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At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Synthesis and Characterization of Natural Nano-hydroxyapatite Derived from Turkey Femur-Bone Waste

Hydroxyapatite (HAp) is a bioactive and vital material which has found many applications in the biomedical and clinical fields. This bio-ceramic powder can be synthesized via different bio-waste materials. In this study, the production of natural nanohydroxyapatite was produced through calcination of untreated turkey femur-bone waste powder at 850 °C followed by ball milling the powder. The obtained powder was characterized using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis. The morphology, size, and elemental composition of obtained turkey hydroxyapatite (THA) particles were investigated by scanning electron microcopy (SEM), transmission electron microcopy (TEM), and energy dispersive spectroscopy (EDS) analysis, in which the average particle size of ball milled THA was found to be about 85 nm with a Ca/P ratio of 1.63. The powder was then cold pressed and later sintered at 850, 950, 1050, and 1150 °C to evaluate its mechanical properties in terms of compressive strength and hardness. The results revealed that the strength and hardness of the samples increased by increasing the sintering temperature up to 1150 °C. Finally, the maximum values of hardness and compressive strength of the sintered THA were obtained at 1150 °C (37.44 MPa and 3.2 GPa, respectively).

60 APPLIED LIFE SCIENCES↗
DOE OSTI2012

Post-translational modification of osteopontin: Effects on in vitro hydroxyapatite formation and growth

Highlights: Black-Right-Pointing-Pointer Thrombin-cleaved fragments of milk-osteopontin effect hydroxyapatite formation differently. Black-Right-Pointing-Pointer N- and C-terminal fragments promoted hydroxyapatite formation and growth. Black-Right-Pointing-Pointer A central fragment inhibited hydroxyapatite formation and growth. Black-Right-Pointing-Pointer Binding to collagen or hydroxyapatite seed crystals modified these effects. -- Abstract: The manuscript tests the hypothesis that posttranslational modification of the SIBLING family of proteins in general and osteopontin in particular modify the abilities of these proteins to regulate in vitro hydroxyapatite (HA) formation. Osteopontin has diverse effects on hydroxyapatite (HA) mineral crystallite formation and growth depending on the extent of phosphorylation. We hypothesized that different regions of full-length OPN would also have distinct effects on the mineralization process. Thrombin fragmentation of milk OPN (mOPN) was used to test this hypothesis. Three fragments were tested in a de novo HA formation assay; an N-terminal fragment (aa 1-147), a central fragment (aa 148-204) denoted SKK-fragment and a C-terminal fragment (aa 205-262). Compared to intact mOPN the C- and N-terminal fragments behaved comparably, promoting HA formation and growth, but the central SKK-fragment acted as a mineralization inhibitor. In a seeded growth experiment all fragments inhibited mineral proliferation, but the SKK-fragment was the most effective inhibitor. These effects, seen in HA-formation and seeded growth assays in a gelatin gel system and in a pH-stat experiment were lost when the protein or fragments were dephosphorylated. Effects of the fully phosphorylated protein and fragments were also altered in the presence of fibrillar collagen. The diverse effects can be explained in terms of the intrinsically disordered nature of OPN and its fragments which enable them to interact with their multiple partners.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Human alpha A-crystallin missing N-terminal domain poorly complexes with filensin and phakinin

Highlights: • In vitro complexes between αA, its deletion mutants with filensin and phakinin was determined. • Complexes were determined following ultracentrifugation and by electron microscopic methods. • N-terminal domain of αA-crystallin is needed to form complex with filensin and phakinin in vitro. The aim of this study was to determine relative importance of N-terminal domain and C-terminal extension of αA-crystallin during their in vitro complex formation with phakinin and filensin (the two lens-specific intermediate filament [IF] proteins). Cloned phakinin, filensin and vimentin were purified under a denaturing conditions by consecutive DEAE-cellulose-, hydroxyapatite- and Sephadex G-75-column chromatographic methods. WTαA-crystallin, αA-NT (N-terminal domain [residue number 1–63])-deleted and αA-CT (C-terminal terminal extension [residue number 140–173]-deleted), were cloned in pET 100 TOPO vector, expressed in BL-21 (DE3) cells using 1% IPTG, and purified using a Ni{sup 2+}-affinity column. The following two in vitro methods were used to determine complex formation of WT-αA, αA-NT, or αA-CT with phakinin, filensin or both phakinin plus filensin together: an ultracentrifugation sedimentation (centrifugation at 80,000 × g for 30 min at 20 °C) followed by SDS-PAGE analysis, and an electron microscopic analysis. In the first method, the individual control proteins (WT-αA, αA-NT and αA-CT crystallin species) remained in the supernatant fractions whereas phakinin, filensin, and vimentin were recovered in the pellet fractions. On complex formation by individual WT-αA-, αA-NT or αA-CT-species with filensin, phakinin or both phakinin and filensin, WT-αA and αA-CT were recovered in the pellet fraction with phakinin, filensin or both filensin and phakinin, whereas αA-NT remained mostly in the supernatant, suggesting its poor complex formation property. EM-studies showed filamentous structure formation between WT-αA and αA-CT with phakinin or filensin, or with both filensin and phakinin together but relatively poor filamentous structures with αA-NT. Together, the results suggest that the N-terminal domain of αA-crystallin is required during in vitro complex formation with filensin and phakinin.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Direct evidence that KLK4 is a hydroxyapatite-binding protein

