Weicheng Jiao

Synthesis and characterization of a new hierarchical reinforcement by chemically grafting graphene oxide onto carbon fibers

We proposed a new hierarchical reinforcement consisting of graphene oxide (GO) and carbon fibers (CF). It was confirmed that GO was chemically grafted onto CF via poly(amido amine) dendrimers. The GO grafting significantly changes the surface configuration of CF. The new hierarchical reinforcement has the potential to be applied in high performance polymer matrix composites.

Preparation of MoO3 QDs through combining intercalation and thermal exfoliation

Lots of top-down approaches by weakening the van der Waals interaction between adjacent layers and breaking up the covalent chemical bonds in each layer have been reported to prepare QDs of layered materials due to the stacked structures. However, much attention has been focused on graphene and layered transition-metal dichalcogenides (TMDs), seldomly on layered transition-metal oxides (TMOs). Herein, a modified top-down method combining intercalation and thermal exfoliation is reported to prepare high-yield QDs of layered MoO3. Alkylamine was first intercalated into MoO3 layers to weaken the van der Waals forces. Then, the covalent bonds in each MoO3 layer were broken down under a sudden increase in gas pressure generated by the decomposition of alkylamines after rapid heating. These fractured particles were further incised to QDs by sonication. The as-prepared MoO3 QD dispersion showed a plasmon resonance after simulated solar light illumination. Surprisingly, their plasmon peak red shifted with an extended illumination time, which was different from the reported MoO3 nanosheets. This reported method is expected to extend to other QDs of layered materials providing that their bulk materials can also be intercalated.

Dome Thickness Prediction of Composite Pressure Vessels by a Cubic Spline Function and Finite Element Analysis

Nowadays, finite element analysis (FEA) plays an important role in the design of composite pressure vessel. The more accurate finite element models are created, the more precise results could be obtained. In order to create the accurate finite element model for composite pressure vessels, a cubic spline function was developed to predict the dome thickness basing on the principle of total volume preservation of all bands at dome section. In the paper, the dome thickness of an arbitrary composite pressure vessel was forecasted by the cubic spline function and compared with the existing methods and actual measured values. The results show that the cubic spline function is more realistic than the other methods. Then the FEA considering the dome thickness pre-calculated by various methods was performed and compared with experimental data. The results further indicate that the cubic spline function could provide a more accurate model, which is approaching the real case.

A biomimetic, multifunctional, superhydrophobic graphene film with self-sensing and fast recovery properties for microdroplet transportation

Recently, multifunctional superhydrophobic surfaces with high adhesion behavior have attracted much attention for microdroplet transportation. Here, we report for the first time a multifunctional, rose-petal-like, superhydrophobic graphene film via the self-assembly of graphene oxide (GO) that has self-sensing and fast recovery properties for microdroplet transportation. This superhydrophobic film does not require a hydrophobic coating and has a micro-nanoscale hierarchical structure. Because of its structure, our biomimetic, superhydrophobic film has high adhesive force to water droplets and can be used as a medium for microdroplet transportation. In addition, because the film was constructed using pure graphene, it has excellent conductivity properties and an immediate response system is also built to detect potential damage. Moreover, owing to the gas sensing properties of graphene, our film has self-sensing properties where the resistance of the film increases gradually when water droplets are close to it. Whats more, the film has an ultra-fast Joule heating rate of 18 °C s−1. Based on these properties, the recovery time for the resistance of the film can be reduced by 57.7% for water droplet transportation. Therefore, our multifunctional, superhydrophobic graphene film can be used for smart microdroplet manipulation in the future.

Photothermal healing of a glass fiber reinforced composite interface by gold nanoparticles

The formation of microcracks especially in the interfacial region is a critical problem for fiber reinforced composites. Repairing the microcracks before catastrophic failure of the materials takes place is a promising solution to achieve long lifetime operation. In this context, a novel method is demonstrated for interfacial healing of glass fiber reinforced composites using the photothermal effect of gold nanoparticles (Au NPs). Au NPs were successfully dispersed into the interfacial region of a glass fiber reinforced composite. Once the interfacial damage occurred, a laser could be used to illuminate Au NPs to generate a large amount of heat through the photothermal effect. This would melt the resin and form mechanical interlocking between the fiber and PMMA to create a new interface. It has been confirmed by a micro bond test that the composite containing Au NPs has healing ability with a maximum healing efficiency of 98.5% under optimized conditions. The mechanism of the interfacial healing was also investigated and it is found that the density of Au NPs and irradiation intensity play key roles in the healing process.

