apatites depending on source and method of preparation. In this work, we characterized and compared a synthetic hydroxyapatite with hydroxyapatites prepared from cattle bone calcined at 500 C, 700 C, 900 C and 1100 C. The analysis indicated the synthetic hydroxyapatite was similar in morphology to 500 C prepared cattle hydroxyapatite. With increasing calcination temperature the crystallinity and crystal size of the hydroxyapatites increased and the BET surface area and carbonate concentration decreased. Batch sorption experiments were performed to determine the effectiveness of each material to sorb uranium. Sorption of U was strong regardless of apatite type indicating all apatite materials evaluated. Sixty day desorption experiments indicated desorption of uranium for each hydroxyapatite was negligible.

  7. Containment of uranium in the proposed Egyptian geologic repository for radioactive waste using hydroxyapatite.

    SciTech Connect

    Moore, Robert Charles; Hasan, Ahmed Ali Mohamed; Headley, Thomas Jeffrey; Sanchez, Charles Anthony; Zhao, Hongting; Salas, Fred Manuel; Hasan, Mahmoud A.; Holt, Kathleen Caroline

    2004-04-01

    Currently, the Egyptian Atomic Energy Authority is designing a shallow-land disposal facility for low-level radioactive waste. To insure containment and prevent migration of radionuclides from the site, the use of a reactive backfill material is being considered. One material under consideration is hydroxyapatite, Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}, which has a high affinity for the sorption of many radionuclides. Hydroxyapatite has many properties that make it an ideal material for use as a backfill including low water solubility (K{sub sp}>10{sup -40}), high stability under reducing and oxidizing conditions over a wide temperature range, availability, and low cost. However, there is often considerable variation in the properties of apatites depending on source and method of preparation. In this work, we characterized and compared a synthetic hydroxyapatite with hydroxyapatites prepared from cattle bone calcined at 500 C, 700 C, 900 C and 1100 C. The analysis indicated the synthetic hydroxyapatite was similar in morphology to 500 C prepared cattle hydroxyapatite. With increasing calcination temperature the crystallinity and crystal size of the hydroxyapatites increased and the BET surface area and carbonate concentration decreased. Batch sorption experiments were performed to determine the effectiveness of each material to sorb uranium. Sorption of U was strong regardless of apatite type indicating all apatite materials evaluated. Sixty day desorption experiments indicated desorption of uranium for each hydroxyapatite was negligible.

  8. FORMATION OF CHLOROPYROMORPHITE IN A LEAD-CONTAMINATED SOIL AMENDED WITH HYDROXYAPATITE

    EPA Science Inventory

    To evaluate conversion of soil Pb to pyromorphite, a Pb contaminated soil collected adjacent to a historical smelter was reacted with hydroxyapatite in a traditional incubation experiment and in a dialysis system in which the soil and hydroxyapatite solids were separated by a dia...

  9. Synthesis and release of trace elements from hollow and porous hydroxyapatite spheres

    NASA Astrophysics Data System (ADS)

    Xia, Wei; Grandfield, Kathryn; Schwenke, Almut; Engqvist, Håkan

    2011-07-01

    It is known that organic species regulate fabrication of hierarchical biological forms via solution methods. However, in this study, we observed that the presence of inorganic ions plays an important role in the formation and regulation of biological spherical hydroxyapatite formation. We present a mineralization method to prepare ion-doped hydroxyapatite spheres with a hierarchical structure that is free of organic surfactants and biological additives. Porous and hollow strontium-doped hydroxyapatite spheres were synthesized via controlling the concentration of strontium ions in a calcium and phosphate buffer solution. Similarly, fluoride and silicon-doped hydroxyapatite spheres were synthesized. While spherical particle formation was attainable at low and high temperature for Sr-doped hydroxyapatite, it was only possible at high temperature in the F/Si-doped system. The presence of inorganic ions not only plays an important role in the formation and regulation of biological spherical hydroxyapatite, but also could introduce pharmaceutical effects as a result of trace element release. Such ion release results showed a sustained release with pH responsive behavior, and significantly influenced the hydroxyapatite re-precipitation. These ion-doped hydroxyapatite spheres with hollow and porous structure could have promising applications as bone/tooth materials, drug delivery systems, and chromatography supports.

  10. Influence of Starting Powders on Hydroxyapatite Coatings Fabricated by Room Temperature Spraying Method.

    PubMed

    Seo, Dong Seok; Lee, Jong Kook; Hwang, Kyu Hong; Hahn, Byung Dong; Yoon, Seog Young

    2015-08-01

    Three types of raw materials were used for the fabrication of hydroxyapatite coatings by using the room temperature spraying method and their influence on the microstructure and in vitro characteristics were investigated. Starting hydroxyapatite powders for coatings on titanium substrate were prepared by a heat treatment at 1100 °C for 2 h of bovine bone, bone ash, and commercial hydroxyapatite powders. The phase compositions and Ca/P ratios of the three hydroxyapatite coatings were similar to those of the raw materials without decomposition or formation of a new phase. All hydroxyapatite coatings showed a honeycomb structure, but their surface microstructures revealed different features in regards to surface morphology and roughness, based on the staring materials. All coatings consisted of nano-sized grains and had dense microstructure. Inferred from in vitro experiments in pure water, all coatings have a good dissolution-resistance and biostability in water. PMID:26369193

  11. [In Situ Polymerization and Characterization of Hydroxyapatite/polyurethane Implanted Material].

    PubMed

    Gu, Muqing; Xiao, Fengjuan; Liang, Ye; Yue, Lin; Li, Song; Li, Lanlan; Feng, Feifei

    2015-08-01

    In order to improve the interfacial bonding strength of hydroxyapatite/polyurethane implanted material and dispersion of hydroxyapatite in the polyurethane matrix, we in the present study synthesized nano-hydroxyapatite/polyurethane composites by in situ polymerization. We then characterized and analyzed the fracture morphology, thermal stability, glass transition temperature and mechanical properties. We seeded MG63 cells on composites to evaluate the cytocompatibility of the composites. In situ polymerization could improve the interfacial bonding strength, ameliorate dispersion of hydroxyapatite in the properties of the composites. After adding 20 wt% hydroxyapatite into the polyurethane, the thermal stability was improved and the glass transition temperatures were increased. The tensile strength and maximum elongation were 6.83 MPa and 861.17%, respectively. Compared with those of pure polyurethane the tensile strength and maximum elongation increased by 236.45% and 143.30%, respectively. The composites were helpful for cell adhesion and proliferation in cultivation. PMID:26710455

  12. [Using Metronidazole and Hydroxyapatite for preventing dry socket after extraction of impacted mandibular 3rd molar

    PubMed

    Xue, Z X; Mao, T Q

    1993-03-01

    Dry socket is one of the most frequent complications after teeth extraction,especially in impacted mandibular third molars.The etilogy and prevention is not clear.This study id based on principles of clinical epidemiology.Randomized double-blind method was carried out in 549 patients to test the value of the prophylactic use of Hydroxyapatite,to test the value of the prophylactic use of Hydroxyapatite and Metronidazole,placed in the sockets of extracted impacted mandibular third molars.The results of the incidence of DS was 7.1% of Metronidazole treated sockets,and 2.1% of Hydroxyapatite treated sockets,It is concluded that Hydroxyapatite is an effective preventive factor for dry socket,The possible mechanism of Hydroxyapatite and the dry socket etiology were discussed. PMID:15159869

  13. Surface free energy predominates in cell adhesion to hydroxyapatite through wettability.

    PubMed

    Nakamura, Miho; Hori, Naoko; Ando, Hiroshi; Namba, Saki; Toyama, Takeshi; Nishimiya, Nobuyuki; Yamashita, Kimihiro

    2016-05-01

    The initial adhesion of cells to biomaterials is critical in the regulation of subsequent cell behaviors. The purpose of this study was to investigate a mechanism through which the surface wettability of biomaterials can be improved and determine the effects of biomaterial surface characteristics on cellular behaviors. We investigated the surface characteristics of various types of hydroxyapatite after sintering in different atmospheres and examined the effects of various surface characteristics on cell adhesion to study cell-biomaterial interactions. Sintering atmosphere affects the polarization capacity of hydroxyapatite by changing hydroxide ion content and grain size. Compared with hydroxyapatite sintered in air, hydroxyapatite sintered in saturated water vapor had a higher polarization capacity that increased surface free energy and improved wettability, which in turn accelerated cell adhesion. We determined the optimal conditions of hydroxyapatite polarization for the improvement of surface wettability and acceleration of cell adhesion. PMID:26952425

  14. Is hydroxyapatite a reliable fixation option in unicompartmental knee arthroplasty? A 5- to 13-year experience with the hydroxyapatite-coated unix prosthesis.

    PubMed

    Epinette, Jean-Alain; Manley, Michael T

    2008-10-01

    Hydroxyapatite-coated unicompartmental knee arthroplasty (UKA) is a debatable approach to unicompartmental knee arthritis because UKA isoften viewed as a short-term solution, at best, fora condition that will eventually require a total knee arthroplasty (TKA). Unicompartmental knee arthroplasty is a more technically demanding procedure than TKA, and appropriate patient selection, careful surgical technique, and correct choice of implant geometry are all critical components to its success. A fundamental issue surrounding UKA is whether hydroxyapatite-coated unicompartmental components can provide a long-term solution to unicondylar arthritis. We address this issue in the current study, which is based on a prospective series of 125 hydroxyapatite-coated Unix knee prostheses implanted consecutively between 1994 and 2002, with a 5-year minimum follow-up and a 13-year maximum follow-up. The results of our study indicate that uncemented hydroxyapatite-coated UKA can be successful in the long term. PMID:18979933

  15. Size-controlled hydroxyapatite nanoparticles as self-organized organic-inorganic composite materials.

    PubMed

    Rusu, Viorel Marin; Ng, Chuen-How; Wilke, Max; Tiersch, Brigitte; Fratzl, Peter; Peter, Martin G

    2005-09-01

    This paper presents some results concerning the size-controlled hydroxyapatite nanoparticles obtained in aqueous media in a biopolymer matrix from soluble precursors salts. Taking the inspiration from nature, where composite materials made of a polymer matrix and inorganic fillers are often found, e.g. bone, shell of crustaceans, shell of eggs, etc., the feasibility on making composite materials containing chitosan and nanosized hydroxyapatite was investigated. A stepwise co-precipitation approach was used to obtain different types of composites by means of different ratio between components. The synthesis of hydroxyapatite was carried out in the chitosan matrix from calcium chloride and sodium dihydrogenphosphate in alkaline solutions at moderate pH of 10-11 for 24 h. Our research is focused on studying and understanding the structure of this class of composites, aiming at the development of novel materials, controlled at the nanolevel scale. The X-ray diffraction technique was employed in order to study the kinetic of hydroxyapatite formation in the chitosan matrix as well as to determine the HAp crystallite sizes in the composite samples. The hydroxyapatite synthesized using this route was found to be nano-sized (15-50 nm). Moreover, applying an original approach to analyze the (002) XRD diffraction peak profile of hydroxyapatite by using a sum of two Gauss functions, the bimodal distribution of nanosized hydroxyapatite within the chitosan matrix was revealed. Two types of size distribution domains such as cluster-like (between 200 and 400 nm), which are the habitat of ''small'' hydroxyapatite nanocrystallites and scattered-like, which are the habitat of ''large'' hydroxyapatite nanocrystallites was probed by TEM and CSLM. The structural features of composites suggest that self-assembly processes might be involved. The composites contain nanosized hydroxyapatite with structural features close to those of biological apatites that make them attractive for bone

  16. Enhanced Activity of Nanocrystalline Zeolites for Selective Catalytic Reduction of NOx

    SciTech Connect

    Sarah C. Larson; Vicki H. Grassian

    2006-12-31

    Nanocrystalline zeolites with discrete crystal sizes of less than 100 nm have different properties relative to zeolites with larger crystal sizes. Nanocrystalline zeolites have improved mass transfer properties and very large internal and external surface areas that can be exploited for many different applications. The additional external surface active sites and the improved mass transfer properties of nanocrystalline zeolites offer significant advantages for selective catalytic reduction (SCR) catalysis with ammonia as a reductant in coal-fired power plants relative to current zeolite based SCR catalysts. Nanocrystalline NaY was synthesized with a crystal size of 15-20 nm and was thoroughly characterized using x-ray diffraction, electron paramagnetic resonance spectroscopy, nitrogen adsorption isotherms and Fourier Transform Infrared (FT-IR) spectroscopy. Copper ions were exchanged into nanocrystalline NaY to increase the catalytic activity. The reactions of nitrogen dioxides (NO{sub x}) and ammonia (NH{sub 3}) on nanocrystalline NaY and CuY were investigated using FT-IR spectroscopy. Significant conversion of NO{sub 2} was observed at room temperature in the presence of NH{sub 3} as monitored by FT-IR spectroscopy. Copper-exchanged nanocrystalline NaY was more active for NO{sub 2} reduction with NH{sub 3} relative to nanocrystalline NaY.

  17. Corrosion stability and bioactivity in simulated body fluid of silver/hydroxyapatite and silver/hydroxyapatite/lignin coatings on titanium obtained by electrophoretic deposition.

    PubMed

    Eraković, Sanja; Janković, Ana; Veljović, Djordje; Palcevskis, Eriks; Mitrić, Miodrag; Stevanović, Tatjana; Janaćković, Djordje; Mišković-Stanković, Vesna

    2013-02-14

    Hydroxyapatite is the most suitable biocompatible material for bone implant coatings. However, its brittleness is a major obstacle, and that is why, recently, research focused on creating composites with various biopolymers. In this study, hydroxyapatite coatings were modified with lignin in order to attain corrosion stability and surface porosity that enables osteogenesis. Incorporating silver, well known for its antimicrobial properties, seemed the best strategy for avoiding possible infections. The silver/hydroxyapatite (Ag/HAP) and silver/hydroxyapatite/lignin (Ag/HAP/Lig) coatings were cathaphoretically deposited on titanium from ethanol suspensions, sintered at 900 °C in Ar, and characterized by X-ray diffraction, scanning electron microscopy, field emission scanning electron microscopy, attenuated total reflection Fourier transform infrared, and X-ray photoelectron spectroscopy. The corrosion stability of electrodeposited coatings was evaluated in vitro in Kokubo's simulated body fluid (SBF) at 37 °C using electrochemical impedance spectroscopy. Bioactivity was estimated by immersion in SBF to evaluate the formation of hydroxyapatite on the coating surface. A microcrystalline structure of newly formed plate-shaped carbonate-hydroxyapatite was detected after only 7 days, indicating enhanced bioactive behavior. Both coatings had good corrosion stability during a prolonged immersion time. Among the two, the Ag/HAP/Lig coating had a homogeneous surface, less roughness, and low values of contact angle. PMID:22991920

  18. Infrared absorption study of hydrogen incorporation in thick nanocrystalline diamond films

    SciTech Connect

    Tang, C.J.; Neves, A.J.; Carmo, M.C.

    2005-05-30

    We present an infrared (IR) optical absorbance study of hydrogen incorporation in nanocrystalline diamond films. The thick nanocrystalline diamond films were synthesized by microwave plasma-assisted chemical vapor deposition and a high growth rate about 3.0 {mu}m/h was achieved. The morphology, phase quality, and hydrogen incorporation were assessed by means of scanning electron microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR). Large amount of hydrogen bonded to nanocrystalline diamond is clearly evidenced by the huge CH stretching band in the FTIR spectrum. The mechanism of hydrogen incorporation is discussed in light of the growth mechanism of nanocrystalline diamond. This suggests the potential of nanocrystalline diamond for IR electro-optical device applications.

  19. [Morphological studies of hydroxyapatite crystals exposed to disodium pamidronate].

