In this work, composites of silica and graphitic carbon nitride (g-C3N4) were conveniently synthesized through polymerization of melamine and ethyl silicate. Some basic physicochemical properties of these metal-free p...
详细信息
ISBN:
(纸本)9781118205976
In this work, composites of silica and graphitic carbon nitride (g-C3N4) were conveniently synthesized through polymerization of melamine and ethyl silicate. Some basic physicochemical properties of these metal-free photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), Fourier transform infrared spectrometer (FTIR) spectra, transmission electron microscope (TEM), UV-visible diffuse reflectance spectrum and N2 adsorption-desorption measurement. The XRD patterns of all the prepared materials were dominated by the characteristic (002) peak at 27.5° of a graphitic structure, indicating that the induced Si did not destroy the crystal structure of g-C3N4). As the initial molar ratio of Si to C increased, enhanced photocatalytic activity was observed for H2 evolution from a triethanolamine aqueous solution under visible-light irradiation over the series of composites. It was proved that the introduction of Si resulted in large surface area, which is favorable for reactant-transfer and charge-migration, beneficial for photocatalysis.
This work generalizes Evans' homogenous nonequilibrium molecular dynamics (HNEMD) algorithm for computing the thermal conductivity of strongly-coupled complex (dusty) plasma liquids (SCCDPLs) described by the Yuka...
This work generalizes Evans' homogenous nonequilibrium molecular dynamics (HNEMD) algorithm for computing the thermal conductivity of strongly-coupled complex (dusty) plasma liquids (SCCDPLs) described by the Yukawa potential. The effects of external field strength along with different screening strengths on the conductivity of Yukawa liquids have investigated using HNEMD simulations. We have carried out some more linear and nonlinear molecular dynamics calculations of the thermal conductivity, and the obtained simulation results of SCCDPLs are presented for various plasma coupling and screening parameters. Our calculations show that Yukawa liquid exhibits a non-Newtonian behavior that the thermal conductivity increases with increasing field strength which explains interaction contributions in Yukawa conductivity, for the first time. The simulation results obtained with different external filed strengths are in reasonable agreement with earlier simulation results and with reference set of data showed deviations within less than ±10% for most of the present data point. It is shown that new simulations extended the range of field strength (0.001≤F*≤0.1) used in the earlier studies in order to find out the size of the linear regimes and to explain the nature of nonlinearity of SCCDPLs.
The study of refrigerant-based nanofluid boiling and two-phase flow phenomena is still in its infancy. This field of research provides many opportunities to study new frontiers but also poses great challenges. To summ...
详细信息
The study of refrigerant-based nanofluid boiling and two-phase flow phenomena is still in its infancy. This field of research provides many opportunities to study new frontiers but also poses great challenges. To summarize the current status of research in this newly developing interdisciplinary field and to identify the future research needs as well, this paper presents a comprehensive review of nucleate pool boiling, flow boiling, condensation and two-phase flow of refrigerant-based nanofluids. The effects of nanolubricants on boiling and two phase flow phenomena are presented as well. Furthermore, studies of applications and challenges of refrigerant-based nanofluids are presented and future research needs are identified. For the limited studies done so far, there are some controversies from one study to another. Conclusions and contradictions on the available refrigerant-based studies of physical properties, boiling and two phase flow are presented. According to this review, it has been realized that the physical properties have significant effects on the refrigerant-based nanofluid boiling and two-phase flow characteristics but the lack of the accurate knowledge of these physical properties has greatly limited the study in this interdisciplinary field. Furthermore, the limited available experiments and quite contradictive results have limited the understanding of the fundamentals of boiling and two phase flow phenomena. flow regimes are very important in understanding the phenomena but less investigated so far. Apparently it is still a long way to go to achieve systematic fundamental knowledge and theory in the relevant subject. Therefore, effort should be made to contribute to the physical property database of nanofluids as a first priority. Secondly, systematic accurate experiments and flow regime observations on boiling and two-phase flow phenomena under a wide range of test conditions and nanofluid types should be emphasized to understand the fundamentals.
The synthesis and properties of metal chalcogenides have been extensively researched because of their useful and novel properties. Most of them have been synthesized by traditional high-temperature calcination methods...
详细信息
The synthesis and properties of metal chalcogenides have been extensively researched because of their useful and novel properties. Most of them have been synthesized by traditional high-temperature calcination methods. However, other preparation methods have also been investigated such as solvothermal synthesis method. Pruss et al synthesized layered Cu 2 WS 4 materials with square primitive lattices by using Cu(CH 3 CN) 4 BF 4 and [NH 4 ] 2 WS 4 with the solvothermal method in 1993. Later Crossland group reported the synthesis and characterization of this kind of copper tetrathiometallide materials. In this paper, a new synthesis method of Cu 2 MS 4 ( M = W or Mo) polycrystal was proposed. Cu 2 MS 4 ( M = W or Mo) materials were prepared under the different reaction conditions by hydrothermal synthesis method, the structure of which has been solved from powder X-ray diffraction data, and the scanning electron microscope photographs of which were taken using an JEOL JSM-6700. [NH 4 ] 2 WS 4 crystal and CuCl 2 were used as the raw materials to produce Cu 2 WS 4 crystal. The prepared Cu 2 WS 4 semiconductor crystallizes in space group I-42m with cell parameters a = b = 5.4454 (3) , c = 10.0671(7) . [NH 4 ] 2 MoS 4 crystal, CuCl and ammonia were used as the raw materials to prepare Cu 2 MoS 4 crystal. The Cu 2 MoS 4 material crystallizes in space group I-42m with cell parameters a = b = 5.4087(7) , c = 10.0428(2) . Cu 2 MS 4 ( M = W or Mo) polycrystal contains layers of edge-sharing MS 4 and CuS 4 tetrahedra separated by a van der Waals gap.
Cryogen spray cooling (CSC) can be used in laser dermatology to prevent burning injury of skin during *** uses a short spurt of (40 ~100 ms) on the skin surface before laser irradiation, leading to quick reduction in ...
详细信息
Cryogen spray cooling (CSC) can be used in laser dermatology to prevent burning injury of skin during *** uses a short spurt of (40 ~100 ms) on the skin surface before laser irradiation, leading to quick reduction in the skin *** this work, a systematic experimental study was presented to investigate the spray behavior of R134a.
Great quantities of experiments were performed to study the effects of two-phase spray cooling with high heat flux used R22 as refrigerant. A detailed research of the performance of spray cooling at different subcooli...
Great quantities of experiments were performed to study the effects of two-phase spray cooling with high heat flux used R22 as refrigerant. A detailed research of the performance of spray cooling at different subcooling temperature was conducted. The experimental results show that the critical heat flux can reach 272.04W⋅cm−2 with R22 as the working medium, and the corresponding surface temperature is 21.11°C These figures prove that the spray cooling has the advantages of high heat flux as well as lower surface temperature. With increasing overcooling degree of refrigerant at the entrance of nozzle, CHF rises at first and goes to stable then. Which means the CHF can be developed by adding the overcooling of refrigerant. However, the development is limited to a certain degree according to the characteristics of the system; namely, the overmuch increment plays a little role to improve CHF value.
In present work,the gas-solid two-phase flow in a flat-bottom multiple-spouted bed is simulated by the Eulerian-Eulerian *** kinetic theory of granular flow is used to close the equations,and the Johnson & Jac...
详细信息
In present work,the gas-solid two-phase flow in a flat-bottom multiple-spouted bed is simulated by the Eulerian-Eulerian *** kinetic theory of granular flow is used to close the equations,and the Johnson & Jackson boundary condition is defined for the solid phase at the wall.
暂无评论