The comparison of powder characteristics and physicochemical,mechanical and biological properties between nanostructure ceramics of hydroxyapatite and fluoridated hydroxyapatite

In this study, several fluorine-substituted hydroxyapatite ceramics with the general chemical formula Ca₅(PO₄)₃(OH)_1 ? xF_x (0 ≤ x ≤ 1), where x = 0.0 (hydroxyapatite; HA), x = 0.68 (fluorhydroxyapatite; FHA) and x = 0.97 (fluorapatite; FA) were prepared. The powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infra-red (FTIR), X-ray diffraction (XRD), F-selective electrode, atomic absorption spectroscopy (AAS) and EDTA titration analyses. The powders were uniaxially pressed and were formed as a disc shape. Subsequently, sinterability and thermal stability of synthesized powders were compared together. Also the effect simultaneously of fluoride content and temperature were examined on the lattice parameters and crystallites size of the obtained powders. Mechanical properties including hardness, elastic modulus and fracture toughness were measured using indentation. The in vitro dissolution studies of the samples were carried out at osteoclastic resorption conditions. Finally, the biocompatibility and cytotoxicity of the samples were carried out using osteoblast-like cells and L929 cell line, respectively. The obtained results showed that the thermal stability substantially is increased with increase incorporated fluoride into HA structure. Also it was found that the fluoride reduced the lattice parameters and crystallites size of HA. Finally, the in vitro dissolution studies results suggest that the fluoride substitutions in HA offer the ability to prepare HAs with different degrees of solubility.     

Structure and field emission properties of SnO2 nanowires

SnO₂ nanowires were fabricated using a simple and economical method of rapid heating SnO₂ and graphite powders at 850 °C in a flow of high-purity N₂ as carrier gas. Research by using X-ray diffraction (XRD) indicates that SnO₂ nanowires are primitive tetragonal in structure with the lattice constant a = b = 0.443 nm and c = 0.372 nm. Observations by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that SnO₂ is of nanowire structure. The selected area electron diffraction (SAED) shows that the nanowires are perfect single crystal structure. The Fourier transform infrared (FT-IR) exhibits the difference of nanostructure materials and general materials. The field emission (FE) properties had also been studied.     

In situ fabrication of carbon nanotube–MgAl2O4 nanocomposite powders through hydrogen-free CCVD

Carbon nanotube–MgAl₂O₄ composite powders were successfully prepared through solution combustion synthesis (SCS) followed by catalytic chemical vapor deposition (CCVD) of methane. Catalyst powders were synthesized starting with the stoichiometric ratios of metal nitrates and urea with a small amount of water and different Fe contents followed by subjecting the solution to heat. The obtained powders were placed in a silica tube to react with methane and form carbon nanotubes. It is noteworthy that no hydrogen was used throughout the whole process. Catalysts and composite powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The quality of products were evaluated by I_D/I_G ratio obtained from G and D bands intensities in Raman spectra of samples having 10 and 15 wt.% iron. The final product mostly comprised a mixture of single- and double-walled nanotubes on the catalyst containing 10 wt.% Fe, while no carbon product was formed on the catalyst with 5 wt.% Fe.     

Phase and morphology evolution of bismuth ferrites via hydrothermal reaction route

Phase-controlled synthesis of bismuth ferrites has been achieved via hydrothermal route by adjusting the KOH concentration. The as-prepared powders were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and selected area electron diffraction. The particle morphologies of the as-prepared powders evolve from nanoflakes, to self-assembled particles, and microparticles when the concentration of KOH was changed from 1.5 M, 2.5 M, to 3.5 M, and 5 M. Correspondingly, the main phase of the samples changed from orthorhombic Bi₂Fe₄O₉, both Bi₂Fe₄O₉ and BiFeO₃, to pure rhombohedral BiFeO₃. On the basis of these experiments, the phase formation and morphology evolution mechanism of the samples are discussed. Furthermore, the photocatalytic activity of the as-prepared samples was investigated by the photo-degradation of rhodamine-B solution.     

Hydrothermal synthesis and characterization of TiO2 nanostructures using LiOH as a solvent

In the present study, we performed hydrothermal method as a simple and efficient route for the synthesis of rutile TiO₂ nanostructures in various concentrations of lithium hydroxide solutions. TiO₂ nanopowders with average sizes of 15 and 23 nm were prepared using 4 M and 7 M LiOH solutions. X-ray diffraction analysis (XRD), transmission electron microscope (FEG-STEM), scanning electron microscopy (SEM), and Brunauer–Emmet–Teller (BET) analyses were used in order to characterize the obtained products and comparison of the morphology of the powders obtained in different concentrations of LiOH solvent. It was shown that alkali solution concentration has affected the crystallinity, agglomeration ratio, particle size and specific surface area of the obtained rutile phases.     

