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ABSTRACT: One-dimensional SrSn(OH)6 nanowires were successfully synthesized through a rapid simple method—sonochemical synthesis at room temperature without using any templates or surfactants. The growth mechanism has been proposed, and the reaction conditions were carefully investigated. The experimental results revealed that both the ultrasound irradiation and the presence of Na2CO3 in the synthetic process had an impact on the fast formation of the SrSn(OH)6 nanowires. Moreover, a subsequent precipitation—hydrothermal treatment of SrSn(OH)6 nanowires—was conducted in ethanol at 180 °C for 8 h in order to improve their crystallinity and thermal stalibity. SrSnO3 nanorods were converted by calcination of the hydrothermally treated SrSn(OH)6 nanowires at 700 °C for 3 h in air. In particular, it was the first attempt to test the electrochemical properties of the SrSnO3 products as anode in a Li ion battery. The resulting SrSnO3 nanorods exhibited a better cyclability over 50 cycles with a reversible lithium storage capacity of 200 mA h g−1 than that of SrSnO3 nanoparticles.
12/2009;
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ABSTRACT: This paper describes a facile solvothermal method to synthesize self-assembled three-dimensional (3D) Ni2+-Fe3+ layered double hydroxides (LDHs). Flower-like Ni2+-Fe3+ LDHs constructed of thin nanopetals were obtained using ethylene glycol (EG) as a chelating reagent and urea as a hydrolysis agent. The reaction mechanism and self-assembly process are discussed. After calcinating the as-prepared LDHs at 450 degrees C in nitrogen gas, porous NiO/NiFe2O4 nanosheets were obtained. This work resulted in the development of a simple, cheap, and effective route for the fabrication of large area Ni2+-Fe3+ LDHs as well as porous NiO/NiFe2O4 nanosheets.
Nanotechnology 11/2009; 20(47):475603. · 3.98 Impact Factor
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ABSTRACT: CaSn(OH)(6) nanotubes were fabricated by sonochemical precipitation method at room temperature. A direct rolling process from nanosheets to nanotubes was expected for the synthesis of CaSn(OH)(6) nanotubes. The transient CaSn(OH)(6) nanosheets are formed as intermediates produced by the spontaneous self-assembly and transformation of amorphous colloid clusters. During the crystallization process of intermediate nanosheets, the relaxation of surface strain in the nanosheet interfaces can induce the nanosheets to roll up to form nanotubes under ultrasonic conditions. In this synthesis, the addition of Na(2)CO(3) seems to play an important role in the formation, size, and shape control of the nanotubes. Investigations into the stability performance of the nanotubes indicate that the morphologies are very sensitive to pH and temperature. The method suggests a general strategy for the design and fabrication of functional single-crystalline nanotubes through an intermediate nanosheet rolling process. The in vitro fabrication of such single crystal nanotubes could shed light on fundamental mechanisms for closed hollow nanostructures. Furthermore, nanotubes produced in high yield and at low cost are envisioned to have applications in areas ranging from medicine to pharmaceuticals through to materials science.
Journal of Colloid and Interface Science 05/2009; 334(2):202-7. · 3.07 Impact Factor
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ABSTRACT: Nickel hydroxyl sulfate (Ni(SO4)0.3(OH)1.4) nanobelts were obtained via a simple template-free hydrothermal reaction. The structural evolution of Ni(SO4)0.3(OH)1.4 nanobelts during ex situ heat treatment and in situ electron irradiation are investigated using transmission electron microscopy (TEM) techniques mainly including bright-field imaging, selected-area electron diffraction combined with kinematic simulations, and high-resolution TEM. The transformation from Ni(SO4)0.3(OH)1.4 to NiO can be observed in both ex situ and in situ experiments. Based on the TEM results, the structural evolution is clarified and the preliminary structural framework of Ni(SO4)0.3(OH)1.4 is proposed. This structural evolution also provides an excellent approach for large-scale production and/or modification of NiO nanoparticles.
12/2008;
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ABSTRACT: Low-dimensional single-crystalline CdCO3 nanostructures such as nanowires, nanobelts, nanorolls, and one-dimensional (1D) hierarchical structures have been synthesized through a convenient, low-temperature hydrothermal method, and the products have been characterized by X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, and selected area electronic diffraction. The influences of ammonia concentration, reaction time, and temperature on the morphologies of CdCO3 have been investigated. In addition, these low-dimensional nanostructures can be transformed into oriented CdO nanoporous structures through heat treatment processing, and the corresponding shapes can be preserved completely.
