Enhancement of Electrical and Mechanical Properties of Modified Asphalt Concrete with Graphite Powder

A large number of additives are introduced in asphalt concrete mixtures in purpose of improving the properties of resistance, facing the increasing traffic and more severe climatic conditions. This will guarantee the good comfort for a longer exploitation time. In this article we used graphite powder as an unconventional additive, and then investigate its effect mainly on the electrical resistivity which is in context of our research work on conductive asphalt (with a resistivity around 106 Ω m), As well as on its mechanical properties evaluated using the new Fenix test that gives many information of mechanical especially dissipated energy. A significant improvement was noticed in the reduction of resistivity by reaching 1.7 × 106Ω m and also greater resistance to cracking based on variation of dissipated energy as a result we concluded that introducing graphite powder with an appropriate amount enhance both mechanical and electrical properties asphalt concrete. Doi: 10.28991/CEJ-2022-08-01-09 Full Text: PDF

Influence of Graphite Powder on the Mechanical and Acoustic Emission Characteristics of Concrete

In this paper, uniaxial compressive strength (UCS) test and three-point bending (TPB) test, together with an acoustic emission (AE) system, were performed to investigate the mechanical properties and AE characteristic changes of concrete with different graphite powder (GP) content. The results show that: (1) Poor adhesion and low interlocking of graphite with cement stone increase the initial defects of concrete, reducing its elastic modulus and the cyclo-hoop effect, and thus weakening the compressive strength. (2) For concrete with a low graphite content, the second sharp rise in ringing counts or energy released during the compressive process can be regarded as a failure alarm. However, as GP content increases, the second sharp rise fades away, while the first sharp rise becomes more visible. At high GP content, the first sharp rise is better for predicting failure. (3) The initial defects caused by GP significantly lower the initial fracture toughness, but its bridging effect greatly increases the critical crack mouth opening displacement and thus significantly enhances the unstable fracture toughness of concrete, by up to 9.9% at 9% GP content. (4) In contrast to compressive process, the sharp increase in AE signals preceding failure during the fracture process cannot be used to predict failure because it occurs too close to the ultimate load. However, as GP can significantly increase the AE signals and damage value in the stable period, such failure precursor information can provide a safety warning for damage development.

Phase Formation and the Electrical Properties of YSZ/rGO Composite Ceramics Sintered Using Silicon Carbide Powder Bed

Fully stabilized zirconia/graphene composites are very promising advanced structural materials having mixed ion–electron conductivity for energy storage and energy conversion applications. The existing methods of the composite manufacturing have a number of disadvantages that limit their practical use. Thus, the search for new sintering methods is an actively developing area. In this work, we report for the first time the application of the SiC powder bed sintering technique for fully stabilized zirconia (YSZ) composite fabrication. The reduced graphene oxide (rGO) was used as a graphene derivative. As a result, well-formed ceramics with high density and crystallinity, the maximal microhardness of 13 GPa and the values of the ionic conductivity up to 10−2 S/cm at 650 °C was obtained. The effects of the sintering conditions and rGO concentration on the microstructure and conductivities of ceramics are discussed in detail. The suggested powder bed sintering technique in a layered graphite/SiC/graphite powder bed allowed well-formed dense YSZ/rGO ceramics fabrication and can become a suitable alternative to existing methods for various oxide ceramic matrix composite fabrication: both conventional sintering and non-equilibrium (SPS, flash sintering) approaches.

Cost-Effective 1T-MoS2 Grown on Graphite Cathode Materials for High-Temperature Rechargeable Aluminum Ion Batteries and Hydrogen Evolution in Water Splitting

The high dependence on and high cost of lithium has led to a search for alternative materials. Aluminum ion batteries (AIBs) have gained interest due to their abundance, low cost, and high capacity. However, the use of the expensive 1-ethyl-3-methylimidazolium chloride (EMIC) electrolyte in AIBs curtails its wide application. Recently, high-temperature batteries have also gained much attention owing to their high demand by industries. Herein, we introduce cost-effective 1T molybdenum sulfide grown on SP-1 graphite powder (1T-MoS2/SP-1) as a cathode material for high-temperature AIBs using the AlCl3-urea eutectic electrolyte (1T-MoS2/SP-1–urea system). The AIB using the 1T-MoS2/SP-1–urea system exhibited a capacity as high as 200 mAh/g with high efficiency of 99% over 100 cycles at 60 °C when cycled at the rate of 100 mA/g. However, the AIB displayed a capacity of 105 mAh/g when cycled at room temperature. The enhanced performance of the 1T-MoS2/SP-1–urea system is attributed to reduced viscosity of the AlCl3-urea eutectic electrolyte at higher temperatures with high compatibility of 1T-MoS2 with SP-1. Moreover, the electrocatalytic lithiation of 1T-MoS2 and its effect on the hydrogen evolution reaction were also investigated. We believe that our work can act as a beacon for finding alternative, cost-effective, and high-temperature batteries.

