Jiao Xie,Jia Hu,Xudong Lin,Liang Fang,Fang Wu,Xiaoling Liao,Haijun Luo,Liuting Shi
In this work, micro-nanostructure polydimethylsiloxane/silicon dioxide (PDMS/SiO 2 ) composite coatings were fabricated on the surface of magnesium alloys with two different sizes of SiO 2 nanoparticles by a simple painting method. The effects of the proportion of 40 nm and 50–250 nm SiO 2 on the wettability, wear and corrosion performance of the composite coatings were investigated. The morphology, composition, water contact angles (WCAs), wear and corrosion resistance of the composite coatings were measured by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), the contact angle meter, sandpaper-weight device and electrochemical workstation, respectively. And the mechanical and thermal stability were also respectively obtained by finger-wipe, knife-scratch tests and thermogravimetry. It is found that the PDMS/SiO 2 composite coatings fabricated under optimized parameters are stable and superhydrophobic (SH) ones and their WCAs can maintain at a high level (138°–150° and 133°–153°) under 50 abrasion cycles with sandpaper. The composite coatings exhibit good resistance to knife damaging and finger touching. The electrochemical experiments show that the robust coatings can significantly improve the corrosion resistance of magnesium alloys. It is rationally expected that the results can provide an informative reference to the fabrication of wear-resistant super-hydrophobic composites on magnesium alloys.
Haoyu Ma,Jiaozhu Wu,Chengzhe Gao,Silin He,Pengjian Gong,Qiwu Shi,Zhao Wang,Guangxian Li,Chul B. Park
In the context of the future sixth-generation (6G) communication system, the development of multi-functional materials with ultra-low dielectric permittivity ( D k ) and ultra-low dielectric loss ( D f ) is of paramount importance for the design of terahertz (THz) frequency electromagnetic wave transmission devices. In this work, polyimide- block -polydimethylsiloxane (PI- b -PDMS copolymer, PIC) material with low D k , high flexibility and high supercritical fluid foaming ability was fabricated via copolymerization. Additionally, core–shell SiO 2 @BN nanofillers were synthesized by condensing tetraethyl orthosilicate (TEOS) on hexagonal boron nitride (BN) nanofiller surface. Subsequently, flexible polyimide/SiO 2 @BN foam was fabricated via supercritical N 2 foaming. The resulting PIC/SiO 2 @BN nanocomposites exhibit exceptional flexibility and impressive thermal resistance (thermal decomposition temperature 472.2 °C). Notably, the incorporation of core–shell SiO 2 @BN nanofillers leads to the formation of a molecular interface anchoring structure through hydrogen bonding effect. This structure effectively reduced the mobility of the flexible PIC polymer chains on the SiO 2 @BN nanofiller surfaces. Consequently, the porous PIC/SiO 2 @BN materials show a low shrinkage ratio, low dielectric property ( D k = 1.21, D f = 0.012 at 1 THz), excellent THz transmission rate (91.4 %) and long distance 6G THz signal coverage (125.99 m). Furthermore, porous PIC/SiO 2 @BN materials show superior flame-retardant and thermal infrared stealth properties.
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