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With the increasing demand for composites of multifunctional and integrated performance, graphene-based nanocomposites have been attracting increasing attention in biomedical applications because of their outstanding physicochemical... more
With the increasing demand for composites of multifunctional and integrated performance, graphene-based nanocomposites have been attracting increasing attention in biomedical applications because of their outstanding physicochemical properties and biocompatibility. High product yields and dispersion of graphene in the preparation process of graphene-based nanocomposites have long been a challenge. Further, the mechanical properties and biosafety of final nanocomposites are very important for real usage in biomedical applications. Here, we presented a novel high-throughput method of graphene on mechanical exfoliation in a natural honey medium, and a yield of ∼91% of graphene nanoflakes can be easily achieved with 97.76% of single-layer graphenes. The mechanically exfoliated graphene (MEG) can be well-dispersed in the poly(vinyl alcohol) (PVA) matrix. The PVA/MEG nanocomposite fibers are obtained by gel spinning and stretched 20 times. As a candidate for monofilament sutures, the PVA/...
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Scalable synthesis of accordion-like graphene via low temperature (below 170 °C) thermal expansion exfoliation of alkylated graphite oxide without any auxiliary equipment.
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Pd nanoparticles of 6–10nm in size have been synthesized by formalin reduction method and incorporated into mesoporous SBA-15 silica during hydrothermal synthesis. Characterizations of the Pd nanoparticles encapsulated in mesoporous... more
Pd nanoparticles of 6–10nm in size have been synthesized by formalin reduction method and incorporated into mesoporous SBA-15 silica during hydrothermal synthesis. Characterizations of the Pd nanoparticles encapsulated in mesoporous silica (Pd/SBA-15) reveal that the Pd nanoparticles in the range of 6–10nm are encapsulated within the surfactant micelles during mesoporous silica formation and well dispersed within the mesoporous SBA-15 channels.
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ABSTRACT We studied the effects of Fe addition on the thermal stability and hardness of (Zr46Cu39.2Ag7.8Al7)100−yFey (y = 0–7) bulk metallic glasses (BMGs). Both the supercooled liquid region (ΔTx) width and crystallization temperature of... more
ABSTRACT We studied the effects of Fe addition on the thermal stability and hardness of (Zr46Cu39.2Ag7.8Al7)100−yFey (y = 0–7) bulk metallic glasses (BMGs). Both the supercooled liquid region (ΔTx) width and crystallization temperature of the (Zr46Cu39.2Ag7.8Al7)100−yFey BMGs increase with Fe addition; and the largest ΔTx of 114 K is achieved at y = 4. The average free volume decreases with increasing Fe content. The hardness increases with increasing Fe content, which may result from the decrease in free volume and the precipitation of nanocrystalline phases from glassy matrix due to Fe addition.
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Bayerite [α-Al(OH)3] was ground for 2h and its structure change was characterized. Soft grinding reduces the grain size of bayerite, causes a lattice distortion in bayerite, and accelerates the phase transition from bayerite to the stable... more
Bayerite [α-Al(OH)3] was ground for 2h and its structure change was characterized. Soft grinding reduces the grain size of bayerite, causes a lattice distortion in bayerite, and accelerates the phase transition from bayerite to the stable phases. With addition of α-Al2O3 seeds, calcining the ground bayerite at 300°C leads to the onset of the α-Al2O3 formation. The onset temperature and
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ABSTRACT γ-Al2O3 nanoparticles with a porous structure and spherical shape, agglomerated from finer crystallites, were synthesized via a glycothermal route by using sodium oleate as surfactant and template. Disperse and spherical aluminum... more
ABSTRACT γ-Al2O3 nanoparticles with a porous structure and spherical shape, agglomerated from finer crystallites, were synthesized via a glycothermal route by using sodium oleate as surfactant and template. Disperse and spherical aluminum hydroxide nanoparticles with an average particle size of 77 nm were prepared first by a glycothermal method. After calcining the aluminum hydroxide nanoparticles at 900 °C and eliminating the organic template, disperse, spherical, and porous γ-Al2O3 nanoparticles with an average particle size of 50 nm, agglomerated from 2–10 nm crystalline particles, were obtained. The pore sizes in the porous γ-Al2O3 nanoparticles range between 1.8 and 10 nm.
