Carbon fibres have attracted interest from both the scientific and engineering communities due to their outstanding physical properties. Here we report that recently synthesized ultrathin diamond ...nanothread not only possesses excellent torsional deformation capability, but also excellent interfacial load-transfer efficiency. Compared with (10,10) carbon nanotube bundles, the flattening of nanotubes is not observed in diamond nanothread bundles, which leads to a high-torsional elastic limit that is almost three times higher. Pull-out tests reveal that the diamond nanothread bundle has an interface transfer load of more than twice that of the carbon nanotube bundle, corresponding to an order of magnitude higher in terms of the interfacial shear strength. Such high load-transfer efficiency is attributed to the strong mechanical interlocking effect at the interface. These intriguing features suggest that diamond nanothread could be an excellent candidate for constructing next-generation carbon fibres.
The excellent mechanical properties of carbon nanofibers bring promise for energy-related applications. Through in silico studies and continuum elasticity theory, here we show that the ultra-thin ...carbon nanothreads-based bundles exhibit a high mechanical energy storage density. Specifically, the gravimetric energy density is found to decrease with the number of filaments, with torsion and tension as the two dominant contributors. Due to the coupled stresses, the nanothread bundle experiences fracture before reaching the elastic limit of any individual deformation mode. Our results show that nanothread bundles have similar mechanical energy storage capacity compared to (10,10) carbon nanotube bundles, but possess their own advantages. For instance, the structure of the nanothread allows us to realize the full mechanical energy storage potential of its bundle structure through pure tension, with a gravimetric energy density of up to 1.76 MJ kg
, which makes them appealing alternative building blocks for energy storage devices.
Polyprolylene is commonly used for crude oil spill cleaning, but it has low absorption capacity and is nonbiodegradable. In our work, a green, ultralight, and highly porous material was successfully ...prepared from paper waste cellulose fibers. The material was functionalized with methyltrimethoxysilane (MTMS) to enhance its hydrophobicity and oleophilicity. Water contact angles of 143 and 145° were obtained for the MTMS-coated recycled cellulose aerogel. The aerogel achieved high absorption capacities of 18.4, 18.5, and 20.5 g/g for three different crude oils at 25 °C, respectively. In the investigated temperature range of 10, 25, 40, and 60 °C for the absorption of the tested crude oil on the aerogel, a highest absorption capacity of 24.4 g/g was obtained. It was found that the viscosity of the crude oils is the main factor affecting their absorption onto the aerogel. The strong affinity of the MTMS-coated recycled cellulose aerogel to the oils makes the aerogel a good absorbent for crude oil spill cleaning.
It is generally accepted that material inhomogeneity causes stress concentrations at the interface and thus reduces the overall strength of a composite. To overcome this reduction in strength, some ...groups experimented on coating the nanoinclusions with a layer of rubbery material, aiming for higher energy absorption. However, representative volume element (RVE) nanocomposite models, established with randomly distributed core–shell nanoparticles and single nanoparticle cells, show that the enhancement in strength observed in some experiments remains elusive computationally. By including a pre-existing crack in the matrix of the RVE, the stress concentration at the crack tip is reduced for cases where the nanoparticle and precrack are aligned away from the loading direction. This suggests that stress concentrations around inherent defects in materials can sometimes be reduced by adding nanoparticles to improve material strength. The effect is reversed if the crack and nanoparticle are aligned towards the loading direction. Parametric studies were also carried out in terms of the relative stiffness of the nanoparticle to the matrix and crack length. Validation tests were performed on 3D RVEs with an elliptical crack as the initial defect, and the results match with the 2D findings.
Lead modification of meisoindigo at position 1 of the isoindigo scaffold yield more potent analogs of meisoindigo that have low micromolar antiproliferative activities against K562 and HL60 leukemic ...cell lines.
A series of functionalized isoindigos structurally related to meisoindigo (1-methylisoindigo), a therapeutic agent used for the treatment of a form of leukemia, were synthesized and evaluated for antiproliferative activities on a panel of human cancer cells. Two promising compounds (1-phenpropylisoindigo and 1-(
p-methoxy-phenethyl)-isoindigo) that were more potent than meisoindigo and comparable to 6-bromoindirubin-3′-oxime on leukemic K562 and liver HuH7 cells were identified. Structure–activity relationships showed the importance of keeping one of the lactam NH in an unsubstituted state. Substitution of the other lactam NH with aryl or arylalkyl side chains retained or improved activity in most instances. An intact exocyclic double bond was also essential, possibly to maintain planarity and rigidity of the isoindigo scaffold. None of the compounds were found to inhibit CDK2 in an in vitro assay, in spite of reports linking the antiproliferative activities of meisoindigo and other isoindigos to CDK2 inhibition. Hence, these functionalized isoindigos disrupted cell growth and proliferation by other mechanistic pathways that did not involve CDK2 inhibition.
This work explores the application of a new 1D carbon nanomaterial, the diamond nanothread (DNT), as a reinforcement for nanocomposites. Owing to the existence of Stone–Wales transformation defects, ...the DNT intrinsically possesses irregular surfaces, which is expected to enhance the noncovalent interfacial load transfer. Through a series of in silico pull‐out studies of the DNT in polyethylene (PE) matrix, it is found that the load transfer between DNT and PE matrix is dominated by the noncovalent interactions, in particular the van der Waals interactions. Although the hydrogenated surface of the DNT reduces the strength of the van der Waals interactions at the interface, the irregular surface of the DNT can compensate for the weak bonds. These factors lead to an interfacial shear strength of the DNT/PE interface comparable with that of the carbon nanotube/PE interface. The results show that the DNT/PE interfacial shear strength remains high even as the number of Stone–Wales transformation defects decreases. It can be enhanced further by increasing the PE density or introduction of functional groups to the DNT, both of which greatly increase the noncovalent interactions.
