The incompressible two-phase flows are simulated using combination of an etching multiblock method and a diffuse interface （DI） model, particularly in the com- plex domain that can be decomposed into multiple rectan...The incompressible two-phase flows are simulated using combination of an etching multiblock method and a diffuse interface （DI） model, particularly in the com- plex domain that can be decomposed into multiple rectangular subdomains. The etching multiblock method allows natural communications between the connected subdomains and the efficient parallel computation. The DI model can consider two-phase flows with a large density ratio, and simulate the flows with the moving contact line （MCL） when a geometric formulation of the MCL model is included. Therefore, combination of the etch- ing method and the DI model has potential to deal with a variety of two-phase flows in industrial applications. The performance is examined through a series of numerical exper- iments. The convergence of the etching method is firstly tested by simulating single-phase flows past a square cylinder, and the method for the multiphase flow simulation is vali- dated by investing drops dripping from a pore. The numerical results are compared with either those from other researchers or experimental data. Good agreement is achieved. The method is also used to investigate the impact of a droplet on a grooved substrate and droplet generation in flow focusing devices.展开更多
Anisotropic materials, like carbon nanotubes(CNTs), are the perfect substitutes to overcome the limitations of conventional metamaterials; however, the successful fabrication of CNT forest metamaterial structures is s...Anisotropic materials, like carbon nanotubes(CNTs), are the perfect substitutes to overcome the limitations of conventional metamaterials; however, the successful fabrication of CNT forest metamaterial structures is still very challenging. In this study, a new method utilizing a focused ion beam(FIB) with additional secondary etching is presented, which can obtain uniform and fine patterning of CNT forest nanostructures for metamaterials and ranging in sizes from hundreds of nanometers to several micrometers. The influence of the FIB processing parameters on the morphology of the catalyst surface and the growth of the CNT forest was investigated, including the removal of redeposited material,decreasing the average surface roughness(from 0.45 to 0.15 nm), and a decrease in the thickness of the Fe catalyst.The results showed that the combination of FIB patterning and secondary etching enabled the growth of highly aligned, highdensity CNT forest metamaterials. The improvement in the quality of single-walled CNTs(SWNTs), defined by the very high G/D peak ratio intensity of 10.47, demonstrated successful fine patterning of CNT forest for the first time. With a FIB patterning depth of 10 nm and a secondary etching of 0.5 nm, a minimum size of 150 nm of CNT forest metamaterials was achieved. The development of the FIB secondary etching method enabled for the first time, the fabrication of SWNT forest metamaterials for the optical and infrared regime, for future applications, e.g., in superlenses, antennas,or thermal metamaterials.展开更多
We described a method for obtaining fluorine-free Ti_(3)C_(2)Cl_(2)MXene phases by melting copper in CuCl_(2)instead of aluminum in Ti_(3)AlC_(2).XRD results show that when molten salt CuCl_(2)etches Ti_(3)AlC_(2),it ...We described a method for obtaining fluorine-free Ti_(3)C_(2)Cl_(2)MXene phases by melting copper in CuCl_(2)instead of aluminum in Ti_(3)AlC_(2).XRD results show that when molten salt CuCl_(2)etches Ti_(3)AlC_(2),it forms an intermediate product Ti_(3)CuC_(2),and then reacts with Ti_(3)CuC_(2)to obtain Ti_(3)C_(2)Cl_(2).The reaction of Ti_(3)AlC_(2)and CuCl_(2)at a temperature of 800℃for 2 h to obtain Ti_(3)C_(2)Cl_(2)with an optimal lamellar structure is shown in SEM results.The pseudopotential plane-wave(PP-PW)method is used to calculate on the electronic structure.The etching mechanism is investigated by the total energies of each substance.The chemical reaction of Ti_(3)AlC_(2)and CuCl_(2)will first become Ti_(3)CuC_(2)and Cu,and then become Ti_(3)C_(2)Cl_(2)during the Lewis acid etching process,which are consistent with the experimental results.展开更多
This paper proposes a new step-by-step Chebyshev space-time spectral method to analyze the force vibration of functionally graded material structures.Although traditional space-time spectral methods can reduce the acc...This paper proposes a new step-by-step Chebyshev space-time spectral method to analyze the force vibration of functionally graded material structures.Although traditional space-time spectral methods can reduce the accuracy mismatch between tem-poral low-order finite difference and spatial high-order discre tization,the ir time collocation points must increase dramatically to solve highly oscillatory solutions of structural vibration,which results in a surge in computing time and a decrease in accuracy.To address this problem,we introduced the step-by-step idea in the space-time spectral method.The Chebyshev polynomials and Lagrange's equation were applied to derive discrete spatial goverming equations,and a matrix projection method was used to map the calculation results of prev ious steps as the initial conditions of the subsequent steps.A series of numerical experiments were carried out.The results of the proposed method were compared with those obtained by traditional space-time spectral methods,which showed that higher accuracy could be achieved in a shorter computation time than the latter in highly oscillatory cases.展开更多