Preparation of Expanded Graphite and Graphite Nanosheets for Improving Electrical Conductivity of Polyester Coating Films

Expanded graphite and graphite nanosheets were facilely prepared by the thermal expansion of expandable graphite at 800 °C and sand milling of expanded graphite in water, respectively. When the expandable graphite precursor was prepared by the oxidation and intercalation of natural graphite (5 g) using KMnO4 (6 g) as an oxidant in a concentrated sulfuric acid solution (120 mL) at room temperature (25 °C) for 8 h, the expanded graphite with a maximum volumetric rate of 317 mL g−1 was prepared after the thermal expansion of the expandable graphite precursor at 800 °C for 60 s. The oxidation extent of natural graphite with KMnO4 is crucial for the preparation of expanded graphite. The thicknesses of graphite nanosheets decreased from 8.9 to 3.2 nm when the sand milling time of the expanded graphite in deionized water was prolonged from 6 to 24 h. The prolonging of the sand milling time not only decreased the layer number of the graphite nanosheet but also increased the d002 spacing due to the shocking and shearing forces. The addition of the expanded graphite powder and graphite nanosheets in a polyester paint efficiently improved the electrical conductivity of the resultant polyester coating films.

Fabrication of an All-Solid-State Ammonium Paper Electrode Using a Graphite-Polyvinyl Butyral Transducer Layer

A planar solid-state ammonium-selective electrode, employing a composite mediator layer of graphite particles embedded in a polyvinyl butyral matrix on top of an inkjet-printed silver electrode, is presented in this paper. The effect of graphite powder mass fraction on the magnitude of the potentiometric response of the sensor was systematically verified using a batch-mode and a flow injection measurement setup. Under steady-state conditions, the paper electrode provided a Nernstian response of 57.30 mV/pNH4 over the concentration range of 10−5 M to 10−1 M with a detection limit of 4.8 × 10−6 M, while the analytical performance of the array in flow mode showed a narrower linear range (10−4 M to 10−1 M; 60.91 mV/pNH4 slope) with a LOD value of 5.6 × 10−5 M. The experimental results indicate that the prepared electrode exhibited high stability and fast response to different molar concentrations of ammonium chloride solutions. The pH-response of the paper NH4-ISE was also investigated, and the sensor remained stable in the pH range of 2.5–8.5. The potentiometric sensor presented here is simple, lightweight and inexpensive, with a potential application for in-situ analysis of environmental water samples.

Conductive Polymer Composites Made from Polypropylene and Recycled Graphite Scrap

Electric Discharge Machining (EDM) process uses electrodes made from graphite that wear out over time and are turned into scrap. In this research, EDM electrode scraps were recycled and turned into graphite powder (rGP). This rGP was used as a conductive filler to produce conductive polymer composite (CPC) material by combining it with polypropylene (PP) resin via melt compounding and compression moulding processes. The percolation threshold of this composite material changed when 30 wt% of rGP was added, whereby the insulative material changed became antistatic. The composite was able to achieve surface resistivity as low as 105 ohm/sq. However, the addition of higher rGP content deteriorated the tensile properties of composite, whereby the tensile strength of composite significantly decreased as compared to neat PP. The results also showed that the tensile modulus of this composite became higher, and the material became more brittle as compared to neat PP. However, the PP/rGP composite with 50 wt% filler content reduced the tensile modulus due to plasticising effect caused by the agglomeration of rGP. The addition of high filler content on PP/rGP composite also caused an increase in processing torque. This was due to the restriction of rGP particles to the melt flow of molten PP. The morphological analysis found that the PP/rGP composites with higher amounts of filler content were highly agglomerated and formed conductivity paths within the PP matrix. The increase of rGP content highly improved the thermal stability of composite. The findings of this study show that the rGP has the potential to be used as a conductive filler for producing conductive composite material.

Analysis on the Improvement of Thermal Performance of Phase Change Material Ba (OH)2·8H2O

Benefitting from the characteristics of a high latent heat capacity and stable phase change behavior, phase change materials have widely received concerns in the field of thermodynamic management. Ba(OH)2·8H2O is an ideal phase change material (PCM) in the mid-to-low temperature range, but its large-scale application is still limited by severe supercooling during the nucleation process. In this paper, the experimental analysis and comparison are performed via an Edisonian approach, where Ba(OH)2·8H2O is adopted as an original substrate; BaCO3, CaCl2, NaCl, KH2PO4, and NaOH are selected as nucleating agents; and graphite is used as a heat-conducting agent. The results show that Ba(OH)2·8H2O containing 1.2% BaCO3 and 0.2% graphite powder has the best performance. Compared with pure Ba(OH)2·8H2O, the supercooling degree is reduced to less than 1 °C, the phase change latent heat duration is extended, and the thermal conductivity is significantly improved. Therefore, this study not only provides a reference for the application of Ba(OH)2·8H2O, but can also be used as a guidance for other material modifications.