    PubMed

    Hein, L E; Grassi, R L; Roldán, E J; Gregori, D; Varela, M E; Piccinni, E P

    1997-01-01

    "In vitro" effects of disodium pamidronate on hydroxyapatite crystals morphology, and some "in vivo" data from bone powder of tibia and vertebrae from treated young and mature rabbits are here reported. Hydroxyapatite, synthesized following Rigoli et al method, and bone powder from rabbits were studied with X-ray, infrared and raman emission techniques for crystallographic analysis. Adsorption studies were also performed with a balanced solution of hydroxyapatite exposed to different times, 48, 120 and 168 hours and concentrations 1 x 10(-5) M, 3 x 10(-5) M, 8 x 10(-5) M y 1 x 10(-4) M of pamidronate. Infrared and raman spectrometry were not conclusive due to technical bias, but X-ray difractograms showed pure hydroxyapatite crystals in an hexagonal system. At constant time, pamidronate concentrations were varied, showing after 48 hours of exposition, a slight growth in the 002 plane, an aleatoric behavior in 213 and a marked increase in 004. After 120 hours, 002 plane is steady with a net growth in 004 and 213. After 168 hours, the 3 mentioned planes grow in proportion to pamidronate concentrations, tending to enlarge the crystal shape. Plane 13 markedly grow with pamidronate 8 x 10(-5) M a 1 x 10(-4) M, which are biologically high concentrations. Potentiometric assessments, in the 1 x 10(-5) to 1 x 10(-4) M range of concentrations show that bisphosphonate was completely adsorbed to the crystals. Additional "in vivo" observations showed changes in bone powder crystals isolated from pamidronate treated young animals, involving a growing of planes 002 and 211, in samples from both epiphysis and diaphysis, regarding untreated samples. Changes were more evident at epiphysis. In mature rabbits, it was shown a decrease in basal plane 002 and growing at 210, 211 and 310 with a trend to enlarge the crystal shape in diaphysis and to shorten it in vertebrate spongiosa. The "in vivo" doses are equivalent to those used by Ferretti et al. in intact rats with pamidronate low

  20. Factorial design analysis for sorption of zinc on hydroxyapatite.

    PubMed

    Meski, S; Ziani, S; Khireddine, H; Boudboub, S; Zaidi, S

    2011-02-28

    A factorial design was employed to evaluate the quantitative removal of zinc from aqueous solutions on synthesized hydroxyapatite. The experimental factors and their respective levels studied were the initial zinc concentration in solution (35≤C(Zn)≤85 mg/L), adsorbent dosage (4.5≤C(susp)≤9.5 g/L), Ca/P molar ratio (1.667≤Ca/P≤2) and calcination temperature of hydroxyapatite (600≤T(Cal)≤800 °C). The adsorption parameters were analysed statistically by means of variance analysis by using the STATISTICA software. The experimental results and statistical analysis show that increasing in the calcination temperature from 600 to 800 °C decrease the zinc adsorption whereas the increase of adsorbent dosage increases it. Based on the analysis of variance and the factorial design of experiments, adsorbent dosage has a positive effect on the removal of zinc, whereas zinc concentration, Ca/P molar ratio and calcination temperature have a negative effect on this process. The factorial results also demonstrate the existence of statistically significant binary interactions of the experimental factors. The experimental results were fitted to the Langmuir and Freundlich equations to find out adsorption capacities. In most cases, the results indicate that the sorption data fits well in the Freundlich isotherm model. The results of XRD analysis, pH(PZC) and pH(Final) values indicated that ion exchange and dissolution/precipitation mechanisms predominate for the sorption of zinc on our hydroxyapatite. PMID:21159426

  1. Induction suspension plasma sprayed biological-like hydroxyapatite coatings.

    PubMed

    Loszach, Max; Gitzhofer, François

    2015-04-01

    Substituted hydroxyapatite coatings with different ions (Mg, Na, K, Cl, F) have been developed by the induction suspension plasma spray process. Suspensions were prepared with sol-gel. The main objective of this study was to demonstrate that induction suspension plasma spray technology possesses high material composition flexibility that allows as-sprayed coatings to closely mimic natural bone composition. Long-term in vitro behaviour of as-sprayed substituted coatings was evaluated with simulated body fluid. Data on the suspensions showed the formation of a pure hydroxyapatite phase. Transmission electron microscopy characterized various preparation stages of the suspensions. As-sprayed samples were distinguished by X-ray diffraction and scanning electron microscopy. Substituted elements were quantified by neutron activation. A well-crystallized hydroxyapatite phase was produced with concentration in various substitutions very close to natural bone composition. Ca/P and (Ca + Mg + Na + K)/P ratios provided evidence of the introduction of different cations into apatite structures. The immersion of samples into simulated body fluid led to the nucleation and growth of a flake-like octacalcium phosphate crystal layer at the surface of as-sprayed coatings after one week. Proof of octacalcium phosphate transformation and its partial dissolution and direct re-precipitation into apatite was disclosed by local energy dispersive spectroscopy and microstructure observation. Formation of a Ca/P ratio gradient from the precipitated layer surface to the as-sprayed coatings interface was observed after four weeks once the octacalcium phosphate crystals reached a critical size, resulting in the formation of a rich apatite layer at the interface after six weeks. A set of mechanisms has been proposed to explain these findings. PMID:25586411

  2. Nucleation and Growth of Hydroxyapatite on Hierarchically Ordered Polymer Nanofibers

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Dong, Bin; Wang, Bingbing; Li, Christopher

    2011-03-01

    The hierarchically ordered polymer nanofibers, named as nanofiber shish kebabs (NFSKs), were constructed via combination of electrospinning polycaprolactone (PCL) (shish polymer) and controlled crystallization of polycaprolactone-b-poly acrylic acid (PCL-b-PAA) (kebab polymer). These NFSKs were then employed as a template to control the nucleation and growth of hydroxypatite nanocrystals. Electron microscopy and diffraction technique were used to characterize this novel hybrid structure. The growth of minerals starts on the surface of single crystal kebabs and eventually covers the surface of NFSKs. The formation mechanism of hydroxyapatite on NFSKs is of great interest because of the NFSKs' potential application as bone scaffold materials.

  3. Polyether sulfone/hydroxyapatite mixed matrix membranes for protein purification

    NASA Astrophysics Data System (ADS)

    Sun, Junfen; Wu, Lishun

    2014-07-01

    This work proposes a novel approach for protein purification from solution using mixed matrix membranes (MMMs) comprising of hydroxyapatite (HAP) inside polyether sulfone (PES) matrix. The influence of HAP particle loading on membrane morphology is studied. The MMMs are further characterized concerning permeability and adsorption capacity. The MMMs show purification of protein via both diffusion as well as adsorption, and show the potential of using MMMs for improvements in protein purification techniques. The bovine serum albumin (BSA) was used as a model protein. The properties and structures of MMMs prepared by immersion phase separation process were characterized by pure water flux, BSA adsorption and scanning electron microscopy (SEM).

  4. Hydroxyapatite-binding peptides for bone growth and inhibition

    DOEpatents

    Bertozzi, Carolyn R.; Song, Jie; Lee, Seung-Wuk

    2011-09-20

    Hydroxyapatite (HA)-binding peptides are selected using combinatorial phage library display. Pseudo-repetitive consensus amino acid sequences possessing periodic hydroxyl side chains in every two or three amino acid sequences are obtained. These sequences resemble the (Gly-Pro-Hyp).sub.x repeat of human type I collagen, a major component of extracellular matrices of natural bone. A consistent presence of basic amino acid residues is also observed. The peptides are synthesized by the solid-phase synthetic method and then used for template-driven HA-mineralization. Microscopy reveal that the peptides template the growth of polycrystalline HA crystals .about.40 nm in size.

  5. Novel multiform morphologies of hydroxyapatite: Synthesis and growth mechanism

    NASA Astrophysics Data System (ADS)

    Mary, I. Reeta; Sonia, S.; Viji, S.; Mangalaraj, D.; Viswanathan, C.; Ponpandian, N.

    2016-01-01

    Morphological evolution of materials becomes a prodigious challenge due to their key role in defining their functional properties and desired applications. Herein, we report the synthesis of hydroxyapatite (HAp) microstructures with multiform morphologies, such as spheres, cubes, hexagonal rods and nested bundles constructed from their respective nanoscale building blocks via a simple cost effective hydro/solvothermal method. A possible formation mechanism of diverse morphologies of HAp has been presented. Structural analysis based on X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirms the purity of the HAp microstructures. The multiform morphologies of HAp were corroborated by using Field emission scanning electron microscope (FESEM).

  6. Collagen hydrolysate based collagen/hydroxyapatite composite materials

    NASA Astrophysics Data System (ADS)

    Ficai, Anton; Albu, Madalina Georgiana; Birsan, Mihaela; Sonmez, Maria; Ficai, Denisa; Trandafir, Viorica; Andronescu, Ecaterina

    2013-04-01

    The aim of this study was to study the influence of collagen hydrolysate (HAS) on the formation of ternary collagen-hydrolysate/hydroxyapatite composite materials (COLL-HAS/HA). During the precipitation process of HA, a large amount of brushite is resulted at pH = 7 but, practically pure HA is obtained at pH ⩾ 8. The FTIR data reveal the duplication of the most important collagen absorption bands due to the presence of the collagen hydrolysate. The presence of collagen hydrolysate is beneficial for the management of bone and joint disorders such as osteoarthritis and osteoporosis.

  7. Ion-exchange properties of strontium hydroxyapatite under acidic conditions

    SciTech Connect

    Sugiyama, Shigeru; Nishioka, Hitoshi; Moriga, Toshihiro; Hayashi, Hiromu; Moffat, J.B.

    1998-09-01

    The ion exchange of strontium hydroxyapatite (SrHAp) with Pb{sup 2+} has been investigated under acidic conditions at 293 K. The addition of various acids to the exchanging solution enhanced the exchange capacity in the order HCl > HBr > HF > HNO{sub 3} > no acid, corresponding to the formation of halogen apatites with the former three acids or hydrogen phosphate with HNO{sub 3}. Since the ion-exchange capacity of SrHAp under nonacidic conditions is higher than that of chlorapatite, the aforementioned observations can be attributed to the participation of the protons introduced by the acids.z

  8. Pyroelectric, piezoelectric, and photoeffects in hydroxyapatite thin films on silicon

    NASA Astrophysics Data System (ADS)

    Lang, S. B.; Tofail, S. A. M.; Gandhi, A. A.; Gregor, M.; Wolf-Brandstetter, C.; Kost, J.; Bauer, S.; Krause, M.

    2011-03-01

    Hydroxyapatite (HA) is the major component of bone and is used in artificial form in many biomedical applications. It was once believed to have a centrosymmetric crystal structure. In theoretical and experimental studies published in 2005, it was shown to have a monoclinic P21 structure. In the work reported here, 500 nm films of HA were spin-coated on silicon wafers. The materials were not poled. They had a nonuniform polarization distribution and exhibited pyroelectricity, piezoelectricity, and photoeffects. Structures of this type may have a number of technological applications.

  9. Characterization of processed tooth hydroxyapatite for potential biomedical implant applications.

    PubMed

    Oktar, F N; Kesenci, K; Pişkin, E

    1999-07-01

    In this study hydroxyapatite (HA) (100-150 microns) derived from freshly-extracted human teeth in laboratory conditions was investigated. Scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDXS), wet chemical, ion chromatographic peak method (ICP), atomic absorption, x-ray diffraction and infra-red (IR) were performed separately for HA obtained from dentine and enamel. This naturally derived HA did not differ from synthetic ones. Its production was simple when compared with other methods. Processed tooth HA could safely be used in animal subjects prior to human studies as a graft material after biocompatibility studies fully conducted. PMID:10427420

  10. Microstructural characterization of glass-reinforced hydroxyapatite composites.

    PubMed

    Santos, J D; Knowles, J C; Reis, R L; Monteiro, F J; Hastings, G W

    1994-01-01

    The influence of phosphate-based glasses and a bioactive silica glass on the sintering mechanism of hydroxyapatite was studied over a wide range of temperatures. The composites were microstructurally characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Small additions of phosphate-based glasses proved to be beneficial to the sintering process and fully dense materials were obtained. A significant improvement in mechanical properties was achieved. beta-TCP and alpha-TCP were found in the microstructure depending on the sintering temperature. Additions of bioactive glass led to the development of calcium phosphate silicate. PMID:8161658

  11. 188Re-labeled hydroxyapatite particles for radiation synovectomy.

    PubMed

    Kothari, K; Suresh, S; Sarma, H D; Meera, V; Pillai, M R A

    2003-04-01

    A new procedure for labeling hydroxyapatite (HA) particles with 188Re for radiation synovectomy is described and standardized. The particles were labeled with 188Re in high yields (99%) in acidic medium. HA particle size remained unaffected by reaction conditions as checked by laser diffraction particle analyzer. 188Re-HA was found to be stable retaining 99% radiochemical purity after 4 days when stored in ascorbic acid solution (10mg/ml, pH 5). Intra-articular injection in rats revealed approximately 98% retention of 188Re-HA in the knee after 48-h pi. PMID:12672625

  12. The Fate of Porous Hydroxyapatite Granules Used in Facial Skeletal Augmentation

    PubMed Central

    Jacobson, Steve R.; Lavoipierre, Alain M.; Huggins, Richard J.

    2010-01-01

    Facial appearance is largely determined by the morphology of the underlying skeleton. Hydroxyapatite is one of several materials available to enhance projection of the facial skeleton. This study evaluated the long-term maintenance of augmented bony projection when porous hydroxyapatite granules are used on the facial skeleton. Ten female patients aged 28–58 years were studied following aesthetic augmentation of the facial skeleton at 24 sites using porous hydroxyapatite granules. Postoperative CT scans at 3 months served as the baseline measurement and compared with scans taken at 1 and 2 years, with the thickness of the hydroxyapatite measured in axial and coronal planes. Thickness of original bone plus overlay of hydroxyapatite, thickness of the overlying soft tissue, and the overall projection (bone plus soft tissue) were recorded. It was found that 99.7% of the hydroxyapatite was maintained at 2 years, with no statistical difference (t test) from the baseline measurement. The overall projection (bony and soft tissue) was maintained as there was no evidence of native bone resorption or soft tissue atrophy. Radiographic results confirmed that the use of porous hydroxyapatite granules for enhancement of the facial skeleton is not only a predictable procedure, but maintains full bony projection at 2 years. PMID:20186415

  13. Relative contributions of chemistry and topography to the osseointegration of hydroxyapatite coatings.

    PubMed

    Hacking, S A; Tanzer, M; Harvey, E J; Krygier, J J; Bobyn, J D

    2002-12-01

    The purpose of the current study was to ascertain the relative contributions of surface chemistry and topography to the osseointegration of hydroxyapatite-coated implants. A canine femoral intramedullary implant model was used to compare the osseous response to commercially pure titanium implants that were either polished, grit-blasted, plasma-sprayed with hydroxyapatite, or plasma-sprayed with hydroxyapatite and masked with a very thin layer of titanium using physical vapor deposition (titanium mask). The titanium mask isolated the chemistry of the underlying hydroxyapatite layer without functionally changing its surface topography and morphologic features. At 12 weeks, the bone-implant specimens were prepared for undecalcified thin section histologic evaluation and serial transverse sections were quantified with backscattered scanning electron microscopy for the percentage of bone apposition to the implant surface. Bone apposition averaged 3% for the polished implants and 23% for the grit-blasted implants. Bone apposition to the hydroxyapatite-coated implants averaged 74% whereas bone apposition to the titanium mask implants averaged 59%. Although there was significantly greater osseointegration with the hydroxyapatite-coated implants, 80% of the maximum bone forming response to the implant surfaces developed with the titanium mask implants. This simple, controlled experiment revealed that topography is the dominant factor governing bone apposition to hydroxyapatite-coated implants. PMID:12461353

  14. An improved biofunction of titanium for keratoprosthesis by hydroxyapatite-coating.

    PubMed

    Dong, Ying; Yang, Jingxin; Wang, Liqiang; Ma, Xiao; Huang, Yifei; Qiu, Zhiye; Cui, Fuzhai