In-situ characterization of non-aqueous nano-dispersion systems（NANDS） by freeze-etching transmission electron microscope（FETEM） was reported.To improve just-for-once successive rate of specimen preparation and ge...In-situ characterization of non-aqueous nano-dispersion systems（NANDS） by freeze-etching transmission electron microscope（FETEM） was reported.To improve just-for-once successive rate of specimen preparation and get good characterization results,an improving specimen preparation method of freezing etching was developed.Size,distribution and morphology of NANDS were directly visualized.Some information of particle dispersion feature and particle density can also be obtained.Reproductivity of the FETEM characterization is excellent.Comparing with laser scattering method,which is liable to give positive error especially for small size particle anchoring disperser,FETEM characterization can give more accurate measurement of particle size.Moreover,FETEM can give dispersion feature of nanoparticle in non-aqueous medium.展开更多
The adsorption of CO_(2) on MgAl layered double hydroxides(MgAl-LDHs) based adsorbents has been an effective way to capture CO_(2),however the adsorption capacity was hampered due to the pore structure and the dispers...The adsorption of CO_(2) on MgAl layered double hydroxides(MgAl-LDHs) based adsorbents has been an effective way to capture CO_(2),however the adsorption capacity was hampered due to the pore structure and the dispersibility of adsorption active sites.To address the problem,we investigate the effect of intercalated anion and alkaline etching time on the structure,morphology and CO_(2) uptake performances of MgAl-LDHs.MgAl-LDHs are synthesized by the onepot hydrothermal method,followed by alkaline etching of NaOH,and characterized by x-ray diffraction,N_(2) adsorption,scanning electron microscopy and Fourier transform infrared spectroscopy.The CO_(2) adsorption tests of the samples are performed on a thermogravimetric analyzer,and the adsorption data are fitted by the first-order,pseudo-second-order and Elovich models,respectively.The results demonstrate that among the three intercalated samples,MgAl(Cl) using chloride salts as precursors possesses the highest adsorption capacity of CO_(2),owing to high crystallinity and porous structure,while MgAl(Ac) employing acetate salts as precursors displays the lowest CO_(2) uptake because of poor crystallinity,disorderly stacked structure and unsatisfactory pore structure.With regard to alkaline etching,the surface of the treated MgAl(Cl) is partly corroded,thus the specific surface area and pore volume increase,which is conducive to the exposure of adsorption active sites.Correspondingly,the adsorption performance of the alkaline-etched adsorbents is significantly improved,and MgAl(Cl)-6 has the highest CO_(2) uptake.With the alkaline etching time further increasing,the CO_(2) adsorption capacity of MgAl(Cl)-9 sharply decreases,mainly due to the collapse of pore structure and the fragmentized sheet-structure.Hence,the CO_(2) adsorption performance is greatly influenced by alkaline etching time,and appropriate alkaline etching time can facilitate the contact between CO_(2) molecules and the adsorbent.展开更多
Process technology of multiple cylindrical micro-pins by wire-electrical discharge machining （wire-EDM） and electrochemical etching was presented. A row of rectangular micro-columns were machined by wire-EDM and the...Process technology of multiple cylindrical micro-pins by wire-electrical discharge machining （wire-EDM） and electrochemical etching was presented. A row of rectangular micro-columns were machined by wire-EDM and then machined into cylindrical shape by electrochemical etching. However, the shape of the multiple electrodes and the consistent sizes of the electrodes row are not easy to be controlled. In the electrochemical process, the shape of the cathode electrode determines the current density distribution on the anode and so the forming of multiple electrodes. This paper proposes a finite element method （FEM） to accurately optimize the electrode profile. The microelectrodes row with uniformity diameters with size from hundreds micrometers to several decades could be fabricated, and mathematical model controlling the shape and diameter of multiple microelectrodes was provided. Furthermore, a good agreement between experimental and theoretical results was confirmed.展开更多