La0.5Sr0.5TiO3 nanopowders prepared by the hydrothermal method

La_0.5Sr_0.5TiO₃ nanopowders were prepared by the hydrothermal method. The influence of processing parameters, including KOH concentration, reaction temperature and reaction time on the obtained products were studied. The structure and morphology of the obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD results show that pure phase La_0.5Sr_0.5TiO₃ nanopowders can be successfully synthesized with 2 M KOH concentration at a low temperature of 220 °C for 24 h. In addition, the product has a plate-like shape with particle sizes in the range of 25–100 nm as estimated by TEM.     

Synthesis and characterization of thermally evaporated Cu2SnSe3 ternary semiconductor

Copper Tin Selenide (CuSnSe) powder was mechanically alloyed by high energy planetary ball milling, starting from elemental powders. Synthesis time and velocity have been optimized to produce Cu₂SnSe₃ materials. Thin films were prepared by thermal evaporation on Corning glass substrate at T_s = 300 °C. The structural, compositional, morphological and optical properties of the synthesized semiconductor have been analyzed by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), scanning electron microscopy (SEM) and transmission electron microscopy. The analyzed powder exhibited a cubic crystal structure, with the presence of Cu₂Se as a secondary phase. On the other hand, the deposited films showed a cubic Cu₂SnSe₃ ternary phase and extra peaks belonging to some binary compounds. Furthermore, optical measurements showed that the deposited layers have a relatively high absorption coefficient of 10⁵ cm⁻¹ and present a band gap of 0.94 eV.     

Anionic surfactant-assisted hydrothermal synthesis of high-aspect-ratio ZnO nanowires and their photoluminescence property

ZnO nanowires with high-aspect-ratio of up to ca. 600 were synthesized in a quaternary reverse microemulsion containing sodium dodecyl sulfate (SDS) / water / heptane / n-hexane via a hydrothermal method. SDS, as an anionic surfactant, plays an important role in the formation of morphologies. Subsequently, we studied lots of key influencing factors including the molar ratio (w) value of NaOH to Zn(OAc)₂, the reaction temperature, and the instance without the quaternary reverse microemulsion. The selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) reveal the single-crystal nature of the ZnO nanowires. The morphologies and crystalline structure of the as-obtained products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and powder X-ray diffraction (XRD), respectively. Through this route, we can obtain a mass of products and the method is both convenient and reproducible. Finally, we measured the photoluminescence (PL) spectra and found that the ZnO nanowires exhibited green-orange emission at 525 nm and short ultraviolet emission at 380 nm and the ZnO nanomaterials with different aspect ratio (length to diameter) (L / D) showed PL intensity disciplinary change. Aiming at this phenomenon, we propose a reasonable mechanism to explain the PL spectra of the ZnO nanomaterials in detail.     

An investigation of the synthesis,consolidation and mechanical behaviour of Al 6061 nanocomposites reinforced by TiC via mechanical alloying

Nanostructured Al 6061–x wt.% TiC (x = 0.5, 1.0, 1.5 and 2.0 wt.%) composites were synthesised by mechanical alloying with a milling time of 30 h. The milled powders were consolidated by cold uniaxial compaction followed by sintering at various temperatures (723, 798 and 873 K). The uniform distribution and dispersion of TiC particles in the Al 6061 matrix was confirmed by characterising these nanocomposite powders by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential thermal analysis (DTA) and transmission electron microscopy (TEM). The mechanical properties, specifically the green compressive strength and hardness, were tested. A maximum hardness of 1180 MPa was obtained for the Al 6061–2 wt.% TiC nanocomposite sintered at 873 K, which was approximately four times higher than that of the Al 6061 microcrystalline material. A maximum green compressive strength of 233 MPa was obtained when 2 wt.% TiC was added. The effect of reinforcement on the densification was studied and reported in terms of the relative density, sinterability, green compressive strength, compressibility and Vickers hardness of the nanocomposites. The compressibility curves of the developed nanocomposite powders were also plotted and investigated using the Heckel, Panelli and Ambrosio Filho and Ge equations.     