    2014-03-01

    Titanium framework keratoprosthesis has been commonly used in the severe corneal blindness, but the tissue melting occurred frequently around titanium. Since hydroxyapatite has been approved to possess a good tissue integration characteristic, nanostructured hydroxyapatite was coated on the surface of titanium through the aerosol deposition method. In this study, nanostructured hydroxyapatite coating was characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, and auger electronic spectrometer. Biological evaluations were performed with rabbit cornea fibroblast in vitro and an animal model in vivo. The outcomes showed the coating had a grain-like surface topography and a good atomic mixed area with substrate. The rabbit cornea fibroblasts appeared a good adhesion on the surface of nanostructured hydroxyapatite in vitro. In the animal model, nanostructured hydroxyapatite-titanium implants were stably retained in the rabbit cornea, and by contrast, the corneal stroma became thinner anterior to the implants in the control. Therefore, our findings proved that nanostructured hydroxyapatite-titanium could not only provide an improved bond for substrate but also enhance the tissue integration with implants in host. As a promising material, nanostructured hydroxyapatite-titanium-based keratoprosthesis prepared by the aerosol deposition method could be utilized for the corneal blindness treatment. PMID:23749719

  15. Synthesis and structure of nanocrystalline mixed Ce–Yb silicates

    SciTech Connect

    Małecka, Małgorzata A. Kępiński, Leszek

    2013-07-15

    Graphical abstract: - Highlights: • New method of synthesis of nanocrystalline mixed lanthanide silicates is proposed. • Formation of A-type (Ce{sub 1−y}Yb{sub y}){sub 2}Si{sub 2}O{sub 7} in well dispersed Ce{sub 1−x}Yb{sub x}O{sub 2−(x/2)}–SiO{sub 2} system. • Formation of Yb{sub y}Ce{sub 9.33−y}(SiO{sub 4}){sub 6}O{sub 2} in agglomerated Ce{sub 1−x}Yb{sub x}O{sub 2−(x/2)}–SiO{sub 2} system. - Abstract: This work presents results of studies on synthesis and structure of mixed, nanocrystalline Ce–Yb silicates. Using TEM, XRD and FTIR we showed that heat treatment of nanocrystalline Ce{sub 1−x}Yb{sub x}O{sub 2−(x/2)} (x = 0.3, 0.5) mixed oxide supported on amorphous silica in reducing atmosphere, results in formation of Ce–Yb mixed silicates. Dispersion of the oxide on the silica surface and thus a local lanthanide/Si atomic ratio determines the stoichiometry of the silicate. Oxide crystallites uniformly dispersed on the silica surface transformed into A-(Ce{sub 1−y}Yb{sub y}){sub 2}Si{sub 2}O{sub 7} disilicate, while the agglomerated nanoparticles converted into Yb{sub y}Ce{sub 9.33−y}(SiO{sub 4}){sub 6}O{sub 2} oxyapatite silicate as an intermediate phase.

  16. Morphological, luminescence and structural properties of nanocrystalline silicon thin films

    SciTech Connect

    Ali, Atif Mossad; Kobayashi, Hikaru; Inokuma, Takao; Al-Hajry, Ali

    2013-03-15

    Highlights: ► The PL spectra showed two stronger peaks and one weaker peak. ► The PL peak energies and optical band-gap values were found higher than 1.12 eV. ► The structural change from an amorphous to nanocrystalline with increasing [SiH{sub 4}]. - Abstract: Nanocrystalline silicon (nc-Si) thin films deposited by plasma-enhanced chemical vapor deposition at various silane flow rates ([SiH{sub 4}]) are studied. The characterization of these films by high-resolution transmission electron microscopy, Raman spectroscopy and X-ray diffraction reveals that no film and very thin film is deposited at [SiH{sub 4}] = 0.0 and 0.1 sccm, respectively. In addition, the structural change from an amorphous to a nanocrystalline phase occurs at around [SiH{sub 4}] = 0.2 sccm. In this study, the importance of arriving species at surfaces and precursors is clearly demonstrated by the effect of a small addition of SiH{sub 4} on the frequency and width of a Raman peak and the structure of the grown film. The infrared spectroscopic analysis shows no hydrogen incorporation in the nc-Si film deposited at the low value of [SiH{sub 4}]. However, the intensity of the peak around 2100 cm{sup −1} due to SiH decreases with increasing [SiH{sub 4}]. All fabricated films give photoluminescence in the range between 1.7 and 2.4 eV at room temperature, indicating enlargement of the band-gap energy. The presence of very small crystallites leads to the appearance of quantum confinement effects. The variations of the photoluminescence energy and spectral width are well correlated with the structural properties of the films such as crystallite size, crystalline volume fraction, and the density of Si-H bonds.

  17. Superhard Nanocrystalline Homometallic Stainless Steel on Steel for Seamless Coatings

    NASA Technical Reports Server (NTRS)

    Tobin, Eric J.; Hafley, R. (Technical Monitor)

    2002-01-01

    The objective of this work is to deposit nanocrystalline stainless steel onto steel substrates (homometallic) for enhanced wear and corrosion resistance. Homometallic coatings provide superior adhesion, and it has been shown that ultrafine-grained materials exhibit the increased hardness and decreased permeability desired for protective coatings. Nanocrystals will be produced by controlling nucleation and growth and use of an ion beam during deposition by e-beam evaporation or sputtering. Phase I is depositing 31 6L nanocrystalline stainless steel onto 31 6L stainless steel substrates. These coatings exhibit hardnesses comparable to those normally obtained for ceramic coatings such ZrO2, and possess the superior adhesion of seamless, homometallic coatings. Hardening the surface with a similar material also enhances adhesion, by avoiding problems associated with thermal and lattice mismatch. So far we have deposited nanocrystalline homometallic 316L stainless steel coatings by varying the ions and the current density of the ion beams. For all deposition conditions we have produced smooth, uniform, superhard coatings. All coatings exhibit hardness of at least 200% harder than that of bulk materials. Our measurements indicate that there is a direct relationship between nanohardness and the current density of the ion beam. Stress measurements indicate that stress in the films is increasingly proportional to current density of the ion beam. TEM, XPS, and XRD results indicate that the coated layers consist of FCC structure nanocrystallites with a dimension of about 10 to 20 nm. The Ni and Mo concentration of these coating are lower than those of bulk 316L but the concentration of Cr is higher.

  18. Tailoring the Matrix in Ultra-Nanocrystalline Diamond Films

    NASA Astrophysics Data System (ADS)

    Buck, Volker; Woehrl, Nicolas

    2008-10-01

    By depositing films in argon-rich plasmas it is possible to produce ultra-nanocrystalline diamond (UNCD) films with grain sizes of 5-100 nm. By reducing the grain size, these films feature rather distinctive combinations of properties making them potential materials for emerging technological developments such as nano/micro-electro-mechanical systems (N/MEMS), optical coatings, bioelectronics, surface acoustic wave (SAW) filters, and tribological applications. The majority of works dealing with nanocrystalline diamond (NCD) up to now have concentrated on diamond grains (e.g., grain size, texture). In doing so the surrounding crystal matrix has been neglected and its effect on the substrate properties has been dismissed as a grain boundary effect. This view does not accord with its relevance to film properties. Because the matrix consists of amorphous carbon structures, approved methods for the characterization of this appropriate special class of materials were used here such as Raman and Fourier transform infrared spectroscopy (FTIR). The use of an amorphous matrix for nanocrystalline diamond grains has lead to an enormous field of new materials, because a whole class of carbon-based materials (diamondlike carbon, DLC) can be used as a matrix that may contain only carbon (a-C) or carbon and hydrogen (a-C:H) as well as other components such as metals (Me-C:H); additionally, other dopants such as silicon, oxygen, halogens, or nitrogen may be included. As an example, it is shown how the mechanical stress in films can be adjusted by tailoring the matrix.

  19. Microstructural heterogeneity and the mechanical behavior of nanocrystalline metals

    NASA Astrophysics Data System (ADS)

    Rajagopalan, Jagannathan

    Ultrafine grained and nanocrystalline metals have attracted increasing interest, both scientific and commercial, in recent years because of their potentially superior mechanical properties. Their properties, such as very high strength, primarily arise from the change in the underlying deformation mechanisms. Experimental and simulation studies have shown that because of the extremely small grain size conventional dislocation plasticity is curtailed in these materials and grain boundary mediated mechanisms become more important. Although the deformation behavior and the underlying mechanisms in these materials have been investigated in depth, relatively little attention has been focused on the inhomogeneous nature of their microstructure and its influence on their macroscopic response. In this study, we have demonstrated through experiments on nanoscale metal films how the interplay between microstructural heterogeneity and size in ultrafine grained and nanocrystalline metals leads to unusual mechanical behavior. In the first part of the study, we have shown that (a) nanocrystalline metals, unlike their coarse grained counterparts, recover a substantial fraction (50 to 100%) of their plastic deformation after unloading, and (b) ultrafine grained metal films show a pronounced Bauschinger effect even at high tensile stresses during unloading. Then, we have presented evidence from in situ transmission electron microscopy and x-ray diffraction experiments that strongly indicate that these unusual phenomena are a direct consequence of the coupling between the small size and heterogeneity of the microstructure. Based on the in situ experiments, we have proposed simple mechanistic models to interpret these phenomena. Finally, we have shown that in nanoscale metal films with a homogeneous microstructure Bauschinger effect is substantially reduced.

  20. Mechanical properties of micro- and nanocrystalline diamond foils

    PubMed Central

    Lodes, M. A.; Kachold, F. S.; Rosiwal, S. M.

    2015-01-01

    Diamond coating of suitable template materials and subsequent delamination allows for the manufacturing of free-standing diamond foil. The evolution of the microstructure can be influenced by secondary nucleation via control of process conditions in the hot-filament chemical vapour deposition process. Bending tests show extraordinarily high strength (more than 8 GPa), especially for diamond foils with nanocrystalline structure. A detailed fractographic analysis is conducted in order to correlate measured strength values with crack-initiating defects. The size of the failure causing flaw can vary from tens of micrometres to tens of nanometres, depending on the diamond foil microstructure as well as the loading conditions. PMID:25713455

  1. Optical switch based on nanocrystalline VOx thin film

    NASA Astrophysics Data System (ADS)

    Chen, Xiqu; Dai, Jun

    2009-11-01

    An optical switch is fabricated based on nanocrystalline vanadium oxide (VOx) thin film using micromachining technology. An "on" state with semiconducting phase to an "off" state with metallic phase is controlled by applying a DC power to Aurum electrodes of the optical switch. The optical switching performance for the fabricated device is investigated at optical communication wavelength of 1.55μm. The heater power requires to achieve switching action is about 15mW. The testing results show that the extinction ratio and switching response time are 14dB and 2ms, respectively.

  2. Nanocrystalline vanadium dioxide: synthesis and mid-infrared properties

    NASA Astrophysics Data System (ADS)

    Guinneton, Frédéric; Valmalette, Jean-Christophe; Gavarri, Jean-Raymond

    2000-11-01

    This work describes the first successful synthesis of nanocrystalline thermochromic VO 2 powder using the low temperature irreversible structural transformation of the metastable VO 2(B). At this step, the transformation is associated with a total rearrangement of VO 6 octahedra, and a strong increasing of density. The reversible metal-insulator phase transition (MIPT) of vanadium dioxide ( Tt=68°C) is associated with strong changes in electrical, magnetic and optical properties. The contrast of the optical transition in mid-infrared (MIR) region and the optical transparency are remarkably increased for these nanosized particles. Modifications in coloration are also observed.

  3. Nanocrystalline todorokite-like manganese oxide produced by bacterial catalysis.

    PubMed

    Kim, Hack-Sung; Pastén, Pablo A; Gaillard, Jean-François; Stair, Peter C

    2003-11-26

    We describe the characterization of an unknown and difficult to identify but geochemically and environmentally significant MnOx structure produced by a freshwater bacterium, Leptothrix discophora SP-6, using combined transmission electron microscopy (TEM), extended X-ray absorption fine structure (EXAFS), and UV Raman spectroscopy. The large surface-to-volume ratio of the needle-shaped nanocrystalline MnO2 formed around the bacterial cells coupled to the porous, zeolite-like structure has the potential to catalyze reactions and oxidize and adsorb metals. PMID:14624570

  4. Photo- and thermionic emission of MWPECVD nanocrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Cicala, G.; Magaletti, V.; Valentini, A.; Nitti, M. A.; Bellucci, A.; Trucchi, D. M.

    2014-11-01

    Nanocrystalline diamond (NCD) films with and without a diamond buffer layer (BL) have been grown on p-type silicon substrates by microwave plasma enhanced chemical vapor deposition technique at different values of deposition temperature (652-884 °C). The photo- and thermionic electron emission properties of NCD films have been investigated, illustrated and explained by analyzing the surface morphology and the grain shape determined by atomic force microscopy, the chemical-structural properties by Raman spectroscopy and nanocrystallites size by X-ray diffraction. The NCD films with BL grown at the highest deposition temperature have shown the highest photo- and thermionic emission currents.

  5. Vibrational Properties of Nanograins and Interfaces in Nanocrystalline Materials

    SciTech Connect

    Stankov, S.; Sergueev, I.; Chumakov, A. I.; Rueffer, R.; Yue, Y. Z.; Hu, L.; Miglierini, M.; Sepiol, B.; Svec, P.

    2008-06-13

    The vibrational dynamics of nanocrystalline Fe{sub 90}Zr{sub 7}B{sub 3} was studied at various phases of crystallization. The density of phonon states (DOS) of the nanograins was separated from that of the interfaces for a wide range of grain sizes and interface thicknesses. The DOS of the nanograins does not vary with their size and down to 2 nm grains still closely resembles that of the bulk. The anomalous enhancement of the phonon states at low and high energies originates from the DOS of the interfaces and scales linearly to their atomic fraction.

  6. Mechanical properties of micro- and nanocrystalline diamond foils.

    PubMed

    Lodes, M A; Kachold, F S; Rosiwal, S M

    2015-03-28

    Diamond coating of suitable template materials and subsequent delamination allows for the manufacturing of free-standing diamond foil. The evolution of the microstructure can be influenced by secondary nucleation via control of process conditions in the hot-filament chemical vapour deposition process. Bending tests show extraordinarily high strength (more than 8 GPa), especially for diamond foils with nanocrystalline structure. A detailed fractographic analysis is conducted in order to correlate measured strength values with crack-initiating defects. The size of the failure causing flaw can vary from tens of micrometres to tens of nanometres, depending on the diamond foil microstructure as well as the loading conditions. PMID:25713455

  7. Synthesis of nanocrystalline rare earth oxides by glycothermal method

    SciTech Connect

    Hosokawa, Saburo; Iwamoto, Shinji; Inoue, Masashi

    2008-11-03

    The reaction of yttrium acetate hydrate in 1,2-propanediol at 300 deg. C yielded a product containing acetate groups and glycol moieties. From this product, Y{sub 2}O{sub 3} was directly crystallized at 400 deg. C without the formation of a carbonate oxide phase. The thus-obtained Y{sub 2}O{sub 3} samples had a small crystallite size (2.2 nm) and significantly large surface area (280 m{sup 2}/g). Other nanocrystalline rare earth (Gd-Yb) oxides were also obtained by this method.

  8. Stress-induced phase transformation in nanocrystalline UO2

    SciTech Connect

    Uberuaga, Blas Pedro; Desai, Tapan

    2009-01-01

    We report a stress-induced phase transfonnation in stoichiometric UO{sub 2} from fluorite to the {alpha}-PbO{sub 2} structure using molecular dynamics (MD) simulations and density functional theory (DFT) calculations. MD simulations, performed on nanocrystalline microstructure under constant-stress tensile loading conditions, reveal a heterogeneous nucleation of the {alpha}-PbO{sub 2} phase at the grain boundaries followed by the growth of this phase towards the interior of the grain. The DFT calculations confinn the existence of the {alpha}-PbO{sub 2} structure, showing that it is energetically favored under tensile loading conditions.

  9. Photoluminescence of nanocrystalline titanium dioxide films loaded with silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Preclíková, Jana; Galář, Pavel; Trojánek, František; Rezek, Bohuslav; Němcová, Yvonne; Malý, Petr

    2011-04-01

    We report on a systematic study of the photoluminescence properties of nanocrystalline titanium dioxide films loaded with silver nanoparticles under various ambient conditions: in the temperature interval of 10 to 300 K, under different values of ambient air pressure (5 to 105 Pa), and under visible light irradiation that causes the photochromic transformation of the film. Our results enable us to follow the electron transfer from titanium dioxide into silver nanoparticles and to observe the oxidation of silver nanoparticles during the photochromic transformation. We propose a microscopic model explaining the behavior of extinction and photoluminescence of the Ag-TiO2 film under different values of ambient air pressure.

