Abstract
A composite material based on expanded graphite (EG) and copper compounds was obtained by natural graphite oxidation with 95% nitric acid, copper (II) nitrate and granular carbamide addition with further rapid heat treatment at three different exfoliation temperatures: 800, 1000 and 1200 °С. It was found that the composition of copper containing graphite material depends on the temperature and the atmosphere of thermal expansion. The formation of copper oxides can be eliminated if rapid heat treatment is conducted in nitrogen at 1200 °С. Thermal conductive properties: thermal diffusivity and specific heat capacity of obtained Cu-expanded graphite samples were measured. It was revealed that the dependence of thermal conductivity (TC) of Cu-graphite material has non-linear character in the studied range of copper content. The incorporation of 3% copper into expanded graphite allows to increase its thermal conductivity by 20% while the further Cu content growth leads to the TC decrease from 6 to 4.5 W/(m∙K). The specific heat capacity is constant at ω(Cu)<3% and reduces in the range (3‒8)% Cu. The advantage of proposed technique of Cu-expanded graphite materials preparation is exclusion graphite intercalation compounds hydrolysis step with further drying because of carbamide addition.
Highlights
Materials based on expanded graphite have been the subject of scientific interest for many years because of their relatively simple production method and the possibility of a wide variation in properties
According to literature data [10] hydrated copper nitrate is converted to copper (II) oxide at 263 ∙ 310 °С: 2Cu(NO3. It was determined by X-ray phase analysis that obtained samples of expanded graphite (EG)-based composites contain three different phases of copper compounds: Cu, Cu2O and CuO
It has been shown that the composition of expanded graphite ‒ Cu composite materials strongly depends on the temperature and the atmosphere of thermal expansion
Summary
Materials based on expanded graphite have been the subject of scientific interest for many years because of their relatively simple production method and the possibility of a wide variation in properties. The general approach is to apply metal compounds to the substrate in various ways, followed by annealing at high temperature and reduction of the oxides to the metal In this way the authors of the paper [4] successfully obtained FeGr composite by exfoliation of graphite intercalation compound modified with iron nitrate (III) followed by reduction treatment in hydrogen.
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