Preparation of nano-sized flower-like ZnO bunches by a direct precipitation method

In this work, nano-sized ZnO particles were prepared by a direct precipitation method with Zn(NO₃)₂·6H₂O and NH₃·H₂O as raw materials, and the impact of the synthesis process was studied. The optimal thermal calcined temperature of precursor precipitates of ZnO was obtained from the differential thermal analysis (DTA) and the thermal gravimetric analysis (TGA) curves. The purity, microstructure, morphology of the calcined ZnO powders were studied by X-ray diffraction (XRD), energy dispersive X-ray spectrum (EDS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The synthesized ZnO powders had a wurtzite structure with high purity. The final products were of flower-like shape and the nanorods which consisted of the flower-like ZnO bunches were 20–100 nm in diameter and 0.5–1 μm in length. The effect of process conditions on the morphology of ZnO was discussed.     

Effects of aluminum substitution on photocatalytic property of BiVO4 under visible light irradiation

Novel visible-light-driven Al/BiVO₄ photocatalysts were synthesized via a facile hydrothermal method for the first time. The samples were characterized by X-ray diffraction, N₂-sorption, UV–vis diffuse reflectance spectra, scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transformed infrared spectra and X-ray photoelectron spectroscopy. The photocatalytic activity of the samples was evaluated by the decomposition of methylene blue under visible light irradiation (400 nm < λ <580 nm) and was compared with that of single-phase BiVO₄. The results revealed that the introduction of Al can improve photocatalytic performance greatly and different concentration of Al resulted in different photocatalytic activity. The highest activity is obtained by the sample with a doping concentration of 12 at%. The reason for the enhanced photocatalytic activities of Al/BiVO₄ samples was also discussed in this paper.     

TEM,XRD and DSC analysis of thin films and foils of FeSiBNb alloys doped with Mn

The FINEMET based amorphous alloys in forms of thin films of 20 ÷ 40 nm thickness and 20 μm thick foils of Fe_73.5?xSi_13.5B₉Cu₁Nb₃Mn_x with Mn doping (x = 11 ÷ 15 at.%), as-quenched (a-q) and after annealing (a) were analyzed with transmission electron microscopy (TEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The structure and composition of the films differ from those of the foils, first of all in size of crystallites and the lattice constants.     

Preparation of nano-silver iodide powders and their efficiency as ice-nucleating agent in weather modification

Nano-meter-sized silver iodide (n-AgI) powders were prepared by precipitation method at room temperature. The size, structure and specific surface area of the n-AgI powders were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscope and Brunner–Emmett–Teller, respectively. The n-AgI powders obtained have an average particle size of ～90 nm, similar surface lattice structure with ice crystal (H₂O) and larger specific surface area than conventional micro-meter-sized silver iodide (m-AgI) powders. The cloud chamber experiment revealed that the n-AgI powders exhibit higher ice nucleation efficiency and higher threshold temperature value than conventional m-AgI powders.     

Fabrication of large-scale ultra-fine Cd-doped ZnO nanowires

We demonstrate bulk synthesis of highly crystal Cd-doped ZnO nanowires by using (Cd + Zn) powders at 600 °C. These mass ultra-fine ZnO nanowires with about 0%, 1%, 4% and 8% Cd so obtained have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), selected area electron diffraction (SAED) and high-resolution TEM (HRTEM). They have the uniform diameter of about 20 nm and several hundred microns in length. The growth of the as-synthesized nanowires is suggested for self-catalyzed vapor–liquid–solid.     

Microwave-induced combustion synthesis of Li0.5Fe2.5−xCrxO4 powder and their characterization

Li_0.5Fe_2.5−xCr_xO₄ (0 ≦ x ≦ 1.0) powders with small and uniformly sized particles were successfully synthesized by microwave-induced combustion, using lithium nitrate, iron nitrate, chromium nitrate, and carbohydrazide as the starting materials. The process takes only a few minutes to obtain as-received Cr-substituted lithium ferrite powders. The resultant powders annealed at 650 °C for 2 h and were investigated by thermogravimeter/differential thermal analyzer (TG/DTA), X-ray diffractometer (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and thermomagnetic analysis (TMA). The results revealed that the lattice constant decreases linearly with increasing of Cr content in Li_0.5Fe_2.5−xCr_xO₄ specimens. Moreover, the magnetic properties of Cr-substituted lithium ferrite were also strongly affected by Cr content. The saturation magnetization, remanent magnetization, and coercive force decrease monotonously with increasing of Cr content.     

