Insitu measurements of layer thickness during oxidation of titanium

Thermochimica Acta, 133 (1988) 299-304 Elsevier Science Publishers B.V., Amsterdam

INSITU

MEASUREMENTS

OF

LAYER

299

THICKNESS

DURING

OXIDATION

OF

TITANIUM

13. NEUER

Institut University

and

F.

fiir Kernenergetik

of

Stuttgart,

GUNTERT

und

Postfach

Energiesysteme

80

11

40,

(IKE)

G-7000

Stuttgart

80

ABSTRACT Thermal radiance measurements are described as a method well suited for insitu measurement of layer thickness during the oxidation of titanium at temperatures between 700 *C and 1000 *C. The results confirmed the parabolic function of the oxide growth with a constant C increasing up to 0.029 um21s with increasing oxidation temperature.

INTRODUCTION

The

thermal

strongly

dependent

oxidation the

radiation

has

metals

can

k)

stant

during

the oxide

be

both

calculated

the

the

the

of

metal

out

have

clearly

by

the

on

of

of

refraction

n and

and

the

oxide

process authors

demonstrated

the

related

to

be

layer

thickness.

These

results

are

By

means

a thin

are

steel

the

P~c.9thIcTRCongress,~e~~,fs~~~2I-2~

Q 1988 Blsevier Science Publishers B.V.

the on

the

and

con-

measuresamples variation

increase

encouraging

of

coeffi-

known

Emjttance

observed

of

film if

extinction

oxidizing

that

could

variation

thickness

film

( ref.1). on

roughness,

the

of

its

are

the

metals.

a function

emittance

Therm&An&sis

Amongst

reflectivity

spectral

~~3~/88/~3.50

surfaces

influence

emittance

oxidation

carried

metallic

topography.

as

(index

of

of

important

respectively

constants

cient

(ref.2)

their

most

electro-dynamic-theory

optical

ments,

on

the

reflectance

classic

properties

to

Aug. I988

of

of the

apply

radiation

measurement

thickness

during

are

to in situ

techniques

oxidation’processes.

measurements

In

principle

of

two

film

methods

possible:

a)

irradiation source

of (e.g.

reflected b)

at

the

the

of

aid

order

;ially

observe

developed uses

be

I

where

X is

both 0.5

the

KX

0.9

the

only

depends

and

the

Eq.(ll. the

aid

measured law

the

the

data 5

ratio

of

the

usually

oxidation

be

directly

measured

with

1 * expi-

pyrometer places

the

The the

T of

of

a thermocouple

direct using

the

a speci-

‘LinearpyroI . ph ” equation

photocurrent

therefore

Wien’s

(11 which

of

filter

interwheels

between

were

carriedout

(=

1,438O

are

spectral

at PmK)

to using

variables

technique

calculated the

from

Kirchoff’s the

which emittance

potential

independent

According ph’ is calculated

an

‘Linearpyrometer’, The

be

by

ranging

constant the

sample

can

given two

filters

measurements

an eX

is

equippedwith

radiation

the

I

p

by

This

whose

wavelength.

T using

photocurrent

the

applied

(ref.3).

such

described

chosen

measuring

reflectance

is for

factor

By

titanium

c2/AT),

second

temperature

on been

wavelength,

calibration on

has

evaluation:

six

is

growth

and

The

urn.

pm c2 is

which

detector,

radiance

effective

containing

X = 0.71 and

for

filter.

pm and

the

flux.

can

pyrometer photo

the

= KX(eX/X

ph

ference

spectral

to

used

oxide

technique

asilicon

proportional can

of

light

detector.

the

measurement

meter’

at

radiance

lineaf

a monochromatic

measurement

radiation

500°C,

spectrel

by

TECHNIQUE

to

radiance

and

incident above

a

surface

beam)

the

temperatures

occurs,

metallic

laser to

EXPERIMENTAL

In

the

relation

-

e.g.

the radiation

E*

in with

301 p=l-e

For

the

determination

reflectance

of

values

culated film

(21

as on

a

have

function

metal

Fig.

to

oxide be

to 2,

thickness,

compared

of layer

leads

reflectance,

the

with

thickness.

measured

those

As

interferences.

shows

the

which

indicated

Thereforethe

maxima

and

minima

out

samples

are in

cal-

Fig.

1 a

calculated

with

increasing

thickness.

RESULTS

AND

DISCUSSION

were

Measurements punched

out

pure).

The

certain the

from samples

flow

from

the

spectral

which

first

maximum

after

about

40

(dew (A

is a

the

metal

atmosphere

by

= -45’C).

990 is

the

100

K higher,

few

seconds

and

correspond

to

the

the

resulting

in

moderate.

At

reaches

second

maximum

first

shows,

and

emittance a

3

before

oxidation

extremely

a

gas

Fig.

0.5

begins,

K the

to

reached the

As

nearly

(99,86X

up was

switching

oxidation

At

mm diameter

temperature

Mm,) is

emittance

These

s.

inert

point

= 0.71

line

the

after

two

a

the appears

maxima

in

2.

The positions thicknesses ness

10).

of as

the

from

the

With

room

the

for

calculations.

the

of

5 X variation

of

For

and

n =

is the

is

ref.

varied position

the

The

2,53

and

the

k = 0,33

Fig.

between of

2.4 the

of

maxima

the

thick(ref.

values

values for as

2 whereby and

layer

literature

reported mean

emittance in

distinct

calculation from

5 all

resulting

plotted

marking

taken

measurements.

