摘要：
This study represents a facile but effective electrodeposition method to fabricate vanadium dioxide (VO2) thin films on fluorine doped tin oxide (FTO) glass at room temperature. The film microstructure (thickness, surface structure, particle size and composition) and relevant optical properties were investigated by several advanced techniques. The pertinent variables that can affect the thin film formation and structure, such as deposition potential, time and post-treatment annealing temperature were also studied. It was found that the film thickness could be tuned from 35 to 130 nm by adjusting the potential from -1.22 to -1.35 V, and consequently leading to optical transmittance decreasing from similar to 60% to similar to 38% in the wavelength of 500-1000 nm, further confirmed by computational simulations using three-dimension (3D) finite-difference time-domain method. The hysteresis loop of the generated VO2 film on FTO glass shows that the phase transition temperature from monoclinic to rutile is around 73 degrees C, a little higher than pure monoclinic VO2 (similar to 68 degrees C) in this study. This proposed electrodeposition method is possible to extend into obtaining metal oxide films with tuneable surface properties for thermochromic smart devices.
摘要：
In the present work we systematically study alpha decay half-lives of Z > 51 nuclei using the modified Gamow-like model which includes the effects of the centrifugal potential and electrostatic shielding. For the case of even-even nuclei, this model contains two adjustable parameters: the parameter a related to the screened electrostatic barrier and the radius constant r(0), while for the case of odd-odd and odd-A nuclei, it is added a new parameter i.e. hindrance factor h which is used to describe the effect of an odd-proton and/or an odd-neutron. Our calculations can well reproduce the experimental data. In addition, we use this modified Gamow-like model to predict the alpha-decay half-lives of seven even-even nuclei with Z = 120 and some un-synthesized nuclei on their alpha decay chains. (C) 2019 Elsevier B.V. All rights reserved.
期刊：
Journal of Raman Spectroscopy,2019年50(12):1969-1976 ISSN：0377-0486
通讯作者：
Cao, Fangcheng;He, Zhen
作者机构：
[Cao, Fangcheng] Univ South China, Sch Chem & Chem Engn, 28 Changsheng West Rd, Hengyang 421001, Hunan, Peoples R China;[Cao, Fangcheng] Univ South China, Cooperat Innovat Ctr Nucl Fuel Cycle Technol & Eq, Hengyang, Peoples R China;[He, Zhen] Jiangsu Univ Sci & Technol, Sch Mat Sci & Engn, Zhenjiang 212003, Jiangsu, Peoples R China
通讯机构：
[Cao, Fangcheng] U;[He, Zhen] J;Univ South China, Sch Chem & Chem Engn, 28 Changsheng West Rd, Hengyang 421001, Hunan, Peoples R China. Jiangsu Univ Sci & Technol, Sch Mat Sci & Engn, Zhenjiang 212003, Jiangsu, Peoples R China.
关键词：
graphite;proving volume;Raman shift;thermal conductivity;three-dimensional heating model
摘要：
The thermal conductivity of isotropic graphite was investigated using Raman spectroscopy technique. In this method, the Raman laser acted simultaneously as an excitation source and a heating source. The dependences of the Raman peak position on temperature and laser power for the isotropic graphite were analyzed to establish Raman thermometry. Meanwhile, the local temperature rise induced by the laser irradiation was also theoretically described using a three-dimensional heating model, which can be related to the thermal conductivity. The laser absorptivity, the spot size, and the probing volume of Raman spectra were discussed, respectively. Besides, simulations of the localized temperature distribution were performed. On the basis of the Raman thermometry and the three-dimensional heating model, the thermal conductivity of 55 W/m K for the isotropic graphite was estimated, which was comparable with the value (60 W/m K) obtained by the laser flash technique.
