PRL 153

THERMOPHYSICAL PROPERTIES OF POCO GRAPHITE

A Report to

Air Force Office of Scientific Research

from

PROPERTIES RESEARCH LABORATORY

R E Taylor and H. GrootSchool of Mechanical Engineering

Purdue UnhersityWest Lafayette. Indiana 4-906

UNGbASSIFIEB

UNCLASSIFIED73, JAN 73

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AF.OSIFm- 78-1375 /

•• TlTL.E (and Subtitle) S. TYPE OF---REPORT & PERIOD COVERED.INTERIM

THERMOPHYSICAL PROPERTIES OF POCO GRAPHITE /•• PERFORMING ORG. REPORT NUMBER

7. AUTHOR(s) B. CONTRACT OR GRANT NUMBER(e)

R E TAYLORH GROOT AFOSR-77-3280 ~

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PROPERTIES RESEARCH LABORATORY 2308B1

47906, 61102FWEST LAFAYETTE, IN

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18. SUP_PLEMENTARY NOTES

19. KEY WORDS (Continue on reverse side if necessary and Iden~lfy by block number)

STANDARD REFERENCE MATERIAL SPECIFIC HEAT ;

POCO GRAPHITEELECTRICAL RESISTIVITYTHERMAL CONDUCTIVITYTHERMAL DIFFUSIVITY

.::; 20. ABSTRACT (ContInue on reverse side If necessary and IdentUy by block number)

The thermal conductivity, specific heat, and electrical resistivity of two sampleof POCO AXM 5Q graphite obtained from NBS were measured. These results, combinedwith previous results for thermal expansion and high temperature specific heatwere used to compute therma 1 diffusivity values from 400 to 2400K. The computeddiffusivity values agreed well with measured values. The electrical resistivityof the two samples differed significantly from each other and also varied alongthe length of the rods. Differences in thermal conductivity values between thetwo samples were directly related to difference in resistivity. In genera 1 the

DD FORM 14 EDITION OF 1 NOV 65 IS OBSOLE::TE ~

SECURITY CL.ASSIFICATION OF THIS PAGE (When Data Entered)

Table of Contents

APPARATUS AH> TECHNIQUES

RESULTS ,

DISCU55Im-

SUMMARY Ali"D CONCLUSIONS,

REFERE:l-CCES

Page

1

4

_ 14

. 26

2-.'

i 1

.1 f

LIst of Tables

Page

L Reslsti'·Uy of POCO Graphite Along Length of Rod 5

2.. Thermal Conducti'·ity and Electrical Resisthity Kohlrausch Method 6

3. Thermal Conductivity Results Multiproperty

4. Electrical Resistl1'ity of POCO Graphite

5. f'pecific Heat Results ..

Electrical Resistivity of POCO Graphite

Thermal Conducthity of POCO Graphite

8

9

13

17

• 21

Li st of Figures

1. Thermal ConducU"ity Results

2. Electrical Resistivity Results

J. 5peciflo Heat Results DSC

4. Specific Heat of POCO Graphite.

5. Electrical Resistivity of POCO GraphIte.

6. Thermal Conductivity of POCO Graphite.

Inc'erse Conducthrity rersus Temperature

8. Thermal Dlffusivity of POCO Graphite

•

Page

11

• 12

15

16

• 20

23

24

THERMOPHYSICAL PROPERTIES OF POCO GRAPHITE

IFTLODUCTIOJ"·

Pesults from round-robin cooperathe programs ha"e indicated that POCO

AXH-5Ql graphite' "as a sUItable 1.2 material for a high temperature thermal

coniuctiity standard, Subsequently a batch of this material was obtained by the

Fa~ional Bureau of Standards for use as a standard reference material SRM ,

U,for~urately the room temperature electrlcal resistivity ,rariations from billet­

to-blllet and e"en within the same billet ha'e been much larger than anticipated

3. It IS the purpose of the present work to in'estigate the thermal conducthity

an~' elec~rical resisti'ity o,er an extended temperature range of two samples whose

reslsti it) differed sigmficantly. These results elucidate the relationship between

the electrical resisthity and the thermal conducthity for POCO graphite and dem­

onstrate the degree of 'ariability in the magnitude of the thermal conductivity of

thiE batch of materiaL

The Properties Research Laboratory has a unique multi-property apparatus

ca~a'Jle of state-of-the-art accuracy for high temperature thermophysical prop­

erties. This apparatus has been used previously to measure the thermal conduc­

t! It and electrical resistivity of SRM's -30 and -99 tungsten to very high tem­

. eL tures 4 aE well as a number of other materials 5, 6. -, ThlS apparatus

has been deserlbed elsewhere 8. 9 .

