Zeyu Lu

Mechanism of cement paste reinforced by graphene oxide/carbon nanotubes composites with enhanced mechanical properties

This study presents the enhanced mechanical properties of cement paste reinforced by graphene oxide (GO)/carbon nanotubes (CNTs) composites. The UV-vis spectroscopy and optical microscopy results show that the dispersion of CNTs in the GO solution is much better than in an aqueous solution due to the higher electrostatic repulsion, which allows a completely new approach of dispersing CNTs rather than by incorporating a dispersant. More importantly, the GO/CNTs composite plays an important role in improving the compressive and flexural strength of cement paste by 21.13% and 24.21%, which is much higher than cement paste reinforced by CNTs (6.40% and 10.14%) or GO (11.05% and 16.20%). The improved mechanical properties of cement paste are attributed to better dispersed CNTs and enhanced interactions among CNTs by the GO incorporation. Finally, the space interlocking mechanism of the GO/CNTs/cement paste composite with enhanced mechanical properties is proposed.

A new smart traffic monitoring method using embedded cement-based piezoelectric sensors

Cement-based piezoelectric composites are employed as the sensing elements of a new smart traffic monitoring system. The piezoelectricity of the cement-based piezoelectric sensors enables powerful and accurate real-time detection of the pressure induced by the traffic flow. To describe the mechanical-electrical conversion mechanism between traffic flow and the electrical output of the embedded piezoelectric sensors, a mathematical model is established based on Duhamels integral, the constitutive law and the charge-leakage characteristics of the piezoelectric composite. Laboratory tests show that the voltage magnitude of the sensor is linearly proportional to the applied pressure, which ensures the reliability of the cement-based piezoelectric sensors for traffic monitoring. A series of on-site road tests by a 10 tonne truck and a 6.8 tonne van show that vehicle weight-in-motion can be predicted based on the mechanical-electrical model by taking into account the vehicle speed and the charge-leakage property of the piezoelectric sensor. In the speed range from 20 km h−1 to 70 km h−1, the error of the repeated weigh-in-motion measurements of the 6.8 tonne van is less than 1 tonne. The results indicate that the embedded cement-based piezoelectric sensors and associated measurement setup have good capability of smart traffic monitoring, such as traffic flow detection, vehicle speed detection and weigh-in-motion measurement.

Mechanism of UV-assisted TiO2/reduced graphene oxide composites with variable photodegradation of methyl orange

TiO2/reduced graphene oxide (TiO2/rGO) composites with variable photodegradation efficiency of methyl orange (MO) were synthesized by combining TiO2 and graphene oxide (GO) under ultraviolet (UV) irradiation. In this study, the influences of TiO2 content and UV irradiation time on the reduction degree of GO during fabrication of the TiO2/rGO composite were investigated and characterized by X-ray diffraction (XRD), Raman spectrum, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The experimental results showed that the maximum reduction degree of GO can be achieved by controlling the weight ratio (TiO2/GO) of 10 under 15 min UV irradiation, and the corresponding composite showed 1.71 times the higher photodegradation efficiency of MO over pure TiO2, which results from the newly generated rGO with high electrical conductivity that decreases the recombination rate of excited electrons–holes in TiO2. The results also demonstrated that the photodegradation efficiency of the TiO2/rGO composite was closely related to the reduction of GO during fabrication of the composite. The more UV irradiation during fabrication of the composite, the higher reduction degree of GO, and therefore higher photodegradation efficiency of the TiO2/rGO composite can be achieved, but excessive UV irradiation plays a negative effect on the photodegradation efficiency of the composite. Finally, the mechanism of UV-assisted TiO2/rGO composites with variable photodegradation efficiency was proposed in terms of the reduction degree of GO.

Preparation and characterization of an expanded perlite/paraffin/graphene oxide composite with enhanced thermal conductivity and leakage-bearing properties

A novel phase change material (PCMs) of expanded perlite/paraffin/graphene oxide (EP/PA/GO) with enhanced thermal conductivity and leakage-bearing properties was fabricated by depositing GO films on the surface of the EP/PA composite. The as-prepared EP/PA/GO composite was characterized by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) techniques. The experimental results indicated that due to the small loading of the GO incorporated, the EP/PA/GO composite showed a small latent heat capacity and weight loss, and the thermal conductivity significantly increased with increasing the content of GO up to 0.5 wt%. The heat storage/release performance test results demonstrated that the EP/PA composite with 0.5 wt% GO had 2 times faster heat storage/release rate compared to the EP/PA composite because of the enhanced thermal conductivity. In addition, the FTIR and TGA results indicated that the EP/PA/GO composite had good chemical compatibility and thermal stability. More importantly, the GO films covering the surface of the EP/PA composite can greatly prevent the leakage problems of molten paraffin. No leakage of paraffin occurred even after thermal cycling 3000 times. Therefore, the EP/PA/GO composite has a great potential for thermal energy storage applications due to its enhanced thermal properties, good leakage-bearing properties and excellent chemical compatibility.

Design of magnesium phosphate cement based composite for high performance bipolar plate of fuel cells

In this work, we report a comprehensive study on a magnesium phosphate cement (MPC) based composite as the construction material for high performance bipolar plates of fuel cells. MPC with partial replacement of fly ash was employed as the binding matrix. Some carbon-based materials, such as graphite, carbon black, carbon fiber, and multi-walled carbon nanotubes were used to construct the conductive phase. A simple hot-press process was applied to produce the composite. The formula and the structure of the composite was modified and adjusted to optimize the properties of the composite to meet the US DOE 2015 technical targets, including the introducing of a reinforcement support. Finally, all the technical targets such as electrical conductivity (>100 S cm−1), the flexural strength (>25 MPa), the corrosion resistance (<1 μA cm−2), and gas permeability (<10−5 cm3 (s cm2)−1) were achieved as well as low cost (<5

Preparation and characterization of expanded perlite/paraffin composite as form-stable phase change material

per kW). The optimized formula and the detailed procedures to fabricate the MPC based composite were concluded.