摘要：
Through nanoscratch experiments with a spherical diamond indenter, a contrastive study of the nanotribological properties of Ga- and N-faced gallium nitride (GaN) samples was carried out. Nanoindentation results revealed that the elastic modulus of the Ga-faced GaN sample was slightly higher than that of N-faced GaN sample. Particularly, Ga- and N-faced GaN samples exhibited rather different nanotribological properties, and the Ga-faced sample showed a stronger wear resistance. The study indicated that the critical normal load required to cause material removal of N-faced GaN sample was almost two times that of Ga-faced GaN sample. Both Ga- and N-faces exhibited a rather low frictional coefficient at the elastic and elastoplastic stages of material, e.g., similar to 0.06 for Ga-face and similar to 0.075 for N-face when scratching under the progressive normal load. Combined with transmission electron microscopy and X-ray photoelectron spectroscopy, we speculated that, except for the intrinsic atomic arrangements attributed to the non-reverse crystallographic symmetry of c-plane wurtzite GaN, the difference of nanotribological properties between Ga- and N-faces may also be related to the preferential formation of a native oxide layer and a slight lattice damage layer on the N-faced GaN surface. This study can enrich the understanding of the nanotribological properties of Ga- and N-polar-faced bulk monocrystalline GaN materials fabricated by the conventional technique.
摘要：
By using vacuum sintering method, the shielding materials made of iron-tungsten-carbon-boron (Fe-W-C-B) alloys with different boron (B) contents were prepared. The influences of different B contents on mechanical properties, shielding performance and microstructures of the alloys were investigated. The research results showed that with increasing B content, the fracture of alloys changed from plastic to brittle fractures and the higher the B content was, the more serious the brittle fracture. Moreover, the content of brittle amorphous phase FeWB increased and therefore the hardness and density of alloys increased at first and then reduced. When the B content was 2.5%, the alloy phase was mainly composed of Fe2B, Fe3(C, B) and alpha-Fe phases, with compact microstructure, shown as continuous network microstructure and tiny, long, round rod-like microstructure. In this case, the density, tensile strength and hardness of alloys were 10.05 g/cm(3), 410 MPa and 468 HV, respectively. The gamma-ray shielding performance of the alloy reduced at first, then increased and finally declined with the increase of B contents. When the B content was 1.5%, the half-value thickness reached to the minimum (about 6.36 mm). The transmittance of neutron shields reduced at first and then increased in a low-energy zone (0-4 MeV). When the B content was 2.5%, the alloys showed the lowest transmittance about 0.10842. (C) 2019 Elsevier B.V. All rights reserved.
摘要：
The entrance shape of spread die plays a crucial role in the quality control of large-scale aluminum panel production. The conventional design of spread die is generally based on the experience and expertise of the die designers or costly plant trials. Thus, it is difficult to guarantee the material flow through subsequent feeder die with the same velocity and ensure the die strength. In this work, the extrusion processes of three spread dies with different entrance shapes used generally in the real extrusion production for large-scale aluminum panel were investigated by FE simulations. Firstly, 3D-FE models for simulating the extrusion processes of the three spread dies were established by using HyperXtrude software based on ALE algorithm. Then, the effects of different die designs on the material flow behavior, extrusion load, temperature, residual stress distribution, and die deflection were synthetically studied by analyzing and comparing the simulated results. Finally, the optimal die was manufactured and corresponding extrusion experiment was carried out on a 2600-t extrusion press. The simulation and experimental results show that the die 2 with fan-shaped entrance was the optimum one among the three spread dies, where the minimum required extrusion load, uniform flow velocity at the die exit, minimum residual stress in extruded profile, and minimum die deflection were obtained. This study could provide effective guidance on the entrance shape design of spread extrusion die for the large-scale aluminum panel.
摘要：
This study represents a facile but effective room-temperature strategy for the synthesis of shape/size-controlled cuprous oxide (Cu2O) nanoparticles under mild conditions. The proposed synthesis method offers several advantages/novelties including: room-temperature processing, simple operation procedures, controllable shape and size, high yield, and available for scaling up. The effects of the pertinent variables on the particle formation and growth have been investigated, such as concentration of copper ions (Cu2+), surfactants, reducing agents, and the molar ratios among variables. The composition, microstructure and optical properties were then characterized using advanced techniques. It was found that the use of different surfactants may result in significant morphology changes from spheres to octahedrons and/or wires under the reported conditions. To enhance photocatalytic performance in dye degradation, the Cu2O nanoparticles could be further surface decorated by titanium dioxide (TiO2) to form heterogeneous nanocomposites that can improve the electron-hole separation. This study may be useful to develop simple but general approaches to obtain cuprous/copper oxides and other hybrid semiconductor nanostructures with structure and functional control for catalysis and sensing applications. (C) 2018 Elsevier B.V. All rights reserved.