  10. Structural Modification of Nanocrystalline Ceria using Ion Beams

    SciTech Connect

    Zhang, Yanwen; Edmondson, Philip D; Varga, Tamas; Moll, Sandra; Namavar, Fereydoon; Weber, William J

    2011-01-01

    Exceptional size-dependent electronic-ionic conductivity of nanostructured ceria can significantly alter materials properties in chemical, physical, electronic and optical applications. Using energetic ions, we have demonstrated effective modification of interface volume and grain size in nanocrystalline ceria from a few nm up to ~ 25 nm, which is the critical region for controlling size-dependent material property. The unique self-healing response of radiation damage at grain boundaries is applied to control the grain size at nanoscale as a function of ion dose and irradiation temperature. Structural modification by energetic ions is proposed to achieve disirable electronic-ionic conductivity.

  11. Influence of Nanocrystalline Ferrite Particles on Properties of Magnetic Systems

    NASA Astrophysics Data System (ADS)

    Mueller, Robert; Habisreuther, Tobias; Hiergeist, Robert; Steinmetz, Hanna; Zeisberger, Matthias; Gawalek, Wolfgang

    Nanocrystalline mainly superparamagnetic ferrite particles ≈ 10 nm are used for the preparation of magnetic fluids. Barium hexaferrite BaFe12-2xTixCoxO19 powders with mean particle sizes < 30 nm show the transition to single domain Stoner-Wohlfarth behaviour. Hysteresis parameters, losses and the initial susceptibility versus temperature were obtained by VSM. Ba-ferrite ferrofluids have been prepared using Isopar M or dodecane as carrier liquid. Small Angle Neutron Scattering curves lead to a bimodal size distribution consisting of single magnetic particles and aggregated magnetic particles. Particle size investigations were done by TEM.

  12. Nanocrystalline zirconia can be amorphized by ion irradiation.

    PubMed

    Meldrum, A; Boatner, L A; Ewing, R C

    2002-01-14

    Nanocrystalline composites are finding applications in high-radiation environments due to their excellent mechanical and electronic properties. We show, however, that at the smallest particle sizes, radiation damage effects can be so strongly enhanced that under the right conditions, materials that have never been made amorphous can become highly susceptible to irradiation-induced amorphization. Because light-weight, high-strength nanocomposites are potential materials for spacecraft shielding and sensor systems, these fundamental results have significant implications for the design and selection of materials to be used in environments where a large ion flux will be encountered. PMID:11801024

  13. Hysteresis modeling of anisotropic and isotropic nanocrystalline hard magnetic films

    NASA Astrophysics Data System (ADS)

    Cornejo, D. R.; Azevedo, A.; Rezende, S. M.

    2003-05-01

    In the Hauser model, the magnetic state of a system is obtained by minimizing the so-called total energy function for a statistical set of magnetic domains. In this article, this energetic model of ferromagnetic materials is used in order to calculate hysteresis loops of isotropic and anisotropic nanocrystalline SmCo films at room temperature. A qualitative very good agreement between the calculated and experimental curves is obtained, mainly in the anisotropic case. Also, it has been verified that, under suitable approximations, the free parameters of the model can tie with intrinsic characteristics of the reversal magnetization process.

  14. Exciton annihilation in dye-sensitized nanocrystalline semiconductor films

    NASA Astrophysics Data System (ADS)

    Namekawa, Akihiro; Katoh, Ryuzi

    2016-08-01

    Exciton annihilation in dye-sensitized nanocrystalline semiconductor (Al2O3) films has been studied through laser-induced fluorescence spectroscopy. The relative quantum yield of the fluorescence decreases with increasing excitation light intensity, the indication being that exciton annihilation occurred. The rate constants of the annihilation were estimated for three dyes, N719, D149, and MK2, that are known to be sensitizing dyes for efficient dye-sensitized solar cells. The hopping time between dye molecules and the diffusion length of excitons within their lifetime were also estimated to facilitate discussion of the relevance of exciton annihilation to primary processes in dye-sensitized solar cells.

  15. A crossover in the mechanical response of nanocrystalline ceramics.

    PubMed

    Szlufarska, Izabela; Nakano, Aiichiro; Vashishta, Priya

    2005-08-01

    Multimillion-atom molecular dynamics simulation of indentation of nanocrystalline silicon carbide reveals unusual deformation mechanisms in brittle nanophase materials, resulting from the coexistence of brittle grains and soft amorphous grain boundary phases. Simulations predict a crossover from intergranular continuous deformation to intragrain discrete deformation at a critical indentation depth. The crossover arises from the interplay between cooperative grain sliding, grain rotations, and intergranular dislocation formation similar to stick-slip behavior. The crossover is also manifested in switching from deformation dominated by indentation-induced crystallization to deformation dominated by disordering, leading to amorphization. This interplay between deformation mechanisms is critical for the design of ceramics with superior mechanical properties. PMID:16081730

  16. Complex electric modulus and dielectric relaxation of nanocrystalline zinc ferrite

    NASA Astrophysics Data System (ADS)

    Choudhury, S.; Sinha, M.; Mandal, M. K.; Pradhan, S. K.; Meikap, A. K.

    2015-06-01

    We report the complex electric modulus and dielectric relaxation studies of nanocrystalline zinc ferrite. The dielectric constant exhibits strong temperature dependence at higher temperature and lower frequencies and this has been analyzed in terms of electric modulus vector. The real part of complex impedance has also been modeled by an ideal equivalent circuit consisting of grain and grain boundary resistances and capacitances. The metallic electrode and semiconductor junction forms Schottky diode, whose parameters like built in voltage and space charge density have been extracted from the capacitance-voltage characteristics.

  17. A reduction boronation route to nanocrystalline titanium diboride

    NASA Astrophysics Data System (ADS)

    Chen, Luyang; Gu, Yunle; Shi, Liang; Yang, Zeheng; Ma, Jianhua; Qian, Yitai

    2004-04-01

    Nanocrystalline titanium diboride (TiB 2) has been prepared through a reduction-boronation route by using Ti powders and BBr 3 as titanium and boron sources, and metallic sodium as reductant at 400 °C. X-ray powder diffraction (XRD) pattern can be indexed as hexagonal TiB 2 with the lattice constants of a=3.028 and c=3.223 Å. Transmission electron microscopy images show particle morphology with average size of 15 nm. Selected area electron diffraction patterns confirm the preparation of the hexagonal TiB 2.

  18. Osteoblastic cells trigger gate currents on nanocrystalline diamond transistor.

    PubMed

    Izak, Tibor; Krátká, Marie; Kromka, Alexander; Rezek, Bohuslav

    2015-05-01

    We show the influence of osteoblastic SAOS-2 cells on the transfer characteristics of nanocrystalline diamond solution-gated field-effect transistors (SGFET) prepared on glass substrates. Channels of these fully transparent SGFETs are realized by hydrogen termination of undoped diamond film. After cell cultivation, the transistors exhibit about 100× increased leakage currents (up to 10nA). During and after the cell delamination, the transistors return to original gate currents. We propose a mechanism where this triggering effect is attributed to ions released from adhered cells, which depends on the cell adhesion morphology, and could be used for cell culture monitoring. PMID:25835144

  19. The affect of densification and dehydroxylation on the mechanical properties of stoichiometric hydroxyapatite bioceramics

    SciTech Connect

    Laasri, S.; Taha, M.; Laghzizil, A.; Hlil, E.K.; Chevalier, J.

    2010-10-15

    This paper reports the effects of processing densification on the mechanical properties of hydroxyapatite bioceramics. Densification of synthetic hydroxyapatite is conducted in the range 1000-1300 {sup o}C. X-ray diffraction and SEM microscopy are used to check the microstructure transformations. Vickers hardness, toughness and Young's modulus are analyzed versus the density and grain size. The sintering temperature and the particle size influence strongly the densification and the resulting mechanical properties. In addition, the critical sintering temperature appears around 1200 {sup o}C and the declined strength at the temperature up to 1200 {sup o}C is found sensitive to the dehydroxylation process of hydroxyapatite.

  20. Effect of osteogenesis imperfecta mutations in tropocollagen molecule on strength of biomimetic tropocollagen-hydroxyapatite nanocomposites

    NASA Astrophysics Data System (ADS)

    Dubey, Devendra K.; Tomar, Vikas

    2010-01-01

    Osteogenesis Imperfecta (OI) is a genetic disorder that affects cellular synthesis of Type-I collagen fibrils and causes extreme bone fragility. This study reports the effects of OI mutations in Tropocollagen (TC) molecules on strength of model Tropocollagen-Hydroxyapatite biomaterials with two different mineral [hydroxyapatite (HAP)] distributions using three dimensional atomistic simulations. Results show that the effect of TC mutations on the strength of TC-HAP biomaterials is insignificant. Instead, change in mineral distribution showed significant impact on the overall strength of TC-HAP biomaterials. Study suggests that TC mutations manifest themselves by changing the mineral distribution during hydroxyapatite growth and nucleation period.

  1. Novel selenium-doped hydroxyapatite coatings for biomedical applications.

    PubMed

    Rodríguez-Valencia, C; López-Álvarez, M; Cochón-Cores, B; Pereiro, I; Serra, J; González, P

    2013-03-01

    Nowadays there is a short-term need of investigating in orthopedic implants with a greater functionality, including an improved osseointegration and also antibacterial properties. The coating of metallic implants with hydroxyapatite (HA) remains to be the main proposal, but superior quality HA coatings with compositions closer to natural bone apatites, including carbonates, trace elements are required. Selenium is an essential nutrient in biological tissues and, at the same time, it also presents antibacterial properties. A pioneering study on the fabrication of selenium-doped carbonated hydroxyapatite (iHA:Se) coatings by Pulsed Laser Deposition (PLD) is presented. Different proportions of selenium were incorporated to obtain the iHA:Se coatings. Their physicochemical characterization, performed by SEM/EDS, FTIR, FT-Raman, Interferometric Profilometry and XPS, revealed typical columnar growth of HA in globular aggregates and the efficient incorporation of selenium into the HA coatings by the, most probably, substitution of SeO(3)(2-) groups in the CO(3)(2-) sites. Biological evaluation illustrated the absence of cytotoxicity when an amount of 0.6 at.% of Se was added to the iHA:Se coatings and excellent proliferation of the MC3T3-E1 preosteoblasts. Antibacterial properties were also proved with the inhibition of P. aeruginosa and S. aureus from establishing bacterial biofilms. PMID:22968925

  2. Intrinsic magnetism and hyperthermia in bioactive Fe-doped hydroxyapatite.

    PubMed

    Tampieri, Anna; D'Alessandro, Teresa; Sandri, Monica; Sprio, Simone; Landi, Elena; Bertinetti, Luca; Panseri, Silvia; Pepponi, Giancarlo; Goettlicher, Joerg; Bañobre-López, Manuel; Rivas, Jose

    2012-02-01

    The use of magnetic activation has been proposed to answer the growing need for assisted bone and vascular remodeling during template/scaffold regeneration. With this in mind, a synthesis procedure was developed to prepare bioactive (Fe2+/Fe3+)-doped hydroxyapatite (Fe-HA), endowed with superparamagnetic-like properties. This new class of magnetic hydroxyapatites can be potentially employed to develop new magnetic ceramic scaffolds with enhanced regenerative properties for bone surgery; in addition, magnetic Fe-HA can find application in anticancer therapies, to replace the widely used magnetic iron oxide nanoparticles, whose long-term cytotoxicity was recently found to reach harmful levels. An extensive physicochemical, microstructural and magnetic characterization was performed on the obtained Fe-HA powders, and demonstrated that the simultaneous addition of Fe2+ and Fe3+ ions during apatite nucleation under controlled synthesis conditions induces intrinsic magnetization in the final product, minimizing the formation of magnetite as secondary phase. This result potentially opens new perspectives for biodevices aimed at bone regeneration and for anti-cancer therapies based on hyperthermia. PMID:22005331

  3. Quantification of bone ingrowth into porous block hydroxyapatite in humans.

    PubMed

    Ayers, R A; Wolford, L M; Bateman, T A; Ferguson, V L; Simske, S J

    1999-10-01

    This study sought to quantify bone ingrowth from a single bone-implant surface into porous block hydroxyapatite used in maxillofacial applications. Seventeen maxillary hydroxyapatite implants (implant time of 4-138 months, 39-month mean) were harvested for analysis from 14 patients. The implants had been placed into the lateral maxillary wall during orthognathic surgery, juxtapositioned to the maxillary sinus. Ingrowth was measured in 100-microm increments from a bone-implant interface to a depth of 1500 microm. Bone ingrowth averaged over the 14 patients (0-1100 microm depth) is described by the equation % ingrowth - 20% * (depth in millimeters) + 41.25% (R2 = 0.98, n = 10 incremental depths). Beyond 1100 microm, the average ingrowth remained constant at 15.0 +/- 0.7%. The duration of implantation also showed as affect on the percent ingrowth into the implants at the incremental depths, and the percent ingrowth asymptotically approached a maximum. Overall, the composite average data from all depths is best described by the logarithmic function % ingrowth = 15% * ln(implantation time in months) - 24.0% (R2 = 0.71, n = 14 patients). Several factors may come into play in determining bone ingrowth including the mechanical environment, the osteoconductivity of the implant material, and the osteogenic capability of the tissues in the pore spaces. Measurements of bone ingrowth are most influenced by the depth into the implant and the time the implant was in the body; the age of the patient had little affect on bone ingrowth. PMID:10400880

  4. Properties of pulsed laser deposited fluorinated hydroxyapatite films on titanium

    SciTech Connect

    Rau, J.V.; Smirnov, V.V.; Laureti, S.; Generosi, A.; Varvaro, G.; Fosca, M.; Ferro, D.; Cesaro, S. Nunziante; Albertini, V. Rossi; Barinov, S.M.

    2010-09-15

    Fluorinated hydroxyapatite coated titanium was investigated for application as implant coating for bone substitute materials in orthopaedics and dentistry. Pulsed laser deposition technique was used for films preparation. Fluorinated hydroxyapatite target composition, Ca{sub 10}(PO{sub 4}){sub 6}F{sub 1.37}(OH){sub 0.63}, was maintained at 2 J/cm{sup 2} of laser fluence and 500-600 {sup o}C of the substrate temperature. Prepared films had a compact microstructure, composed of spherical micrometric-size aggregates. The average surface roughness resulted to be of 3 nm for the film grown at 500 {sup o}C and of 10 nm for that grown at 600 {sup o}C, showing that the temperature increase did not favour the growth of a more fine granulated surface. The films were polycrystalline with no preferential growth orientation. The films grown at 500-600 {sup o}C were about 8 {mu}m thick and possessed a hardness of 12-13 GPa. Lower or higher substrate temperature provides the possibility to obtain coatings with different fine texture and roughness, thus tayloring them for various applications.