06/2008;
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ABSTRACT: Chemically ordered FePt nanoparticles were obtained by high temperature annealing a mixture of FePt particles with NaCl. After the NaCl was removed with de-ionized water, the transformed FePt nanoparticles were redispersed in cyclohexanone. X-ray diffraction patterns clearly show the L10 phase. Scherrer analysis indicates that the average particle size is about 8 nm, which is close to the transmission electron microscopy (TEM) statistical results. The coercivity ranges from 16 kOe to more than 34 kOe from room temperature down to 10 K. High resolution TEM images reveal that most of the FePt particles were fully transformed into the L10 phase, except for a small fraction of particles which were partially chemically ordered. Nano-energy dispersive spectroscopy measurements on the individual particles show that the composition of the fully transformed particles is close to 50/50, while the composition of the partially transformed particles is far from equiatomic. TEM images and electron diffraction patterns indicate c-axis alignment for a monolayer of L10 FePt particles formed by drying a dilute dispersion on copper grids under a magnetic field. For thick samples dried under a magnetic field, the degree of easy axis alignment is not as high as predicted due to strong interactions between particles.
Journal of Applied Physics 05/2007; 101(9):09J113-09J113-3. · 2.17 Impact Factor
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ABSTRACT: Chemically synthesized FePt nanoparticles were coated with nonmagnetic SiO2 and MnO shells by sol-gel and polyol processes. TEM images show that the FePt/SiO2 nanoparticles exhibit a thick spherical shell. The size and morphology of the MnO shell can be controlled by changing the reaction temperature, the molar ratio of surfactants/Mn(acac)2, and/or the concentration of precursor. The morphology of the MnO shell can be either spherical-like or cubic-like, depending on whether the molar ratio of surfactants/Mn(acac)2 is less than or larger than 2. From XRD measurements, the spherical core/shell nanoparticles exhibit 3D random crystallographic orientation, while the cubic core/shell nanoparticles prefer (200) texture. The magnetic moment of FePt particles can be enhanced by coating with SiO2 and MnO shells. Furthermore, the agglomeration of FePt particles upon the thermal annealing can be significantly inhibited with SiO2 and MnO shells.
Journal of Nanoscience and Nanotechnology 02/2007; 7(1):350-5. · 1.56 Impact Factor
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ABSTRACT: Uniform crystalline CdSnO3.3H2O nanocubes with a 28-35 nm edge length have been obtained via the ion-exchange reaction of Na2Sn(OH)6 in a CdSO4 aqueous solution, assisted by ultrasonic treatment. Precursor Na2Sn(OH)6 crystals were prepared via hydrothermal treatment in an ethanol/water solution. The formation of CdSnO3.3H2O nanocubes resulted from the strain during the ion-exchange process. The influences of reaction conditions, such as ion-exchange (ultrasonic treatment) duration, solvent constitutes, surfactant, and pH on the formation of CdSnO3.3H2O crystals were described. Crystalline CdSnO3 and Cd2SnO4 have been obtained by thermal treatment at 300 and 500 degrees C, respectively, for 5 h under an inert-gas protecting condition using CdSnO3.3H2O nanocubes as the precursor. The cube shape of CdSnO3.3H2O was sustained after thermal decomposition to CdSnO3.
Inorganic Chemistry 01/2007; 45(26):10774-9. · 4.60 Impact Factor
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ABSTRACT: Chemically synthesized FePt nanoparticles were coated with nonmagnetic SiO2 and MnO shells by sol-gel and polyol processes. TEM images show that the FePt/SiO2 nanoparticles exhibit a thick spherical shell. The size and morphology of the MnO shell can be controlled by changing the reaction temperature, the molar ratio of surfactants/Mn(acac)2, and/or the concentration of precursor. The morphology of the MnO shell can be either spherical-like or cubic-like, depending on whether the molar ratio of surfactants/Mn(acac)2 is less than or larger than 2. From XRD measurements, the spherical core/shell nanoparticles exhibit 3D random crystallographic orientation, while the cubic core/shell nanoparticles prefer (200) texture. The magnetic moment of FePt particles can be enhanced by coating with SiO2 and MnO shells. Furthermore, the agglomeration of FePt particles upon the thermal annealing can be significantly inhibited with SiO2 and MnO shells.