Highlights: • Contradictions about KLK4 binding to hydroxyapatite were resolved biochemically. • A proxy substrate stabilises KLK4 against inactivation, aggregation and autolysis. • A mechanistic model involving KLK4 retention and autodegradation is proposed. The protease kallikrein 4 (KLK4) plays a pivotal role during dental enamel formation by degrading the major enamel protein, amelogenin, prior to the final steps of enamel hardening. KLK4 dysfunction is known to cause some types of developmental defect in enamel but the mechanisms responsible for transient retention of KLK4 in semi-hardened enamel matrix remain unclear. To address contradictory reports about the affinity of KLK4 for enamel hydroxyapatite-like mineral, we used pure components in quasi-physiological conditions and found that KLK4 binds hydroxyapatite directly. Hypothesising KLK4 self-destructs once amelogenin is degraded, biochemical analyses revealed that KLK4 progressively lost activity, became aggregated, and autofragmented when incubated without substrate in both the presence and absence of reducer. However, with non-ionic detergent present as proxy substrate, KLK4 remained active and intact throughout. These findings prompt a new mechanistic model and line of enquiry into the role of KLK4 in enamel hardening and malformation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Natural fluorapatite as a raw material for Portland clinker

The present work focuses on the mineralogy and the reactivity of clinkers made from the integration of natural fluorapatite in the raw meals with percentages ranging from 0 up to15%. The samples were characterized by infrared spectrometry, X-ray diffraction and microscopy techniques. The distribution of phosphorous and fluorine into clinkers minerals was determined by MEB/EDS mapping. The mineralogical composition was determined by XRD/Rietveld and the samples reactivity followed by isothermal microcalorimetry. It has been found that fluorine stabilizes C{sub 3}S and β-C{sub 2}S which still are found with high levels of P{sub 2}O{sub 5}. Cements obtained from up to 8% natural fluorapatite incorporation still present acceptable properties. Natural fluorapatite could have an important potential as decarbonised source of CaO contributing to decrease the CO{sub 2} emission in cement industry.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Reduction of water content in calcium aluminate cement with/out phosphate modification for alternative cementation technique

Cementation of the secondary aqueous wastes from TEPCO Fukushima Daiichi Nuclear Power Plant is challenging due to the significant strontium content and radioactivity, leading to a potential risk of hydrogen gas generation via radiolysis of water content. The present study investigates the reduction of water content in calcium aluminate cement (CAC) with/out phosphate modification by a heat-treatment during the solidification. The reduction of water in the CAC was found restricted by the rapid formation of crystalline hydration phases, whereas the phosphate-modified system allowed the gradual reduction of water, achieving the reduction of 60% water content at 95 °C. Curing at 60–95 °C also eliminated the significant cracks found at 35 °C in the phosphate system. The possible difference in the amorphous products, NaCaPO{sub 4}·nH{sub 2}O type at 35°C and Ca(HPO{sub 4})·xH{sub 2}O type at 60–95 °C, may have contributed to the improvement in the microstructure together with the change in the pore size distribution.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effect of temperature curing on properties and hydration of wollastonite blended magnesium potassium phosphate cements