  5. Hydroxyapatite-titanium bulk composites for bone tissue engineering applications.

    PubMed

    Kumar, Alok; Biswas, Krishanu; Basu, Bikramjit

    2015-02-01

    The research work on bulk hydroxyapatite (HA)-based composites are driven by the need to develop biomaterials with better mechanical properties without compromising its bioactivity and biocompatibility properties. Despite several years of research, the mechanical properties of the HA-based composites still need to be enhanced to match the properties of natural cortical bone. In this regard, the scope of this review on the HA-based bulk biomaterials is limited to the processing and the mechanical as well as biocompatibility properties for bone tissue engineering applications of a model system that is hydroxyapatite-titanium (HA-Ti) bulk composites. It will be discussed in this review how HA-Ti based bulk composites can be processed to have better fracture toughness and strength without compromising biocompatibility. The advantages of the functionally gradient materials to integrate the mechanical and biocompatibility properties is a promising approach in hard tissue engineering and has been emphasized here in reference to the limited literature reports. On the biomaterials fabrication aspect, the recent results are discussed to demonstrate that advanced manufacturing techniques, like spark plasma sintering can be adopted as a processing route to restrict the sintering reactions, while enhancing the mechanical properties. Various toughening mechanisms related to careful tailoring of microstructure are discussed. The in vitro cytocompatibilty, cell fate processes as well as in vivo biocompatibility results are also reviewed and the use of flow cytometry to quantify in vitro cell fate processes is being emphasized. PMID:24737723

  6. Alkoxide route for preparing hydroxyapatite and its coatings.

    PubMed

    Weng, W; Baptista, J L

    1998-01-01

    The preparation of hydroxyapatite using n-butanol or ethanol solutions of P2O5 and Ca glycoxide as precursors of P and Ca was investigated by nuclear magnetic resonance (NMR), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Stable mixed solutions of the precursors could be obtained in the presence of acetic acid (HOAC). For the mixed solution of Ca glycoxide with the ethanol solution of P2O5, a lower HOAC/Ca ratio was needed since the ethanol solution of P2O5 contained a lower concentration of H3PO4, a species that easily forms precipitates in the presence of the Ca containing species. An amorphous powder was obtained by heating the stable solution of Ca glycoxide and PO(OH)x(OEt)3-x with an HOAC/Ca ratio of 4 in a hot plate at approximately 150 degrees C. Hydroxyapatite (HAP) was directly formed after calcining the amorphous powder at 500 degrees C. The stable mixed solutions of Ca glycoxide and the alcoholic solutions of P2O5 were used to prepare HAP coatings on alumina substrates using a dip-coating method. The resulting ceramic coatings have a rough surface and an adhesion strength of about 10 MPa. The morphology of the coatings is dependent on the preparation chemistry. PMID:9678859

  7. Bioactive glass/hydroxyapatite composites: mechanical properties and biological evaluation.

    PubMed

    Bellucci, Devis; Sola, Antonella; Anesi, Alexandre; Salvatori, Roberta; Chiarini, Luigi; Cannillo, Valeria

    2015-06-01

    Bioactive glass/hydroxyapatite composites for bone tissue repair and regeneration have been produced and discussed. The use of a recently developed glass, namely BG_Ca/Mix, with its low tendency to crystallize, allowed one to sinter the samples at a relatively low temperature thus avoiding several adverse effects usually reported in the literature, such as extensive crystallization of the glassy phase, hydroxyapatite (HA) decomposition and reaction between HA and glass. The mechanical properties of the composites with 80wt.% BG_Ca/Mix and 20wt.% HA are sensibly higher than those of Bioglass® 45S5 reference samples due to the presence of HA (mechanically stronger than the 45S5 glass) and to the thermal behaviour of the BG_Ca/Mix, which is able to favour the sintering process of the composites. Biocompatibility tests, performed with murine fibroblasts BALB/3T3 and osteocites MLO-Y4 throughout a multi-parametrical approach, allow one to look with optimism to the produced composites, since both the samples themselves and their extracts do not induce negative effects in cell viability and do not cause inhibition in cell growth. PMID:25842126

  8. Strontium and zoledronate hydroxyapatites graded composite coatings for bone prostheses.

    PubMed

    Boanini, Elisa; Torricelli, Paola; Sima, Felix; Axente, Emanuel; Fini, Milena; Mihailescu, Ion N; Bigi, Adriana

    2015-06-15

    Both strontium and zoledronate (ZOL) are known to be useful for the treatment of bone diseases associated to the loss of bone substance. In this work, we applied an innovative technique, Combinatorial Matrix-Assisted Pulsed Laser Evaporation (C-MAPLE), to deposit gradient thin films with variable compositions of Sr-substituted hydroxyapatite (SrHA) and ZOL modified hydroxyapatite (ZOLHA) on Titanium substrates. Compositional gradients were obtained by simultaneous laser vaporization of the two distinct material targets. The coatings display good crystallinity and granular morphology, which do not vary with composition. Osteoblast-like MG63 cells and human osteoclasts were co-cultured on the thin films up to 21 days. The results show that Sr counteracts the negative effect of relatively high concentration of ZOL on osteoblast viability, whereas both Sr and ZOL enhance extracellular matrix deposition. In particular, ZOL promotes type I collagen production, whereas Sr increases the production of alkaline phosphatase. Moreover, ZOL exerts a greater effect than Sr on osteoprotegerin/RANKL ratio and, as a consequence, on the reduction of osteoclast proliferation and activity. The deposition method allows to modulate the composition of the thin films and hence the promotion of bone growth and the inhibition of bone resorption. PMID:25706198

  9. Titanium--hydroxyapatite porous structures for endosseous applications.

    PubMed

    Popa, C; Simon, V; Vida-Simiti, I; Batin, G; Candea, V; Simon, S

    2005-12-01

    Materials for uncemented endosseous implants have to assure an as short as possible osseointegration time. Thus, a material with both surface bioactivity and a porous outer structure can become a preferred choice for this type of applications. This paper presents a class of titanium-base PM composites, reinforced with particulate hydroxyapatite. Raw materials were titanium powder, obtained through hydriding--milling--dehydriding, with the grain size of 63-100 microm, and sol-gel hydroxyapatite (HA) powder, produced by the reaction between Ca(NO3)2 x 4H2O and (NH4)2HPO4. Blends with 5 to 50% HA were prepared and pressed in a rigid die, producing single composition or gradual composition samples. The applied pressure was of 400, 500 or 600 MPa. Sintering was performed in vacuum, at 1160 ( composite function)C. All samples, although well sintered, displayed swelling during sintering, due to diffusion into the matrix. The increase in volume is more severe for higher amounts of HA in the green compacts and for higher applied compaction pressure. Compacts with a gradual increase of the HA content are recommended from the functional and mechanical point of view, but the increase should be slow, not to produce interlayer cracks. The outer surface shows interconnected pores, suitable for the ingrowth of vital new bone. PMID:16362217

  10. Hydroxyapatite substituted by transition metals: experiment and theory.

    PubMed

    Zilm, M E; Chen, L; Sharma, V; McDannald, A; Jain, M; Ramprasad, R; Wei, M

    2016-06-28

    Bioceramics are versatile materials for hard tissue engineering. Hydroxyapatite (HA) is a widely studied biomaterial for bone grafting and tissue engineering applications. The crystal structure of HA allows for a wide range of substitutions, which allows for tailoring materials properties. Transition metals and lanthanides are of interest since substitution in HA can result in magnetic properties. In this study, experimental results were compared to theoretical calculations of HA substituted with a transition metal. Calculation of a 10 atomic percent substitution of a transition metal ion Mn(2+), Fe(2+), and Co(2+) substituted HA samples lead to magnetic moments of 5, 4, and 3 Bohr magnetons, respectively. Hydroxyapatite substituted by transition metals (MHA) was fabricated through an ion exchange procedure and characterized with X-ray diffraction, Fourier transform infra-red spectroscopy (FTIR), X-ray photoelectron spectroscopy, and vibrating sample magnetometer, and results were compared to theoretical calculations. All the substitutions resulted in phase-pure M(2+)HA with lattice parameters and FTIR spectra in good agreement with calculations. Magnetic measurements revealed that the substitution of Mn(2+) has the greatest effect on the magnetic properties of HA followed by the substitution of Fe(2+) and then Co(2+). The present work underlines the power of synergistic theoretical-experimental work in guiding the rational design of materials. PMID:27264723

  11. Gallium increases bone calcium and crystallite perfection of hydroxyapatite.

    PubMed

    Bockman, R S; Boskey, A L; Blumenthal, N C; Alcock, N W; Warrell, R P

    1986-12-01

    Gallium, a group IIIa metal, is known to interact with hydroxyapatite as well as the cellular components of bone. In recent studies we have found gallium to be a potent inhibitor of bone resorption that is clinically effective in controlling cancer-related hypercalcemia as well as the accelerated bone resorption associated with bone metastases. To begin to elucidate gallium's mechanism of action we have examined its effects on bone mineral properties. After short-term (14 days) administration to rats, gallium nitrate produced measurable changes in bone mineral properties. Using atomic absorption spectroscopy, low levels of gallium were noted to preferentially accumulate in regions of active bone formation, 0.54 +/- .07 microgram/mg bone in the metaphyses versus 0.21 +/- .03 microgram/mg bone in the diaphyses, P less than 0.001. The bones of treated animals had increased calcium content measured spectrophotometrically. Rats injected with radiolabeled calcium during gallium treatment had greater 45-calcium content compared to control animals. By wide-angle X-ray analyses, larger and/or more perfect hydroxyapatite was observed. The combined effects of gallium on bone cell function and bone mineral may explain its clinical efficacy in blocking accelerated bone resorption. PMID:3026592

  12. Alendronate functionalized mesoporous hydroxyapatite nanoparticles for drug delivery

    SciTech Connect

    Li, Dongdong; Zhu, Yuntao; Liang, Zhiqiang

    2013-06-01

    Highlights: ► The synthesized mesoporous hydroxyapatite has nanostructure and bioactivity. ► The materials have high surface area and amino group. ► The materials show higher drug loading and slower release rate than pure HAP. - Abstract: Mesoporous nanosized hydroxyapatite (HAP) functionalized by alendronate (ALN) was synthesized using cationic surfactant CTAB as template. The structural, morphological and textural properties were fully characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and N{sub 2} adsorption/desorption. Then the obtained materials were performed as drug delivery carriers using ibuprofen (IBU) as a model drug to investigate their drug storage/release properties in simulated body fluid (SBF). The materials showed relatively slower release rate compared with HAP due to the ionic interaction between -NH{sub 3}{sup +} on the matrix and -COO{sup −}belongs to IBU. The system provides a new concept for improving the drug loading or slowing down the release rate.

  13. Effect of hydroxyapatite-based biomaterials on human osteoblast phenotype.

    PubMed

    Trombelli, L; Penolazzi, L; Torreggiani, E; Farina, R; Lambertini, E; Vecchiatini, R; Piva, R

    2010-03-01

    The present study evaluated human primary osteoblasts and two different osteoblast-like cell lines behaviour when cultured in presence of different hydroxyapatite-based (HA) biomaterials (SINTlife-FIN-CERAMICA S.p.a., Faenza, Italy; Bio-Oss, Geistlich Biomaterials, Woulhusen, Switzerland; Biostite-GABA Vebas, San Giuliano Milanese, MI, Italy), focusing attention on the effect of HA/Biostite in terms of modulation of osteoblastic differentiation. Analysis were about adhesion, proliferation and mineralization activity. Runt-related transcription factor 2 (Runx2), Estrogen Receptor alpha (ERalfa) expression and alkaline phosphatase activity (ALP) were measured as osteoblastic differentiation markers. Determination of viable cells was done with MTT colorimetric assay. Scanning electron microscopy (SEM) analysis was performed on biomaterial-treated cells. All hydroxyapatite-based biomaterials didn't affect cells morphology and viability, whereas only presence of HA/Biostite improved cells adhesion, growth and differentiation. Adhesion and spreading of the primary cells on HA/Biostite were the same showed by two different osteoblast-like cell lines. These results have important implications for both tissue-engineered bone grafts and enhancement of HA implants performance, to develop new teeth's supporting structure therapies and replacement. PMID:20357737

  14. Antibacterial coatings of fluoridated hydroxyapatite for percutaneous implants.

    PubMed

    Ge, Xiang; Leng, Yang; Bao, Chongyun; Xu, Sherry Li; Wang, Renke; Ren, Fuzeng

    2010-11-01

    Percutaneous orthopedic and dental implants require not only good adhesion with bone but also the ability to attach and form seals with connective tissues and the skin. To solve the skin-seal problem of such implants, an electrochemical deposition method was used to modify the surfaces of metallic implants to improve their antibacterial ability and skin seals around them. A dense and uniform fluoridated calcium phosphate coating with a thickness of about 200 nm was deposited on an acid-etched pure titanium substrate by controlling the current density and reaction duration of the electrochemical process. The as-deposited amorphous fluoridated calcium phosphate transformed to fluoridated hydroxyapatite (FHA) after heat treatment at 600°C in a water vapor environment for 3 h. Both single crystal diffraction patterns and high-resolution transmission electron microscope (HRTEM) images confirmed the phase of the fluoridated calcium phosphate after the heat treatment. The antibacterial activities of FHA coatings were tested against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Porphyromonas gingivalis (P. gingivalis) with the film attachment method. The antibacterial activity of FHA coating is much higher than that of pure hydroxyapatite (HA) coating and acid-etched pure titanium surface. The promising features of FHA coating make it suitable for orthopedic and dental applications. PMID:20725973

  15. Hydroxyapatite electrodeposition on anodized titanium nanotubes for orthopedic applications

    NASA Astrophysics Data System (ADS)

    Parcharoen, Yardnapar; Kajitvichyanukul, Puangrat; Sirivisoot, Sirinrath; Termsuksawad, Preecha

    2014-08-01

    Nanotubes modification for orthopedic implants has shown interesting biological performances (such as improving cell adhesion, cell differentiation, and enhancing osseointegration). The purpose of this study is to investigate effect of titanium dioxide (TiO2) nanotube feature on performance of hydroxyapatite-coated titanium (Ti) bone implants. TiO2 nanotubes were prepared by anodization using ammonium fluoride electrolyte (NH4F) with and without modifiers (PEG400 and Glycerol) at various potential forms, and times. After anodization, the nanotubes were subsequently annealed. TiO2 nanotubes were characterized by scanning electron microscope and X-ray diffractometer. The amorphous to anatase transformation due to annealing was observed. Smooth and highly organized TiO2 nanotubes were found when high viscous electrolyte, NH4F in glycerol, was used. Negative voltage (-4 V) during anodization was confirmed to increase nanotube thickness. Length of the TiO2 nanotubes was significantly increased by times. The TiO2 nanotube was electrodeposited with hydroxyapatite (HA) and its adhesion was estimated by adhesive tape test. The result showed that nanotubes with the tube length of 560 nm showed excellent adhesion. The coated HA were tested for biological test by live/dead cell straining. HA coated on TiO2 nanotubes showed higher cells density, higher live cells, and more spreading of MC3T3-E1 cells than that growing on titanium plate surface.

  16. Biopolymers for Medical Applications: Polyglycerol Sebacate (PGS) doped Hydroxyapatite (HA)

    NASA Astrophysics Data System (ADS)

    Teruel, Maria; Kuthirummal, Narayanan; Levi, Nicole; Wake College Team

    2011-04-01

    In the investigation to engineer the ideal scaffolding device for cleft palate repair, polyglycerol sebacate (PGS) doped with hydroxyapatite (HA) were chosen for their elastomeric and biodegradable properties, as well as their cost-effective synthesis. Hydroxyapatite was integrated into the PGS to form a composite with high porosity and improved mechanical properties yielding a good substrate for cell attachment during the repair process. FT-IR scans were performed to characterize the composite polymer. Differential Scanning Calorimetry (DSC) was utilized to identify an acceptable glass transition temperature (Tg), between -18 and - 21°C. At this Tg, it was determined that the material was sufficiently polymerized to a point where it was durable yet pliable enough to use for cleft palate devices. In the synthesis of PGS 3% and 5% HA, a Tg of - 20.10°C and - 21.72°C, respectively, was achieved and further analytical tests were then performed on the polymers. Methods of analysis included X-Ray Diffraction and Tensile Strength Testing. Acknowledgements to the Research Department of Plastic and Reconstructive Surgery, Wake Forest University and College of Charleston.

  17. Phosphate reduction in a hydroxyapatite fluoride removal system

    NASA Astrophysics Data System (ADS)

    Egner, A.

    2012-12-01

    Fluorosis is a widespread disease that occurs as a result of excess fluoride consumption and can cause severe tooth and bone deformations. To combat fluorosis, several previous studies have examined the potential to replace traditional bone char filters with synthetic hydroxyapatite. Calcite particles with a synthetic hydroxyapatite coating have been shown to effectively removed fluoride, yet the low-cost method for forming these particles leaves high amounts of phosphate both in synthesis waste-water and in filter effluent. High phosphate in filter effluent is problematic because consumption of extremely high phosphate can leach calcium from bones, further exacerbating the fluoride effect. This study examines ways of reducing and reusing waste. In particular, a method of fluoride removal is explored in which fluorapatite coatings may be formed directly. In preliminary studies, batches of 4.1g of Florida limestone (<710 μm) were equilibrated with 100 mL of 10ppm fluoride. In a control batch containing lime but no added phosphate, 14% treatment was achieved, but with added phosphate, 100% treatment was achieved in all batches. Batches with lower levels of phosphate took longer to reach 100% treatment, ranging from less than 24 hours in the highest phosphate batches to approximately 42 hours in the lowest batches. The lower levels tested were well within reasonable levels for drinking water and reached 0ppm fluoride in 42 hours or less.