In addition the specific heat of the two samples was measured at lower tem­

perl,ures to HooK. as an aid in resohing diserepencies between thermal con­

d, etlit~' ,alues measured directly and those computed from thermal diffusivity­

fDeofic heat results. A standard Perkin-Elmer differential scanning calorimeter

interfaced to the PRL digital data acquisition system was used for the specific heat

determinatlOns.

Product of POCO Graphite. Inc•• Garland. Texas, Grade descnption AXM:medium grain fuel cell grade; 5Q: 25000 C graphitization temperature: 1:purified.

APPARATUS A:r--n TECHHQUES

At the lower temperatures SSC -11S0 K _ the modified Koblrausch technique

-'af used for thermal conducth'ity and electrical resistivity measurements. The

Kohlrausch method In'-ohes the determination of the product of the thermal con­

duc"lit:- k and the electrical resisthityo'. Since the electrical resisthity is

als - meamred at the same time. k can be calculated. The method in'- oh-es passing

ccnstant dlrect current through the specimen to heat the sample while the ends are

kert at constant temperature. Radial heat losses are minimized by an external

tea~er maintained at the sample- s midpoint temperature. Wlth these provisions. at

s"ead:- st?te a parabola-like mnal temperature profile is obtained. Thermocouples

are olace.:l at the center and one centimeter on each side of the center. The thermo­

c U:kf also act as '-oltage probes. :r--umbering the center thermocouples as the' 2'

pOfltion and the other posltions as co 1 and co 03". it IS possible to get the products of

k and 0:

1

"here -- - '-2 is '-oltage drop between the third and middle thermocouple. T1 ~ T3 is

the sum of the temperatures at the outside thermocouples. and T2 is the center temp­

erature. Since 0 is also measured simultaneously using Eq. 1. k can be calculated,

The data collection T 1• T2. T3• '3 - '2' I are computerized and the results calcul­

ateJ for a set of measurements performed while the sample is under vacuum and the

heater temperature matched to that of T2' Then additional current is used. a new set

of eJuilibnum conditions is obtained. and the process repeated. At higher temper­

atures the multiproperty apparatus was used to measure the thermal conducthity

and electrical resisthity.

The go'-ernmg equation for Joulean heat long thin rods in "acuum subjected to

raJlation loss from the surface is

dkdT

-ul dT=C ddTA dZ P dt 2

"-here P is the circumference. C1 is the Stefan-Boltzmann constant. To is the temp­

era~ure of the vacuum enclosure. <H is the total hemispherical emittance. u is the

Thomson coefficient. Cp is the specific heat at constant pressure, d is the density,

Z 15 the length coordinate in polar coordinates. and t is time. At steady state dT dt

1S zero In the case of long rods at steady state dT dZ = ct2T dZ2 = 0 and Eq. 2

bec.:mes

3

here T 1S the uniform central temperature. Thus by measuring L v. and T. 0

and ~H can be calculated.

In nractice the sample is heated to about 33((, F and 0 and E'H measured during

the cooling cycle to about 14-0 F. The data are taken using the PRL digital data acqui­

si:1en system and the values of 0 and E'H are calculated. plotted. and fitted to least

squ.cre cur'es automatically. Following temperature profile data. 0 and E'H are re­

meae .. red. Then the long sample is heated to 440C F and 0 and "H measured bet-"een

44 a 1.: 330 L Temperature profiles on short samples are taken o"er this temp­

eraure range. then the long sample measurements are repeated. Because the pre­

se~1 sreClmens are too short for d2T dZ2 to be equal to zero. long samples are fab­

ricated by slip-fitting extender rods made from the same billet on each end of the

"ample. The short sample configuration 1S achie'ed by moving the electrical clamps

se hat the center of the long sample remains the center of the short sample. Above

?3 0 r :he long sample is 4 inches long so that the slip-joints are near the water­

ccled clamps. At lower temperatures the long sample is about 12 inches long.