K-struvite, the main hydrate of magnesium potassium phosphate (MKP) cements, dehydrates at ~50 °C, thus elevated temperatures at service conditions could affect cement properties and durability. In this study, properties and hydration of MKP cement without and with wollastonite were investigated at 20 and 50 °C. In hydrated pure MKP cement K-struvite decomposes progressively over time to MgKPO{sub 4}·H{sub 2}O at 50 °C, which leads to a strong reduction of solid volume and severe strength loss. The presence of wollastonite significantly slows down the decomposition rate of K-struvite, which is still observed after 393 days at 50 °C. K-struvite together with amorphous hydroxyapatite, M-(C)-S-H and CaK{sub 3}H(PO{sub 4}){sub 2} from the wollastonite reaction result in a cement with good short and long-term strength at both 20 and 50 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A high-efficiency self-healing cementitious material based on supramolecular hydrogels impregnated with phosphate and ammonium

High-efficiency self-healing cementitious materials using hydroxyapatites as healing product were described. Supramolecular hydrogels impregnated with phosphate and ammonium ions were designed. Morphology of the supramolecular hydrogel and its capability to release phosphate in solution, the structure of healing products and the self-healing efficiency were characterized with a range of analytical techniques. Cracks in the cementitious materials with width up to 1 mm are closed and completely healed. The healing product in the cracks without ammonium ions was brushite with a sponge-like morphology. Released ammonium ions reacted with calcium hydroxide in the cement matrix, increasing the concentration of soluble calcium ions up to 300 times that in reference pore solution. Ammonium ions facilitated the formation and aggregation of healing products which were converted into hydroxyapatites, improving the maximum healable crack width.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Solubility of pyromorphite Pb 5 (PO 4 ) 3 Cl at 5–65°C and its experimentally determined thermodynamic parameters

Here, the solubility of synthetic pyromorphite Pb 5 (PO 4 ) 3 Cl was determined in a series of dissolution experiments conducted at 5–65 °C and at pH = 2.0. The equilibrium was established within 4 months. The dissolution of pyromorphite was congruent at all the temperatures, and the measured solubility product log K sp,298 for the dissolution reaction: Pb 5 (PO 4 ) 3 Cl ⇌ 5Pb 2+ + 3PO 4 3- + Cl - was determined to be –79.6 ± 0.15. The equilibrium ion activity product of pyromorphite increased with temperature, indicating a positive enthalpy of the dissolution reaction in the temperature range from 5 to 65 °C. The temperature dependence of the log K sp was nonlinear: log K sp = A – B/T + D log(T), where A = 478.77 ± 136.62, B = 29,378 ± 6215, and D = –185.81 ± 46.77. This allowed for calculation of ΔG° r = 454.0 ± 1.7 kJ·mol –1 , ΔH° r = 101.8 ± 6.0 J·mol –1 ·K –1 , ΔC° p,r = –1545 ± 388.9 J·mol –1 ·K –1 , and ΔS° r = –1181 ± 382 J·mol –1 ·K –1 of the dissolution reaction. Using these values and the published standard state quantities for constituent ions, the values of ΔG° f = –3764.3 ± 3.5 kJ·mol –1 , ΔH° f = –4108.4 ± 7.9 J·mol –1 ·K –1 , S° f = 622 ± 382 J·mol –1 ·K –1 , and C° pf = 402 ± 398 J·mol –1 ·K –1 were calculated for synthetic pyromorphite Pb 5 (PO 4 ) 3 Cl.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Polyacrylamide-hydroxyapatite composite: Preparation, characterization and adsorptive features for uranium and thorium

The composite of synthetically produced hydroxyapatite (HAP) and polyacrylamide was prepared (PAAm-HAP) and characterized by BET, FT-IR, TGA, XRD, SEM and PZC analysis. The adsorptive features of HAP and PAAm-HAP were compared for UO{sub 2}{sup 2+} and Th{sup 4+}. The entrapment of HAP into PAAm-HAP did not change the structure of HAP. Both structures had high affinity to the studied ions. The adsorption capacity of PAAm-HAP was than that of HAP. The adsorption dependence on pH and ionic intensity provided supportive evidences for the effect of complex formation on adsorption process. The adsorption kinetics was well compatible to pseudo second order model. The values of enthalpy and entropy changes were positive. Th{sup 4+} adsorption from the leachate obtained from a regional fluorite rock confirmed the selectivity of PAAm-HAP for this ion. In consequence, PAAm-HAP should be considered amongst favorite adsorbents for especially deposition of nuclear waste containing U and Th, and radionuclide at secular equilibrium with these elements. - Graphical abstract: SEM images of hydroxyapatite (HAP) and polyacrylamide-hydroxyapatite (PAAm-HAP), and the adsorption isotherms for Uranium and Thorium. Highlights: Black-Right-Pointing-Pointer Composite of PAAm-HAP was synthesized from hydroxyapatite and polyacrylamide. Black-Right-Pointing-Pointer The materials were characterized by BET, FT-IR, XRD, SEM, TGA and PZC analysis. Black-Right-Pointing-Pointer HAP and PAAm-HAP had high sorption capacity and very rapid uptake for UO{sub 2}{sup 2+} and Th{sup 4+}. Black-Right-Pointing-Pointer Super porous PAAm was obtained from PAAm-HAP after its removal of HAP content. Black-Right-Pointing-Pointer The composite is potential for deposition of U, Th and its associate radionuclides.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Highly dispersive α″-Fe{sub 16}N{sub 2} particle synthesis using hydroxyapatite coating