Molecular dynamics （MD） simulations were performed to investigate F＋ continuously bombarding SiC surfaces with energies of 100 eV at different incident angles at 300 K. The simulated results show that the steady-st...Molecular dynamics （MD） simulations were performed to investigate F＋ continuously bombarding SiC surfaces with energies of 100 eV at different incident angles at 300 K. The simulated results show that the steady-state uptake of F atoms increases with increasing incident angle. With the steady-state etching established, a Si-C-F reactive layer is formed. It is found that the etching yield of Si is greater than that of C. In the F-containing reaction layer, the SiF species is dominant with incident angles less than 30°. For all incident angles, the CF species is dominant over CF2 and CF3.展开更多
Refined control of etched profile in microelectronic devices during plasma etching process is one of the most important tasks of front-end and back-end microelectronic devices manufacturing technologies. A comprehensi...Refined control of etched profile in microelectronic devices during plasma etching process is one of the most important tasks of front-end and back-end microelectronic devices manufacturing technologies. A comprehensive simulation of etching profile evolution requires knowledge of the etching rates at all the points of the profile surface during the etching process. Electrons do not contribute directly to the material removal, but they are the source, together with positive ions, of the profile charging that has many negative consequences on the final outcome of the process especially in the case of insulating material etching. The ability to simulate feature charging was added to the 3D level set profile evolution simulator described earlier. The ion and electron fluxes were computed along the feature using Monte Carlo method. The surface potential profiles and electric field for the entire feature were generated by solving Laplace equation using finite elements method. Calculations were performed in the case of simplified model of Ar+/CF4 non-equilibrium plasma etching of SiO2.展开更多
In this paper, large-sized sapphire （Φ230×210 mm, 27.5 kg） was grown by SAPMAC method （sapphire growth technique with micro-pulling and shoulder-expanding at the cooled center）. Dislocation peculiarity in la...In this paper, large-sized sapphire （Φ230×210 mm, 27.5 kg） was grown by SAPMAC method （sapphire growth technique with micro-pulling and shoulder-expanding at the cooled center）. Dislocation peculiarity in large sapphire boule （0001） basal plane was investigated by chemical etchiing, scanning electron microscopy and X-ray topography method. The triangular dislocation etch pit measured is 7.6× 10^1-8.0×10^2 cm^2, in which relative high-density dislocations were generated at both initial and final stages of crystal growth. The analysis of single-crystal X-ray topography shows that there are no apparent sub-grain boundaries; the dislocation lines are isolated and straight. Finally, the origins of low-density dislocation in sapphire crystal are discussed by numerical analysis method.展开更多
ZnO single crystals were grown by the innovated hydrothermal method. The crystal surfaces were polished, and then studied by atom force microscope （AFM） and wet-chemical etching （WCE）. It was found that the Zn pol...ZnO single crystals were grown by the innovated hydrothermal method. The crystal surfaces were polished, and then studied by atom force microscope （AFM） and wet-chemical etching （WCE）. It was found that the Zn polar plane was smoother than O polar plane under the same polishing conditions. The etch pit density of Zn polar plane is 4.3×10^3 cm^-2, which is consistent with the previous report, while the density of etch pit of O polar plane is more than 103cm^-2. After annealing treatment, the density of etch pit of Zn plane reduces to 5.8×102 cm^2 and is superior to the current report. This investigation reveals that the high quality ZnO single crystals with fine Zn polar plane can be obtained by the innovated hydrothermal method.展开更多
基金Project supported by the National Natural Science Foundation of China(No.11425210)the Fundamental Research Funds for the Central Universities(No.WK2090050025)
文摘The incompressible two-phase flows are simulated using combination of an etching multiblock method and a diffuse interface （DI） model, particularly in the com- plex domain that can be decomposed into multiple rectangular subdomains. The etching multiblock method allows natural communications between the connected subdomains and the efficient parallel computation. The DI model can consider two-phase flows with a large density ratio, and simulate the flows with the moving contact line （MCL） when a geometric formulation of the MCL model is included. Therefore, combination of the etch- ing method and the DI model has potential to deal with a variety of two-phase flows in industrial applications. The performance is examined through a series of numerical exper- iments. The convergence of the etching method is firstly tested by simulating single-phase flows past a square cylinder, and the method for the multiphase flow simulation is vali- dated by investing drops dripping from a pore. The numerical results are compared with either those from other researchers or experimental data. Good agreement is achieved. The method is also used to investigate the impact of a droplet on a grooved substrate and droplet generation in flow focusing devices.