  18. Molecular Recognition at the Protein-Hydroxyapatite Interface

    SciTech Connect

    Stayton, Partick S.; Drobny, G. P.; Shaw, Wendy J.; Long, Joanna R.; Gilbert, Michelle R.

    2003-09-01

    Proteins found in mineralized tissues act as nature's crystal engineers, where they play a key role in promoting or inhibiting the growth of minerals, such as hydroxyapitite (bones/teeth) and calcium oxalate (kidney stones). Despite their importance in hard-tissue formation and remodeling, and in pathological processes such as stone formation and arterial calcification, there is little known of the protein structure-function relationships that govern hard-tissue engineering. Here we review early studies that have utilized solid-state NMR (ssNMR) techniques to provide in situ secondary-structure determination of statherin and statherin peptides on their biologically relevant hydroxyapatite (HAP) surfaces. In addition to direct structural study, molecular dynamics studies have provided considerable insight into the protein-binding footprint on hydroxyapatite. The molecular insight provided by these studies has also led to the design of biomimetic fusion peptides that utilize nature's crystal-recognition mechanism to display accessible and dynamic bioactive sequences from the HAP surface. These peptides selectively engage adhesion receptors and direct specific outside-in signaling pathway activation in osteoblast-like cells.

  19. Synthesis, characterization and cell behavior of fluoridated hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Qu, Haibo

    Fluorine-containing hydroxyapatite (Ca5(PO4) 3(OH)1-xFx FHA), where F- partially replaces OH- in hydroxyapatite (HA), is recognized as a possible biomaterial for bone and tooth implants and gaining attention in the last several years as a possible alternative to HA. In this study, FHA powders were synthesized through a pH-cycling method. It was discovered that fluorine incorporation increased with the fluorine content in the initial solution and the number of pH cycles employed. A relatively low fluorine incorporation efficiency, ˜60%, was attained for most of the FHA samples. The short time of stay at each pH cycle and the limited number of cycles used are believed to be the main reasons of the low fluorine incorporation into the apatite structure. It was also revealed that the FHA particles produced by the pH-cycling method were inhomogeneous. They were a mixture of hydroxyapatite and F-rich apatite (or FA) particles. The mechanisms of incorporation of fluorine ions into hydroxyapatite by a pH cyclicing method were studied using TEM, XRD and fluorine measurement. Instead of forming laminated structures as reported by other research groups, a mixture of nano-sized F-rich apatite (FHA) and hydroxyapatite (HA) particles were obtained using the pH-cyclicing method. After calcination, these FHA particles were homogenized and became single phased FHA. The effect of fluorine content, preparing method, and sintering temperature on both the bulk density and biaxial flexural strength of sintered FHA was studied. Both uniaxially pressed un-milled (UPU) and cold isostatically pressed milled (IPM) FHA discs were sintered at temperatures between 1200˜400°C at an interval of 100°C. It was found that the fluorine content had a significant impact on the sintering behavior, densification, and mechanical properties of FHA discs. A close correlation between the sintered density and biaxial flexural strength of the specimens was revealed, where the biaxial flexural strength

  20. Characterization of Sr-substituted hydroxyapatite thin film by sputtering technique from mixture targets of hydroxyapatite and strontium apatite.

    PubMed

    Ozeki, K; Goto, T; Aoki, H; Masuzawa, T

    2014-01-01

    Sr-substituted hydroxyapatite thin films were prepared by sputtering technique from mixture targets of hydroxyapatite (HA) and strontium apatite (SrAp). The HA and SrAp powders were mixed at 0-100% Sr/(Sr+Ca) target ratios. The coated films were recrystallized by a hydrothermal treatment to reduce film dissolution. The films were then characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and inductively coupled plasma atomic emission spectrometry (ICP). The osteocompatiblity of the films was also evaluated by the size of the bone formation area in osteoblast cells.In the XRD patterns, peaks shifted to lower 2θ values with increasing Sr/(Sr+Ca) target ratios, which indicated Sr incorporation into the HA lattice. In the SEM observation of the hydrothermally treated films, the surface was covered with globular particles, and the size of the globular particles increased from Sr0 to Sr40, and then the size decreased from Sr60 to Sr100. The ICP analysis showed that the Sr/(Sr+Ca) film ratios were almost the same as the target ratios. In the cell culture, the bone formation area on the Sr-substituted HA films increased with increasing Sr concentration, and saturated at Sr60. PMID:24642972

  1. Electrode characteristics of nanocrystalline AB{sub 5} compounds prepared by mechanical alloying

    SciTech Connect

    Chen, Z.; Chen, Z.; Zhou, D.; Huang, P.; Su, Y.; Lue, M.

    1998-10-01

    Nanocrystalline LaNi{sub 5} and LaNi{sub 4.5}Si{sub 0.5} synthesized by mechanical alloying were used as negative materials for Ni-MH batteries. It was found that the electrodes prepared with the nanocrystalline powders had similar discharge capacities, better activation behaviors, and longer cycle lifetimes, compared with the negative electrode prepared with polycrystalline coarse-grained LaNi{sub 5} alloy. The properties of the electrodes prepared with these nanocrystalline materials were attributed to the structural characteristics of the compounds caused by mechanical alloying.

  2. Effect of process parameters on the chemical vapour synthesis of nanocrystalline titania

    NASA Astrophysics Data System (ADS)

    Md, Imteyaz Ahmad; Bhattacharya, S. S.

    2008-08-01

    In this investigation nanocrystalline titania powders were produced by the chemical vapour synthesis (CVS) route and characterized by standard techniques of XRD, HRTEM and BET. The effects of precursor/gas flow rates, hotwall temperature and system pressure on the particle size and distribution, as well as phase composition of the synthesized nanocrystalline titania powder, were studied. It was demonstrated that by suitably adjusting the process parameters during CVS it becomes possible to control the anatase crystallite size, specific surface area and the rutile content in the synthesized nanocrystalline titania powders.

  3. Nanocrystalline titanium dioxide and magnesium oxide in vitro dermal absorption in human skin.

    PubMed

    van der Merwe, Deon; Tawde, Snehal; Pickrell, John A; Erickson, Larry E

    2009-01-01

    The dermal absorption potential of a nanocrystalline magnesium oxide (MgO) and titanium dioxide (TiO(2)) mixture in dermatomed human skin was assessed in vitro using Bronaugh-type flow-through diffusion cells. Nanocrystalline material was applied to the skin surface at a dose rate of 50 mg/cm(2) as a dry powder, as a water suspension, and as a water/surfactant (sodium lauryl sulfate) suspension, for 8 hours. Dermal absorption of nanocrystalline MgO and TiO(2) through human skin with intact, functional stratum corneum was not detectable under the conditions of this experiment. PMID:19514931

  4. Nanocrystalline silicon: Lattice dynamics and enhanced thermoelectric properties

    DOE PAGESBeta

    Claudio, Tania; Stein, Niklas; Stroppa, Daniel G.; Klobes, Benedikt; Koza, Michael Marek; Kudejova, Petra; Petermann, Nils; Wiggers, Hartmut; Schierning, Gabi; Hermann, Raphaël P.

    2014-12-21

    In this study, silicon has several advantages when compared to other thermoelectric materials, but until recently it was not used for thermoelectric applications due to its high thermal conductivity, 156 W K-1 m-1 at room temperature. Nanostructuration as means to decrease thermal transport through enhanced phonon scattering has been a subject of many studies. In this work we have evaluated the effects of nanostructuration on the lattice dynamics of bulk nanocrystalline doped silicon. The samples were prepared by gas phase synthesis, followed by current and pressure assisted sintering. The heat capacity, density of phonons states, and elastic constants were measured,more » which all reveal a significant, ≈25%, reduction in the speed of sound. The samples present a significantly decreased lattice thermal conductivity, ≈25 W K-1 m-1, which, combined with a very high carrier mobility, results in a dimensionless figure of merit with a competitive value that peaks at ZT ≈ 0.57 at 973 °C. Due to its easily scalable and extremely low-cost production process, nanocrystalline Si prepared by gas phase synthesis followed by sintering could become the material of choice for high temperature thermoelectric generators.« less

  5. Nanocrystalline silicon: Lattice dynamics and enhanced thermoelectric properties

    SciTech Connect

    Claudio, Tania; Stein, Niklas; Stroppa, Daniel G.; Klobes, Benedikt; Koza, Michael Marek; Kudejova, Petra; Petermann, Nils; Wiggers, Hartmut; Schierning, Gabi; Hermann, Raphaël P.

    2014-12-21

    In this study, silicon has several advantages when compared to other thermoelectric materials, but until recently it was not used for thermoelectric applications due to its high thermal conductivity, 156 W K-1 m-1 at room temperature. Nanostructuration as means to decrease thermal transport through enhanced phonon scattering has been a subject of many studies. In this work we have evaluated the effects of nanostructuration on the lattice dynamics of bulk nanocrystalline doped silicon. The samples were prepared by gas phase synthesis, followed by current and pressure assisted sintering. The heat capacity, density of phonons states, and elastic constants were measured, which all reveal a significant, ≈25%, reduction in the speed of sound. The samples present a significantly decreased lattice thermal conductivity, ≈25 W K-1 m-1, which, combined with a very high carrier mobility, results in a dimensionless figure of merit with a competitive value that peaks at ZT ≈ 0.57 at 973 °C. Due to its easily scalable and extremely low-cost production process, nanocrystalline Si prepared by gas phase synthesis followed by sintering could become the material of choice for high temperature thermoelectric generators.

  6. Low cost and efficient photovoltaic conversion by nanocrystalline solar cells

    SciTech Connect

    Graetzel, M.

    1996-09-01

    Solar cells are expected to provide environmentally friendly solutions to the world`s energy supply problem. Learning from the concepts used by green plants we have developed a molecular photovoltaic device whose overall efficiency for AM 1.5 solar light to electricity has already attained 8-11%. The system is based on the sensitization of nanocrystalline oxide films by transition metal charge transfer sensitizers. In analogy to photosynthesis, the new chemical solar cell achieves the separation of the light absorption and charge carrier transport processes. Extraordinary yields for the conversion of incident photons into electric current are obtained, exceeding 90% for transition metal complexes within the wavelength range of their absorption band. The use of molten salt electrolytes together with coordination complexes of ruthenium as sensitizers and adequate sealing technology has endowed these cells with a remarkable stability making practical applications feasible. Seven industrial cooperations are presently involved in the development to bring these cells to the market. The first cells will be applied to supply electric power for consumer electronic devices. The launching of production of several products of this type is imminent and they should be on the market within the next two years. Quite aside from their intrinsic merits as photovoltaic device, the mesoscopic oxide semiconductor films developed in our laboratory offer attractive possibilities for a number of other applications. Thus, the first example of a nanocrystalline rocking chair battery will be demonstrated and its principle briefly discussed.

  7. Large piezoresistive effect in surface conductive nanocrystalline diamond

    SciTech Connect

    Janssens, S. D. Haenen, K.; Drijkoningen, S.

    2014-09-08

    Surface conductivity in hydrogen-terminated single crystal diamond is an intriguing phenomenon for fundamental reasons as well as for application driven research. Surface conductivity is also observed in hydrogen-terminated nanocrystalline diamond although the electronic transport mechanisms remain unclear. In this work, the piezoresistive properties of intrinsic surface conductive nanocrystalline diamond are investigated. A gauge factor of 35 is calculated from bulging a diamond membrane of 350 nm thick, with a diameter of 656 μm and a sheet resistance of 1.45 MΩ/sq. The large piezoresistive effect is reasoned to originate directly from strain-induced changes in the resistivity of the grain boundaries. Additionally, we ascribe a small time-dependent fraction of the piezoresistive effect to charge trapping of charge carriers at grain boundaries. In conclusion, time-dependent piezoresistive effect measurements act as a tool for deeper understanding the complex electronic transport mechanisms induced by grain boundaries in a polycrystalline material or nanocomposite.

  8. Magneto-optical Faraday effect in nanocrystalline oxides

    NASA Astrophysics Data System (ADS)

    Morales, J. R.; Amos, N.; Khizroev, S.; Garay, J. E.

    2011-05-01

    Magneto-optical materials have widespread applications in communication and optical devices. Besides existing applications such as optical diodes, untapped potential applications could be accessed should magneto-optical properties be improved such that smaller magnetic fields can be employed. Here we present an efficient method for fabricating oxide materials that possess excellent optical and magnetic properties—they are transparent to visible light yet have high magnetic susceptibility. Combined, these properties produce large Faraday rotations; the measured Verdet constant is >-300 rad T-1 m-1 at 632.8 nm, a high value for a thick, optically transparent material. Because this Verdet constant is more than twice that of the state of the art material, these nanocrystalline oxides produce polarized light rotations with less than half the applied magnetic field necessary. They are made by densifying rare earth nanocrystalline powder into dense, large-sized bodies using an electric current activated technique (sometimes known as spark plasma sintering). The processing temperature is optimized in order to achieve sufficient density without causing excessive phase changes that would destroy light transparency. This process produces materials quickly (<20 min), which, combined with high magneto-optical properties, promises less expensive, smaller, more portable magneto-optical devices.

  9. Magnetic field-dependent spin structures of nanocrystalline holmium

    PubMed Central

    Szary, Philipp; Kaiser, Daniel; Bick, Jens-Peter; Lott, Dieter; Heinemann, André; Dewhurst, Charles; Birringer, Rainer; Michels, Andreas

    2016-01-01

    The results are reported of magnetic field-dependent neutron diffraction experiments on polycrystalline inert-gas condensed holmium with a nanometre crystallite size (D = 33 nm). At T = 50 K, no evidence is found for the existence of helifan(3/2) or helifan(2) structures for the nanocrystalline sample, in contrast with results reported in the literature for the single crystal. Instead, when the applied field H is increased, the helix pattern transforms progressively, most likely into a fan structure. It is the component of H which acts on the basal-plane spins of a given nanocrystallite that drives the disappearance of the helix; for nanocrystalline Ho, this field is about 1.3 T, and it is related to a characteristic kink in the virgin magnetization curve. For a coarse-grained Ho sample, concomitant with the destruction of the helix phase, the emergence of an unusual angular anisotropy (streak pattern) and the appearance of novel spin structures are observed. PMID:27047307

  10. Nanocrystalline materials: recent advances in crystallographic characterization techniques

    PubMed Central

    Ringe, Emilie

    2014-01-01

    Most properties of nanocrystalline materials are shape-dependent, providing their exquisite tunability in optical, mechanical, electronic and catalytic properties. An example of the former is localized surface plasmon resonance (LSPR), the coherent oscillation of conduction electrons in metals that can be excited by the electric field of light; this resonance frequency is highly dependent on both the size and shape of a nanocrystal. An example of the latter is the marked difference in catalytic activity observed for different Pd nanoparticles. Such examples highlight the importance of particle shape in nanocrystalline materials and their practical applications. However, one may ask ‘how are nanoshapes created?’, ‘how does the shape relate to the atomic packing and crystallography of the material?’, ‘how can we control and characterize the external shape and crystal structure of such small nanocrystals?’. This feature article aims to give the reader an overview of important techniques, concepts and recent advances related to these questions. Nucleation, growth and how seed crystallography influences the final synthesis product are discussed, followed by shape prediction models based on seed crystallography and thermodynamic or kinetic parameters. The crystallographic implications of epitaxy and orientation in multilayered, core-shell nanoparticles are overviewed, and, finally, the development and implications of novel, spatially resolved analysis tools are discussed. PMID:25485133

  11. Oxygen Diffusion in Nanocrystalline CeO2

    SciTech Connect

    Saraf, Laxmikant V.; Shutthanandan, V; Wang, Chong M.; Zhang, Yanwen; Marina, Olga A.; Thevuthasan, Suntharampillai

    2003-08-14

    A unique ability of CeO2 to gain or lose oxygen ion has valued importance in the area of solid oxide fuel cells and catalysts. The macroscopic nature of oxygen storage, release and thereby vacancy generation, transport is explained with the help of quantum mechanical phenomena of electron localization. In this study, 18O diffusion and related transport on 1-2 mm thick nanocrystalline ceria films prepared by sol-gel process with an average grain-size in the range of 3-6 nm are studied. Initial 18O diffusion results indicate increased diffusion in 6 nm average grain-size nano-ceria films compared to {approx} 38 nm average grain-size poly-ceria films. Conductivity values in the case of {approx} 3nm average grain size CeO2 films grown at 300 0C observed to be marginally increased compared to {approx} 6 nm average grain size ceria films grown at 450 0C. A detailed nano-grain analysis by high-resolution transmission electron microscopy (HRTEM) was carried out to understand the effect of nanocrystallinity on the blocking phenomena.

