With the development of aero-engine,gas import temperatures of hot section structural materials are increasingly higher.Metal alloy materials due to the rapidly decreased mechanical properties at relative high temperature are gradually replaced with silicon-based non-oxide silicon carbide ceramics.However,silicon carbide ceramic materials tend to spall and deform in engine combustion environment,need environmental barrier coatings for the protection of the matrix.The preparation of Si/mullite/Yb2Si2O7 environmental barrier coatings onto silicon carbide was realized with plasma spraying and sol-gel method.Coatings structure,surface morphology and layer components were principally discussed through the test of X-ray diffraction(XRD),thermogravimetric analysis(TG) and scanning electron microscopy(SEM).This paper explored how to match coefficient of thermal expansion(CTE) and enhance chemical compatibility effectively.The results showed that most areas of the environmental barrier coatings were uniform,close-grained and crack-free,which could maintain excellent adherence.Their oxidation resistance would be better with the increase of dipping time and spraying time in preparation.
A network structure surface-enhanced Raman scattering(SERS)-active substrate is fabricated by adding Ag sol dropwise on adhesive tape.Scanning electron microscope(SEM) is employed to characterize the structure of the as-prepared substrate.The substrate shows great SERS enhancement ability and good uniformity by using p-aminothiophenol(PATP) as probe molecules.The detection of crystal violet(CV) in aqueous solution is demonstrated,and the detection limit is as low as 10-12M with the aid of the substrate.The results indicate that the proposed method is a potential approach for the fabrication of SERS substrates.
Hierarchical Cu2O/Au/CuO nanostructures have been achieved by water-based green fabrication at a low temperature.Precluding the requirement of the template removal,the generation of hierarchical architecture relied on the catalytic activity of gold nanoparticles attached on the Cu2O nanocubes.Notably,we creatively developed the dual-roles catalytic ability of gold,which not only remarkably increased the specific surface area of this architecture,but also provided the enhanced performance for gas sensing.
In this review we have summarized some recent results mainly reported by our group that focused on the development of smart gating nanochannels based on polymer films. These nanochannels were prepared using a track-etch process. The responsive materials/molecules and modification methods/techniques have also been demonstrated, from which we have obtained a series of smart gating nanochannels that can respond to single/dual external stimuli, e.g., pH, ion, temperature, light, and so on. These studies utilize responsive behaviors to regulate ionic transport properties inside a single nanochannel and demonstrate the fea-sibility of designing other smart nanodevices in the future.
The viscoelastic properties of synthetic polyisoprenes(PI) reinforced by white carbon black(WCB) have been investigated and compared with WCB reinforced natural rubber(NR), including cure characteristics, physio-mechanical and dynamic mechanical properties. Compared with NR, PI loaded with the same amount of WCB(PI/WCB) exhibited shorter scorch time and optimal cure time, indicating that WCB fillers are comparatively easier to conjugate with PI. The tensile strength and elongation at break decreased with WCB filling in both PI and NR vulcanizates. The hardness of the rubber vulcanizates increased with the WCB filling in the rubber matrix. PI/WCB blends exhibited smaller hardness data, lower tensile strength, as well as lower elongation at break and tensile stress. Increasing the amount of WCB in rubber matrix induced the Payne effect. However, the Payne effect is much more obvious for the PI/WCB system, and PI/WCB also displayed higher storage modulus whereas lower loss modulus and loss tangent than NR/WCB, which could all be attributed to the poor dispersibilities of WCB in the PI matrix.
Uniform arrays of coarse and smooth gold nanoparticles with diameter about 130 nm were successfully synthesized through seed-mediated growth method, separately. Scanning and transmission electron microscopy(SEM and TEM) and X-ray diffraction(XRD) have been used to study the formation and structure of the nanocomposites. The high enhancement factor for surface-enhanced Raman scattering of coarse and smooth gold nanoparticles were estimated to be about 3.1 106 and 2.0 106,respectively. It is evident that the coarse gold nanostructures has higher influence factor than the smooth gold nanostructures. Therefore, these unique properties of the coarse Au nanoparticles appear to be very promising for applications as high-performance SERS substrates.
Yan ZhangLian-Meng WangEn-Zhong TanShi-He YangLi-Dong LiLin Guo