文摘Anisotropic materials, like carbon nanotubes(CNTs), are the perfect substitutes to overcome the limitations of conventional metamaterials; however, the successful fabrication of CNT forest metamaterial structures is still very challenging. In this study, a new method utilizing a focused ion beam(FIB) with additional secondary etching is presented, which can obtain uniform and fine patterning of CNT forest nanostructures for metamaterials and ranging in sizes from hundreds of nanometers to several micrometers. The influence of the FIB processing parameters on the morphology of the catalyst surface and the growth of the CNT forest was investigated, including the removal of redeposited material,decreasing the average surface roughness(from 0.45 to 0.15 nm), and a decrease in the thickness of the Fe catalyst.The results showed that the combination of FIB patterning and secondary etching enabled the growth of highly aligned, highdensity CNT forest metamaterials. The improvement in the quality of single-walled CNTs(SWNTs), defined by the very high G/D peak ratio intensity of 10.47, demonstrated successful fine patterning of CNT forest for the first time. With a FIB patterning depth of 10 nm and a secondary etching of 0.5 nm, a minimum size of 150 nm of CNT forest metamaterials was achieved. The development of the FIB secondary etching method enabled for the first time, the fabrication of SWNT forest metamaterials for the optical and infrared regime, for future applications, e.g., in superlenses, antennas,or thermal metamaterials.
基金Funded by the National Natural Science Foundation for Young Scholars of China(No.51302073)the Hubei Provincial Key Laboratory of Green Materials for Light IndustryHubei University of Technology(No.202307B07)。
文摘We described a method for obtaining fluorine-free Ti_(3)C_(2)Cl_(2)MXene phases by melting copper in CuCl_(2)instead of aluminum in Ti_(3)AlC_(2).XRD results show that when molten salt CuCl_(2)etches Ti_(3)AlC_(2),it forms an intermediate product Ti_(3)CuC_(2),and then reacts with Ti_(3)CuC_(2)to obtain Ti_(3)C_(2)Cl_(2).The reaction of Ti_(3)AlC_(2)and CuCl_(2)at a temperature of 800℃for 2 h to obtain Ti_(3)C_(2)Cl_(2)with an optimal lamellar structure is shown in SEM results.The pseudopotential plane-wave(PP-PW)method is used to calculate on the electronic structure.The etching mechanism is investigated by the total energies of each substance.The chemical reaction of Ti_(3)AlC_(2)and CuCl_(2)will first become Ti_(3)CuC_(2)and Cu,and then become Ti_(3)C_(2)Cl_(2)during the Lewis acid etching process,which are consistent with the experimental results.
基金supported by the Advance Research Project of Civil Aerospace Technology(Grant No.D020304)National Nat-ural Science Foundation of China(Grant Nos.52205257 and U22B2083).