Journal of Nanoscience and Nanotechnology 12/2006; 7(1):350-355. · 1.56 Impact Factor
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ABSTRACT: Uniform crystalline CdSnO3·3H2O nanocubes with a 28−35 nm edge length have been obtained via the ion-exchange reaction of Na2Sn(OH)6 in a CdSO4 aqueous solution, assisted by ultrasonic treatment. Precursor Na2Sn(OH)6 crystals were prepared via hydrothermal treatment in an ethanol/water solution. The formation of CdSnO3·3H2O nanocubes resulted from the strain during the ion-exchange process. The influences of reaction conditions, such as ion-exchange (ultrasonic treatment) duration, solvent constitutes, surfactant, and pH on the formation of CdSnO3·3H2O crystals were described. Crystalline CdSnO3 and Cd2SnO4 have been obtained by thermal treatment at 300 and 500 °C, respectively, for 5 h under an inert-gas protecting condition using CdSnO3·3H2O nanocubes as the precursor. The cube shape of CdSnO3·3H2O was sustained after thermal decomposition to CdSnO3.
12/2006;
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ABSTRACT: Nanobelts of nickel hydroxyl sulfate have been prepared on a large scale via a simple template-free hydrothermal reaction on the basis of a complex [Ni(NH(3))(6)](2+) formed with Ni(2+) and ammonia in an ethanol-water solution. The as-synthesized nanobelts were single crystals, with several tens of microns in length and 50-150 nm in width. The nanobelts were enclosed by top surfaces (100) and side surfaces (001) and their growth direction was parallel to [010]. The function of aqueous ammonia and ethanol was discussed. Furthermore, nanostructures of a mixture of crystralline NiO and amorphous nickel sulfate with various morphologies, such as nanobelts, porous nanobelts, and nanoparticles, were obtained by the thermal treatment of the as-synthesized Ni(SO(4))(0.3)(OH)(1.4) nanobelts at different temperatures.
Nanotechnology 11/2006; 17(22):5686-90. · 3.98 Impact Factor
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ABSTRACT: Recent studies have shown a strong correlation between grain growth and chemical ordering in chemically synthesized FePt nanoparticles. In order to study this effect, we have prepared a series of samples in which 3.5 nm FePt nanoparticles are dispersed in a matrix of Cu nanoparticles. The samples were annealed at 600 degrees C and at 800 degrees C. Grain size was determined by XRD Scherrer analysis and time-dependent remanent coercivity measurements were made to determine the intrinsic remanent coercivity, Hcr0. For samples annealed at 600 degrees C, Hcr0 increases strongly with grain size up to approximately 5 nm and increases weakly with additional grain growth. By contrast, after annealing at 800 degrees C, Hcr0 appears nearly independent of grain size. The results suggest that isolated 3.5 nm FePt nanoparticles can be weakly ordered when annealed at 600 degrees C and sintering is necessary for significant chemical ordering.
Journal of Nanoscience and Nanotechnology 08/2006; 6(7):2147-50. · 1.56 Impact Factor
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ABSTRACT: The disordered face-centered-cubic A1 to the chemical ordered face-centered-tetragonal L10 phase transformation of chemically synthesized magnetic FePt nanoparticles has been studied in the millisecond regime using
a pulsed high-density plasma arc light source. Under select annealing conditions, relatively high magnetic coercivities (Hc)
and anisotropies (Hk) of FePt nanoparticles were obtained with the millisecond pulse processing without significant sintering
of the nanoparticles.
JOM: the journal of the Minerals, Metals & Materials Society 05/2006; 58(6):43-45. · 1.42 Impact Factor
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ABSTRACT: FePt and [FePt]95Au5 nanoparticles with an average size of about 4 nm were chemically synthesized and spin coated onto silicon substrates. Samples were subsequently thermally annealed at temperatures ranging from 250 to 500 °C for 30 min. Three-dimensional structural characterization was carried out with small-angle neutron scattering (SANS) and small-angle x-ray diffraction (SAXRD) measurements. For both FePt and [FePt]95Au5 particles before annealing, SANS measurements gave an in-plane coherence length parameter a = 7.3 nm, while SAXRD measurements gave a perpendicular coherence length parameter c = 12.0 nm. The ratio of c/a is about 1.64, indicating the as-made particle array has a hexagonal close-packed superstructure. For both FePt and FePtAu nanoparticles, the diffraction peaks shifted to higher angles and broadened with increasing annealing temperature. This effect corresponds to a shrinking of the nanoparticle array, followed by agglomeration and sintering of the nanoparticles, resulting in the eventual loss of positional order with increasing annealing temperature. The effect is more pronounced for FePtAu than for FePt. Dynamic coercivity measurements show that the FePtAu nanoparticles have both higher intrinsic coercivity and higher switching volume at the same annealing temperature. These results are consistent with previous studies that show that additive Au both lowers the chemical ordering temperature and promotes sintering.