The irregular surfaces of the new diamond nanothread (DNT) are expected to enhance the noncovalent interfacial load transfer between DNT and polymer. Through pull‐out studies, it is found that the shear strength of the DNT/polyethylene interface is comparable with that of the carbon nanotube/polyethylene interface, which can be enhanced further by increasing the polyethylene density or introduction of functional groups to the DNT.
Crustacean-inspired helicoidal laminates Shang, J.S.; Ngern, Nigel H.H.; Tan, Vincent B.C.
Composites science and technology,
05/2016, Letnik:
128
Journal Article
Recenzirano
Comprising layers of aligned chitin filaments stacked together, the exoskeletons of many crustaceans are analogous to fibre reinforced composites. A unique feature of crustacean laminates is their ...helicoidal lay-up. Each ply is rotated a slight angle from the ply like the steps of a spiral staircase – an unusual configuration for structural composites. Carbon fibre reinforced epoxy with helicoidal lay-ups were fabricated and tested to determine if they offered any advantage. Under transverse loads, these bio-inspired plates displayed a monotonically increasing load-displacement response followed by abrupt failure without the intermittent load drops seen in cross-plys. When the interply angle in the helicoidal laminates is small, they can sustain higher loads than the crossplys. A 34% increase in peak load was obtained for 19-ply helicoidal laminates over crossplys. Micro-CT scans reveal obvious transverse cracks and delamination at all interply interfaces around the point of loading in crossplys whereas delamination in helicoidal specimens climbs from one interface to the next forming a spiral pattern which extends to the edge of the specimens. Load-displacement predictions from finite element simulations showed quantitative agreement with experiments and key damage features were also replicated.
We report an efficient method to synthesize vertically aligned Co3O4 nanostructures on the surface of cobalt foils. This synthesis is accomplished by simply heating the cobalt foils in the presence ...of oxygen gas. The resultant morphologies of the nanostructures can be tailored to be either one‐dimensional nanowires or two‐dimensional nanowalls by controlling the reactivity and the diffusion rate of the oxygen species during the growth process. A possible growth mechanism governing the formation of such nanostructures is discussed. The field‐emission properties of the as‐synthesized nanostructures are investigated in detail. The turn‐on field was determined to be 6.4 and 7.7 V μm–1 for nanowires and nanowalls, respectively. The nanowire samples show superior field‐emission characteristics with a lower turn‐on field and higher current density because of their sharp tip geometry and high aspect ratio.
Vertically aligned nanostructures of Co3O4 with various morphologies (the figure shows nanowires; nanowalls were also obtained) are made on cobalt foil in a controlled manner using a facile method. The morphological variations are achieved by varying the reactivity and diffusivity of the oxidizing species by creating a plasma environment in the system. The field‐emission properties of the as‐synthesized nanostructures are investigated.
Abstract
Background
Inconsistent associations between coffee consumption and bone mineral density (BMD) have been observed in epidemiological studies. Moreover, the relationship of bioactive ...components in coffee with BMD has not been studied. The aim of the current study is to identify coffee-associated metabolites and evaluate their association with BMD.
Methods
Two independent cohorts totaling 564 healthy community-dwelling adults from the Hong Kong Osteoporosis Study (HKOS) who visited in 2001–2010 (N = 329) and 2015–2016 (N = 235) were included. Coffee consumption was self-reported in an food frequency questionnaire. Untargeted metabolomic profiling on fasting serum samples was performed using liquid chromatography–mass spectrometry platforms. BMD at lumbar spine and femoral neck was measured by dual-energy X-ray absorptiometry. Multivariable linear regression and robust regression were used for the association analyses.
Results
12 serum metabolites were positively correlated with coffee consumption after Bonferroni correction for multiple testing (P < 4.87 × 10–5), with quinate, 3-hydroxypyridine sulfate, and trigonelline (N’-methylnicotinate) showing the strongest association. Among these metabolites, 11 known metabolites were previously identified to be associated with coffee intake and 6 of them were related to caffeine metabolism. Habitual coffee intake was positively and significantly associated with BMD at the lumbar spine and femoral neck. The metabolite 5-acetylamino-6-formylamino-3-methyluracil (AFMU) (β = 0.012, SE = 0.005; P = 0.013) was significantly associated with BMD at the lumbar spine, whereas 3-hydroxyhippurate (β = 0.007, SE = 0.003, P = 0.027) and trigonelline (β = 0.007, SE = 0.004; P = 0.043) were significantly associated with BMD at the femoral neck.
Conclusions
12 metabolites were significantly associated with coffee intake, including 6 caffeine metabolites. Three of them (AFMU, 3-hydroxyhippurate, and trigonelline) were further associated with BMD. These metabolites could be potential biomarkers of coffee consumption and affect bone health.
We present a theoretical study on a series of novel organometallic sandwich molecular wires (SMWs), which are constructed with alternating iron atoms and cyclopentadienyl (Cp) rings, using DFT and ...nonequilibrium Green's function techniques. It is found that that the SMWs are stable, flexible structures having half-metallic (HM) properties with 100% negative spin polarization near the Fermi level in the ground state. Some SMWs of finite size show a nearly perfect spin filter effect (SFE) when coupled between ferromagnetic electrodes. Moreover, their I − V curves exhibit negative differential resistance (NDR), which is essential for certain electronic applications. The SMWs are the first linear molecules with HM, high SFE, and NDR and can be easily synthesized. In addition, we also analyze the underlying mechanisms via the transmission spectra and spin-dependent calculations. These findings strongly suggest that the SMWs are promising materials for application in molecular electronics.
PDF
