Morphological and structural characterisation of osseointegrable Mn2+ and CO32− doped hydroxylapatite thin films

We report a morphological and structural study of osseointegrable hydroxylapatite thin films doped with divalent manganese and carbonate ions. The films were grown by pulsed laser deposition on medical grade Ti substrates at low oxygen pressure (13 Pa). Deposition targets were prepared from powders obtained by precipitation. During deposition, the substrates were kept at constant temperature within the temperature range 350–450 °C and the obtained films were subsequently annealed in hot water vapours at the deposition temperature. The films were characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), grazing incidence X-ray diffraction (GIXRD), energy dispersive X-ray spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS). Film specimens for cross-section TEM were prepared by focused ion beam (FIB) machining. The inferred Ca/P atomic ratio in films varied between 1.6 and 1.8, depending on experimental conditions. XPS confirmed the presence of chemically bonded Mn²⁺. Cross-section TEM micrographs showed uniform thickness of the coatings, which consisted of amorphous and crystalline domains. Examination of the SEM micrographs revealed an increased smoothness of the surface with increase in substrate deposition temperature. XRD patterns of samples processed at temperatures over 400 °C showed well-crystallized hydroxylapatite, suggesting that deposition and annealing have to be performed at higher substrate temperature if highly crystalline coatings are required.     

The synthesis of long-term stable amorphous calcium carbonate in water-free ethylene glycol system without any phase stabilizer

Amorphous calcium carbonate (ACC) plays an important role in the biomineralization process and has a wide application in biological medicine area. In the present work, stable ACC was successfully prepared in water-free ethylene glycol system, by mixing the ethylene glycol solution of CaCl₂ and K₂CO₃ without phase stabilizer. The CaCO₃ obtained at different aging times (from 1 min to 3 months) and reaction temperatures (from 0 °C to 60 °C) were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electronic diffraction (SAED). XRD results indicate that ACC is the only phase in all samples and SAED results verify the existence of ACC. SEM and TEM images display that the irregular nano-particles were aggregated into irregular porous micro-particles, the pores become smaller with the aging time increase and the reaction temperature elevating, and some relative regular particles (near ellipsoidal or spherical) were formed when system is aged for a long time (3 months) at a low temperature (20 °C) or for a short time (30 min) at a high temperature (60 °C). As-synthesized ACC can be persistent in vacuum or organic solvent for a long time (1 month) at room temperature.     

Synthesis of single-crystal GaN nanowires on Si(111) substrate by ammonification technology

GaN nanowires have been synthesized on Si(111) substrate through ammoniating Ga₂O₃/BN films under flowing ammonia atmosphere at the temperature of 900 °C. The as-synthesized GaN nanowires were characterized by X-ray diffraction (XRD), selected-area electron diffraction (SAED), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM) and transmission electron microscope (TEM). The results demonstrated that the nanowires are hexagonal wurtzite GaN and possess a smooth surface with diameters ranging from 40 to 100 nm and lengths up to several tens of micrometers. The growth mechanism of crystalline GaN nanowires is discussed briefly.     

Synthesis and characterization of nanoporous hydroxyapatite using cationic surfactants as templates

Nanoporous hydroxyapatite was synthesized utilizing cationic surfactants as templates. The effects of cetyltrimethylammonium bromide and reaction temperatures on the phase and morphology of HA were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The thermal stability of nanoporous structures was studied by XRD and thermal analyzers (TGA/DTA), while the pore structure of HA was observed using high resolution TEM. It was found that the pore size was about 1 nm, and the pore structure of HA was thermally stable up to 700 °C and the pore size did not change with reaction temperature and CTAB:PO₄^3? ratio. The possible formation mechanism of nanoporous structure was proposed.     

Optical properties of amorphous/crystalline ZnO nano-powder prepared by solid state reaction

This paper presents a simple and efficient method to prepare amorphous and crystalline ZnO nano-powders via thermal decomposition of the mixture of Zn(CH₃COO)₂·2H₂O and NaHCO₃. X-ray diffraction (XRD) pattern and transmission electron microscope (TEM) images indicated that thermal decomposition of the mixture at 160° C for 3 h, amorphous ZnO powder was obtained. Otherwise, temperature above 160°C, the amorphous ZnO would begin transform into crystalline. Photoluminescence (PL) spectra of amorphous ZnO revealed it had very strong UV emission, but its visible emission was barely observed. The UV intensity of amorphous ZnO was about 3 times of that of crystalline ZnO. This can be explained by quantum size effect.     