Journal of Applied Physics 04/2006; 99(8):08N704-08N704-3. · 2.17 Impact Factor
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ABSTRACT: Partially ordered FePtAu nanoparticles with size around 8 nm were prepared by the simultaneous decomposition of iron pentacarbonyl and reduction of gold acetate and platinum acetylacetonate. The high boiling point chemical, hexadecylamine, was used as a solvent, and 1-adamantanecarboxylic acid was used as a stabilizer. The final temperature was controlled between 300°C-360°C during synthesis, where disordered FePt particles could be partially transformed into the ordered L1<sub>0</sub> phase. A nonmagnetic mechanical stirrer was used in order to avoid agglomeration of the fct-FePt particles during synthesis. XRD patterns of as-made samples showed weak superlattice peaks, indicating partial chemical ordering of the FePtAu particles. The coercivities of partially transformed as-made particles vary from a few hundred oersteds to a few thousand oersteds, depending on the concentration of gold additive and the temperature of synthesis. Dynamic coercivity measurements yield thermal stability factors and switching volumes that are slightly higher than would be expected for noninteracting particles.
IEEE Transactions on Magnetics 11/2005; · 1.36 Impact Factor
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ABSTRACT: Partially ordered Fe53Pt47 nanoparticles with size around 8 nm were prepared by the simultaneous decomposition of iron pentacarbonyl and platinum acetylacetonate. The high boiling point chemical, hexadecylamine, was used as a solvent, and 1-adamantanecarboxylic acid was used as a stabilizer. The reflux temperature of the solution could exceed 360 °C, where disordered FePt particles could be partially transformed into the ordered L10 phase. A nonmagnetic mechanical stirrer was used in order to avoid agglomeration of the fct-FePt particles during synthesis. The particles were dispersed in toluene and films of the particles were cast onto silicon wafers from the solution. X-ray diffraction patterns of as-made samples showed weak superlattice peaks, indicating partial chemical ordering of the Fe53Pt47 particles. The room-temperature hysteresis loop of the as-made sample reveals a small coercivity ( ∼ 600 Oe) because of thermal fluctuations; however, the loop is wide open and hard to saturate. The remanence coercivity from the dcd curve is about 2.5 kOe, which is four times larger than the hysteresis coercivity. The large remanent to hysteresis coercivity ratio and the shapes of the hysteresis loop and dcd curve suggest a broad distribution of anisotropies in the partially ordered particles. By coating the ordered nanoparticles with a polymer binder, the easy axis of the particles could be aligned under an external field.
Journal of Applied Physics 05/2005; 97(10):10J318-10J318-3. · 2.17 Impact Factor
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ABSTRACT: There is growing evidence that FePt nanoparticles become increasingly difficult to chemically order as the size approaches a few nanometers. We have studied the chemical ordering of FePt and FePtAu nanoparticle arrays as a function of particle size. Monodisperse Fe49Pt51 and Fe48Pt44Au8 nanoparticles with a size about 6 nm were synthesized by the simultaneous decomposition of iron pentacarbonyl and reduction of platinum acetylacetonate and gold (III) acetate in a mixture of phenyl ether and hexadecylamine (HDA), with 1-adamantanecarboxylic acid and HDA as stabilizers. The nanoparticles were dispersed in toluene, films of the particles were cast onto silicon wafers from the dispersion, and the films were annealed in a tube furnace with flowing Ar+5% H2. The magnetic anisotropy and switching volumes were determined from time- and temperature-dependent coercivity measurements. By comparing with 3‐nm FePt and FePtAu nanoparticles of comparable composition, the phase transformation is easier for the larger particles. Under the same annealing conditions, the larger particles have higher anisotropy and order parameter. Additive Au is very effective in enhancing the chemical ordering in both small and large particles, with x-ray diffraction superlattice peaks appearing after annealing at 350 °C. Dynamic remnant coercivity measurements and magnetic switching volumes suggest particle aggregation at the higher annealing temperatures in both small and large particles.