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ABSTRACT A novel non-aqueous route for the preparation of aluminum hydroxide nanoparticles, from aluminum nitrate nonahydrate and anhydrous sodium acetate in ethylene glycol (EG), has been developed. Aluminum hydroxide nanoparticles... more
ABSTRACT A novel non-aqueous route for the preparation of aluminum hydroxide nanoparticles, from aluminum nitrate nonahydrate and anhydrous sodium acetate in ethylene glycol (EG), has been developed. Aluminum hydroxide nanoparticles modified with ethyl acetoacetate (EAA) as surface modification agent were prepared by chemical surface-modification method. The surface-modified wet aluminum hydroxide nanoparticles can be well dispersed in n-hexane when using the appropriate ligand concentration. EAA is chemically attached to the surface of the aluminum hydroxide nanoparticles. The mass percentage of the chemisorbed EAA on the modified aluminum hydroxide nanoparticles is 2.4%. The phase transformation temperature of the surface-modified aluminum hydroxide nanoparticles to the stable α-alumina rises about 50 °C compared with that of the as-prepared aluminum hydroxide nanoparticles without surface modification. The EAA-surface modified aluminum hydroxide nanoparticles lead to fine and weak-agglomerated alumina nanoparticles after calcination.
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Following the report of a single-exponential activation behavior behind the super-Arrhenius structural relaxation of glass-forming liquids in our preceding paper, we find that the non-exponentiality in the structural relaxation of... more
Following the report of a single-exponential activation behavior behind the super-Arrhenius structural relaxation of glass-forming liquids in our preceding paper, we find that the non-exponentiality in the structural relaxation of glass-forming liquids is straightforwardly determined by the relaxation time, and could be calculated from the measured relaxation data. Comparisons between the calculated and measured non-exponentialities for typical glass-forming liquids, from fragile to intermediate, convincingly support the present analysis. Hence the origin of the non-exponentiality and its correlation with liquid fragility become clearer.
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The reported relaxation time for several typical glass-forming liquids was analyzed by using a kinetic model for liquids which invoked a new kind of atomic cooperativity--thermodynamic cooperativity. The broadly studied... more
The reported relaxation time for several typical glass-forming liquids was analyzed by using a kinetic model for liquids which invoked a new kind of atomic cooperativity--thermodynamic cooperativity. The broadly studied 'cooperative length' was recognized as the kinetic cooperativity. Both cooperativities were conveniently quantified from the measured relaxation data. A single-exponential activation behavior was uncovered behind the super-Arrhenius relaxations for the liquids investigated. Hence the mesostructure of these liquids and the atomic mechanism of the glass transition became clearer.
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ABSTRACT Single-crystal alpha alumina (α-Al2O3) platelets were synthesized by calcining a powder mixture of bayerite (α-Al(OH)3) and potassium sulfate (K2SO4) at 900°C. The crystalline phase evolutions and morphologies of the samples were... more
ABSTRACT Single-crystal alpha alumina (α-Al2O3) platelets were synthesized by calcining a powder mixture of bayerite (α-Al(OH)3) and potassium sulfate (K2SO4) at 900°C. The crystalline phase evolutions and morphologies of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The synthesized samples mainly consisted of single-crystal α-Al2O3 platelets with a diameter of 0.5–1.5 μm and a thickness of 50–150 nm. Moreover, with 3, 5, and 8 wt% (referred to the obtained alumina) α-Al2O3 seeds adding into the powder mixture of bayerite and potassium sulfate, the average diameter of α-Al2O3 platelets can be reduced to 450, 240, and 220 nm, respectively. It is found that the sequence of the phase transformation is the bayerite (α-Al(OH)3) → boehmite (γ-AlOOH) → γ-Al2O3 → α-Al2O3. Further analysis indicated that K2SO4 can promote the phase transformation from γ-Al2O3 to α-Al2O3 and the formation of single-crystal α-Al2O3 platelets might be attributed to the liquid phase K3Al(SO4)3.
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Perovskite-type complex ferrite Re0.67Ca0.33FeO3 (Re=La, Sm, Gd) nanoparticles of nearly the same particle size were prepared using sol–gel method. The influence of rare-earth ions on weak ferromagnetism in the Re0.67Ca0.33FeO3... more
Perovskite-type complex ferrite Re0.67Ca0.33FeO3 (Re=La, Sm, Gd) nanoparticles of nearly the same particle size were prepared using sol–gel method. The influence of rare-earth ions on weak ferromagnetism in the Re0.67Ca0.33FeO3 nanoparticles has been studied. The spontaneous magnetization Ms of the Sm0.67Ca0.33FeO3 nanoparticles is greater than that of Gd0.67Ca0.33FeO3 nanoparticles; and Ms of Gd0.67Ca0.33FeO3 nanoparticles is greater than that of La0.67Ca0.33FeO3
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The magnetic and microwave properties of Ni nanospheres and conical nanorods have been investigated through experimental and theoretical methods. Ni nanospheres and conical nanorods have the same crystal structure and close particle size,... more
The magnetic and microwave properties of Ni nanospheres and conical nanorods have been investigated through experimental and theoretical methods. Ni nanospheres and conical nanorods have the same crystal structure and close particle size, whereas the remanence ratio, coercivity, dynamic permeability and microwave absorbing properties show great dependence on their shape. Ni conical nanorods self-assembled into urchin-like structure have higher natural resonance frequency due to the large shape anisotropy compared to the Ni nanospheres. Supposing random spatial distribution of magnetic easy axes and using the Landau-Lifshitz-Gilbert equation associated with the Bruggeman's effective medium theory, we simulate the complex permeability of Ni nanoparticles, which agrees well with the experimental results.