Alpha″-Fe{sub 16}N{sub 2} nanoparticles (NPs) with high magnetic crystalline anisotropy are useful for practical applications such as recording media. However, due to their strongly aggregated and/or sintered form, which occurs during synthesis, the utilization of the NPs has been limited thus far. Here, we report a method for synthesizing highly dispersive α″-Fe{sub 16}N{sub 2} NPs using hydroxyapatite (HAp). The chemically and thermally stable structure of the HAp coating results in the isolation of individual NPs, such that sintering is prevented during synthesis. Additionally, the acicular shape of the HAp crystal did not hinder gas diffusion during the gas reaction. Finally, HAp can be removed by a chelating agent without deteriorating the magnetic properties, resulting in highly dispersive α″-Fe{sub 16}N{sub 2} NPs. - Graphical abstract: Synthesis process of highly dispersive α″-Fe{sub 16}N{sub 2} particles using hydroxyapatite coating and SEM images of nanoparticles. - Highlights: • Highly dispersed α″-Fe{sub 16}N{sub 2} NPs were synthesized using hydroxyapatite (HAp). • HAp coating was stable chemically and thermally during gas reaction of α″-Fe{sub 16}N{sub 2} synthesis. • The magnetic property of the resultant Fe{sub 16}N{sub 2} NPs are M{sub s} of 170 emu/g and H{sub C} of 2450 Oe.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Well-aligned polycrystalline lanthanum silicate oxyapatite grown by reactive diffusion between solid La{sub 2}SiO{sub 5} and gases [SiO+1/2O{sub 2}]

The c-axis-oriented polycrystalline lanthanum silicate oxyapatite, La{sub 9.48}(Si{sub 5.89}□{sub 0.11})O{sub 26} (□ denotes a vacancy in the Si site), was successfully prepared by the reactive diffusion between randomly grain-oriented La{sub 2}SiO{sub 5} polycrystal and [SiO+1/2O{sub 2}] gases at 1873 K in Ar atmosphere. The polycrystal was characterized using optical microscopy, scanning electron microscopy equipped with energy dispersive X-ray spectroscopy, micro-Raman spectroscopy, X-ray diffractometry, and impedance spectroscopy. The crystal structure (space group P6{sub 3}/m) showed the deficiency of Si site at ca. 1.9%. The bulk oxide-ion conductivity along the grain-alignment direction steadily increased from 9.2 × 10{sup −3} to 1.17 × 10{sup −2} S/cm with increasing temperature from 923 to 1073 K. The activation energy of conduction was 0.23(2) eV. - Graphical abstract: We have successfully prepared the highly c-axis-oriented polycrystalline La{sub 9.48}(Si{sub 5.89}□{sub 0.11})O{sub 26} by the reactive diffusion between randomly grain-oriented La{sub 2}SiO{sub 5} polycrystal and [SiO + 1/2O{sub 2}] gases at 1873 K in Ar atmosphere. The crystal structure (space group P6{sub 3}/m) showed the deficiency of Si site of ca. 1.9%. - Highlights: • The c-axis-oriented polycrystalline La{sub 9.48}(Si{sub 5.89}□{sub 0.11})O{sub 26} is successfully prepared. • Crystal structure of La{sub 9.48}(Si{sub 5.89}□{sub 0.11})O{sub 26} is determined by single-crystal XRD. • The polycrystal shows relatively high oxide ion conductivity along the common c-axis. • Reactive diffusion is successfully used for the preparation of grain-aligned ceramics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Crystal structure and luminescence properties of Bi{sup 3+}activated Ca{sub 2}Y{sub 8}(SiO{sub 4}){sub 6}O{sub 2} phosphors under near UV excitation

