scholarly journals Перколяционный переход в углеродном композите на основе фуллеренов и терморасширенного графита

2018 ◽  
Vol 60 (1) ◽  
pp. 202
Author(s):  
В.И. Берёзкин ◽  
В.В. Попов
Keyword(s):  
Electrical Conductivity ◽  
Percolation Theory ◽  
Adsorption Process ◽  
Three Dimensional ◽  
Carbon Composite ◽  
Relative Content ◽  
Exfoliated Graphite ◽  
Disordered Media ◽  
Sharp Transition ◽  
Conductive State

AbstractThe electrical conductivity of a carbon composite on the basis of C_60 fullerenes and exfoliated graphite is investigated in the range of relative contents of components from 0 to 100%. The samples are obtained by the thermal treatment of the initial dispersed mixtures in vacuum in the diffusion–adsorption process and their further cold pressing. The resistivity of the samples gradually increases with an increase in the fraction of fullerenes, and a sharp transition from the conductive state to the dielectric one is observed after achieving certain concentrations of C_60. The interpretation of the results within the percolation theory makes it possible to evaluate the percolation threshold (expressed as a relative content of graphite) as equal to 4.45 wt % and the critical conductivity index as equal to 1.85 (which is typical for three-dimensional twocomponent disordered media including those having pores).

Numerical study of random lasing in three dimensional amplifying disordered media

2012 ◽  
Vol 285 (6) ◽  
pp. 1314-1322 ◽  
Author(s):  
Abbas Ghasempour Ardakani ◽  
Ali Reza Bahrampour ◽  
Seyed Mohammad Mahdavi ◽  
Mojtaba Golshani Gharyeh Ali
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Disordered Media ◽  
Random Lasing

Semi-Electrical Conductivity of Gelcast Alumina Sintered under Nitrogen Atmosphere

2006 ◽  
Vol 11-12 ◽  
pp. 493-496 ◽  
Author(s):  
Ruben L. Menchavez ◽  
Koichiro Adachi ◽  
Masayoshi Fuji ◽  
Minoru Takahashi
Keyword(s):  
Electrical Conductivity ◽  
Electrical Resistance ◽  
Sintered Sample ◽  
Carbon Composite ◽  
Nitrogen Atmosphere ◽  
Potential Candidate ◽  
Nitrogen Gas ◽  
Conductive Property ◽  
Carbon Network

This work demonstrated an in-situ pyrolysis of gelcast alumina under reduction sintering to make alumina and carbon composite in providing semi-electrical conductivity. To increase the carbon content, the monomer was varied in the premix solution with reduction sintering in nitrogen gas. Two-probe method was used to measure electrical resistance of the sintered samples. The results revealed that the increase of monomer addition and sintering treatment were effective in reducing electrical resistance. The lowest value was 3.6×106-cm, which is a potential candidate for electrostatic shielding application. The reduction-sintered sample was re-sintered in an air in order to gain insight on the conductive path due to carbon network. Further tests such as XRD, TGA/DTA, and scanning electron microscopywere used to explain the semi-conductive property of the material.

scholarly journals Propagation Analysis of the Coronavirus Pandemic on the Light of the Percolation Theory

2021 ◽  
Author(s):  
Moez Guettari ◽  
Ahmed El Aferni
Keyword(s):  
Electrical Conductivity ◽  
Percolation Theory ◽  
Scaling Laws ◽  
High Accuracy ◽  
The Novel ◽  
Infected People ◽  
Boltzman Equation ◽  
Novel Approach ◽  
Propagation Analysis ◽  
Speed Of Propagation

Efforts to combat the Covid-19 pandemic have not been limited to the processes of vaccine production, but they first began to analyze the dynamics of the epidemic’s spread so that they could adopt barrier measures to bypass the spread. To do this, the works of modeling, predicting and analyzing the spread of the virus continue to increase day after day. In this context, the aim of this chapter is to analyze the propagation of the Coronavirus pandemic by using the percolation theory. In fact, an analogy was established between the electrical conductivity of reverse micelles under temperature variation and the spread of the Coronavirus pandemic. So, the percolation theory was used to describe the cumulate infected people versus time by using a modified Sigmoid Boltzman equation (MSBE) and several quantities are introduced such as: the pandemic percolation time, the maximum infected people, the time constant and the characteristic contamination frequency deduced from Arrhenius equation. Scaling laws and critical exponents are introduced to describe the spread nature near the percolation time. The speed of propagation is also proposed and expressed. The novel approach based on the percolation theory was used to study the Coronavirus (Covid-19) spread in five countries: France, Italy, Germany, China and Tunisia, during 6 months of the pandemic spread (the first wave). So, an explicit expression connecting the number of people infected versus time is proposed to analyze the pandemic percolation. The reported MSBE fit results for the studied countries showed high accuracy.