The

Ti02

minima

1.

exceptfon

thickness of

Tab.

were

t?‘tanium

layer

refraction

in

and

constants

temperature

for

oxide

maxima

given

optical

k = 3,5

f

air

emittance. of

an

stable

30

tantalum

initiated

eI

dashed

the

increase

temperature,

to

the

of

the

dry

emittance At

a

with

rolled

in

after

was

to

argon

a variation

on cold

heated

and

process

oxidation.

Fig.

were

temperature

oxidation

thus

carried

a 3 mm thick

2.6. and

result

n = 2,6 Ti02

a

and

were

function the

4

of

index

This minima.

used

of

leads

to

Because

a

302 Fig.

AIn

I:,

Model

of

the

behaviour on

olnw

of

radiation thin

films

metals

MErAL

0.4

-

TITANIUM N,K

0.5 0.2 _

0.0

Fia.

_ 6.6

2:

1 0.1

I 0.2

Spectral titanium,

Fia.

3: dizing

-

---.--- 2.6,S.S 2.53..33 2.6,J.S 2.40..33 ----2.11,3.5 2.60..33

al 0.1

TIOZ N,K

Spectral titanium different

I 0.3

I 0.4

BXiDE

CIYERTHlCKHESS

emittance

1 L 0.5-0.8

samples annealing

1 0.6

1 0.6

CjBil

eI(k

calculated

emittance

I 0.7

-

= 0.71

as

as

a function

= 0.71

E~(X a

Pm)

function

temperatures

of

a Ti02

film

of

layerthickness

-----

980

K

-

1090

Y

UV) Of

measured time

at

on

oxi-

on

303 all

other

the

positions

The

accuracy

tude,

optical

of

which

resolution

Tab.

minima

Max

the

I the

of

d as

2.

I

I

values

whereby

oxide

of the

of

growth

measured listed

Tab.

in

2:

constants e

=

the

x Tab.

Growth

-

2 for

EKI

=

C

(3)

by

magni-

1 X and

below

to the

the

maxima

eX

I

3.

Max

I

1 0.345

Iym

versus appear

the

the in

with

time

Fig.

3

at form

increasing

expected

According

parabolic

to

that,

the

thick-

- t. can

linear

for

the on

(3)

be

determined

from

regression.

investigated

Temperature T

the

method

increases

111.

Eq.

oxidized

Oxidation

is

is

curves

constants

titanium,

film

at

plotted

confirms

time

the

of

amplitude,

is

0.270

I

emittance

(ref.

C in

f(t)

changes the

proposed

2. Min

I

gradient

d=

The

Max

0.200

This

function

the

emittance

values

growth

the

a TiO2-layer

spectral

0.125

temperature.

function

of

thickness

extreme

of

of

urn.

1. Min

I

0.055

lines

oxidation

ness

reproducibility

of

the

straight

of

accuracy

0.01

only

refraction

the

around

remarkable

but

The

of

squares

cause

limiting

and

1.

not

values

of

thicknesses

I which

index

Calculated

I

The

do

‘extreme

thickness

is

1:

the the

is

oxide

measure

properties

of

The

oxidation

oxidation

of

temperatures.

cold

air

Growth c

Constant

[rm’/sl

x

990

c 0.05

1090

1.81

1190

20.4

1290

29.2

10’

the

results

rolfed

are

304 CONCLUSION

Radiance

measurements

thickness cally the

of

The

thin. index

of

constants the

are

oxide

layers

accuracy

in

for

in

range

is

refraction

of

especially

accuracy

suited

at

the

in

mainly the

high

Situ

the

influenced

oxide.

by

spectral

are

are

the of

to

the opti-

knowledge

needed

emittance

of

films

Measurements

temperatures

correlating

measurements

where

the

of

optical

to

improve

oxide

thick-

ness.

ACKNOWLEDGEMENT

The

described

work

meinschaft

was

financially

industrieller

supported

by

the

Forschungsvereinigungen

Arbeitsge-

e.V.,

AIF.

REFERENCES

O.S.

Heavens:

Optical

Butterworth

121

G.

Neuer,

(1985), /3/

B.

GUntert

in: and

and

B.

Thin

Solid

London

Warner:

Temperature,

Industry

1982,

Hass

of

Publications,

Films.

1955

Thermochimica

Acta

E

295-298

Wiirner,

York, G.

F. pp.

Science

Properties

Scientific

pp.

and

Its

Measurements

American

5,

and

Institute

of

Control

Physics,

in New

429-432

A.P.

Bradford:

J.

Opt.

Sot.

Am.

47

(1957),

pp.

125-129

1st

T.

161

P.B.

Smith:

J.

Johnson

Opt.

Sot.

and

Am.

62

R.W.Christy:

(1972),

pp.

Phys.

774-780

Rev.

89

(1974),

pp.

‘3056-5070 171

181

M.M.

Kirillova

15

(1963),

A.

Gagnaire,

and pp.

B.A.

Charikov:

J.

Joseph:

ClO,

191

G.

Hass:

Vacuum

2

(1952),

pp.

/IO/

T.

Tanaka:

Jpn.

J.

Appl.

Phys.

/II/

P .: Wiley

and

44

Journal

Colloque

Kofstad:

Phys.

Met.

Metallogr.

138-139

(1983),

High Sons

Inc.,

pp.

Temperature New

York,

de

Physique

(Paris),

195-198 331-345 18

(1979),

Oxidation London,

pp. of

1043-1047

Metals.

Sidney,

1966

John

(SU)