Hengchang Bi

Carbon Fiber Aerogel Made from Raw Cotton: A Novel, Efficient and Recyclable Sorbent for Oils and Organic Solvents

Twisted carbon fiber (TCF) aerogel with good selective sorption is produced in large scale by using raw cotton as the precursor. TCF aerogel shows highly efficient sorption of organic liquids (pump oil: up to 192 times its own weight; chloroform: up to 115 times its own weight). Moreover, it could be regenerated many times without decrease of sorption capacity by distillation, combustion or squeezing, which depends on the type of pollutants.

Ultrahigh humidity sensitivity of graphene oxide

Humidity sensors have been extensively used in various fields, and numerous problems are encountered when using humidity sensors, including low sensitivity, long response and recovery times, and narrow humidity detection ranges. Using graphene oxide (G-O) films as humidity sensing materials, we fabricate here a microscale capacitive humidity sensor. Compared with conventional capacitive humidity sensors, the G-O based humidity sensor has a sensitivity of up to 37800% which is more than 10 times higher than that of the best one among conventional sensors at 15%–95% relative humidity. Moreover, our humidity sensor shows a fast response time (less than 1/4 of that of the conventional one) and recovery time (less than 1/2 of that of the conventional one). Therefore, G-O appears to be an ideal material for constructing humidity sensors with ultrahigh sensitivity for widespread applications.

Low Temperature Casting of Graphene with High Compressive Strength

has attracted attention due to its fascinating properties such as high carrier mobility, [ 6–8 ] high thermal conductivity, [ 9 , 10 ] extraordinary elasticity and stiffness [ 11 ] and other properties. While mechanical exfoliation, [ 6 ] liquid exfoliation, [ 12 ] and epitaxial growth [ 13 ] can produce pristine graphene, graphene yields are currently too low for large-scale production of macrostructures. In contrast, chemical reduction of graphene oxide provides ‘graphene’ sheets in large scale for graphene macrostructures. [ 14–16 ] Graphene-based macrostructures prepared to date have been relatively weak mechanically, given their fl exible and often relatively porous or open structures, [ 17–26 ] particularly with respect to compressive strength when compared with commercial graphite products. [ 27–29 ] Achieving highly compacted and thus “fully dense” macrostructures based on graphene and measuring the physical properties of such material(s) is thus an important goal. Here, we report a pH-mediated hydrothermal reduction which is combined with moulding methods and allows controllable fabrication of compact high density graphene macrostructures with various shapes. The compact graphene (CG) product that is fabricated in this study shows great advantages over hitherto reported 3-D graphene products, [ 17–26 ] e.g. , a solid microstructure and a high density ( ∼ 1.6 g cm − 3 ) which is comparable to conventional graphite products [ 27–29 ] and an ultrahigh compressive strength ( ∼ 361 Mpa) which is 6 times higher than

Liquid-like pseudoelasticity of sub-10-nm crystalline silver particles

In nanotechnology, small-volume metals with large surface area are used as electrodes, catalysts, interconnects and antennae. Their shape stability at room temperature has, however, been questioned. Using in situ high-resolution transmission electron microscopy, we find that Ag nanoparticles can be deformed like a liquid droplet but remain highly crystalline in the interior, with no sign of dislocation activity during deformation. Surface-diffusion-mediated pseudoelastic deformation is evident at room temperature, which can be driven by either an external force or capillary-energy minimization. Atomistic simulations confirm that such highly unusual Coble pseudoelasticity can indeed happen for sub-10-nm Ag particles at room temperature and at timescales from seconds to months.

Carbon Microbelt Aerogel Prepared by Waste Paper: An Efficient and Recyclable Sorbent for Oils and Organic Solvents

A carbon microbelt (CMB) aerogel with good selective sorption can be produced in large scale by using waste paper as a precursor. The CMB aerogel shows highly efficient sorption of organic liquids (pump oil: up to 188 times its own weight; chloroform: up to 151 times its own weight). Moreover, the CMB aerogel can be regenerated many times without decrease of sorption capacity by distillation, or squeezing depending on the type of pollutants.

Large-range Control of the Microstructures and Properties of Three-dimensional Porous Graphene

Graphene-based three-dimensional porous macrostructures are believed of great importance in various applications, e.g. supercapacitors, photovoltaic cells, sensors and high-efficiency sorbents. However, to precisely control the microstructures and properties of this material to meet different application requirements in industrial practice remains challenging. We herein propose a facile and highly effective strategy for large-range tailoring the porous architecture and its properties by a modified freeze casting process. The pore sizes and wall thicknesses of the porous graphene can be gradually tuned by 80 times (from 10 to 800 μm) and 4000 times (from 20 nm to 80 μm), respectively. The property experiences the changing from hydrophilic to hydrophobic, with the Youngs Modulus varying by 15 times. The fundamental principle of the porous microstructure evolution is discussed in detail. Our results demonstrate a very convenient and general protocol to finely tailor the structure and further benefit the various applications of porous graphene.

Highly enhanced performance of spongy graphene as an oil sorbent

This work demonstrates a brand-new spongy graphene with a highly enhanced performance as an oil sorbent. The absorption capacity of the new spongy graphene to chloroform reaches 616 times of its own weight, which is approximately 8 times higher than that in previous reports. The absorption capacity towards other organic chemicals is also greatly improved.

Thermodynamic and Kinetic Analysis of Lowtemperature Thermal Reduction of Graphene Oxide

The thermodynamic state and kinetic process of low-temperature deoxygenation reaction of graphene oxide (GO) have been investigated for better understanding on the reduction mechanism by using Differential Scanning Calorimetry (DSC), Thermogravimetry-Mass Spectrometry (TG-MS), and X-ray Photo-electron Spectroscopy (XPS). It is found that the thermal reduction reaction of GO is exothermic with degassing of CO2, CO and H2O. Graphene is thermodynamically more stable than GO. The deoxygenation reaction of GO is kinetically controlled and the activation energy for GO is calculated to be 167kJ/mol (1.73 eV/atom).

Microscopic bimetallic actuator based on a bilayer of graphene and graphene oxide

We present an actuator, consisting of a bilayer of graphene and graphene oxide, which allows us to exert forces in micromechanical systems that are at least 50 times higher than reported for other actuators of comparable size. The durability of such a device and stability during many cycles are demonstrated, and the related mechanism is discussed in detail.

Graphene and carbon-based nanomaterials as highly efficient adsorbents for oils and organic solvents

Abstract This paper provides a comprehensive review of recent progress in the synthesis and performance of graphene and carbon-based nanomaterials as efficient adsorbents for oils and organic solvents. Several advantages of these adsorbents are emphasized, including adjustable three-dimensional networks, high surface area, high chemical/thermal stability, high flexibility and elasticity, and extremely high surface hydrophobicity/ oleophilicity. Technical challenges are discussed, and future research directions are proposed.