11 addition the standard four probe method using knife blade voltage probes

as t:sed :0 measure the electrical resisti"ity along the samples at room temperature.

Bull, denSities "'ere determined from geometry and mass. The specific heat from

33 to 1 .. K was measured usmg a Perkin-Elmer DSC-2 interfaced to the digital

aCluisition system and using saphire as the reference materiaL

r-·o Eamples L 4 in. diameter by 12 mches long were recei"ed from NBS.

Bo l:er. One rod "as designated as JA-1 henceforth referred to as Sample 1

and the second rod was designated as 3A-2 Sample 2 .

4

HL~ULTS

--alues of the bulk densities of Samples 1 and 2 were found to be L 7424 and

L -8 4 gm cm-:: respecth'ely.

- alue!; of the electrical resisth ity at one inch inter':als along the samples are

gJ en In Table L It can be seen that there is a considerable variation along the rods

ane; that the electrical resistheity of Sample 1 is generally 20 to 140 microhm cm

higher ~han that of Sample 2.

The thermal conductb:ity and electrical resistivity results measured with the

Kohlrausch method are given in Table 2. The thermal conductivity values ha'-e been

c.:rrected for thermal expansion using the TPRC reco=ended "alues for POCO

graphite 10. The room temperature resistb'-ity "alues for the sections used for

~he Kchlrausch methods were 1409.9 and 1326.7 microhm cm for Samples 1 and 2,

resrectheely. These sections are near the ends of the rods. The conductivity values

for Sample 1 are significantly lower than those for Sample 2. The results are plotted

in Figure 1.

The thermal conductivity results obtained on different sections of the same rods

usmg the multiproperty apparatus are given in Table 3. These values has been cor­

rected for expansion. The room temperature resistivity values for these sections

--ere 13-5.1 and 1295.9 microhm cm. These sections are near the center of the rod.

The thermal conducti'-ity results from the multiproperty apparatuses are included in

Figure 1. While one could join the higher temperature results from the multiproperty

arT'·- ratus -'-ith the lo"er temperature results from the Kohlrausch apparatus, there is

a dI~contlruity caused by the difference in resisthity along the rods.

The electrical resistivity results from the Kohlrausch apparatus are included in

Table 2. The resistheity results for the multiproperty apparatus are gi'en in Table 4.

Both sets of results are plotted in Figure 2. The differences in electrical resistivity

bet een the sections from the same rods are clearly e"ident in Figure 2.

Specific heat values were obtained at 50 intervals from 335K to 700K and from

C2:iK to 9950 K. The data are plotted in Figure 3 and part of these data are ghen in

Ta~le 5. The specific heat values from the two rods as ,n excellent agreement. The

agreement in the temperature o'-erlap region using aluminum and gold pans is reason­

able maxImum difference of 3. -""', and average difference of less than 2""'0 •

TABLE 1

...RESISTIVITY OF POCO GRAPHITE

ALONG LE NGTH OF ROD

5

Sample 3A-1

1.385, ­14(1.014 -9. (1414.5142-, -1.3'3.5135;;.51.3f3, 31348.01358.(

uDcm

Sample 3A-2

1284.41282.5126-.212-2.0126-.61299. ­1319,51331.21325.31313.6

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8

THERMAL CO~lDUCTI"lTYRESULTSMULTIPROPERTY

13; •1350140014501501551600165:1-0e1-50180e185(19((195(20:)2(50210(215022((225(23(235(24·;0

Sample1

0,519',493(,4-9L46­0,4600.45.30.4420,4260,41­0.412OA060, .3990.3960,3910.3880.38­0.3840,3820.3-5O• .3-30,3-10.3680.364

Sample2

0,5450.5350,5250.5140,5010.488(A-50,462OA550,444OAr0,431OA240.419OA150.4130,4100.4060,4020.3980.3950.3940.390

.." .. em-1 K-1. corrected for expansion

TABLE 4

ELECTRICAL RESISTIVITY OFPOCO GRAPHITE

Sample 3A-1

Fun Temp. Ox 101 Run Temp. ox 10·r K ohm em ]:\-0. K ohm em

3A-1 221P. -- 11C6.31 3A-3 2226.91 111C- 842156.8C 1094.34 2193. -3 11C4.2-2C8L -2 10-9.63 2126.83 10PO.542J3-.8C 1C -0.84 2061. -5 10-9.51'1865. -3 1C36.23 1968.5- 1059.6C1-43.59 1011.93 19C4.21 1046. -C1685.13 1000.82 1853.54 1036.551591'.83 984.54 1805.61 1025.9r