摘要：
We have investigated the properties of strange quark matter and quark stars at finite temperature within the confined isospin-density-dependent mass (CIDDM) model. The newly discovered heavy compact stars PSR J0348+0432 ( 2.01±0.04 M⊙) and MSP J0740+6620 ( 2.14±0.090.10 M⊙ of 68.3% credibility interval and 2.14±0.180.20 M⊙ of 95.4% credibility interval) can be well described as quark stars with large quark matter symmetry energy within the CIDDM model in this work. In particular, we also calculate the properties of the protoquark stars (PQSs) at the heating and cooling stages along the star evolution line, and we find that the tidal deformability of PQSs increases with temperature in the heating stages within the CIDDM model.
期刊：
Journal of Crystal Growth,2019年528:UNSP 125270 ISSN：0022-0248
通讯作者：
Li, MW
作者机构：
[Wang, P. F.; Li, M. W.; Liu, H.] Chongqing Univ, Sch Energy & Power Engn, Key Lab Low Grade Energy Utilizat Technol & Syst, Minist Educ, Chongqing 400030, Peoples R China;[Hu, Z. T.] Univ South China, Sch Mech Engn, Hengyang 421001, Peoples R China
通讯机构：
[Li, M. W.] C;Chongqing Univ, Sch Energy & Power Engn, Key Lab Low Grade Energy Utilizat Technol & Syst, Minist Educ, Chongqing 400030, Peoples R China.
关键词：
Computer simulation;Fluid flows;Growth models;Mass transfer;Growth from solutions;Seed crystals
摘要：
Numerical simulation of the hydrodynamics and mass transfer involved in the capping of large size Z-cut KDP plates has been performed. The variations of surface supersaturation with thin layer height, bulk supersaturation and rotation rate are analyzed. The results show that keeping still is very unfavorable for the growth of thin layer, a certain rotation rate should be applied to the Z-cut plate to increase the concentration gradient across the (0 0 1) face, thus making sure that thin layers can grow from the edges while small pyramids barely grow from the face center. Given the result that end faces of thin layers nearly bear a bulk supersaturation, a relative low bulk supersaturation will be better to ensure both the growth of thin layers and the good surface uniformity brought by low supersaturation. Moreover, as thin layers grow, rotation rate should be increased to make up the insufficient solute supply resulting from the decreasing linear speed. The optimal parameters for rapid and high-quality capping of large size Z-cut plates are suggested, the relevant simulation results are also presented.
关键词：
Gear transmission;Meshing stiffness;Thermal dynamic characteristics;Experimental study
摘要：
In order to study the influences of heat on dynamic characteristics of gear transmission system, the thermodynamics equation of torsional vibration of gear transmission system was derived based on the meshing thermal stiffness of gears. Meanwhile, an experimental platform for vibration testing of the system was established. The dynamic responses of the system under different working conditions were tested. The effects of load, rotational speed and heat on the dynamic characteristics of the system were studied by comparing and analyzing the experimental data, and the influence mechanism of the heat on the dynamic response was also studied. The results show that the load and rotational speed are the main factors that affect the dynamic characteristics of the system; the larger the system load, the larger the amplitude of vibration response, and similarly, the higher the rotational speed, the larger the amplitude of vibration response. The heat (temperature) affects the dynamic characteristics of the system by changing the involute characteristic and the meshing stiffness of the gear. When the initial temperature of the gear is lower than the calibration temperature, with the increases of the temperature, the vibration amplitude of the system decreases first and then increases. However, the natural frequency increases first and then decreases. Both of them showing a nonlinear variation. The experimental results effectively verify the correctness of the theoretical model. (C) 2018 Elsevier Ltd. All rights reserved.