Solution combustion synthesis of LiMn2O4 fine powders for lithium ion batteries

In this work, fine powders of spinel-type LiMn₂O₄ as cathode materials for lithium ion batteries (LIBs) were produced by a facile solution combustion synthesis using glycine as fuel and metal nitrates as oxidizers. Single phase of LiMn₂O₄ products were successfully prepared by SCS with a subsequent calcination treatment at 600–1000 °C. The structure and morphology of the powders were studied in detail by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The electrochemical properties were characterized by galvanostatic charge–discharge cycling and cyclic voltammetry. The crystallinity, morphology, and size of the products were greatly influenced by the calcination temperature. The sample calcined at 900 °C had good crystallinity and particle sizes between 500 and 1000 nm. It showed the best performance with an initial discharge capacity of 115.6 mAh g⁻¹ and a capacity retention of 93% after 50 cycles at a 1 C rate. In comparison, the LiMn₂O₄ sample prepared by the solid-state reaction showed a lower capacity of around 80 mAh g⁻¹.     

An improved method for preparation of SrTiO3 nanoparticles

SrTiO₃ nanoparticles were synthesized for the first time via a modified polymeric precursor method. The samples were characterized by thermogravimetry, X-ray diffraction (XRD), BET surface area, micro-Raman spectroscopy, field emission scanning and transmission electron microscopy (FE-SEM and FE-STEM), high-resolution transmission electron microscopy (HRTEM) and photoluminescence measurements. It is found that calcination atmosphere (air, nitrogen and oxygen) plays an important role of both crystal size and photolumiscence behavior of the SrTiO₃ nanocrystallites. Results show that the powders obtained in nitrogen/oxygen atmosphere possess controllable particles size of approximately 11 nm presenting the highest photoluminescence emission.     

Facile synthesis,characterization and photocatalytic activity of niobium carbide

Niobium carbide (NbC) powders were prepared via a novel route at 550 °C and 8 h, using metallic magnesium powders, niobium pentoxide (Nb₂O₅), and potassium acetate (CH₃COOK) as starting materials. The structure and morphology of the product were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that as-prepared product was crystallized in pure cubic NbC phase and the size of the sample was estimated to be around 120 nm. The Rietveld refinement of the XRD data gives the cell constant a = 4.4718 Å. According to the Scherrer formula, the real grain size was about 70 nm. The BET surface area of the sample was ca.29.3 m²/g. The grain size distribution of the sample was about 467 nm, which was characterized by N4 PLUS submicron Particle Size Analyzer. The cubic NbC powders exhibited photocatalytic activity in degradation of Rhodamine-B (RhB) under 300 W mercury lamp light irradiation.     

The effect of HNO3 on morphology,phase transformation,and luminescence properties of LaPO4:Eu3+ phosphors

LaPO₄:Eu³⁺ powders with different morphologies were hydrothermally constructed by adjusting the amount of HNO₃ without using a catalyst, surfactant, or template. The as-prepared products were characterized by photoluminescence spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution-transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), infrared (IR) spectra, and X-ray photoelectron spectroscopy. The SEM study revealed that the amount of HNO₃ played a crucial role in the morphology of the final products. The XRD results indicated that the as-prepared samples were in the monoclinic phase when 3 mL of HNO₃ was used. The HR-TEM micrographs and SAED results demonstrated that the prepared nanorods were single and crystalline in nature with HNO₃, and that they grew preferentially along the [0 1 2] direction. The emission spectra showed that the LaPO₄:Eu³⁺ samples had the strongest emission intensity when prepared with HNO₃.     

Magnetic and structural properties of nanostructured (Fe65Co35)100−xCrx (x = 0, 10) powders prepared by mechanical alloying process

This work focuses on the preparation of nanostructured (Fe₆₅Co₃₅)_100−xCr_x (x = 0, 10) powders by mechanical alloying. The powders are milled for different milling times (up to 90 h). Characterizations of the milled powders were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibratory sample magnetometer (VSM). It was observed that the formation of bcc-FeCo and bcc-FeCoCr phases were completely accomplished after 60 and 90 h of milling, respectively. The grain size decreases and the microstrain increases with increasing the milling time. In the initial stages of milling (up to 15 h) for the (Fe₆₅Co₃₅)₉₀Cr₁₀ powders, the saturation magnetization (M_s) decreased but further milling (up to 90 h) increased the M_s. However, the trend for coercivity was different and three stages were observed. An initial increasing stage (up to 15 h of milling), followed by a reducing middle stage (up to 60 h of milling) and then again an increasing final stage (up to 90 h milling). Besides, for the same milling time of 90 h, the addition of 10 at.% of Cr to Fe₆₅Co₃₅ powders leads to higher coercivity and lower saturation magnetization.