Lotus-type porous silicon with elongated pores was fabricated by unidirectional solidification under pressurized hydrogen. Porosity, pore diameter, and pore length can be adjusted by changing solidification speed and ...Lotus-type porous silicon with elongated pores was fabricated by unidirectional solidification under pressurized hydrogen. Porosity, pore diameter, and pore length can be adjusted by changing solidification speed and hydrogen pressure. The porosity of the ingot is nearly constant under different solidification speeds, but decreases with the increase of hydrogen pressure. The overall porosities of ingots fabricated at different hydrogen pressures were evaluated through a theoretical model. Findings are in good agreement with experimental values. The average pore diameter and pore length increase simultaneously while the average pore aspect ratio changes slightly with the decreases of solidification speed and hydrogen pressure. The average pore length is raised from 7 to 24 mm and the pore aspect ratio is raised from 8 to 20 respectively with the average pore diameter promoted by about 0.3 mm through improving the superheat degree of the melt from 200 to 300 K.展开更多
The effect of gas pressures on the mean pore size, the porosity and the pore size distribution of lotus-type porous magnesium fabricated with Gasar process were investigated. The theoretical analysis and the experimen...The effect of gas pressures on the mean pore size, the porosity and the pore size distribution of lotus-type porous magnesium fabricated with Gasar process were investigated. The theoretical analysis and the experimental results all indicate that there exists an optimal ratio of the partial pressures of hydrogen PH2 to argon PAr for producing lotus-type structures with narrower pore size distribution and smaller pore size. The effect of solidification mode on the pore size distribution and pore size was also discussed.展开更多
As metallic foams used for energy absorption in the automotive and aerospace industries, recently invented lotus-type porous metals are viewed as potential energy absorbers. Yet, solid conclusion on their eligibility ...As metallic foams used for energy absorption in the automotive and aerospace industries, recently invented lotus-type porous metals are viewed as potential energy absorbers. Yet, solid conclusion on their eligibility as energy absorbers is still in question, particularly when compression is in the direction perpendicular to the axial orientation of cylindrical pores. In this work, the energy absorption of lotus-type porous coppers in the perpendicular direction is investigated at strain rates from 0.001 s^（-1） to^2400 s^（-1）. The energy absorption capacity and the energy absorption efficiency are calculated to be4–16 k J/kg and 0.32–0.7, respectively, slightly inferior to metal foams and the same porous solid compressed in the parallel direction due to the shortened extent of the plateau stress region. The deformation mechanism is examined experimentally in conjunction with finite element modeling. Both suggest that gradual squeeze and collapse of pores are the mechanisms accommodating the energy absorption. The deformation is generally evenly distributed over pore ligaments and independent of strain rate.展开更多
The aim of this work is to understand the effect of a thin coating on the compressive properties of the porous metal.In our work,the uniaxial compressive behavior and the energy absorption properties of the lotus-type...The aim of this work is to understand the effect of a thin coating on the compressive properties of the porous metal.In our work,the uniaxial compressive behavior and the energy absorption properties of the lotus-type porous copper deposited with Ni coatings with thickness from 3.9 to 4.8μm on pore walls were investigated.It is found that the Ni coating on pore walls shows a clear enhancement effect on compressive properties of the lotus-type porous copper,in which the specific yield strength and the energy absorption per unit mass at densification strain increase from 5.27 to 7.31 MPa cm3 g-1 and from 11.50 to 18.21 J g-1 with the Ni coating,respectively.Furthermore,the enhancement appears to be insensitive to the coating thickness.It is considered that the resistance of the interface between the nickel coating and the pore walls to the dislocation slip plays an important role in the improvement on compressive properties of the lotus-type porous copper.展开更多
The widely used photocatalytic self-cleaning coating materials are often made of polymers and polymer based composites,where the photocatalyst immobilization occurs with macromolecules.However,these organic polymers a...The widely used photocatalytic self-cleaning coating materials are often made of polymers and polymer based composites,where the photocatalyst immobilization occurs with macromolecules.However,these organic polymers are often unstable under exposure to UV irradiation and easily degraded by reactive radicals produced in the photocatalytic reaction.In order to solve this problem,in this paper,we present the facile preparation of a multifunctional coating with dual superhydrophobic and photocatalytic properties,where the fixation and the hydrophobization of the plasmonic Ag-TiO2 photocatalyst particles with visible light activity was performed with non-water soluble sulfur,which is a cheap and easily available material.The resulted novel nanocomposite with rough and nano-tructured surface roughness(1.25–2.45 nm determined by small-angle X-ray scattering)has sufficient low surface energy(3.3 mJ/m2)for superhydrophobic(θ=151.1°v)properties.Moreover,in contrast of the organic and expensive fluoropolymer based composites,this non-wetting nature was durable,because the measured was higher than 150°during the long-term LED(λmax=405 nm)light irradiation.展开更多
基金Project(51271096)supported by the National Natural Science Foundation of ChinaProject(NCET-12-0310)supported by the Program for New Century Excellent Talents in University,China
文摘Lotus-type porous silicon with elongated pores was fabricated by unidirectional solidification under pressurized hydrogen. Porosity, pore diameter, and pore length can be adjusted by changing solidification speed and hydrogen pressure. The porosity of the ingot is nearly constant under different solidification speeds, but decreases with the increase of hydrogen pressure. The overall porosities of ingots fabricated at different hydrogen pressures were evaluated through a theoretical model. Findings are in good agreement with experimental values. The average pore diameter and pore length increase simultaneously while the average pore aspect ratio changes slightly with the decreases of solidification speed and hydrogen pressure. The average pore length is raised from 7 to 24 mm and the pore aspect ratio is raised from 8 to 20 respectively with the average pore diameter promoted by about 0.3 mm through improving the superheat degree of the melt from 200 to 300 K.
