Poly(organophosphazenes) have potential applications in making water-soluble and biocompatible quantum dots (QDs) due to their wide variety of properties. The CdSe QDs of green emission and the core-shell CdSe/ZnS QDs...
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Poly(organophosphazenes) have potential applications in making water-soluble and biocompatible quantum dots (QDs) due to their wide variety of properties. The CdSe QDs of green emission and the core-shell CdSe/ZnS QDs of red emission were prepared. Subsequently the trioctylphosphine oxide-stabilized CdSe/ZnS QDs were transferred from chloroform into water through a ligand exchange process with poly(glycino amino acid)phosphazenes, which can be obtained from the saponification of poly (glycino amino ester)phosphazenes at room temperature. The resulting QDs-polymer nanocomposite particles can form colloidally stable suspensions in water and exhibit good photostability.
The quantum entanglement dynamics of a one-dimensional spin-1/2 anisotropic XXZ model is studied using the method of the adaptive time-dependent density-matrix renormalization group when two cases of quenches are perf...
The quantum entanglement dynamics of a one-dimensional spin-1/2 anisotropic XXZ model is studied using the method of the adaptive time-dependent density-matrix renormalization group when two cases of quenches are performed in the system. An anisotropic interaction quench and the maximum number of domain walls of a staggered magnetization quench are considered. The dynamics of the pairwise entanglement between the nearest two qubits in the spin chain is investigated. The entanglement of the two spin qubits can be created and oscillates in both cases of the quench. The anisotropic interaction has a strong influence on the oscillation frequency of the entanglement.
The structures,grain sizes and magnetism were analyzed and computed for three typical samples:the stock of polycrystalline metal Gd(sample 1),the bulk nanocrystalline Gd prepared by spark plasma sintering(SPS) techniq...
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The structures,grain sizes and magnetism were analyzed and computed for three typical samples:the stock of polycrystalline metal Gd(sample 1),the bulk nanocrystalline Gd prepared by spark plasma sintering(SPS) technique and subjected to the annealing process of 623 K for 0.5 h(sample 2) and the bulk nanocrystalline Gd prepared by the SPS technique at 573 K(sample 3).The computation results indicated that the sample 3 had the efficiency of space filling up to 99.38%.The computation results of magnetization i...
Hydrogen spillover on carbon-based systems has been proposed as a viable alternative for room-temperature storage. Given the strength of the C-H bonds, however, it is unclear if spillover indeed takes place in such ma...
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Hydrogen spillover on carbon-based systems has been proposed as a viable alternative for room-temperature storage. Given the strength of the C-H bonds, however, it is unclear if spillover indeed takes place in such materials. We performed a first-principles study of H spillover on IRMOF-1. Spillover becomes thermodynamically stable only at high H coverage with a calculated Gibbs free energy of −14 kJ/mol at ambient condition. In general, however, spillover may not proceed due to high-energy states at lower H coverage. We propose that hole doping can substantially lower the energies as well as barriers to enable spillover at ambient conditions.
The thermal features of the nanograin boundary were described by a developed thermodynamic model. Using the nanocrystalline Cu as an example, the pressure, the bulk modulus, and the volume thermal expansion coef- fici...
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The thermal features of the nanograin boundary were described by a developed thermodynamic model. Using the nanocrystalline Cu as an example, the pressure, the bulk modulus, and the volume thermal expansion coef- ficient were calculated to characterize the thermodynamic properties of the grain boundaries on the nanoscale. Based on the parabola-type relationship between the excess free energy and the excess volume of the nanograin boundary, the thermal stability, as well as its evolution characteristics, was analyzed. The experimental re- sults of the temperature-varying grain growth in the nanocrystalline Cu, which exhibited the discontinuous nanograin growth behavior, verified the thermodynamic predictions. In addition, the quantitative relationships correlating the excess volume and the lattice expansion with the nanograin size were discussed.
The removal of acetyls from konjac glucomannan (KGM) can modify the molecular structure via a molecular modification method by mechano-chemical treatment to increase the film performance of the KGM in engineering. The...