文摘This paper proposes a new step-by-step Chebyshev space-time spectral method to analyze the force vibration of functionally graded material structures.Although traditional space-time spectral methods can reduce the accuracy mismatch between tem-poral low-order finite difference and spatial high-order discre tization,the ir time collocation points must increase dramatically to solve highly oscillatory solutions of structural vibration,which results in a surge in computing time and a decrease in accuracy.To address this problem,we introduced the step-by-step idea in the space-time spectral method.The Chebyshev polynomials and Lagrange's equation were applied to derive discrete spatial goverming equations,and a matrix projection method was used to map the calculation results of prev ious steps as the initial conditions of the subsequent steps.A series of numerical experiments were carried out.The results of the proposed method were compared with those obtained by traditional space-time spectral methods,which showed that higher accuracy could be achieved in a shorter computation time than the latter in highly oscillatory cases.
基金Funded by National Natural Science Foundation of China(No.50572121) Key Pre-research Foundation of Weapon and Equipment(No. 9140A27010206JB35)
文摘In-situ characterization of non-aqueous nano-dispersion systems（NANDS） by freeze-etching transmission electron microscope（FETEM） was reported.To improve just-for-once successive rate of specimen preparation and get good characterization results,an improving specimen preparation method of freezing etching was developed.Size,distribution and morphology of NANDS were directly visualized.Some information of particle dispersion feature and particle density can also be obtained.Reproductivity of the FETEM characterization is excellent.Comparing with laser scattering method,which is liable to give positive error especially for small size particle anchoring disperser,FETEM characterization can give more accurate measurement of particle size.Moreover,FETEM can give dispersion feature of nanoparticle in non-aqueous medium.
基金Project supported by the National Natural Science Foundation of China(Grant No.21606058)the Natural Science Foundation of Guangxi,China(Grant Nos.2017GXNSFBA198193 and 2017GXNSFBA198124)the Startup Foundation for Doctors of Guilin University of Technology(Grant No.GLUTQD2015008)。
文摘The adsorption of CO_(2) on MgAl layered double hydroxides(MgAl-LDHs) based adsorbents has been an effective way to capture CO_(2),however the adsorption capacity was hampered due to the pore structure and the dispersibility of adsorption active sites.To address the problem,we investigate the effect of intercalated anion and alkaline etching time on the structure,morphology and CO_(2) uptake performances of MgAl-LDHs.MgAl-LDHs are synthesized by the onepot hydrothermal method,followed by alkaline etching of NaOH,and characterized by x-ray diffraction,N_(2) adsorption,scanning electron microscopy and Fourier transform infrared spectroscopy.The CO_(2) adsorption tests of the samples are performed on a thermogravimetric analyzer,and the adsorption data are fitted by the first-order,pseudo-second-order and Elovich models,respectively.The results demonstrate that among the three intercalated samples,MgAl(Cl) using chloride salts as precursors possesses the highest adsorption capacity of CO_(2),owing to high crystallinity and porous structure,while MgAl(Ac) employing acetate salts as precursors displays the lowest CO_(2) uptake because of poor crystallinity,disorderly stacked structure and unsatisfactory pore structure.With regard to alkaline etching,the surface of the treated MgAl(Cl) is partly corroded,thus the specific surface area and pore volume increase,which is conducive to the exposure of adsorption active sites.Correspondingly,the adsorption performance of the alkaline-etched adsorbents is significantly improved,and MgAl(Cl)-6 has the highest CO_(2) uptake.With the alkaline etching time further increasing,the CO_(2) adsorption capacity of MgAl(Cl)-9 sharply decreases,mainly due to the collapse of pore structure and the fragmentized sheet-structure.Hence,the CO_(2) adsorption performance is greatly influenced by alkaline etching time,and appropriate alkaline etching time can facilitate the contact between CO_(2) molecules and the adsorbent.
基金the financial support from China Aviation Science Foundation (04H52055).