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Highly ordered mesoporous titania-silica (TiO2-SiO2) composite thin films have been prepared by spin-coating technique using poly(alkaline oxide) triblock copolymers EO20PO70EO20 (P123) as structure-directing agent. Low-angle X-ray... more
Highly ordered mesoporous titania-silica (TiO2-SiO2) composite thin films have been prepared by spin-coating technique using poly(alkaline oxide) triblock copolymers EO20PO70EO20 (P123) as structure-directing agent. Low-angle X-ray diffraction analysis shows that the mesoporous composite thin films remain a long range periodic ordered structure even if the TiO2/SiO2 ratio in the thin films is as high as 80%. Wide-angle X-ray diffraction analysis reveals that the average grain size of TiO2 increases from 2.2 to 5.1 nm as the TiO2/SiO2 ratio increases from 20% to 80%. The crystal structure of TiO2 is identified to be the anatase phase. Transmission electron microscopy observations confirm that the mesoporous titania-silica composite thin films have a hexagonally ordered pore array nanostructure. Ultraviolet-visible absorption spectra give the evidence that the TiO2 nanocrystals as well as the four-coordinate Ti co-exist in the silica matrix. The semiconductor TiO2 nanocrystals in the silica matrix have an obvious blue shift phenomenon of the absorption edge. As the average TiO2 grain size increases from 2.2 to 5.1 nm, the band gap of the TiO2 nanocrystals in the mesoporous titania-silica composite thin films decreases from 3.9 to 3.45 eV.
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ABSTRACT Under refluxing conditions in alcoholic solution, nickel sea-urchin-like particles and nickel spherical nanoparticles self-assembled into nanochains have been synthesized by a simple wet chemical method in which aqueous hydrazine... more
ABSTRACT Under refluxing conditions in alcoholic solution, nickel sea-urchin-like particles and nickel spherical nanoparticles self-assembled into nanochains have been synthesized by a simple wet chemical method in which aqueous hydrazine (N2H4·H2O) was used as reducing reagent and sodium hydroxide (NaOH) was used as alkaline reagent. The structure and morphology of the final nanoparticle products are controlled by the adding sequence of N2H4·H2O, NiCl2, and NaOH solutions. The sea-urchin-like Ni particles and the spherical Ni nanoparticles self-assembled into nanochains were obtained by varying the adding sequence of these reactants. In addition, a relatively higher temperature is advantageous to the formation of both sea-urchin-like and chain-like Ni nanoparticles. Finally, the dependence of the magnetic parameters such as coercivity (Hc) and squareness (Mγ/Ms) on the morphology of as-prepared Ni nanocrystals will be discussed.
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Nanocomposite powders of magnetic cobalt nanoparticles dispersed by nonmagnetic Al2O3 particles have been prepared by planetary ball milling. Ball milling of the CoO and Al mixture powder after a certain milling duration reduces CoO to... more
Nanocomposite powders of magnetic cobalt nanoparticles dispersed by nonmagnetic Al2O3 particles have been prepared by planetary ball milling. Ball milling of the CoO and Al mixture powder after a certain milling duration reduces CoO to (fcc and hcp) Co completely and oxidizes Al to α-Al2O3 simultaneously. The average grain sizes of the nanocomposite powders are 19nm for Co and 28nm
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Yttria-stabilized ZrO2/Al2O3 (abridged as YSZ/Al2O3) nanocomposite ceramics were prepared by pressureless sintering of the green sheets of the YSZ/Al2O3 nanopowders synthesized by co-precipitation method. The relative density, average... more
Yttria-stabilized ZrO2/Al2O3 (abridged as YSZ/Al2O3) nanocomposite ceramics were prepared by pressureless sintering of the green sheets of the YSZ/Al2O3 nanopowders synthesized by co-precipitation method. The relative density, average grain size, and phase microstructure of the YSZ/Al2O3 nanoceramics as a function of YSZ contents were investigated. The relative densities of the YSZ/Al2O3 nanoceramics are over 95% as the YSZ contents of