  12. Photoreduction of Sm(3+) in Nanocrystalline BaFCl.

    PubMed

    Riesen, Nicolas; François, Alexandre; Badek, Kate; Monro, Tanya M; Riesen, Hans

    2015-06-18

    We demonstrate that exposure of nanocrystalline BaFCl:Sm(3+) X-ray storage phosphor to blue laser pulses with peak power densities on the order of 10 GW/cm(2) results in conversion of Sm(3+) to Sm(2+). This photoreduction is found to be strongly power-dependent with an initial fast rate, followed by a slower rate. The photoreduction appears to be orders of magnitude more efficient than that for previously reported systems, and it is estimated that up to 50% of the samarium ions can be photoreduced to the divalent state. The main mechanism is most likely based on multiphoton electron-hole creation, followed by subsequent trapping of the electrons in the conduction band at the Sm(3+) centers. Nanocrystalline BaFCl:Sm(3+) is an efficient photoluminescent X-ray storage phosphor with possible applications as dosimetry probes, and the present study shows for the first time that the power levels of the blue light have to be kept relatively low to avoid the generation of Sm(2+) in the readout process. A system comprising the BaFCl:Sm(3+) nanocrystallites embedded into a glass is also envisioned for 3D memory applications. PMID:25984960

  13. Implantation induced hardening of nanocrystalline titanium thin films.

    PubMed

    Krishnan, R; Amirthapandian, S; Mangamma, G; Ramaseshan, R; Dash, S; Tyagi, A K; Jayaram, V; Raj, Baldev

    2009-09-01

    Formation of nanocrystalline TiN at low temperatures was demonstrated by combining Pulsed Laser Deposition (PLD) and ion implantation techniques. The Ti films of nominal thickness approximatly 250 nm were deposited at a substrate temperature of 200 degrees C by ablating a high pure titanium target in UHV conditions using a nanosecond pulsed Nd:YAG laser operating at 1064 nm. These films were implanted with 100 keV N+ ions with fluence ranging from 1.0 x 10(16) ions/cm2 to 1.0 x 10(17) ions/cm2 The structural, compositional and morphological evolutions were tracked using Transmission Electron Microscopy (TEM), Secondary Ion Mass Spectrometry (SIMS) and Atomic Force Microscopy (AFM), respectively. TEM analysis revealed that the as-deposited titanium film is an fcc phase. With increasing ion fluence, its structure becomes amorphous phase before precipitation of nanocrystalline fcc TIN phase. Compositional depth profiles obtained from SIMS have shown the extent of nitrogen concentration gradient in the implantation zone. Both as-deposited and ion implanted films showed much higher hardness as compared to the bulk titanium. AFM studies revealed a gradual increase in surface roughness leading to surface patterning with increase in ion fluence. PMID:19928244

  14. Weakened Flexural Strength of Nanocrystalline Nanoporous Gold by Grain Refinement.

    PubMed

    Gwak, Eun-Ji; Kim, Ju-Young

    2016-04-13

    High density of grain boundaries in solid materials generally leads to high strength because grain boundaries act as strong obstacles to dislocation activity. We find that the flexural strength of nanoporous gold of grain size 206 nm is 33.6% lower than that of grain size 238 μm. We prepared three gold-silver precursor alloys, well-annealed, prestrained, and high-energy ball-milled, from which nanoporous gold samples were obtained by the same free-corrosion dealloying process. Ligaments of the same size are formed regardless of precursor alloys, and microstructural aspects of precursor alloys such as crystallographic orientation and grain size is preserved in the dealloying process. While the nanoindentation hardness of three nanoporous golds is independent of microstructural variation, flexural strength of nanocrystalline nanoporous gold is significantly lower than that of nanoporous golds with much larger grain size. We investigate weakening mechanisms of grain boundaries in nanocrystalline nanoporous gold, leading to weakening of flexural strength. PMID:26982460

  15. Thermal stability of nanocrystalline layers fabricated by surface nanocrystallization

    NASA Astrophysics Data System (ADS)

    Mai, Yong-jin; Jie, Xiao-hua; Liu, Li-li; Yu, Neng; Zheng, Xiang-xin

    2010-01-01

    A nanocrystalline layer with ultrafine grains (about 30-40 nm) on the surface of 7050 aluminum alloy was fabricated by a new technique called High Pressure Shot Peening (HPSP) which is the combination of common Shot Peening equipment with a pressurizing vessel. Relationship between hot flow and temperature was observed by Differential Scanning Calorimetry (DSC) and the activation energy, calculated by Kisssinger equation, of the as-treated sample increased 26.6 kJ/mol when it is compared with the as-reserved sample. The Bragg peaks of the as-prepared samples, respectively treated with various annealing treatments were characterized by XRD and the microhardness distribution along the depth from the treated surface were measured at the same time, which indicated that the broadening of Bragg peaks decreased with the increasing of anneal temperature; the grain size, calculated by Scherrer-Wilson equation, increased obviously during 180-220 °C, accordingly, the microhardness obviously decreased. According to the results of DSC, XRD and microhardness, it is reasonable to deduce that the temperature range of thermal stability for aluminum alloy nanocrystalline layer is lower than 200 °C.

  16. Nanocrystalline silicon: lattice dynamics and enhanced thermoelectric properties.

    PubMed

    Claudio, Tania; Stein, Niklas; Stroppa, Daniel G; Klobes, Benedikt; Koza, Michael Marek; Kudejova, Petra; Petermann, Nils; Wiggers, Hartmut; Schierning, Gabi; Hermann, Raphaël P

    2014-12-21

    Silicon has several advantages when compared to other thermoelectric materials, but until recently it was not used for thermoelectric applications due to its high thermal conductivity, 156 W K(-1) m(-1) at room temperature. Nanostructuration as means to decrease thermal transport through enhanced phonon scattering has been a subject of many studies. In this work we have evaluated the effects of nanostructuration on the lattice dynamics of bulk nanocrystalline doped silicon. The samples were prepared by gas phase synthesis, followed by current and pressure assisted sintering. The heat capacity, density of phonons states, and elastic constants were measured, which all reveal a significant, ≈25%, reduction in the speed of sound. The samples present a significantly decreased lattice thermal conductivity, ≈25 W K(-1) m(-1), which, combined with a very high carrier mobility, results in a dimensionless figure of merit with a competitive value that peaks at ZT≈ 0.57 at 973 °C. Due to its easily scalable and extremely low-cost production process, nanocrystalline Si prepared by gas phase synthesis followed by sintering could become the material of choice for high temperature thermoelectric generators. PMID:24848359

  17. Organically modified porous hydroxyapatites: A comparison between alkylphosphonate grafting and citrate chelation

    SciTech Connect

    El-Hammari, L.; Marroun, H.; Laghzizil, A.; Saoiabi, A.; Roux, C.; Livage, J.; Coradin, T.

    2008-04-15

    Two alternative methods to prepare organically modified porous hydroxyapatites following a 'one pot' approach were compared. The partial substitution of inorganic phosphates by alkylphosphonates leads to mesoporous materials with high specific surface area (>200 m{sup 2} g{sup -1}). The incorporation of the organic moieties within the hydroxyapatite structure is confirmed by Infra-red and solid-state NMR spectroscopy and depends on the nature of the alkyl chain. However, it induces a significant loss of the material crystallinity. In contrast, the introduction of citrate, a calcium-chelating agent, to the precursor solution does not improve the material specific surface area but allows a better control of the hydroxyapatite structure, both in terms of crystallinity and pore size distribution. - Graphical abstract: Evolution of pore size distribution of hydroxyapatite (HAp) after alkylphosphonate grafting (20% TPOH) or citrate addition (c-HAp) demonstrates the formation of organically modified mesoporous materials.

  18. Micro- and nano-hydroxyapatite as active reinforcement for soft biocomposites.

    PubMed

    Munarin, F; Petrini, P; Gentilini, R; Pillai, R S; Dirè, S; Tanzi, M C; Sglavo, V M

    2015-01-01

    Pectin-based biocomposite hydrogels were produced by internal gelation, using different hydroxyapatite (HA) powders from commercial source or synthesized by the wet chemical method. HA possesses the double functionality of cross-linking agent and inorganic reinforcement. The mineralogical composition, grain size, specific surface area and microstructure of the hydroxyapatite powders are shown to strongly influence the properties of the biocomposites. Specifically, the grain size and specific surface area of the HA powders are strictly correlated to the gelling time and rheological properties of the hydrogels at room temperature. Pectin pH is also significant for the formation of ionic cross-links and therefore for the hydrogels stability at higher temperatures. The obtained results point out that micrometric-size hydroxyapatite can be proposed for applications which require rapid gelling kinetics and improved mechanical properties; conversely the nanometric hydroxyapatite synthesized in the present work seems the best choice to obtain homogeneous hydrogels with more easily controlled gelling kinetics. PMID:25109458

  19. Template-directed synthesis and selective adsorption of oligoadenylates in hydroxyapatite

    NASA Technical Reports Server (NTRS)

    Gibbs, D.; Lohrmann, R.; Orgel, L. E.

    1980-01-01

    Polyuridylic acid is adsorbed completely from aqueous solution by hydroxyapatite under conditions that permit template-directed synthesis of oligoadenylates in free solution. The yield of oligoadenylates is enhanced to almost the same extent by poly(U) in the presence or the absence of hydroxyapatite. Under very similar conditions small quantities of hydroxyapatite adsorb higher-molecular-weight oligoadenylates selectively from a mixture of oligomers. On the basis of these results a mechanism for prebiotic oligonucleotide formation is proposed in which selective adsorption on hydroxyapatite or some other immobilized anion-exchanging material plays a major role. Monomers are released from the surface for reactivation, while oligomers are retained in a protected environment by adsorption to the apatite surface.

  20. Crystalline hydroxyapatite coatings synthesized under hydrothermal conditions on modified titanium substrates.

    PubMed

    Suchanek, Katarzyna; Bartkowiak, Amanda; Gdowik, Agnieszka; Perzanowski, Marcin; Kąc, Sławomir; Szaraniec, Barbara; Suchanek, Mateusz; Marszałek, Marta

    2015-06-01

    Hydroxyapatite coatings were successfully produced on modified titanium substrates via hydrothermal synthesis in a Ca(EDTA)(2-) and (NH4)2HPO4 solution. The morphology of modified titanium substrates as well as hydroxyapatite coatings was studied using scanning electron microcopy and phase identification by X-ray diffraction, and Raman and FTIR spectroscopy. The results show that the nucleation and growth of hydroxyapatite needle-like crystals with hexagonal symmetry occurred only on titanium substrates both chemically and thermally treated. No hydroxyapatite phase was detected on only acid etched Ti metal. This finding demonstrates that only a particular titanium surface treatment can effectively induce the apatite nucleation under hydrothermal conditions. PMID:25842108

  1. Bio resorbability of the modified hydroxyapatite in Tris-HCL buffer

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    The solubility of carbonated hydroxyapatite powders and granulated carbonated hydroxyapatite produced from the synovial biofluid model solution has been studied. The kinetic characteristics of dissolution were determined. It was found that the solubility of carbonated hydroxyapatite is higher as compared to that of hydroxyapatite. The impact of the organic matrix on the rate of sample dissolution was revealed. For HA-gelatin composites, as the gelatin concentration grows, the dissolution rate becomes greater, and a sample of 6.0 g / L concentration has higher resorbability. The results of the research can be used to study the kinetics of dissolution and the biocompatibility of ceramic materials for medicine, namely for reconstructive surgery, dentistry, and development of drug delivery systems.

  2. 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.

  3. Preparation and characterization of an iron oxide-hydroxyapatite nanocomposite for potential bone cancer therapy

    PubMed Central

    Sneha, Murugesan; Sundaram, Nachiappan Meenakshi

    2015-01-01

    Recently, multifunctional magnetic nanostructures have been found to have potential applications in biomedical and tissue engineering. Iron oxide nanoparticles are biocompatible and have distinctive magnetic properties that allow their use in vivo for drug delivery and hyperthermia, and as T2 contrast agents for magnetic resonance imaging. Hydroxyapatite is used frequently due to its well-known biocompatibility, bioactivity, and lack of toxicity, so a combination of iron oxide and hydroxyapatite materials could be useful because hydroxyapatite has better bone-bonding ability. In this study, we prepared nanocomposites of iron oxide and hydroxyapatite and analyzed their physicochemical properties. The results suggest that these composites have superparamagnetic as well as biocompatible properties. This type of material architecture would be well suited for bone cancer therapy and other biomedical applications. PMID:26491311

  4. Simple and Rapid Synthesis of Magnetite/Hydroxyapatite Composites for Hyperthermia Treatments via a Mechanochemical Route

    PubMed Central

    Iwasaki, Tomohiro; Nakatsuka, Ryo; Murase, Kenya; Takata, Hiroshige; Nakamura, Hideya; Watano, Satoru

    2013-01-01

    This paper presents a simple method for the rapid synthesis of magnetite/hydroxyapatite composite particles. In this method, superparamagnetic magnetite nanoparticles are first synthesized by coprecipitation using ferrous chloride and ferric chloride. Immediately following the synthesis, carbonate-substituted (B-type) hydroxyapatite particles are mechanochemically synthesized by wet milling dicalcium phosphate dihydrate and calcium carbonate in a dispersed suspension of magnetite nanoparticles, during which the magnetite nanoparticles are incorporated into the hydroxyapatite matrix. We observed that the resultant magnetite/hydroxyapatite composites possessed a homogeneous dispersion of magnetite nanoparticles, characterized by an absence of large aggregates. When this material was subjected to an alternating magnetic field, the heat generated increased with increasing magnetite concentration. For a magnetite concentration of 30 mass%, a temperature increase greater than 20 K was achieved in less than 50 s. These results suggest that our composites exhibit good hyperthermia properties and are promising candidates for hyperthermia treatments. PMID:23629669

  5. Surface modification for titanium implants by hydroxyapatite nanocomposite

    PubMed Central

    Family, Roxana; Solati-Hashjin, Mehran; Namjoy Nik, Shahram; Nemati, Ali

    2012-01-01

    Background: Titanium (Ti) implants are commonly coated with hydroxyapatite (HA). However, HA has some disadvantages such as brittleness, low tensile strength and fracture toughness. It is desirable to combine the excellent mechanical properties of ZrO2 and the chemical inertness of Al2O3 with respect to the purpose of this project which was coating Ti implants with HA-ZrO2-Al2O3 to modify the surface of these implants by adding ZrO2 and Al2O3 to HA. The purpose of this study was to evaluate the efficacy of hydroxyapatite coating nonocomposite. Methods: From September 2009 to January2011, functionally graded HA-Al2O3-ZrO2 and HA coatings were applied on Ti samples. HA-Al2O3-ZrO2 and HA sols were orderly dip coated on the substrates and calcined. Scanning electron microscopy and EDS were used to estimate the particle size of the surfaces and for morphological analysis. The morphology of non-coated HA-coated HA-Al2O3-ZrO2 (composite-coated) and double-layer composite coated samples were compared with one other. Mechanical test (heat & quench) was also done for comparing single-phase (HA), composite and double-layer composite samples. Results: The morphology of HA-Al2O3-ZrO2 coating is more homogenous than HA-coated and uncoated samples. Furthermore, single-layer coating is more homogenous than double-layer coating. EDS analysis was done on HA-coated sample and showed that the Ca/P ratio in the film was similar to the theoretical value 1.67 in HA. Conclusion: Surface modification of Ti implants can be done by coating them with single-layer of HA-Al2O3-ZrO2. Single-layer hydroxyapatite-alumina-zirconia coated sample has the most homogenous morphology on the surface. PMID:24009915

  6. Synthesis of nanocrystalline barium-hexaferrite from nanocrystalline goethite using the hydrothermal method: Particle size evolution and magnetic properties

    SciTech Connect

    Penn, R.L.; Banfield, J.F.; Voigt, J.