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The removal of acetyls from konjac glucomannan (KGM) can modify the molecular structure via a molecular modification method by mechano-chemical treatment to increase the film performance of the KGM in engineering. The de-acetylation from the KGM was performed with potassium hydroxide (KOH) as a modifier through a mechano-chemical treatment in a high energy intensive vibrating mill. The results showed that the mechano-chemical treatment was an effective modification method to remove the acetyls from the KGM. The removal rate of acetyls from the KGM sample could be 90% when the KGM sample was treated by this effective mechano-chemical method for 30 min. The mass loss of de-acetylated KGM sample was lower than that of original sample. The de-acetylated KGM samples possessed a better swelling rate and a stability in water.
High-refractive-index materials LaF3, NdF3, and GdF3 and low-refractive-index materials MgF2, A1F3, and Na3A1F6 single thin films are deposited by a resistive-heating boat at different depositing rates and specific su...
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High-refractive-index materials LaF3, NdF3, and GdF3 and low-refractive-index materials MgF2, A1F3, and Na3A1F6 single thin films are deposited by a resistive-heating boat at different depositing rates and specific substrate temperatures on single crystal MgF2 substrates. Transmittances of all fluoride thin films are measured using commercial spectrometer in the ambient atmosphere and under vacuum using synchrotron radiation instrument in the wavelength region from 190 to 500 am. The optical constants of these materials are determined by envelope method and iterative algorithm on the basis of transmittance measurements.
Polycrystalline ZnS films were prepared by pulsed laser deposition （PLD） on quartz glass substrates under different growth conditions at different substrate temperatures of 20, 200, 400, and 600 ℃, which is a suita...
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Polycrystalline ZnS films were prepared by pulsed laser deposition （PLD） on quartz glass substrates under different growth conditions at different substrate temperatures of 20, 200, 400, and 600 ℃, which is a suitable alternative to chemical bath deposited （CBD） CdS as a buffer layer in Cu（In,Ga）Se2 （CIGS） solar cells. X-ray diffraction studies indicate the films are polycrystalline with zinc-blende structure and they exhibit preferential orientation along the cubic phase β-ZnS （111） direction, which conflicts with the conclusion of wurtzite structure by Murali that the ZnS films deposited by pulse plating technique was polycrystalline with wurtzite structure. The Raman spectra of grown films show Al mode at approximately 350 cm^-1, generally observed in the cubic phase β-ZnS compounds. The planar and the cross-sectional morphology were observed by scanning electron microscopic. The dense, smooth, uniform grains are formed on the quartz glass substrates through PLD technique. The grain size of ZnS deposited by PLD is much smaller than that of CdS by conventional CBD method, which is analyzed as the main reason of detrimental cell performance. The composition of the ZnS films was also measured by X-ray fluorescence. The typical ZnS films obtained in this work are near stoichiometric and only a small amount of S-rich. The energy band gaps at different temperatures were obtained by absorption spectroscopy measurement, which increases from 3.2 eV to 3.7 eV with the increasing of the deposition temperature. ZnS has a wider energy band gap than CdS （2.4 eV）, which can enhance the blue response of the photovoltaic cells. These results show the high-quality of these substitute buffer layer materials are prepared through an all-dry technology, which can be used in the manufacture of CIGS thin film solar cells.
Ultrafine-grained WC-Co bulk materials were prepared by a new method that contains pretreatment of the milled powder mixture and subsequent spark plasma sintering （SPS）. Ball milling parameters and the pretreatment ...
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Ultrafine-grained WC-Co bulk materials were prepared by a new method that contains pretreatment of the milled powder mixture and subsequent spark plasma sintering （SPS）. Ball milling parameters and the pretreatment temperature have significant effects on the microstructure and properties of WC-Co cermets. The prepared cermets have a mean grain size of less than 0.5 μm even with a pretreatment temperature as high as 1300℃. The WC-10wt.%Co cermet bulk prepared by the optimized milling, pretreatment, and SPS processing achieves excellent mechanical properties with a Vickers hardness of HV 1643, a fracture toughness of 13.1 MPa.m^1/2 and a transverse rapture strength of 3100 MPa.
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