文摘Process technology of multiple cylindrical micro-pins by wire-electrical discharge machining （wire-EDM） and electrochemical etching was presented. A row of rectangular micro-columns were machined by wire-EDM and then machined into cylindrical shape by electrochemical etching. However, the shape of the multiple electrodes and the consistent sizes of the electrodes row are not easy to be controlled. In the electrochemical process, the shape of the cathode electrode determines the current density distribution on the anode and so the forming of multiple electrodes. This paper proposes a finite element method （FEM） to accurately optimize the electrode profile. The microelectrodes row with uniformity diameters with size from hundreds micrometers to several decades could be fabricated, and mathematical model controlling the shape and diameter of multiple microelectrodes was provided. Furthermore, a good agreement between experimental and theoretical results was confirmed.
基金supported by the Program for Outstanding Young Scientific and Technological Personnel Training of Guizhou Province of China （No. 700968101） and the International Thermonuclear Experimental Reactor （ITER） Special Program of China （No. 2009GB104006）
文摘Molecular dynamics （MD） simulations were performed to investigate F＋ continuously bombarding SiC surfaces with energies of 100 eV at different incident angles at 300 K. The simulated results show that the steady-state uptake of F atoms increases with increasing incident angle. With the steady-state etching established, a Si-C-F reactive layer is formed. It is found that the etching yield of Si is greater than that of C. In the F-containing reaction layer, the SiF species is dominant with incident angles less than 30°. For all incident angles, the CF species is dominant over CF2 and CF3.
基金The Ministry of Education and Science, Republic of Serbai, Projects O171037 and III41011
文摘Refined control of etched profile in microelectronic devices during plasma etching process is one of the most important tasks of front-end and back-end microelectronic devices manufacturing technologies. A comprehensive simulation of etching profile evolution requires knowledge of the etching rates at all the points of the profile surface during the etching process. Electrons do not contribute directly to the material removal, but they are the source, together with positive ions, of the profile charging that has many negative consequences on the final outcome of the process especially in the case of insulating material etching. The ability to simulate feature charging was added to the 3D level set profile evolution simulator described earlier. The ion and electron fluxes were computed along the feature using Monte Carlo method. The surface potential profiles and electric field for the entire feature were generated by solving Laplace equation using finite elements method. Calculations were performed in the case of simplified model of Ar+/CF4 non-equilibrium plasma etching of SiO2.
基金the National Defensive Preliminary Research Funds of China (No. 41312040404)
文摘In this paper, large-sized sapphire （Φ230×210 mm, 27.5 kg） was grown by SAPMAC method （sapphire growth technique with micro-pulling and shoulder-expanding at the cooled center）. Dislocation peculiarity in large sapphire boule （0001） basal plane was investigated by chemical etchiing, scanning electron microscopy and X-ray topography method. The triangular dislocation etch pit measured is 7.6× 10^1-8.0×10^2 cm^2, in which relative high-density dislocations were generated at both initial and final stages of crystal growth. The analysis of single-crystal X-ray topography shows that there are no apparent sub-grain boundaries; the dislocation lines are isolated and straight. Finally, the origins of low-density dislocation in sapphire crystal are discussed by numerical analysis method.
基金Supported by the Knowledge Innovation Program of the Chinese Academy of SciencesSpecial Project on Science and Technology of Fujian Province (2005HZ1023)+4 种基金Knowledge Innovation Project of the Chinese Academy of Sciences (KJCX2.YW.W01)Outstanding Youth Fund (50625205)Youth Talent of Fujian Province (2006F3140)Fujian Engineering Research Center for Optoelectronic Materials (2007K02, 2005DC105003)the National Key Project of China for Basic Research (2007CB936703)
文摘ZnO single crystals were grown by the innovated hydrothermal method. The crystal surfaces were polished, and then studied by atom force microscope （AFM） and wet-chemical etching （WCE）. It was found that the Zn polar plane was smoother than O polar plane under the same polishing conditions. The etch pit density of Zn polar plane is 4.3×10^3 cm^-2, which is consistent with the previous report, while the density of etch pit of O polar plane is more than 103cm^-2. After annealing treatment, the density of etch pit of Zn plane reduces to 5.8×102 cm^2 and is superior to the current report. This investigation reveals that the high quality ZnO single crystals with fine Zn polar plane can be obtained by the innovated hydrothermal method.
