Advanced Nanocomposites最新文献

This article presents a systematic review over recent preparation techniques and their mechanisms for epoxy/graphene nanocomposites. Special honeycomb lattice nanostructure of graphene provides epoxy resins with mechanical stiffening, toughening, thermal and electrical conductivities, and anti-corrosion performance. To form epoxy/graphene nanocomposites with optimized structure and mechanical and functional performance, many efforts have been undertaken to exfoliate and disperse graphene nanoplatelets (GNPs) in epoxy, by utilizing single or combined mechanical, thermal, electromagnetic, and chemical strategies. Below is a list of design criteria summarized from recent studies: (i) the lowest thickness (below 10 nm) with appropriate lateral dimension is always preferred for GNPs prior to compounding with epoxy, (ii) physical techniques such as heat and sonic waves, mechanical methods like shearing, and chemical surface modification should be combined to achieve a high degree of exfoliation and dispersion of GNPs in epoxy, (iii) the destruction of graphene lattice must be carefully controlled during preparation because otherwise it deteriorates the intrinsic properties of graphene and hence the resulting nanocomposites, and (iv) the fraction of GNPs in epoxy should also be carefully determined due to a trade-off between the mechanical performance and the functional properties of the nanocomposites. Noteworthy are those recent less toxic or surfactant-free yet effective methods for the modification of graphene surface and the preparation of epoxy nanocomposites. All in all, cost-effective and environmentally friendly approaches are always preferred, forming a major research theme in the years to come.

In this study, nanolaminated tantalum (Ta)/cobalt (Co) composites (NTCCs) with an individual layer thickness (h) ranging from 5 nm to 100 nm were fabricated via magnetron sputtering. The microstructures and nanomechanical properties of the NTCCs were affected by variation in h. The NTCCs showed nanograin structures in Ta and Co layers, with Ta and Co textures that were randomly oriented. Nanohardness (H) and corresponding yield strength, ${\sigma }_{\mathrm{ys}}=H/2.7$, of the NTCCs gradually increased from 5.75 ± 0.15 GPa to 7.20 ± 0.13 GPa and from 2.12 ± 0.06 GPa to 2.67 ± 0.05 GPa, respectively, with reducing h from 100 nm to 5 nm. NTCC showed an extraordinarily high yield strength (∼ 2.67 GPa) at h = 5 nm due to its reduced individual layer thickness and non-defective microstructures, which is well above the maximum yield strength of studied nanolaminated materials (comprised of at least one hcp constituent), to date. The creep depth of 5 nm NTCC was lower than that of the 100 nm NTCC, and the creep deformation of 5 nm NTCC is related to the bending, breaking, and intermixing of Ta and Co layers, whereas the 100 nm NTCC exhibited bending and thinning of Ta and Co layers with more deformation. Strain rate sensitivity (m) of NTCC increased from 0.0666 to 0.2076 with increasing h from 5 nm to 100 nm. The Hall–Petch and Confined Layer Slip strengthening mechanisms governed the strength of the NTCCs for h = 25–100 nm and h = 10 nm, respectively. It is worth noting that the 5 nm NTCC did not follow any of the strengthening mechanisms and became independent of h; rather, the strength at this length scale was greatly influenced by grains, layer thickness, and microstructural variations at the interfaces. The increased σ_ys and E at h = 5 nm may facilitate tailoring the mechanical properties of NTCCs with high strength and ductility.

Thermoelectric (TE) materials have garnered significant attention in recent years due to their potential for converting waste heat into usable electricity. However, traditional TE materials are plagued by limitations such as low energy efficiency, toxicity, and high temperature requirements for synthesis. Consequently, researchers have turned their focus to organic conducting polymers, specifically poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS), due to their high electrical conductivity, processability, stability, and flexibility. This review provides a detailed examination of recent advancements in boosting the TE performance of PEDOT: PSS. It focuses on two key strategies: innovative chemical treatments and nanocomposite approaches. By dissecting the mechanisms, processing techniques, and resultant performance improvements, this review brings a unique perspective to the PEDOT: PSS field. Interestingly, there's a notable lack of dedicated reviews exploring the enhancement of the PEDOT: PSS's TE performance through chemical treatments, whilst the growing popularity of nanocomposite strategies underscores the need for a timely overview. This review bridges both gaps, offering valuable insights. Furthermore, the review also looks ahead, suggesting important areas for future research. These include augmenting carrier mobility, fine-tuning polymer architecture, optimizing doping levels, and formulating economically viable and scalable methodologies for synthesizing nanocomposites. Considering its relevance today, this paper has the potential to be a useful resource for researchers exploring the changing field of thermoelectric advancements.