THERMOPHYSICAL PROPERTIES OF CARBON-CARBON MATERIALS
BASED ON GRAPHITE FOAM
A. S. Tikhomirov,
N. E. Sorokina, A. P. Malakho,
O. N. Shornikova,
S. V. Filimonov,
and V. V. Avdeev
Translated from Novye Ogneupory, No. 2, pp. 16 – 19, February, 2016.
Original article submitted November 17, 2015.
Laser flashing and thermal analysis are used to determine thermal conductivity and linear thermal expansion
coefficient of low density carbon-carbon materials based on two types of graphite foam differing in degree of
graphite matrix defectiveness, and pyrocarbon. It is shown that density after compaction and not the ratio of
carbon components has the main effect on thermal conductivity. Carbon-carbon material based on electro
chemical graphite foam has low values of thermal conductivity l = 0.5 – 2.0 W/(m·K) over a wide tempera
ture range (30 – 900°C), whereas for specimens based on traditional graphite foam low values of l are only
typical at high temperature.
Keywords: graphite foam, carbon-carbon materials, thermal conductivity, strength.
In recent years graphite foam (GF) has attracted interest
not only as a material for preparing asbestos-free packing,
substrates for catalysts, and an absorbent, but also a promis-
ing material for heat distribution. The high heat and electrical
conductivity of graphite along graphene layers is well known
and gives rise to extensive use of graphite and graphene in
electronics and allied areas [1 – 3]. By varying the density of
pressed graphite foam it is possible to prepare material
whose conductivity varies from 0.5 to 40 W/(m·K) [4 – 8].
The main disadvantage of low-density materials based on GF
is low strength. In order to improve mechanical properties
use of polymer additives is most popular [9, 10] that how
ever reduce composite thermal shock resistance. An alterna
tive to these materials may be a composite based on different
carbon: graphite foam – pyrolytic carbon (PC) that is a prod
uct of thermal decomposition of carbon-containing com
pounds condensing at solid phase surfaces or within the vol
ume. It is well known that deposition of PC, not only on a
surface, but also within the volume of a specimen provides a
marked increase in structural material strength . The aim
of this work is evaluation of the efficiency of using PC for
creating low-density carbon-carbon materials.
Carbon-carbon composites based on graphite foam were
prepared by chemical infiltration from a gas phase by a pro
cedure described in . The matrix for deposition was
graphite foam of two types, prepared by thermal foaming of
graphite nitrate stage II (GF-1) and product GF-2 of anodic
polarization graphite in 58% nitric acid solution up to
Q = 1500 C/g (Q is amount of transmitted electricity). Meth
ane was used as a gas-precursor.
The microstructure of carbon-carbon composites was
studied by electron-probe microanalysis in Femtoscan mi
croscope. The objects studied were specimens with a density
of 1.0 g/cm
, since a study of less dense specimens is diffi
cult by means of this method.
Linear thermal expansion coefficient (LTEC) was deter
mined by means of a Netzsch 402 thermal analyzer fitted
with an induction transducer for measuring the change in
specimen length (sensitivity ~1 nm). Specimens were heated
from 30 to 750°C at a rate of 10 °C/min in a dynamic nitro
gen atmosphere (flushing rate 100 ml/min).
Refractories and Industrial Ceramics Vol. 57, No. 1, May, 2016
1083-4877/16/05701-0018 © 2016 Springer Science+Business Media New York
FGBOU VPO M. V. Lomonosov Moscow State University, Mos
ZAO Institute of New Carbon Materials and Technology, Mos