1533.1'9 9-3. -5 1-6L 04 101-. -11462.84 961. -6 1-06.91 1:0-.041384.13 950.14 1633.51 994.081335.0C 94C- -0 1634.53 994.0112-4.18 936. -6 1610.35 989.49124L -4 933.58 1550.52 9-8. -8

149-.37 969. -21438.40 960.33

3A-2 2228.89 111(,13 1385.-3 952.632180.39 1100.46 1354. -9 948.43218(, 4- 11CO.04 1299.15 941.612141. -- 10B2.6- 1231.39 934.1'9214L 90 1C92.88 1194.85 931.8028-.21 108L 80 1151.89 929.C5208-.20 1C8L 962:13.35 106-.522015. " 106-.49 3A-4 2445.39 1153.44196-.64 105-.38 2413.95 114-.811£14.04 1C46. -8 2361. 51 1138.951864. -4 H36.81 2324.13 1131.4818C4.67 1024.64 2288.55 1124.901-63.51 1(1-.19 2238.90 1113.831-21. -9 1008. -3 2201.99 1106.90164-.44 944.89 2130.56 1092.631598. C8 986.46159-. -8 985.5-1553. -3 9--.88 3A-5 2583.65 1181.1215L 58 969.60 251-.28 1169.141435.38 P58.52 2459.16 1162.421390.9- 952.03 2386.64 1147.581359.39 947. -4 2234.76 1118.411300.92 940.54 2152.00 1101. 03

TABLE 4 Con't

ELECTRICAL RESISTIVITY OFPOCO GRAPHITE

Sample 3A-2

Run Temp. ox 10' Run Temp. ox 10'Fe K ohm em ~TO. K ohm em

2A-1 2232.51 1(16.68 2A-2 223-.99 lor. 922118.19 994. -2 2193.09 1008.812; 2C. - - 9-(, 05 2143.90 999.691£34.54 939.85 2066.44 984.65185L C8 943. -9 2}28.04 9T.301- 6.-4 n-.62 19-3.02 965.971- -.OC 9r.63 1921. 15 956.9-16Z1. 6- DC 8.02 1868.89 94-.24159-.11 899.91 1815.25 936.951564.24 893.60 1-77.3- 930.0215C 5. 03 884.42 1716.11 918.951444. -9 875.68 1679.08 912.62139.1- 868.64 1636.60 904.911344.9C 863.25 1600.95 899.111296.04 858.19 1565.9- 893.481252.38 854.34 1533. 7- 888.41

1501. 83 883.561456.62 8--.031397.90 869.181341.31 862.551288.34 85-.141245.43 853.38

2A-3 2582.43 1095.042519.31 100 0.212457.12 1069.342381.46 1:5L 15223-.6- 1019.322154.21 999.12

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TABLE 5

SPECIFIC HEAT RESULTS

Temp 3A-1 3A-1 3A-2 3A-2oK A1 PAJI,C AU PAI,- Al PAJI,T AU PAN

>~ . ,8212 0.8246~ ... ~

4 :,9442 0,956245[ 1.063 1. [-85CC 1.1-6 1.195"50 1.2T 1.286o. 1.36- 1.374

r5( 1.45- 1.454 1.45- 1.4591.546 1.5(5 1.543 1.522

-5- 1.556 1.589SC 1.604 1.663e5C 1.651 1.6669 1. 7(2 1.-10[5 1. 761 1. -62

13

14

DIECUSSlm,'

A. Specific Heat

As expected the specific heat is relatively insensitive to fabrication. micro­

structure or impurity variations among the samples. Thus the present spedfic

heat results can be joined with the high temperature values for POCO graphite gen­

erated 'Jl' Cezairliyan and Righini 11. Since these cur"es join smoothly Figure 4 . the

speufic heat of POCO graphite is known within 3~ over the range 350 to at least 2500 K.