Journal of Applied Physics 05/2005; 97(10):10J310-10J310-3. · 2.17 Impact Factor
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ABSTRACT: Partially ordered Fe53Pt47 nanoparticles with size around 8 nm were prepared by the simultaneous decomposition of iron pentacarbonyl and platinum acetylacetonate. The high boiling point chemical, hexadecylamine, was used as a solvent, and 1-adamantanecarboxylic acid was used as a stabilizer. X-ray diffraction measurements reveal that as-made FePt particles were partially transformed into the ordered L10 phase with some weak superlattice peaks. The room-temperature hysteresis loop and remanence curve suggest a broad distribution of anisotropies in the partially ordered particles. By coating the partially ordered FePt nanoparticles with a polyvinylchloride polymer binder, the particles could be re-dispersed in cyclohexanone. Furthermore, the easy axis of the particles coated with the polyvinylchloride polymer binder could be aligned under an external field. Easy axis alignment was confirmed from both alternating gradient magnetometer and x-ray diffraction measurements.
Applied Physics Letters 01/2005; 86(6):062503-062503-3. · 3.84 Impact Factor
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ABSTRACT: Fe <sub>54</sub> Pd <sub>46</sub> nanoparticles were prepared by the simultaneous chemical reduction of palladium acetylacetonate and iron chloride. The particle size can be tunable from 2 to 10 nm by controlling the amount of surfactants. Similarly, Fe <sub>50</sub> Pd <sub>x</sub> Pt <sub>50-x</sub> (x=8, 15, 25) nanoparticles were prepared by the simultaneous reduction of palladium acetylacetonate, platinum acetylacetonate, and iron chloride. The average diameter for the Fe <sub>50</sub> Pd <sub>x</sub> Pt <sub>50-x</sub> particles was always 3.5 nm and independent of the amount of surfactants. Films of the particles were cast onto silicon wafers from hydrocarbon dispersion. The coercivity of Fe <sub>54</sub> Pd <sub>46</sub> nanoparticles increases with annealing temperature up to 550 ° C , indicating fcc to fct phase transition. After further increasing the annealing temperature, the coercivity of the Fe <sub>54</sub> Pd <sub>46</sub> nanoparticles decreased, suggesting the formation of a soft magnetic phase. This new phase ( Fe <sub>3</sub> Pd ) was confirmed from x-ray diffraction measurements. For Fe <sub>50</sub> Pd <sub>x</sub> Pt <sub>50-x</sub> nanoparticles, the coercivity increases to more than 10 kOe with annealing temperature up to 650 ° C (x=8). With increasing Pd content, the coercivity of the Fe <sub>50</sub> Pd <sub>x</sub> Pt <sub>50-x</sub> nanoparticles decreased, as expected since the anisotropy energy -
of bulk FePd material is only one third of that of bulk FePt. © 2004 American Institute of Physics.
Journal of Applied Physics 07/2004; · 2.17 Impact Factor
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ABSTRACT: [FePt]<sub>1-x</sub>Au<sub>x</sub> nanoparticles were prepared by the simultaneous polyol reduction of platinum acetylacetonate and gold acetate and the thermal decomposition of iron pentacarbonyl, giving 3.5-nm-diameter FePt particles with gold atoms substituted in the lattices. The addition of gold promoted the face-centered cubic to tetragonal phase transition, thereby reducing the temperature required for this transition by more than 150°C compared with FePt nanoparticles with no additives. This effect is even more significant than adding silver to FePt nanoparticles. For a given annealing temperature, the coercivity increases with the content of gold up to 24%, above which the coercivity starts to decrease. The mechanism for the chemical ordering acceleration may relate to the defect and strains introduced by gold atoms. Upon annealing, gold atoms leave the FePt lattice, leaving lattice vacancies that increase the mobility of the FePt atoms to rearrangement. Dynamic coercivity measurements yield thermal stability factors that are slightly higher than would be expected for noninteracting particles.
IEEE Transactions on Magnetics 10/2003; · 1.36 Impact Factor
