H.O. Pierson. Handbook of carbon, graphite, diamond and fullerenes. Properties, processing and applications. 1993

Figure 12.11. Polycrystalline-diamond

drilling

products "Stratapax."

(Photograph

courtesy of GE Superabrasives,

Worthington,

OH)

Applications

of

Diamond

Tools.

Most industrial machining opera-

tions are performed

with coated cemented-carbide tools, usually as indexable

inserts.

Diamond

(and PCD)

increasingly

competes

with these

materials,

in particular

in the

machining

of

non-ferrous

metals

such as

aluminum,

copper,

magnesium,

lead, and their alloys since it does not react chemically

with these

materials.

Of

particular

importance

is the

machining

of aluminum

alloys now

widely used

in automobiles

and

other

areas.

These alloys are difficult to

machine

with carbides,

especially

if a good finish

is required, and diamond

has shown to be the best machining material.

Diamond is used extensively

in machining

abrasive

materials,

such

as

fiber

composites,

ceramics,

cemented

carbides,

graphite,

concrete, and silicon. A major application is

the cutting

of architectural

stones.

Side

View

View in

rotated

principal p-

optical

plane

R I

47

1.

Herbert,

I., The Diamond Diggers, Tom Stacey Pub.,

London

(1972)

2.

Davies,

G.,

Diamond, Adams

Hilger Ltd., Bristol,

UK

(1984)

3.

Krauskopf,

K. B., lnfroduction

to Geochemistry,

McGraw-Hill,

New

York (1967)

Academic Press, London (1979)

5.

Orlov,

Y. L., The Mineralogy of Diamond, John Wiley & Sons, New

York

(1977)

Physics ofcarbon,

Vol. 10 (P. L., Walker, Jr. and P. A. Thrower, eds.),

Marcel

Dekker Inc.

(1973)

8.

Spear,

K. E., J. Amer. Ceram. Sot.,

72(2):171-191

(1989)

9.

Adams,

D. M., /norganicSo/ids, John

Wiley&Sons,

NewYork(l981)

12.

Wedlake,

R. J., The Properties

of Diamond, (J. E. Field,

ed.), 501-

535, Academic

Press, London

(1979)

13.

Cowan,

G.,

Dunnington,

B.,

and

Holtzman,

A.,

“Process for

Synthesizing

Diamond,”

U.S. Patent

3,401 ,019

(Sept.

10,

1968)

17.

Peterman,

L., Proc. SPVRP-Ci, 4 Isf. Annual

Conf. (Jan 1986)

18.

Gardinier,

C. F., Ceramic Bulletin, 67(6):1006-l

009 (1988)

Natural and High-Pressure

Synthetic

Diamond 301

19.

McEachron,

R. W. and Lorence, S. C.,

Ceramic

Bulletin, 67(6):1031-

1036

(1988)

20.

Subramanian,

K., Ceramic Bulletin 67(6):1026-l

029

(1988)

23.

Diamond Heat Sinks, Technical

Brochure

from Drukker

& Zn. NV,

1001

MC. Amsterdam,

The Netherland (1989)

24.

Seal,

M ., interdisciplinary

Science

Review,

14( 1) :64-76

(1989)

1.O

INTRODUCTION

The

production

of diamond

coatings

is now possible

by low-pressure

vapor-phase

synthesis

under

relatively

benign

conditions.

This develop-

ment

should

open

the

door to the full exploitation

of the

unique

properties

of diamond

at

a

cost

that

is

still high

but

that

will

likely

be reduced

as

technology

improves

and production

is achieved

on an industrial

scale.

At

this

time,

the technology

remains

mostly

at the

laboratory

stage

and

only a

few

applications

are

on the

market.

Yet

the

future

appears

promising

with

a broad range of potential

applications

in many

industrial

areassuch

as heat

sinks

for

electronic

devices,

advanced

semiconductors

and

tool

coatings.

The

low-pressure

vapor-phase

process

is based

on

chemical

vapor

deposition

(CVD)

and

the

material

is

often referred

to as

“vapor-phase

diamond,”

“diamond coating,”

or “CVDdiamond”.

“CVD diamond”

will

be

used

in this

book.