Preparation of copper coated carbon nanotubes by decomposition of Cu(II)acetylacetonate in hydrogen atmosphere

In this paper, copper coated carbon nanotubes (CNTs) was synthesized by decomposition of Cu(II) acetylacetonate (Cu(acac)₂) in hydrogen atmosphere at 300 °C. The thickness of the copper coating was in nanoscale according to scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images, and Raman spectra indicated that certain intermediate bonds were formed between copper and the template CNTs. The crystalline structure of copper and its growth orientation were determined by X-ray diffraction (XRD) and selected area electron diffraction (SAED). The copper coating on CNTs had a face-centered cubic structure and its growth orientation was parallel to planes. The method developed in this paper had the advantages of simplicity in both process control and experiment equipments, so that it might provide a possibility of large-scale production.     

Solvothermal synthesis of uniform hexagonal-phase ZnS nanorods using a single-source molecular precursor

Pure and uniform hexagonal-phase ZnS nanorods with quantum confinement effect were synthesized by solvothermal decomposition of an air-stable, easily obtained single-source molecular precursor (zinc diethyldithiocarbamate, Zn-(DDTC)₂) in hydrazine hydrate aqueous solutions at 150–200 °C, and characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and UV–vis absorption spectra. The possible formation mechanism of one-dimensional ZnS nanostructure in the present system was also briefly discussed.     

Characterization of Bi2S3 nanorods and nano-structured flowers prepared by a hydrothermal method

Bismuth sulfide nanorods and nano-structured flowers were synthesized by hydrothermal reaction of bismuth nitrate pentahydrate and thiourea solutions, containing 1 and 2 ml of 65% HNO₃, respectively. By using X-ray diffraction (XRD), selected area electron diffraction (SAED), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high resolution TEM (HRTEM), the products were specified as orthorhombic Bi₂S₃ in the shapes of nanorods and flower-like clusters of nanorods, with the growth of nanorods in the [001] direction. A diffraction pattern was also simulated, and was in good accordance with the SAED pattern obtained from the experiment.     

Characterization and synthesis of KTa0.1Nb0.9O3 particles via high temperature mixing method under hydrothermal conditions

KTa_0.1Nb_0.9O₃ (KTN) particles with an orthorhombic perovskite structure have been synthesized via a high temperature mixing method (HTMM) under hydrothermal conditions. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microcopy (HRTEM). The influence of alkaline concentration and solvent composition on the phase structure and morphology of the obtained powders was investigated. The results show that the well-crystallized KTN powders with sizes of 200–500 nm are successfully prepared at temperatures as low as 240 °C when the KOH concentration is 2.0 M and the isopropanol/water (I/W) volume ratio equals to 100/0.     

Morphological evolution in single-crystalline Bi2Te3 nanoparticles, nanosheets and nanotubes with different synthesis temperatures

A general surfactant-assisted wet chemical route has been developed for the synthesis of a variety of bismuth telluride (Bi₂Te₃) single-crystalline nanostructures with varied morphologies at different temperatures in which hydrazine hydrate plays as an important solvent. Bi₂Te₃ sheet grown nanoparticles, nanosheets and nanotubes have been synthesized by a simplest wet chemical route at 50, 70 and 100 °C within 4 h. Bi₂Te₃ sheet grown nanoparticles are obtained in agglomerate state and they are found with many wrinkles. Various types of Bi₂Te₃ nanotubes are also found which are tapered with one end open and the other closed. X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) pattern and energy dispersive X-ray (EDX) spectroscopy were employed to characterize the powder product. It is found that all nanoparticles, nanosheets and nanotubes are well-crystallized nanocrystals and morphologies of the powder products are greatly affected by different synthesis temperatures. The formation mechanisms of bismuth telluride nanostructures are also discussed.     

Structural study of Li<Subscript>2</Subscript>MnO<Subscript>3</Subscript> by electron microscopy

Detailed crystallographic data on high-quality Li₂MnO₃ material has been obtained using a combination of X-ray diffraction (XRD), selected-area electron diffraction (SAED), high-resolution electron microscopy (HREM), and 0.1 nm probe high-angle annular dark-field imaging (HAADF) in a scanning transmission electron microscope. A high-purity Li₂MnO₃ powder was annealed at 950 °C for 3 days to obtain predominantly defect-free grains which average size was 3.0 ± 1.5 μm. Rietveld refinement indicated that the C2/m spacegroup provided the best fit for the XRD data. Electron diffraction patterns obtained along various zone axes, on defect-free oxide particles, could be uniquely indexed to the monoclinic structure. HREM and HAADF images of defect-free grains were consistent with a Li–Mn–Mn– arrangement, i.e., lithium ordering in the transition metal planes. Low-magnification TEM images occasionally revealed stacking defects within oxide particles. HREM images of sample areas containing defects revealed a low density of stacking faults within the monoclinic sequence, resulting in a trigonal P3 ₁ 12 local arrangement.     

Fabrication and magnetic properties of NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanocrystalline nanotubes

Aligned NiFe₂O₄ polycrystalline nanotubes have been successfully fabricated inside the nanochannels of porous anodic aluminum oxide (AAO) templates by wetting chemical deposition. A mixture of Fe nitrate and Ni nitrate, which was thermally decomposed at no less than 400 °C, was used to yield NiFe₂O₄ tubes. By varying the deposition conditions and the parameters of the templates, we could tailor the lengths and the outer as well as the inner diameters of the tubes. Transmission electron microscopy (TEM) images reveal that the nanotubes are uniform and well isolated. X-ray diffraction (XRD) and selected area electron diffraction (SAED) demonstrate that the as-obtained nanotubes can be indexed to polycrystalline cubic spinel. The Mössbauer spectra show that the magnetic hyperfine field is reduced with the decrease of the metrical temperature as well as the decrease of the size of nanoparticles.     

On the transformations of the ψ-AlCuFe icosahedral phase

In the present investigation, different alloy compositions close to the ternary composition values, where the icosahedral phase in AlFeCu is obtained, have been studied. The specimens were obtained using a rapid solidification technique with subsequent thermal treatments of 600°C, 700°C, 800°C and 900°C. The obtained specimens were characterized with X-ray diffraction patterns (XRD) and transmission electron microscopy (TEM). The experimental results show different transformations of the icosahedral phase to crystalline phases between 800°C and 700°C .The cubic β-phase is a solid solution which regulates the formation and decomposition of the ψ-Al₆Cu₂Fe phase to different crystalline phases such as the tetragonal (Al₇Cu₂Fe) and monoclinic (Al₁₃Fe₄) phases.     

A facile one-step route to nanocrystalline TiB2 powders

Nanocrystalline titanium diboride (TiB₂) has been prepared by the reaction of TiCl₄ with NaBH₄ in the temperature range of 500–700 °C in an autoclave. X-ray powder diffraction (XRD) patterns can be indexed as hexagonal TiB₂ with the lattice constants of a=3.032 and c=3.229 Å. Transmission electron microscopy (TEM) image shows particle morphology, with average size of 15 nm for the powder obtained at 600 °C. Selected area electron diffraction (SAED) pattern confirms the prepared hexagonal TiB₂. The oxidation behavior of TiB₂ is studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA).     

Hydrothermal synthesis,characterization and luminescent properties of lanthanide-doped NaLaF<Subscript>4</Subscript> nanoparticles

Nanoparticles of sodium lanthanum (III) fluoride-doped and co-doped with Eu³⁺/Tb³⁺ were prepared by the hydrothermal method using citric acid as structure-directing agent. Structural aspects and optical properties of synthesized nanoparticles were studied by powder X-ray diffraction (XRPD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy-dispersive X-ray spectra (EDS), particle size by dynamic light scattering (DLS), Fourier transform infrared (FTIR) spectrum and photoluminescence (PL) techniques. Nanoparticles consist of well-crystallized hexagonal phase and the average crystallite size for undoped and doped-NaLaF₄ nanoparticles are in the range of 20–22 nm. TEM images show that nanoparticles have cylindrical shape and crystalline nature of nanoparticles was confirmed by SAED patterns. Down- conversion (DC) luminescent properties of doped NaLaF₄ were also investigated and impact of co-doping has been explored.     

Preparation of Li2B4O7 thin films by chemical solution decomposition method

Li₂B₄O₇ polycrystalline films on silica glass and Si(111) substrates were prepared by chemical solution decomposition(CSD) method. After spin coating, the wet film was dried at 200 °C, and then annealed at different temperatures to form polycrystalline Li₂B₄O₇ film. These annealed films were characterized by using X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), transmission electron microscope (TEM) and selective area electron diffraction (SAED). All these results show that the main component of the film is Li₂B₄O₇ crystalline phase and the average crystalline size of these films is in the range of 20-50 nm.     

Synthesis of CeB6 thin films by physical vapor deposition and their field emission investigations

High quality CeB₆ thin films have been obtained through direct evaporation of raw micron-sized CeB₆ powders at a pressure of 70 Pa. The X-ray diffraction (XRD), Raman spectrum, scanning electron microscope (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED) and the field-emission equipment were used to characterize the morphology, structure, composition and FE properties of the samples. The XRD and Raman spectrum analysis results show the as-prepared product is cubic phase CeB₆. The TEM, SAED and HRTEM analysis reveal that the samples are mixtures of thin films (polycrystalline) and small crystals (single crystallines aligned preferentially in the [1 1 0] direction). Compared to oxide nanostructures, field-emission measurements show that the CeB₆ films have better FE performance with turn-on field and threshold field of 12.93 V/μm and 14.86 V/μm, respectively.     

An analysis of evolution of grain size-lattice parameters dependence in nanocrystalline TiO2 anatase

Due to the specific properties of nanocrystalline materials in comparison with crystalline materials, it is essential to investigate their structural parameters like lattice parameters and grain sizes. We used the Rietveld method and refined electron powder data (recorded with selected area electron diffraction—SAED) on nanocrystalline (nc) TiO₂-anatase prepared by sol–gel route. We correlated refined lattice parameters with average grain size obtained from transmission electron microscopy (TEM) images. We give preliminary results on relative changes of lattice parameters a and c vs. the mean grain size in nc TiO₂-anatase.     

Microstructure and microchemistry of silicon particles formed during electrical-discharge machining

The structure and morphology of particles representing the byproduct of electrical-discharge machining (EDM) were analyzed using transmission electron microscopy (TEM). The EDM process involved high-efficiency and high-accuracy fine boring of a single-crystal silicon ingot by high-frequency electrical spark discharges. As the silver electrode advanced, spark-discharge-melted or vaporized small particles of the silicon workpiece were produced and the particles were flushed away and collected in deionized water. Standard TEM and analytical electron microscopy (AEM) observations were carried out. Bright-field (BF) images, diffraction, and energy-dispersive X-ray spectrometry (EDXS) data were obtained to completely characterize the EDM particles. BF images indicated the presence of large silicon particles decorated by smaller silver particles originating from the electrode as the byproducts of the EDM processing. Analysis of the particle-size distribution resulted in an average silicon particle size of about 500 nm decorated by smaller silver particles of an average size of about 65 nm. EDXS spectra depicted individual silicon and silver particles with characteristic peaks that identify the elements present. Selected-area electron diffraction (SAED) pattern confirmed the presence of crystalline silicon. Finally, a set of SAED patterns, EDXS profiles, and TEM images is included that fully describe the particles' chemistry, structure, and morphology, respectively.     

Transformation of onion-like carbon from nanodiamond by annealing

Onion-like carbon (OLC) was synthesized by annealing nanodiamond in low vacuum (1 Pa) at the temperatures from 500 to 11400°C. The high-resolution transmission electron microscope images, X-ray diffraction patterns and Raman spectra showed that, when the annealing temperatures were lower than 900°C, there was no OLC fabricated. The amorphous carbon and the nanodiamond coexisted. The graphitization started from the surfaces of the nanodiamond particles. When the annealing temperatures were higher than 900°C, the OLC was fabricated. At 900°C, OLC began appearing and the size of the OLC particles was smaller than 5 nm. At the annealing temperature of 1400°C all the nanodiamond particles were transformed into OLC. The OLC particles exhibited similarity to the original nanodiamond particles in shape. Based on these results, a mechanism for the OLC synthesis by the method of annealing in vacuum was provided.