Oxyapatite Ca{sub 2}Y{sub 8−x}(SiO{sub 4}){sub 6}O{sub 2}:xBi{sup 3+}phosphor has been prepared via high temperature solid-state reaction. Its crystal structure and PL properties were investigated by X-ray diffraction, photoluminescence excitation and emission spectra. The results indicated that the Ca{sub 2}Y{sub 8}(SiO{sub 4}){sub 6}O{sub 2} crystallizes as a hexagonal structure with a space group of P6{sub 3}/m and lattice constants of a=b=9.3507 Å, c=6.7899 Å, α=β=90.00°, γ=120.00°, V=514.14 Å{sup 3}; The phosphor has two prominent emission bands: when excited under 320–360 nm, the phosphors emit a broad band centered at 495 nm due to the {sup 3}P{sub 1}–{sup 1}S{sub 0} transition of Bi{sup 3+} in 4f (C{sub 3}) sites; when excited under 380 nm, the phosphors emit a broad band centered at 411 nm due to the {sup 3}P{sub 1}–{sup 1}S{sub 0} transition of Bi{sup 3+} in 6h (C{sub s}) sites. The emission color varies from the greenish blue to blue as the excitation wavelength increases from 335 to 380 nm. The optimal intensity of emission band was observed when x=0.015 in the Ca{sub 2}Y{sub 8−x}(SiO{sub 4}){sub 6}O{sub 2}:xBi{sup 3+} series. The average critical distance Rc among Bi{sup 3+} ions is determined to be 20.15 Å.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

A novel approach to obtain highly intense self-activated photoluminescence emissions in hydroxyapatite nanoparticles

Defect-related photoluminescence (PL) in materials have attracted interest for applications including near ultraviolet (NUV) excitable light-emitting diodes and in biomedical field. In this paper, hydroxyapatite [Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}] nanorods with intense PL bands (bluish- and yellowish-white emissions) were obtained when excited under NUV radiation at room temperature. These nanoparticles were synthesized via chemical precipitation at 90 °C followed by distinct heat treatments temperatures (200–800 °C). Intense and broad emission profiles were achieved at 350 °C (380–750 nm) and 400 °C (380–800 nm). UV–Vis spectroscopy revealed band gap energies (5.58–5.78 eV) higher than the excitation energies (~3.54 and ~2.98 eV at 350 and 415 nm, respectively), confirming the contribution of defect energy levels within the forbidden zone for PL emissions. The structural features were characterized by X-ray diffraction, Rietveld refinement, thermogravimetric analysis, and Fourier transform infrared spectroscopy. By means of these techniques, the relation between structural order-disorder induced by defects, chemical reactions at both lattice and surface of the materials as well as the PL, without activator centers, was discussed in details. - Graphical abstract: The self-activated photoluminescence emissions of chemically precipitated hydroxyapatite nanorods were improved by different heat treatment temperatures. - Highlights: • HA nanorods were synthesized with improved self-activated PL at room temperature. • PL profile and intensity dependents on the temperature of posterior heat treatments. • Bluish- and yellowish-white emissions under NUV excitation (350 and 415 nm). • Broad and intense profiles achieved at 350 °C (380–750 nm) and 400 °C (380–800 nm). • PL from the e′–h{sup •} recombination between defect energy levels within the band gap.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Transmission electron microscopy analysis of hydroxyapatite nanocrystals from cattle bones

In this present study, hydroxyapatite which was obtained from cattle bones has been heat treated at temperature 400 °C and 600 °C. The microstructure after the treatment has been studied in detail using Transmission electron microscopy (TEM) and X-ray diffraction techniques. The TEM results indicate that natural bone consists of collagen and hydroxyapatite nano-crystals which are needle shaped. The heat treatment influences the crystallinity and growth of these hydroxyapatite nano-crystals known as ‘crystal maturation’ or ‘crystal ageing’. - Highlights: • Hydroxyapatite is obtained from cattle bones. • Material has been characterised using XRD and TEM. • Crystal growth and orientation has been studied in detail.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Structural and mechanical characterization of boron doped biphasic calcium phosphate produced by wet chemical method and subsequent thermal treatment