B ElecLrical Reslsthity

It is ob-ious from the results that the electrical resistivity varies significantly

from sample to sample and even at different locations along the same sample. In

ordcr ~c put the 10" and high temperature results from different sections of the same

sanple on a common basis. the low temperature results ha"e been biased so that the

resistn it:' "alues at 1200 K from the two sections agree. This required a subtraction

cf l;Ju ~ cm from the Kohlrausch data for sample 3A-1 and a subtraction of 25u (t em

from the Kohlrausch data of 3A-2. The re"ised curyres are plotted in Figure 5 and

alues are giren at selected temperatures in Table 6. Corrections for thermal ex­

pansion are also included in Table 6. The electrical resisth'ity has a broad minimum

about U5( K. The resisti"ity decreases relatively rapidly with increasing temperature

frem reom temrerature to about 900K and increases at a lower rate abo"e 1200 K. The

dlfference in resistidty between the 1;>vo samples remains relatively constant 85 ± 11un

cm 0' er the range 300 to 2400 K.

Co Thermal ConductiVity

The thermal conducthity values from the multiproperty apparatus Figure 1 and

Table 3 ha"e been included in Figure 6. The KohIrausch values have been biased to

the alues they would have if the sample sections for the Kohlrausch and multiproperty

sa,mples were the same. This was accomplished by assuming that the difference in

~hermal conducthity "alue at 400K related to the difference in resistivity. Such a

reia:ionship has been obser"ed near room temperature for graphites. particularly

-'hen the general types of graphite remains the same. Taylor 12 found that the

rela~ion , = A- Bo -'as good within a few percent for samples from the same grade of

graphite. Moore. Graves and McElroy 13 found that \ = 1.56 X 10-3 0-1 -0.266 x

1:-' 0-2 ga,'e a reasonable approximation for a number of types of graphites at room

temperature. If we solve for B using Taylor's expression at400 K. we get B= 3. 681 x

If -4. Thus the conductivity values should be increased 0.020 and 0.018 w cm-1K-1

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TABLE 6

ELECTRICAL RESISTIVITY OF POCO GRAPHITE

Temr 3A-1 3A-1 3A-2 3A-2oK uncorr. corr. uncorr. corr.

3 1385 1385 1300 13004- 121- 1218 1130 113130 1H8 1109 1023 1C24ace 1Cr 1039 952 954- 0 ?8- 990 905 906C· 948 952 8-3 8-6

930 934 855 85910 925 93) 849 85411 925 931 848 85212 932 939 851 85-1.3CO 94C 948 860 86-14 955 954 8-0 8-8E. 9-0 98C 885 894L.OO 985 996 900 9101- 1:03 1015 915 92618 1022 1035 933 94519C L43 105- 952 9652 C 1:65 1081 9-1 9852LO 108- 1104 991 100622C llC8 1127 1012 102923C 1126 1146 1035 105324 0 1146 1168 1057 107-

18

fOI s?mples 1 and 2 respecti,cely. Using Moore. Graves and McEllroy's equation

the ll1CrKSe ""ould be about the same. Since the conducthity cur"es for the two

sal Irks are about parallel Figure 1 • we can add these values to all the Kohlrausch

resllt~, This is dene in Figure 6 to obtain a smooth CUl" e for each of the two samples.

[hermal eonductinty '" alues at selected temperatures are included in Table 7.

The relatn"e role of phonons and electron conduction to energy transport in POCO

1;L phite 1s discussed))' MInges 1 who concluded that the electronic contribution is

insIgnificant. In this case. the in'"erse conductivity should be a linear function of

temrerature at higher temperatures say above 10fO K where boundary scattering

effect~ ha'"e decreased to low le,cels. Ho""e'"er when we plot 1 , "ersus T for the

1'resent data FIgure - . we note that the increase conductivity above 1200 does not

folle a Imear relationship. If W"e assume that the Lorenz function Lo for graphite

IS Lemperature independent and equal to the classical value; then we can compute the

electronic contribution ., e to the total conductivIty. A plot of 1 '-'e is nearly linear

ma1nmum del'lation of S...., from 400 to 2400K Figure 7 and Table 7 . Quantitati"e

e 21ua11ons based on energy band models predict Lo to be two to three times the clas­

