Ice adhesion to materials is a significant concern in many fields. Hydrophobic surface has been used for anti-icing in fields of aircraft or transmission line, which prove to be efficacious and economical. However, su...Ice adhesion to materials is a significant concern in many fields. Hydrophobic surface has been used for anti-icing in fields of aircraft or transmission line, which prove to be efficacious and economical. However, such technique is seldom employed for road deicing, because of the texture and service environment of pavement. Instead, deicers such as rock salt are frequently used, which leads to serious corrosion problem of roads and bridges. In this paper, a number of studies that characterize mechanism of ice adhesion to common substrates, specifically to pavement, are reviewed. The most important researches undertaken on ice adhesion strength affecting factors are presented. An overview of studies carried out to find hydrophobie surface for asphalt and cement concrete pavement antiicing are presented. It was verified that the hydrophobicity had high correlation with icephobicity, and nano-engineered asphalt and cement concrete pavement surface exhibited favorable hydrophobicity, and also had good performance on weakening pavement-ice bonding. However, most ice-repelling pavements obtain hydrophobic surface via low surface energy coating, which could not exist on pavement for a long time under wheel abrasion. And the nano/micro structures on hydrophobic surfaces are also vulnerable and consumable. Thus, the long-term effect of hydrophobic surface still need to be improved, and durability of the hydrophobic surface should be the research and development priorities of ice-repelling pavement.展开更多
文章介绍了自主研发的高能量电子枪的原理、设计和测试结果。该电子枪主要由电子发射组件、电磁聚焦组件、电磁偏转组件、差分抽真空维持机构和控制电源构成,可以发射、聚焦并偏转高能量电子。测试结果显示,电子枪发射的电子能量最大可...文章介绍了自主研发的高能量电子枪的原理、设计和测试结果。该电子枪主要由电子发射组件、电磁聚焦组件、电磁偏转组件、差分抽真空维持机构和控制电源构成,可以发射、聚焦并偏转高能量电子。测试结果显示,电子枪发射的电子能量最大可达30 ke V,加速电压和发射电流成正比例对应关系,电子束斑直径在100μm以下,电子束偏转角度大于5°。通过实测Si(111)单晶体,获得了良好的电子衍射图像。展开更多
The formation of long-range ordered aperiodic molecular films on quasicrystalline substrates is a new challenge that provides an opportunity for further surface functionalization. This aim can be realized through the ...The formation of long-range ordered aperiodic molecular films on quasicrystalline substrates is a new challenge that provides an opportunity for further surface functionalization. This aim can be realized through the smart selection of molecular building blocks, based on symmetry-matching between the underlying quasicrystal and individual molecules. It was previously found that the geometric registry between the C60 molecules and the 5- and 10-fold surfaces was key to the growth of quasiperiodic organic layers. However, an attempt to form a quasiperiodic C60 network on i-Ag-In-Yb substrates was unsuccessful, resulting in disordered molecular films. Here we report the growth of 5-fold symmetric corannulene C20H10 molecules on the 5-fold surfaces of i-Ag-In-Yb quasicrystals. Low-energy electron diffraction （LEED） and scanning tunneling microscopy （STM） revealed long-range quasiperiodic order and 5-fold rotational symmetry in self-assembled corannulene films. Recurrent decagonal molecular rings were seen, resulting from the decoration of specific adsorption sites with local pentagonal symmetry by corannulenes, adsorbed with their bowl-openings pointing away from the surface. They were identified as （Ag, In）-containing rhombic triacontahedral （RTH） duster centers and pentagonal Yb motifs, which cannot be occupied simultaneously due to steric hindrance. It is proposed that symmetry-matching between the molecule and specific substrate sites drives this organization. Alteration of the molecular rim by the introduction of CH substituents appeared to increase molecule mobility on the potential energy surface and facilitate trapping at these specific sites. This finding suggests that rational selection of molecular moiety enables the templated self-assembly of molecules leading to an ordered aperiodic corannulene layer.展开更多
基金the financial support from the Special Fund for Basic Scientific Research of Central Colleges, Changan University (310831151080, 310831153409, 310831153315 and 310831151085)Natural Science Basic Research Plan in Shaanxi Province of China (2017JQ2025)+1 种基金Xi'an Science and Technology Planning Project (2017137SF/WM031)Transportation Construction & Technology Project of Shanxi Department of Transportation (No. 16-2-12)
文摘Ice adhesion to materials is a significant concern in many fields. Hydrophobic surface has been used for anti-icing in fields of aircraft or transmission line, which prove to be efficacious and economical. However, such technique is seldom employed for road deicing, because of the texture and service environment of pavement. Instead, deicers such as rock salt are frequently used, which leads to serious corrosion problem of roads and bridges. In this paper, a number of studies that characterize mechanism of ice adhesion to common substrates, specifically to pavement, are reviewed. The most important researches undertaken on ice adhesion strength affecting factors are presented. An overview of studies carried out to find hydrophobie surface for asphalt and cement concrete pavement antiicing are presented. It was verified that the hydrophobicity had high correlation with icephobicity, and nano-engineered asphalt and cement concrete pavement surface exhibited favorable hydrophobicity, and also had good performance on weakening pavement-ice bonding. However, most ice-repelling pavements obtain hydrophobic surface via low surface energy coating, which could not exist on pavement for a long time under wheel abrasion. And the nano/micro structures on hydrophobic surfaces are also vulnerable and consumable. Thus, the long-term effect of hydrophobic surface still need to be improved, and durability of the hydrophobic surface should be the research and development priorities of ice-repelling pavement.
文摘文章介绍了自主研发的高能量电子枪的原理、设计和测试结果。该电子枪主要由电子发射组件、电磁聚焦组件、电磁偏转组件、差分抽真空维持机构和控制电源构成,可以发射、聚焦并偏转高能量电子。测试结果显示,电子枪发射的电子能量最大可达30 ke V,加速电压和发射电流成正比例对应关系,电子束斑直径在100μm以下,电子束偏转角度大于5°。通过实测Si(111)单晶体,获得了良好的电子衍射图像。
文摘The formation of long-range ordered aperiodic molecular films on quasicrystalline substrates is a new challenge that provides an opportunity for further surface functionalization. This aim can be realized through the smart selection of molecular building blocks, based on symmetry-matching between the underlying quasicrystal and individual molecules. It was previously found that the geometric registry between the C60 molecules and the 5- and 10-fold surfaces was key to the growth of quasiperiodic organic layers. However, an attempt to form a quasiperiodic C60 network on i-Ag-In-Yb substrates was unsuccessful, resulting in disordered molecular films. Here we report the growth of 5-fold symmetric corannulene C20H10 molecules on the 5-fold surfaces of i-Ag-In-Yb quasicrystals. Low-energy electron diffraction （LEED） and scanning tunneling microscopy （STM） revealed long-range quasiperiodic order and 5-fold rotational symmetry in self-assembled corannulene films. Recurrent decagonal molecular rings were seen, resulting from the decoration of specific adsorption sites with local pentagonal symmetry by corannulenes, adsorbed with their bowl-openings pointing away from the surface. They were identified as （Ag, In）-containing rhombic triacontahedral （RTH） duster centers and pentagonal Yb motifs, which cannot be occupied simultaneously due to steric hindrance. It is proposed that symmetry-matching between the molecule and specific substrate sites drives this organization. Alteration of the molecular rim by the introduction of CH substituents appeared to increase molecule mobility on the potential energy surface and facilitate trapping at these specific sites. This finding suggests that rational selection of molecular moiety enables the templated self-assembly of molecules leading to an ordered aperiodic corannulene layer.