In the current study, boron doped biphasic calcium phosphate bioceramics consisting of a mixture of boron doped hydroxyapatite (BHA) and beta tricalcium phosphate (β-TCP) of varying BHA/β-TCP ratios were obtained after sintering stage. The effects of varying boron contents and different sintering temperatures on the BHA/β-TCP ratios and on the sinterability of the final products were investigated. Particle sizes and morphologies of the obtained precipitates were determined using SEM. XRD and FTIR investigation were conducted to detect the boron formation in the structure of HA and quantitative analysis was performed to determine the BHA/β-TCP ratio before and after sintering stage. In order to determine the sinterability of the obtained powders, pellets were prepared and sintered; the rates of densification were calculated and obtained results were correlated by SEM images. Also Vickers microhardness values of the sintered samples were determined. The experimental results verified that boron doped hydroxyapatite powders were obtained after sintering stage and the structure consists of a mixture of BHA and β-TCP. As the boron content used in the precipitation stage increases, β-TCP content of the BHA/β-TCP ratio increases but sinterability, density and microhardness deteriorate. As the sintering temperature increases, β-TCP content, density and microhardness of the samples increase and sinterability improves. - Highlights: • This is the first paper about boron doped biphasic calcium phosphate bioceramics. • Boron doping affects the structural and mechanical properties. • BHA/β-TCP ratio can be adjustable with boron content and sintering temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Effect of phase composition of calcium silicate phosphate component on properties of brushite based composite cements

The composite cement mixtures were prepared by mixing brushite (B) with, the amorphous hydrated calcium silicate phosphate (CSPH) or annealed calcium silicate phosphate (CSP composed of Si-saturated hydroxyapatite, wollastonite and silica) phases and water as liquid component. The contents of the silicate-phosphate phase in composites were 10.30 and 50 wt%. The significant effect of both the Ca/P ratio and different solubility of calcium silicate phosphate component in starting cement systems on setting time and phase composition of the final composite cements was demonstrated. The compressive strength of the set cements increased with the filler addition and the highest value (~ 48 MPa) exhibited the 50CSP/B cement composite. The final setting times of the composite cements decreased with the CSPH addition from about 25 to 17 min in 50CSHP/B and setting time of CSP/B composites was around 30 min. The higher content of silica in cements caused the precipitation of fine hydroxyapatite particles in the form of nanoneedles or thin plates perpendicularly oriented to sample surface. The analysis of in vitro cement cytotoxicity demonstrated the strong reduction in cytotoxicity of 10CSPH/B composite with time of cultivation (a low cytotoxicity after 9 days of culture) contrary to cements with higher calcium silicate-phosphate content. These results were attributed to the different surface topography of composite substrates and possible stimulation of cell proliferation by the slow continuously release of ions from 10CSPH/B cement. - Highlights: • Ca/P ratio and solubility of calcium silicate-phosphate components affect the self-setting properties of cements. • Strong relationship between the composite in vitro cytotoxicity and surface microtopography was demonstrated. • Plate-like morphology of coarser particles allowed cells to better adhere and proliferate as compared with nanoneedles.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Revealing the nanostructure of calcium phosphate coatings using HRTEM/FIB techniques

Herein, we report on the micro- and nanostructure of the calcium phosphate coating produced by pulsed laser deposition (PLD), using focused ion beam (FIB) lamella sample preparation and transmission electron microscopy (TEM) as the characterization technique. The initial selected area electron diffraction (SAED) data demonstrated the presence of hydroxyapatite (HA) over any other possible calcium phosphate crystalline structure and the polycrystalline nature of the coating. Moreover, the SAED analyses showed clear textured ring patterns coherent with the presence of a preferred orientation in the HA nano-crystal growth. The SAED data also indicated that the coating appears to be textured in the 〈002〉 crystalline direction. Dark-field images obtained using 002 as the working reflection showed a clear oriented crystal growth in columns, from bottom to top. These columns have a peculiar arrangement of nano-crystals since, in some cases, the preferred orientation appears to start at a certain distance from the substrate. Direct d-spacing measurements on high-resolution TEM images provided further proof of the presence of an HA nano-crystal structure. The reported data may be of interest in the future to adjust the microstructure of the HA coatings. - Highlights: •The FIB lift-out technique allows a very site-specific sample preparation method for HRTEM analysis. •It also permits a fast assessment of the HA coating thickness and elemental composition (EDS). •The coatings exhibit a nano-crystalline nature, with a texturing effect along the 002 planes. •PLD is suitable for the production of crystalline c-axis oriented hydroxyapatite coatings. •The crystalline HA phase in the PLD coating is very similar to the present in bone.

36 MATERIALS SCIENCE↗