~icalalue 14. In the present case Lo equal to 1. S times the classical value would

result m a very good linear fit of 1 '-'e versus temperature. While it would appear

tha~ ~hermal conductiv ity and electrical resistivity data above 2400 K would significantly

aId in elucidatlng the role of electronic conduction. it must be remembered that this

material "as graphitized at about 2S00oC so that this temperature range is very close

to ~he fabrication temperature. Thus the stability of the properties of this material

as de~erminedby precise measurement methods may not justify extensive work be­

yond 24:"' K on POCO AXM SQ. In fact the authors noted some tendency for the elec­

trical reslstn"ity to change upon extended heating of the samples at 2400K in vacuum.

e 1S c" ncllded that an electronic contribution ranging from a few percent belo"

"""" K' 0 at least 1S...., at 2400 K is present. This is in line with the findings of an ex­

ten5ne program at PRL on a proprietary graphite in which a similar conclusion was

reached.

The density of the samples was calculated at selected temperatures from the

recommend expanSIOn cune and the results are mcluded in Table -. These values

are combined "lth the thermal conductivity and specific heat results to calculate thethermal diffusbrity. These calculated diffusivity "alues 'lre given in Figure 8 and

compared to values reported by Chu. Taylor. and Donaldson (15), Le Bodo 16 and

AGARD participants 2 • The values of Chu, Taylor, and Donaldson and Le Bodo are

2

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23

in excellent agreement with the present results. The resistivity of Chu, Taylor and

Donaldson's sample "as 1416 uO cm at room temperature. which is slightly abo"-e that

of ,amrle 3A-1 Figure 5 • Thus the diffusivity 'alues should be slightly below about

1- the rresent results and this is close to the observed results Figure 8. The re­

sulLs of the AGARD participants lie below the present results. particularly at the lower

temreratures. The percent difference between the AGARD results and Sample 1 is

about 1.3'-, independent of temperature. The electrical resistivity of the AGARD POCO

AXE 5Q material was rrobably considerably higher than that of the present samples.

OTle AGARD participant reported a room temperature resistivity value of 1579un cm

an~ ~hIS IS considerably abo"'e the 'alues for the present sample Figure 5. Thus

L] conductivity diffuSlvlty "alues for the AGARD samples should be significantly below

L c rcsent results. Usmg the value for B 3.31 x 1(...;\ W U 0-1 cm-2K-1 obtained for

1L .t, sent samples at 4COK and estimating the resisthity of the AGARD material to

be 13-5u( cm at 400K the AGARD material should have a conducthity at 400K of

atcut • -9"V cm-1 K-l less than that of Sample L This is 10"", below the value for

5amrle 1 at 4~ 0 K. Thus it appears that the difference between the AGARD results and

the rresent results can be accounted for by the difference in electrical resistivity.

On the other hand. Moore, Gra"es. and McElroy 13 determined the resistivity

and conductivity of a different piece of POCO AXM 5Q. Their results at 400K were

f °lU (, cm and L 22 w cm-1K-l respectively. Using the "alue for B obtained from the

present work. the value of the thermal conducti"ity of their sample should be

C.13" cm-1 K-1 greater than that for Sample L This value is L 10 w cm-1 K-1 "'hich

is L~ below their measured value. Thus the difference in resisti"ity only accounts

for about one-half of the difference between the present results and that of Moore. Gra"es,

and EcElroy. The conducthity values of Moore, Graves, and McElroy are significantly

abme those obtained by other researchers. Since the results of these researchers have

rren to ':Je very reliable. the conclusion is that their POCO graphite sample "as con­

SIderably different from others. This is borne out by the density of their sample

L 85 gIn cm...'! which is significantly greater than the densities of the thermal con­

:lucttity samples measured by other researchers.

26

The :hermal CO'1ductivity. specific heat. and electrical resistivity of two samples

of POCO .AXM 50 graphite obtained from lI-BS were measured. These results. com­

bIned ·nth previous results for thermal expansion and high temperature specific heat

·'ere used to compute thermal diffushity "alues from 400 to 2400K. The computed

dlffushity 'alues agreed well with measured values.