Enhanced and tunable photochromism of MoO3–butylamine organic–inorganic hybrid composites

Orthorhombic molybdenum trioxide (α-MoO3) as one kind of potential inorganic photochromic material shows a slow response, poor reversibility and monotonic coloration. Here, we provide an efficient way to improve and tune the photochromism of MoO3. Novel inorganic–organic hybrid composites were successfully prepared by intercalating n-butylamine into the layer space of α-MoO3 and enhanced photochromic properties such as a fast response, superior reversibility, and good stability were achieved. Meanwhile, the solutions of as-prepared hybrids showed solvent-dependent discoloration due to the hole scavenger effect of ethanol. A reversible transformation between an intermediate state and an enhanced, but stable state was realized by switching irradiation. The improved photochromism caused the solutions of hybrids to show diverse discoloration varying from yellow to green to blue color.

Oxidative etching of MoS2/WS2 nanosheets to their QDs by facile UV irradiation

Oxidative etching has been proved to be an efficient top-down method to prepare quantum dots (QDs) of layered transition-metal dichalcogenides which possess unique properties and have potential applications in various areas. Here, one facile and green oxidative etching method induced by UV irradiation is reported to prepare the QDs of MoS2/WS2 in aqueous solution, respectively. A prominent morphology change occurred to the nanosheets of MoS2/WS2 after irradiation and finally they were etched to ultrasmall nanoparticles which were proved to be the QDs. Insight into the etching mechanism was discussed in detail and hydroxyl free radicals (˙OH) were conclusively demonstrated to play the main role in etching nanosheets. From another point of view, this work also proves the crucial long-term photo instability of MoS2/WS2 since there are increasing photo-related applications of them and points out an easy way to degrade their nanosheets.

Research on Stability Condition of Polar Winding on the Dished Head

The polar winding, as a kind of non-geodesic winding, is in a serious slippage trend. Based on the Theoretical Model of the filament winding, this paper outlines a kind of numerical methods for determining the stability condition of the polar winding on the composite pressure vessel with dished head. At last, through the providing some examples, this paper shows the stable trend on the dished dome during polar winding to optimize the design result.

Scalable exfoliation for large-size boron nitride nanosheets by low temperature thermal expansion-assisted ultrasonic exfoliation

Hexagonal boron nitride nanosheets (BNNSs) hold great potential in many applications due to their intriguing properties. However, the high-yield preparation of large-size BNNSs still remains a key challenge. Herein, we report a scalable exfoliation process, named as ‘low temperature thermal expansion-assisted ultrasonic exfoliation’, to prepare BNNSs. This method firstly utilizes hydrogen induced low temperature thermal reduction of hydroxyl-functionalized bulk hexagonal boron nitride (BN-OH) to weaken interlayer interaction between adjacent layers, and then employs a brief sonication to completely exfoliate BNNSs from their bulk materials. Few-layer and large-size BNNSs with a high yield of 26% are successfully prepared by this method. Moreover, the large-area BNNSs can effectively enhance the thermal conductivity of thermoplastic polyurethane elastomer on account of the decrease of interfacial thermal resistance. Low temperature thermal expansion-assisted ultrasonic exfoliation can thus provide an efficient approach to scalable fabrication of high-quality BNNSs. Furthermore, this method is promising for the high-yield production of other nanosheets.

Preparation of quantum dots from MoO3 nanosheets by UV irradiation and insight into morphology changes

After UV irradiation of orthorhombic molybdenum trioxide (α-MoO3) nanosheets dispersed in two different solvents including water/ethanol mixed solvents and individual N-methyl-2-pyrrolidinone (NMP), we observed remarkable but distinct morphology changes in combination with different photochromic phenomena. MoO3−x quantum dots (QDs) with both different sizes and oxygen vacancy concentrations could be acquired through this facile and efficient method. The consumption of photoexcited holes played an important role in the morphology changes. In water/ethanol, intercalation of H+ originating from the oxidation of water by photoholes contributes to the acquisition of QDs. While in NMP, we provided a new insight and proved that photocorrosion induced by accumulated holes was responsible for the morphology evolution and acquisition of QDs.