In conjugated polymers excited singlet states are known to dissociate into polarons upon application of an electric field. We show that for excitation intensities exceeding 100 μJ cm−2 in polyfluorene, this is not th...
In conjugated polymers excited singlet states are known to dissociate into polarons upon application of an electric field. We show that for excitation intensities exceeding 100 μJ cm−2 in polyfluorene, this is not the only mechanism of field-induced decrease in the singlet population. Bimolecular annihilation is enhanced via increased overlap between singlet emission and absorption spectra due to Stark effect. We discuss the implications for Förster resonant energy transfer.
The preparation and the mechanism study of bulk pure rare-earth metals with amorphous and nanocrystalline structures, which were produced by spark plasma sintering (SPS), were carried out in this paper. With different...
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The preparation and the mechanism study of bulk pure rare-earth metals with amorphous and nanocrystalline structures, which were produced by spark plasma sintering (SPS), were carried out in this paper. With different processing parameters, the amorphous, two phases of amorphous and nanocrystalline, and complete nanocrystalline microstructures have been obtained. The nano-grain sizes in the bulk nanocrystalline materials are found smaller than the original powder particles sizes, which may change the conventional viewpoint that the grains in the sintered bulk are generally coarser than the raw powder particles. The technique developed in the present work can be extended to the preparation of many other nano bulk metal materials, and thus enables the studies of the nano-size effects on the physical, chemical and mechanical properties of bulk nano materials.
The PCL plates hydrolyzed by NaOH aqueous solutions and carboxylate groups were introduced onto the surfaces of specimen. Specimens were treated by CaCl2 and K2HPO4·3H2O under the normal-pressure condition and lo...
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The PCL plates hydrolyzed by NaOH aqueous solutions and carboxylate groups were introduced onto the surfaces of specimen. Specimens were treated by CaCl2 and K2HPO4·3H2O under the normal-pressure condition and low-pressure of 103 Pa condition for 30min separately. Dense and uniform bone-like layers could be formed on the surface of specimens after mineralizing for less than 24h in simulated body fluids (SBF). The low-pressure condition could accelerate the formation of apatite layer.
In the present study, bioactive functional gradient coatings were prepared using net-energy controlled plasma spraying technology. The microstructure and phases of the bioactive functional gradient coating were examin...
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In the present study, bioactive functional gradient coatings were prepared using net-energy controlled plasma spraying technology. The microstructure and phases of the bioactive functional gradient coating were examined by means of transmission electron microscope, scanning electron microscopy and X-ray diffraction. The results revealed that: (1) as-sprayed coatings contained a large amount of amorphous phases and some nano-sized HA crystals formed during rapid solidification, (2) surface of the coating was very rough with different-sized micropores, and the gradient layer was much denser which firmly bonded to the substrate without gaps and obvious interface between the coating and the substrate.
In the present study, functionally gradient HA-ZrO2-Ti coatings (FGC) on Ti6Al4V were prepared by the plasma spraying process. The residual stress and surfacial morphology of coating were studied by X-ray diffraction ...
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In the present study, functionally gradient HA-ZrO2-Ti coatings (FGC) on Ti6Al4V were prepared by the plasma spraying process. The residual stress and surfacial morphology of coating were studied by X-ray diffraction and scanning electron microscopy with an energy dispersive spectroscopy. The results showed that: (1) the residual stress of FGC is 72.1Mpa, much lower than that of single HA coating, (2) The surfacial morphology of the FGC showed typical characteristics of plasma-sprayed coating, no microcracks was observed because of its the thermal expansion matched between the gradient coating and substrate.
The aim of this study is to describe the remineralization effect of the nano-HA toothpaste on artificial caries. The artificial dental caries is made using sour solution. The demineralized teeth specimen is put into f...
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The aim of this study is to describe the remineralization effect of the nano-HA toothpaste on artificial caries. The artificial dental caries is made using sour solution. The demineralized teeth specimen is put into five kinds of toothpaste solution respectively for 5 days and 10 days, which are: solution of containing needle like nano-HA, solution of containing spherical nano-HA, solution of general HA, fluorine sodium solution and physiological saline. The hardness of specimen is measured and the surface morphology is characterized by SEM. The remineralized test indicates that the nano-HA toothpaste can enhance the hardness of artificial caries and improve the remineralization of artificial caries. The SEM analysis shows that the cavities and defects of enamel surface are decreased and many mineral salts are sedimentated, which indicate that the nano-HA could promote remineralization for the demineralized enamel.
The internal friction and shear modulus at low frequency together with the electrical and magnetic properties have been measured for an ordered oxygen-deficient perovskite GdBaCo2O5+δ ceramics (δ=0.005, 0.499, and 0...
The internal friction and shear modulus at low frequency together with the electrical and magnetic properties have been measured for an ordered oxygen-deficient perovskite GdBaCo2O5+δ ceramics (δ=0.005, 0.499, and 0.515). For δ=0.005, an internal friction peak at 225K and the corresponding softening of shear modulus were observed, showing the existence of lattice distortion. This lattice distortion indicates the presence of charge ordering, which conforms to the slight upturn on the electrical resistivity curve. The anomalies in shear modulus and the internal friction peak at about TCO were suggested to be correlated with the structure change caused by the Jahn-Teller effect of Co3+ (HS state) located in square pyramidal sites. For δ=0.499 and 0.515, a large softening of shear modulus accompanied by an increasing of internal friction was observed at low temperature, which is related to the antiferromagnetic-ferromagnetic transition. And the internal friction peak with the features of phase transition at about 350K can be ascribed the metal-insulator transition. At high temperature, the relaxation internal friction peak accompanied by the corresponding decrease of shear modulus originates from the oxygen hopping in [GdOδ] planes.
A series of a-Si：H films are deposited by hot wire assisted microwave electron cyclotron resonant chemical vapour deposition （HW-MWECR-CVD）, subsequently exposed under simulated illumination for three hours. This p...
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A series of a-Si：H films are deposited by hot wire assisted microwave electron cyclotron resonant chemical vapour deposition （HW-MWECR-CVD）, subsequently exposed under simulated illumination for three hours. This paper studies the microstructure change during illumination by Fourier Transformation Infrared （FTIR） spectra. There are two typical transformation tendencies of microstructure after illumination. It proposes a model of light induced structural change based on the experimental results. It is found that all samples follow the same mechanism during illumination, and intrinsic structure of samples affect the total H content.
We have investigated infrared-to-visible upconversion luminescence of Er^3＋ in bismuth-lead-germanate glasses. The UV cutoff wavelength is shortened while its lifetime is increased almost linearly, with PbF2 substitu...
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We have investigated infrared-to-visible upconversion luminescence of Er^3＋ in bismuth-lead-germanate glasses. The UV cutoff wavelength is shortened while its lifetime is increased almost linearly, with PbF2 substituting for PbO in the bismuth-lead germanate glasses. Three emissions centred at around 529, 545 and 657 nm are clearly observed, which are identified as originating from the ^2H11/2→^4 I15/2,^4S3/2→^4 I15/2 and ^4 F9/2 →^4 I15/2 transitions, respectively. It is noted that all the upconversion emission intensities increase with PbF2 concentration increasing. The ratio between the intensities of red and green emissions increases with the increasing of PbF2 content. Energy transfer processes and nonradiative phonon-assisted decays account for the populations of the ^2 H11/2,^4 S3/2 and ^4F 9/2 levels. The quadratic dependence of fluorescence on excitation laser power confirms a two-photon process to contribute to the upconversion emissions.
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