Enhancement of electrical and thermal properties of graphene by aligned carbon nanotubes

Abstract In order to explore the composite effects of graphene (GR) and carbon nanotubes (CNTs), GR/CNTs aerogels and GR/CNTs coatings were fabricated. Aligned carbon nanotubes (ACNTs) and twining carbon nanotubes (TCNTs) were comparatively examined by integrating them with graphene, which has seldom been studied in detail. Freeze drying was novelly adopted to retain the liquid distribution in GR/CNTs mixture. Fourier Transform Infrared Spectroscopy (FTIR) analysis demonstrated that OH group and carboxylic acid groups were effectively induced onto CNTs via chemical modification. Scanning electron microscopy (SEM) showed that ACNTs achieved better dispersion and homogeneity in graphene than TCNTs. GR/CNTs hybrid composite with various loading of ACNTs or TCNTs were examined by electrical/thermal conductivity tests and practically evaluated for thermal management in LEDs. Results revealed that the electrical and thermal properties of graphene can be dramatically enhanced by the proper addition of ACNTs due to the formation of effective conductive bridges. The GR/ACNTs aerogel with 10 wt% ACNTs attained a high electrical conductivity of 2.08?×?104 S m?1, elevated to 2.76?×?104 S m?1 after annealing treatment. The eco-friendly and low-cost GR/ACNTs coating with 10 wt% ACNTs prominently reduced the operating temperature of LEDs by 8.6 °C, acting as potential thermal management materials in practical applications

Facile in-situ synthesis of floating CeO2@ expanded graphite composites with efficient adsorption and visible light photocatalytic degradation of phenol

A facile solution to obtain efficient, stable and cheap photocatalysts was conducted in this work. CeO2@ expanded graphite (CeO2/EG) composites were in-situ synthesized with a new strategy, in which CeCl3 molecules inserted the graphite intercalation compound (GIC) and converted into CeO2 as GIC changed into EG via instant calcination. The introduction of EG has accelerated the adsorption of contaminant molecules, promoted the charge transfer and improved the photocatalytic efficiency. The best sample, containing 80.75 wt% CeO2 particles of nanometer scale, has achieved the highest pollutant removal efficiency of 97.3% for phenol, displaying the highest reaction rate constant of 0.0262 min(-1), which was 35.4 times higher than CeO2. Besides, it possesses good stability and keeps floating in water pollution treatment, showing great advantages to work in natural water body. Phenol and its degradation intermediates were identified using HPLC/MS, and appropriate reaction pathways were proposed

Innovative technology for defluorination of secondary aluminum dross by alkali leaching

Secondary aluminum dross (SAD) contains harmful fluorides, so it requires a harmless treatment before recy-cling. In this paper, an innovative SAD defluorination technology was developed. It extracts all the soluble so-dium fluoride and active cryolite of SAD; besides, it can also stabilize the harmful fluorides towards deep detoxification. The defluorination process gave a novel idea for the comprehensive wet processing treatment of SAD. A NaOH solution was used to leach active fluorides, including cryolite and soluble fluorides, from SAD. The Effects of NaOH concentration, temperature, liquid-to-solid ratio, and leaching time on the fluoride leaching rate were investigated. The leaching rate of active fluorides was 95.8% at a NaOH concentration of 10 wt%, a leaching temperature of 80 degrees C, a liquid-to-solid ratio of 4, and a leaching time of 20 min. The kinetic analysis showed that the fluoride leaching occurred according to the hybrid control model of solid product layer in -diffusion and interfacial chemical reaction. The apparent activation energy was 39.64 kJ/mol. Meanwhile, 99.9% of fluoride ions in the alkaline solution were converted into CaF2 by adding CaO, stabilizing the active fluorides. The concentration of fluorides in the alkaline solution was 5.944 mg/L, satisfying the Chinese National Standard