基金This research was supported by the National Natural Science Foundation of China （No. 50404002）National Program on Key Basic Research Projects （No. 2004CCA05100）.
文摘The effect of gas pressures on the mean pore size, the porosity and the pore size distribution of lotus-type porous magnesium fabricated with Gasar process were investigated. The theoretical analysis and the experimental results all indicate that there exists an optimal ratio of the partial pressures of hydrogen PH2 to argon PAr for producing lotus-type structures with narrower pore size distribution and smaller pore size. The effect of solidification mode on the pore size distribution and pore size was also discussed.
基金financial support from the National Natural Science Foundation of China (Grant No. 50904004)
文摘As metallic foams used for energy absorption in the automotive and aerospace industries, recently invented lotus-type porous metals are viewed as potential energy absorbers. Yet, solid conclusion on their eligibility as energy absorbers is still in question, particularly when compression is in the direction perpendicular to the axial orientation of cylindrical pores. In this work, the energy absorption of lotus-type porous coppers in the perpendicular direction is investigated at strain rates from 0.001 s^（-1） to^2400 s^（-1）. The energy absorption capacity and the energy absorption efficiency are calculated to be4–16 k J/kg and 0.32–0.7, respectively, slightly inferior to metal foams and the same porous solid compressed in the parallel direction due to the shortened extent of the plateau stress region. The deformation mechanism is examined experimentally in conjunction with finite element modeling. Both suggest that gradual squeeze and collapse of pores are the mechanisms accommodating the energy absorption. The deformation is generally evenly distributed over pore ligaments and independent of strain rate.
基金supported financially by the National Science and Technology Project(No.2017ZX02201001)the National Natural Science Foundation of China(No.51772193).
文摘The aim of this work is to understand the effect of a thin coating on the compressive properties of the porous metal.In our work,the uniaxial compressive behavior and the energy absorption properties of the lotus-type porous copper deposited with Ni coatings with thickness from 3.9 to 4.8μm on pore walls were investigated.It is found that the Ni coating on pore walls shows a clear enhancement effect on compressive properties of the lotus-type porous copper,in which the specific yield strength and the energy absorption per unit mass at densification strain increase from 5.27 to 7.31 MPa cm3 g-1 and from 11.50 to 18.21 J g-1 with the Ni coating,respectively.Furthermore,the enhancement appears to be insensitive to the coating thickness.It is considered that the resistance of the interface between the nickel coating and the pore walls to the dislocation slip plays an important role in the improvement on compressive properties of the lotus-type porous copper.
基金financially supported by the Hungarian Scientific Research Fund(OTKA)K 116323,PD 116224the project of GINOP-2.3.2-15-2016-00013+1 种基金the UNKP-18-4 New National Excellence Program of the Ministry of Human Capacitiesby the János Bolyai Research Scholarship of the Hungarian Academy of Sciences and the Ministry of Human Capacities,Hungary(No.20391-3/2018/FEKUSTRAT).
文摘The widely used photocatalytic self-cleaning coating materials are often made of polymers and polymer based composites,where the photocatalyst immobilization occurs with macromolecules.However,these organic polymers are often unstable under exposure to UV irradiation and easily degraded by reactive radicals produced in the photocatalytic reaction.In order to solve this problem,in this paper,we present the facile preparation of a multifunctional coating with dual superhydrophobic and photocatalytic properties,where the fixation and the hydrophobization of the plasmonic Ag-TiO2 photocatalyst particles with visible light activity was performed with non-water soluble sulfur,which is a cheap and easily available material.The resulted novel nanocomposite with rough and nano-tructured surface roughness(1.25–2.45 nm determined by small-angle X-ray scattering)has sufficient low surface energy(3.3 mJ/m2)for superhydrophobic(θ=151.1°v)properties.Moreover,in contrast of the organic and expensive fluoropolymer based composites,this non-wetting nature was durable,because the measured was higher than 150°during the long-term LED(λmax=405 nm)light irradiation.
