CNT array-induced nanobubble assembly,nanodisk fabrication and enhanced spectral detection of CNT bundle density

Alignment,functionalization and detection of carbon nanotube(CNT)bundles are vital processes for utilizing this onedimensional nanomaterial in electronics.Here,we report a polymer-assisted wet shearing method to acquire super-aligned craterpatterned CNT arrays by nanobubble(NB)self-assembly with a"migrate and aggregation"mechanism and use craters to controllably mold even-sized nanodisks periodically along CNT bundles with tunable densities.This green,low-cost method can be extended to diverse substrates and fabricate different nanodisks.As an example,the Ag-nanodisk-patterned CNT arrays are utilized as substrates of surface-enhanced Raman scattering(SERS)for rhodamine 6G(R6G)and methylene blue(MB)in which a linear correlation is found between the SERS intensity and the CNT bundle density due to the periodic distribution of hot spots,enabling a spectral detection of CNT bundles and their densities by conventional dye molecules.Distinguishing from routine morphological characterization,this spectral method possesses an enhanced accuracy and a detection range of 0.1–2μm^(–1),showing its uniqueness in the detection of CNT bundle density since the intensity of traditional spectral merely relates to the quantity of CNTs,exhibiting its potential in future CNT-bundle-based electronics.

Elucidating the role of preferential oxidation during ablation:Insights on the design and optimization of multicomponent ultra-high temperature ceramics

Multicomponent ultra-high temperature ceramics(UHTCs)are promising candidates for thermal protection materials(TPMs)used in aerospace field.However,finding out desirable compositions from an enormous number of possible compositions remains challenging.Here,through elucidating the role of preferential oxidation in ablation behavior of multicomponent UHTCs via the thermodynamic analysis and experimental verification,the correlation between the composition and ablation performance of multicomponent UHTCs was revealed from the aspect of thermodynamics.We found that the metal components in UHTCs can be thermodynamically divided into preferentially oxidized component(denoted as MP),which builds up a skeleton in oxide layer,and laggingly oxidized component(denoted as ML),which fills the oxide skeleton.Meanwhile,a thermodynamically driven gradient in the concentration of MP and ML forms in the oxide layer.Based on these findings,a strategy for pre-evaluating the ablation performance of multicomponent UHTCs was developed,which provides a preliminary basis for the composition design of multicomponent UHTCs.

Oxidation behavior of non-stoichiometric(Zr,Hf,Ti)C_(x) carbide solid solution powders in air

Multi-component solid solutions with non-stoichiometric compositions are characteristics of ultra-high temperature carbides as promising materials for hypersonic vehicles.However,for group IV transition-metal carbides,the oxidation behavior of multi-component non-stoichiometric(Zr,Hf,Ti)C_(x)carbide solid solution has not been clarified yet.The present work fabricated four kinds of(Zr,Hf,Ti)C_(x)carbide solid solution powders by free-pressureless spark plasma sintering to investigate the oxidation behavior of(Zr,Hf,Ti)C_(x)in air.The effects of metallic atom composition on oxidation resistance were examined.The results indicate that the oxidation kinetics of(Zr,Hf,Ti)C_(x)are composition dependent.A high Hf content in(Zr,Hf,Ti)C_(x)was beneficial to form an amorphous Zr-Hf-Ti-C-0 oxycarbide layer as an oxygen barrier to enhance the initial oxidation resistance.Meanwhile,an equiatomic ratio of metallic atoms reduced the growth rate of(Zr,Hf,Ti)O_(2)oxide,increasing its phase stability at high temperatures,which improved the oxidation activation energy of(Zr,Hf,Ti)C_(x).