The electrical resistivity of the two samples differed significantly from each other

an also 'aried along the length of the rods. Differences in thermal conductivity values

bet een the t,,·o samples were directly related to difference in resistivity. In general

:he results of other researchers could be brought into agreement 'with the present re­

sults. based on differences in resisthity and density. Consequently it was possible

tc generate cun-es of electrical resisthity. thermal conductivity, specific heat and

thermal diffushity of POCO AXM 5Q graphite from 400 to 2400K. There is an elec­

trolllC contritution to the thermal conducthrity. This contribution is less than a few

[ercent at 400K but increases to at least 15"', at 2400K.

L

4.

5.

6.

REFERE]:ITES

n. nges. M.. Analysis of Thermal and Electrical Energy Transport in POCOAXII-5Q1 Graphite. Int. Journal Heat Mass Transfer. ~ pp. 1161-1172. 19T.

ntzer. E.. Thermorhysical Properties of Solid Materials at High Temperatures.Project Section II; Cooperathe Measurements on Heat Transport Phenomenon ofScUd l\Iaterials at HIgh Temperatures'. AGARD Ad"lsory Report. R-6e6. 1973

Bust. J. G•. Personal Communication. l'ational Bureau of Standards. 197-.

Tayler. R.E.. "Thermal Properties of TungstenSRM's no and 799". Journalof Heat Transfer. 1U, pp. 330-333. May 1978.

Ta)'lor. R.E. and Kimbrough. W.D.. Thermophysical Properties of ATJSGrarhite at High Temperatures'. Carbon~ pp. 665--1. 1969.

Taylor. R. E., Thermophysical Properties of Arc-Cast Tungsten Using the TPRCl\Iultlproperty Apparatus' Direct Heating Method. High Temperature-HighPresFure. ~, pp. 641-50. 1970.

Ta,'Lr. R. E. .Suney on Direct Heating Methods for High Temperature Thermo­-h)'SICal Property Measurements of Solids'. High Temperature-High Pressure.i. pr, 523-31. 1P-2.

8, Taylor. R.E.. Da,is. F.E •. Powell, R.W•. and Kimbrough. W.D.. 'Advances,n Direct Heating Methods'. ]:I-inth Conference on Thermal Conductivity H.R.Shanks. edUor . CO}JF-691002 - Physics TID-4500. U.S. Atomic Energy Com­mlSSlcn. March 19-0.

9. TayL~r. R.E .. Da'is. FoE .. and Powell. R.W•• DirectHeatingMethodsforl\Ieasuring Thermal Conducthity of Solids at Hlgh Temperature". High Temp­erature-High Pressure. 1. pp. 663--3. 1969.-

1. Teuloukian. Y.S•. Kirby. R.K.. Taylor. R.E.. and Lee. T.Y.Roo ThermalExranslOn, ]:I-onmetallic Sclids, Volume 13 of Thermophysical Properties ofMa:ter. The TPRC Data Series. 19':17.

11. Cezalrliyan. A. and R.ighini. F •. "Measurements of Heat Capacity, ElectricalResis·nity and Hemispherical Total Emittance of Two Grades of Graphite in theRange 150r to 3COOK by a Pulse Heating Technique". Rev. Int. Htes" Temp. ofRefract•. 12. pp. 124-131. 1975.

12. Taylor. R. E,. Examinatlon of Thermophysical Property Data of an Ad'ancedGraphite'. PRL 108. December 19-5.

13. Moore. J. P .• Grayes. R. S•• and McElroy. D. L.. "Thermal and ElectricalConductivities and Seebeck Coefficients of Unirradiated and Irradiated Graphitesfrom 300 to 10000 K'. Nuclear Technology. 22, pp. 88-93, April 1974.

14. Kelly. B. T, and Taylor, R.E., 'The Thermal Properties of Graphite", Chem.Phys. Carbon 10, pp. 1-140, 1973.

•

28

REFERENCES co~mued

L). Chu. F .1... Taylor. R.E .. and Donaldson. A.B.. 'Flash Diffusivity Measurementsat Hlgh Temperatures by the Axial Heat Flow Method', Proceedings of the Se'·enthSymposium on Thermophysical Properties, Cezairilyan. A•• Ed•• Am. Soc. ofUech. Eng., 1977.

1. Le Bodo. H. P •• Laboratoire National D'essais. Paris, France, Personal Com­munication. 19-8.