Exceptionally high thermal and electrical conductivity of three-dimensional graphene-foam-based polymer composites

RSC Advances ◽  
2016 ◽  
Vol 6 (27) ◽  
pp. 22364-22369 ◽  
Author(s):  
Zhiduo Liu ◽  
Dianyu Shen ◽  
Jinhong Yu ◽  
Wen Dai ◽  
Chaoyang Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Polymer Composites ◽  
Epoxy Matrix ◽  
Three Dimensional ◽  
Neat Epoxy ◽  
Graphene Foam

Three dimensional graphene foam incorporated into epoxy matrix greatly enhance its thermal conductivity (up to 1.52 W mK−1) at low graphene foam loading (5.0 wt%), over an eight-fold enhancement in comparison with that of neat epoxy.

Study on the thermal insulation performance of the core–shell skeleton graphene oxide/carbon composite aerogel

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Hongli Liu ◽  
Peng Wang ◽  
Wenjin Yuan ◽  
Hongyan Li
Keyword(s):  
Graphene Oxide ◽  
Solid Phase ◽  
Three Dimensional ◽  
Carbon Aerogel ◽  
Carbon Composite ◽  
Core Shell ◽  
Composite Aerogel ◽  
Dimensional Network ◽  
Heat Shielding ◽  
Insulation Performance

Abstract Phenolic resin (PR) was grafted onto the surface of graphene oxide (GO) through π–π conjugation and chemical bonding. After carbonization, organic compounds turned into carbon layers with a thickness of about 10 nm and coated on the surface of GO formed a core–shell structure. Besides, the adiabatic interface formed during organic carbonization can effectively connect the aerogels into a three-dimensional network. The optimum mass ratio of GO was determined to be 10 wt% in the preparation of the precursor aerogel. The adiabatic interfaces (carbon) between GO lamellae could effectively reduce the solid phase heat transfer in aerogels (thermal conductivity is 0.0457 W m−1 K−1). At the same time, the existence of GO also ensured better mechanical properties of GO/carbon composite aerogel (compressive strength is 2.43 MPa) compared with the pure carbon aerogel (1.52 MPa), demonstrating the excellent heat-shielding performance and mechanical property of GO/carbon aerogel.

Multi-interfaced graphene aerogel/polydimethylsiloxane metacomposites with tunable electrical conductivity for enhanced electromagnetic interference shielding

2020 ◽  
Vol 8 (34) ◽  
pp. 11748-11759 ◽  
Author(s):  
Jingnan Ni ◽  
Ruoyu Zhan ◽  
Jun Qiu ◽  
Jincheng Fan ◽  
Binbin Dong ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Microwave Absorption ◽  
Electromagnetic Interference ◽  
Three Dimensional ◽  
Interface Structure ◽  
Negative Permittivity ◽  
Electromagnetic Interference Shielding ◽  
Graphene Aerogel

Three-dimensional graphene aerogel/polydimethylsiloxane metacomposites with an integral multi-interface structure possess adjustable negative permittivity, excellent microwave absorption and electromagnetic interference shielding.

Rapid manufacturing of copper-graphene composites using a novel rapid tooling technique

2020 ◽  
Vol 26 (4) ◽  
pp. 765-776 ◽  
Author(s):  
Gurminder Singh ◽  
Pulak Mohan Pandey
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Wear Rate ◽  
Coefficient Of Friction ◽  
Rate Coefficient ◽  
Three Dimensional ◽  
Rapid Tooling ◽  
Content Type ◽  
Three Dimensional Printing ◽  
Dimensional Printing

Purpose The purpose of this study is to study the mechanical, tribological and electrical properties of the copper-graphene (Cu-Gn) composites fabricated by a novel rapid tooling technique consist of three-dimensional printing and ultrasonic-assisted pressureless sintering (UAPS). Design/methodology/approach Four different Cu-Gn compositions with 0.25, 0.5, 1 and 1.5 per cent of graphene were fabricated using an amalgamation of three-dimensional printing and UAPS. The polymer 3d printed parts were used to prepare mould cavity and later the UAPS process was used to sinter Cu-Gn powder to acquire free-form shape. The density, hardness, wear rate, coefficient of friction and electrical conductivity were evaluated for the different compositions of graphene and compared with the pure copper. Besides, the comparison was performed with the conventional method. Findings Cu-Gn composites revealed excellent wear properties due to higher hardness, and the lubrication provided by the graphene. The electrical conductivity of the fabricated Cu-Gn composites started increasing initially but decreased afterwards with increasing the content of graphene. The UAPS fabricated composites outperformed the conventional method manufactured samples with better properties such as density, hardness, wear rate, coefficient of friction and electrical conductivity due to homogeneous mixing of metal particles and graphene. Originality/value The fabrication of Cu-Gn composite freeform shapes was found to be difficult using conventional methods. The novel technique using a combination of polymer three-dimensional printing and UAPS as rapid tooling was introduced for the fabrication of freeform shapes of Cu-Gn composites and mechanical, tribological and electrical properties were studied. The method can be used to fabricate optimized complex Cu-Gn structures with improved wear and electrical applications.

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