    1997-03-01

    To characterize particle size/magnetic property relationships, 9 to 50 nm in diameter barium hexaferrite, BaFe{sub 12}O{sub 19} (BHF), particles were prepared using a new synthesis route. By replacing the conventional 50 to 100 nm particles of goethite with nanocrystalline goethite produced via the microwave anneal method of Knight and Sylva, nanocrystalline BHF was synthesized using the hydrothermal method. Evolution of particle size and morphology with respect to concentration and heat treatment time is reported. Hysteresis properties, including coercivity (0.2--1.0 kOe), magnetization saturation (0.1--33.4 emu/g), and magnetization remanence (0.004--22.5 emu/g) are discussed as a function of particle size. The magnetization saturation and remanence of the 7 nm particles is nearly zero, suggesting the superparamagnetic threshold size for BHF is around this size. In addition, the equilibrium morphology of BHF crystals was calculated to be truncated hexagonal prisms which was verified by experiment, and the isoelectric point, pH of 4.1, was measured for 18 nm BHF particles.

  7. 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.

  8. Preparation and characterization of hydroxyapatite/sodium alginate biocomposites for bone implant application

    NASA Astrophysics Data System (ADS)

    Kanasan, Nanthini; Adzila, Sharifah; Suid, Mohd Syafiq; Gurubaran, P.

    2016-07-01

    In biomedical fields, synthetic scaffolds are being improved by using the ceramics, polymers and composites materials to avoid the limitations of allograft. Ceramic-polymer composites are appearing to be the most successful bone graft substitute in human body. The natural bones itself are well-known as composite of collagen and hydroxyapatite. In this research, precipitation method was used to synthesis hydroxyapatite (HA)/sodium alginate (SA) in various parameters. This paper describes the hydroxyapatite/sodium alginate biocomposite which suitable for use in bone defects or regeneration of bone through the characterizations which include FTIR, FESEM, EDS and DTA. In FTIR, the characteristi peaks of PO4-3 and OH- groups which corresponding to hydroxyapatite are existed in the mixing powders. The needle-size particle of hydroxyapatite/ alginate (HA/SA) are observed in FESEM in the range of 15.8nm-38.2nm.EDS confirmed the existence of HA/SA composition in the mixing powders. There is an endothermic peak which corresponds to the dehydration and the loss of physically adsorbed water molecules of the hydroxyapatite (HA)/sodium alginate (SA) powder which are described in DTA.

  9. Preparation of hollow hydroxyapatite microspheres by the conversion of borate glass at near room temperature

    SciTech Connect

    Yao, Aihua; Ai, Fanrong; Liu, Xin; Wang, Deping; Huang, Wenhai; Xu, Wei

    2010-01-15

    Hollow hydroxyapatite microspheres, consisting of a hollow core and a porous shell, were prepared by converting Li{sub 2}O-CaO-B{sub 2}O{sub 3} glass microspheres in dilute phosphate solution at 37 {sup o}C. The results confirmed that Li{sub 2}O-CaO-B{sub 2}O{sub 3} glass was transformed to hydroxyapatite without changing the external shape and dimension of the original glass object. Scanning electron microscopy images showed the shell wall of the microsphere was built from hydroxyapatite particles, and these particles spontaneously align with one another to form a porous sphere with an interior cavity. Increase in phosphate concentration resulted in an increase in the reaction rate, which in turn had an effect on shell wall structure of the hollow hydroxyapatite microsphere. For the Li{sub 2}O-CaO-B{sub 2}O{sub 3} glass microspheres reacted in low-concentration K{sub 2}HPO{sub 4} solution, lower reaction rate and a multilayered microstructure were observed. On the other hand, the glass microspheres reacted in higher phosphate solution converted more rapidly and produced a single hydroxyapatite layer. Furthermore, the mechanism of forming hydroxyapatite hollow microsphere was described.

  10. In situ synthesis of hydroxyapatite nanocomposites using iron oxide nanofluids at ambient conditions.

    PubMed

    Sheikh, Lubna; Mahto, Neha; Nayar, Suprabha

    2015-01-01

    This paper describes a simple method for the room temperature synthesis of magnetite/hydroxyapatite composite nanocomposites using ferrofluids. The in situ synthesis of magnetic-hydroxyapatite results in a homogenous distribution of the two phases as seen both in transmission electron micrographs and assembled to a micron range in the confocal micrographs. The selected area diffraction pattern analysis shows the presence of both phases of iron oxide and hydroxyapatite. To the dialyzed ferrofluid, the constituents of hydroxyapatite synthesis was added, the presence of the superparamagnetic iron oxide particles imparts directionality to the hydroxyapatite crystal growth. Electron probe microanalysis confirms the co-existence of both iron and calcium atoms. Vibrating Sample magnetometer data shows magnetization three times more than the parent ferrofluid, the local concentration of iron oxide nanoparticles affects the strength of dipolar interparticle interactions changing the energy barrier for determining the collective magnetic behavior of the sample. The limitations inherent to the use of external magnetic fields which can be circumvented by the introduction of internal magnets located in the proximity of the target by a minimal surgery or by using a superparamagnetic scaffold under the influence of externally applied magnetic field inspires us to increase the magnetization of our samples. The composite in addition shows anti-bacterial properties against the two gram (-ve) bacteria tested. This work is significant as magnetite-hydroxyapatite composites are attracting a lot of attention as adsorbents, catalysts, hyperthermia agents and even as regenerative medicine. PMID:25589209

  11. A Novel One-Step Solvothermal Route to Nanocrystalline Sn 4P 3

    NASA Astrophysics Data System (ADS)

    Su, H. L.; Xie, Y.; Li, B.; Liu, X. M.; Qian, Y. T.

    1999-08-01

    A novel solvothermal method has been successfully developed to obtain nanocrystalline Sn4P3 in an autoclave based on the reaction of SnCl2 · 2H2O with yellow phosphorus at 160°C for 10 h, with potassium borohydride (KBH4) used as the reducing agent and ethanol as the solvent. XRD, TEM, and XPS examinations investigated the phase, grain size, morphology, and purity of the product, respectively. The product is spherical nanocrystalline Sn4P3 with a hexagonal structure. Potassium borohydride and ethanol played important roles in the formation of nanocrystalline Sn4P3. A possible mechanism is proposed as: under the solvothermal condition, Sn2+ was steadily reduced by KBH4 to atomic Sn; subsequently these newborn active atoms homogeneously combined with yellow phosphorus to form nanocrystalline Sn4P3.

  12. Framework Stability of Nanocrystalline NaY in Aqueous Solution at Varying pH

    SciTech Connect

    Petushkov, Anton; Freeman, Jasmine; Larsen, Sarah C.

    2010-04-29

    Nanocrystalline zeolites (with crystal sizes of less than 50 nm) are versatile, porous nanomaterials with potential applications in a broad range of areas including bifunctional catalysis, drug delivery, environmental protection, and sensing, to name a few. The characterization of the properties of nanocrystalline zeolites on a fundamental level is critical to the realization of these innovative applications. Nanocrystalline zeolites have unique surface chemistry that is distinct from conventional microcrystalline zeolite materials and that will result in novel applications. In the proposed work, magnetic resonance techniques (solid state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR)) will be used to elucidate the structure and reactivity of nanocrystalline zeolites and to motivate bifunctional applications. Density functional theory (DFT) calculations will enhance data interpretation through chemical shift, quadrupole coupling constant, g-value and hyperfine calculations.

  13. Grain boundary effects on defect production and mechanical properties of irradiated nanocrystalline SiC

    SciTech Connect

    Jin Enze; Niu Lisha; Lin Enqiang; Song Xiaoxiong

    2012-05-15

    Grain boundaries (GBs) are known to play an important role in determining the mechanical and functional properties of nanocrystalline materials. In this study, we used molecular dynamics simulations to investigate the effects of damaged GBs on the mechanical properties of SiC that is irradiated by 10 keV Si atoms. The results reveal that irradiation promotes GB sliding and reduces the ability of GBs to block dislocations, which improves the deformation ability of nanocrystalline SiC. However, irradiation causes local rearrangements in disordered clusters and pinning of dislocations in the grain region, which restrains its deformation. These two mechanisms arise from the irradiation effects on GBs and grains, and these mechanisms compete in nanocrystalline SiC during irradiation. The irradiation effects on GBs dominate at low irradiation doses, and the effects on grains dominate at high doses; the result of these combined effects is a peak ductility of 0.09 dpa in nanocrystalline SiC.

  14. Grain boundary effects on defect production and mechanical properties of irradiated nanocrystalline SiC

    NASA Astrophysics Data System (ADS)

    Jin, Enze; Niu, Li-Sha; Lin, Enqiang; Song, Xiaoxiong

    2012-05-01

    Grain boundaries (GBs) are known to play an important role in determining the mechanical and functional properties of nanocrystalline materials. In this study, we used molecular dynamics simulations to investigate the effects of damaged GBs on the mechanical properties of SiC that is irradiated by 10 keV Si atoms. The results reveal that irradiation promotes GB sliding and reduces the ability of GBs to block dislocations, which improves the deformation ability of nanocrystalline SiC. However, irradiation causes local rearrangements in disordered clusters and pinning of dislocations in the grain region, which restrains its deformation. These two mechanisms arise from the irradiation effects on GBs and grains, and these mechanisms compete in nanocrystalline SiC during irradiation. The irradiation effects on GBs dominate at low irradiation doses, and the effects on grains dominate at high doses; the result of these combined effects is a peak ductility of 0.09 dpa in nanocrystalline SiC.

  15. The improved oxidation resistance of Si-doped SmCo{sub 7} nanocrystalline magnet

    SciTech Connect

    Liu Lili; Jiang Chengbao

    2011-06-20

    A drastic improvement in oxidation resistance of SmCo{sub 7} nanocrystalline magnet was achieved by alloying silicon at 500 deg. C. The maximum energy product (BH){sub max} loss of SmCo{sub 6.1}Si{sub 0.9} nanocrystalline magnet was about 5.6% after oxidation at 500 deg. C for 500 h, which was significantly less than 52.1% of SmCo{sub 7} nanocrystalline magnet. A general mode was proposed to predict the (BH){sub max} loss as a function of oxidation time at 500 deg. C. The formation of SiO{sub 2} oxide in the internal oxidation layer plays an important role in reducing the oxidation rate and oxygen diffusion coefficient, which leads to the enhancement of inherent oxidation resistance of SmCo{sub 6.1}Si{sub 0.9} nanocrystalline magnet.

  16. In situ observation of deformation processes in nanocrystalline face-centered cubic metals

    PubMed Central

    Kobler, Aaron; Brandl, Christian; Hahn, Horst

    2016-01-01

    Summary The atomistic mechanisms active during plastic deformation of nanocrystalline metals are still a subject of controversy. The recently developed approach of combining automated crystal orientation mapping (ACOM) and in situ straining inside a transmission electron microscope was applied to study the deformation of nanocrystalline PdxAu1− x thin films. This combination enables direct imaging of simultaneously occurring plastic deformation processes in one experiment, such as grain boundary motion, twin activity and grain rotation. Large-angle grain rotations with ≈39° and ≈60° occur and can be related to twin formation, twin migration and twin–twin interaction as a result of partial dislocation activity. Furthermore, plastic deformation in nanocrystalline thin films was found to be partially reversible upon rupture of the film. In conclusion, conventional deformation mechanisms are still active in nanocrystalline metals but with different weighting as compared with conventional materials with coarser grains. PMID:27335747

  17. In situ observation of deformation processes in nanocrystalline face-centered cubic metals.

    PubMed

    Kobler, Aaron; Brandl, Christian; Hahn, Horst; Kübel, Christian

    2016-01-01

    The atomistic mechanisms active during plastic deformation of nanocrystalline metals are still a subject of controversy. The recently developed approach of combining automated crystal orientation mapping (ACOM) and in situ straining inside a transmission electron microscope was applied to study the deformation of nanocrystalline Pd x Au1- x thin films. This combination enables direct imaging of simultaneously occurring plastic deformation processes in one experiment, such as grain boundary motion, twin activity and grain rotation. Large-angle grain rotations with ≈39° and ≈60° occur and can be related to twin formation, twin migration and twin-twin interaction as a result of partial dislocation activity. Furthermore, plastic deformation in nanocrystalline thin films was found to be partially reversible upon rupture of the film. In conclusion, conventional deformation mechanisms are still active in nanocrystalline metals but with different weighting as compared with conventional materials with coarser grains. PMID:27335747

  18. Covalent attachment and growth of nanocrystalline films of photocatalytic TiOF2

    NASA Astrophysics Data System (ADS)

    Zhu, Jian; Lv, Fujian; Xiao, Shengxiong; Bian, Zhenfeng; Buntkowsky, Gerd; Nuckolls, Colin; Li, Hexing

    2014-11-01

    This manuscript describes a synthesis of nanocrystalline TiOF2 film. The nanocrystalline TiOF2 becomes chemically attached to the surface of the glass slide. These films are robust and can be recycled as photocatalysts for the degradation of organic dyes and solvents. These films also have significant antibacterial properties upon irradiation.This manuscript describes a synthesis of nanocrystalline TiOF2 film. The nanocrystalline TiOF2 becomes chemically attached to the surface of the glass slide. These films are robust and can be recycled as photocatalysts for the degradation of organic dyes and solvents. These films also have significant antibacterial properties upon irradiation. Electronic supplementary information (ESI) available: Methods for sample preparation, characterization and Fig. S1-S8. See DOI: 10.1039/c4nr05598e

  19. Nanosized hydroxyapatite powder synthesized from eggshell and phosphoric acid.

    PubMed

    Lee, Sang-Jin; Yoon, Young-Soo; Lee, Myung-Hyun; Oh, Nam-Sik

    2007-11-01

    The present research describes synthesis of highly sinterable, nano-sized hydroxyapatite (HAp) powders using a wet chemical route with recycled eggshell and phosphoric acid as calcium and phosphorous sources. The raw eggshell was easily turned to CaO by the calcining process, and phosphoric acid was mixed with the calcined eggshell by the wet, ball-milling method. The crystalline development and microstructures of the synthesized powders and sintered samples were examined by X-ray diffractometry and scanning electron microscopy, respectively. The observed phases on the powder synthesis process were dependent on the mixing ratio (wt%) of the calcined eggshell to phosphoric acid and the heating temperature. The ball-milled, nano-sized HAp powder, which has an average particle size of 70 nm, was fully densified at 1300 degrees C for 1h. The Ca/P ratio for stoichiometric composition of HAp was controlled by adjustment of the mixing ratio. PMID:18047119

  20. Retrospective dosimetry using synthesized nano-structure hydroxyapatite.

    PubMed

    Ziaie, F; Hajiloo, N; Alipour, A; Amraei, R; Mehtieva, S I

    2011-06-01

    Micro and nano-structure hydroxyapatite samples were synthesized via several different methods. The samples were characterised utilising the Fourier transmission infra-red, scanning electron microscope and X-ray diffraction methods, to find out the structure most similar to human tooth enamel, and the best method was found. The electron paramagnetic resonance (EPR) signals of the gamma-irradiated samples were measured using an EPR spectrometer system. A calibration curve was established by irradiation of the samples at four doses of 50-500 mGy. The parameters of the calibration curve, slope and intercept with dose axis are determined by linear regression analysis. This calibration curve can be used for human tooth enamel for retrospective dosimetry purposes. PMID:21131666