Diamond

coatings

are

also

produced

by

physical

vapor

deposition

(PVD).

Such

coatings

however

are

a mixture

of

sp2

(graphite)

and

sp3

(diamond)

bonds

and are considered

a different

material

usually

referred

to

as diamond-like

carbon

(DLC).

They

are reviewed

in Ch.

14.

CVD-diamond

coatings

are polycrystalline,

as opposed

to natural

and

high-pressure

synthetic

diamond

which

are

normally

single

crystals.

This

polycrystalline

characteristic

has

important

bearing

on the

general

proper-

ties

of the

coatings

as shown

in Sec. 4.0.

industrial

reality in 1957 when General Electric started production.

it was

generally

believed

at that time in the U.S. that low-pressure

synthesis was

not feasible or at least not practical and early inconclusive

work at Union

Carbide

and Case

Western University were not actively foliowed.t1)t2]

in the former

Soviet Union, a less skeptical attitude

prevailed

and a

Table 13.1.

Chronology

of Major

Developments

of CVD

Diamond

1950’s

Early

work

on

low-pressure

synthesis

mostly

at

Union

Carbide,

Case

Western,

and

in

the Soviet

Union

1955

First production

of high-pressure

synthetic

diamond

in Sweden,

the U.S. and the Soviet

Union

1956-

Continuing

development

of low

pressure

synthesis

present

by Derjaguin

and

others

in the

Soviet

Union

1974-

NIRIM

and

other

Japanese

laboratories

develop

present

high growth

rate by CVD

process

1985

Consortium

formed at Pennsylvania

State Univer-

sity to

promote

diamond

research

in the

U.S.

1988

Development

of

diamond

tweeter

diaphragm

by

Sumitomo

Electric

1989

Development

of diamond-coated

boring and drilling

tools by

Mitsubishi

Metals

1992

Commercial

production

of free-standing

shapes up to

1 mm thick

by Norton,

General

Electric,

and others

Table 13.2. Material Properties

Affected by CVD-Diamond Coatings

Electrical

Resistivity

Dielectric

constant

Optical

Refraction

Emissivity

Reflectivity

Selective

absorption

Mechanical

Wear

Friction

Hardness

Adhesion

Toughness

Strength

Chemical

Corrosion

resistance

The

principles

of thermodynamics

and

kinetics of CVD as they apply

to the deposition

of graphite

were reviewed

in Ch. 7, Sec. 2.O.p)

These

considerations

are

valid

for the

CVD

of diamond as well.

2.1

Basic Reaction

The

basic

reaction

in the

CVD

of

diamond

is seemingly

simple.

It

involves

the decomposition

of a hydrocarbon

such

as methane as follows:

CH4

(cd

act&ion

C (diamond)

+ 2H,

(g)

In reality,

the

deposition

mechanism

is a complex interaction

of many

factors

and is

not

fully

understood

at

this

time,

although

two

essential

conditions

have been identified:

(a) activation

of the carbon

species

and

(b)

the

action

of atomic

hydrogen.

These

factors

are reviewed

in the following

sections.

Diamond

has been

deposited

from

a large variety

of precursors

which

include,

besides

methane,

aliphatic

and

aromatic

hydrocarbons,

alcohols,

ketones,

and

solid

polymers

such

as

polyethylene,

polypropylene

and

polystyrene

(a special case, deposition

with

halogens,

is reviewed

in Sec.

2.5).

These

substances

generally

decompose

into

two

stable primary

species:

the

methyl

radical

(CH,)

and

acetylene

(C,H,).ts)

The

methyl

radical

is

considered

the

dominant

species

and the

key

compound

in

generating

the

growth

of CVD

diamond,

at least

in the hot-filament

deposition

process (see

Sec.

3.4).t*)tQ)

Direct

deposition

from

acetylene,

although

difficult

experimentally,

has

been

accomplished,

with

a marked

increase

in the

crystallinity

of the

diamond

deposit.tlO)

Deposition

Model.

A two-step

deposition

model was recently pre-

sented

by Frenklash

and Spear. trr)

In the first

step, the

diamond

surface

is

activated

by

the

removal

of

a surface-bonded

hydrogen

ion

by

atomic

hydrogen

as follows: