Amorphous binary alloys obtained by electrolytical and chemical methods

Mutc~riuis C’lrctnistrj~ mtl f%J,sics. 1 I (1984)

AMORPHOUS

BINARY

J.FLECHON,

ALLOYS

F.A. KUHNAST

OBTAINEJ

453

453

459

BY ELECTROLYTICAL

26 March

METHODS

and A. RASHID

Laboratoire de Physique des Dep8ts Mgtalliques, 54506 Vandoeuvre Les Nancy Cedex (France)

Received

AND CHEMICAL

1984; accepted

Universite

de Nancy

1, BP 239

2 Mai 1984

ABSTRACT obtained by splat cooling condensation on a Amorphous alloys, generally cold support or sputtering, were prepared in our laboratory at ambient temperain liquid phase, ture by two other methods. The first one, the oxidoreductlon gives films, the thickness of which is 500 to 2000 A, deposited on an isolating suppo1.t - glas, plastic or ceramic. The second one, electrolysis of adapted allows us to obtain some thick layers the thickness of which is solutions, in this case, 1 to 100 microns. The support is a conductor, for example, a copper leaf. Experiments reveal a local order characterized by the absence of diffraction peaks in the experimental interference function which is chiefly formed by diffuse rings. We can obtain amorphous materials at ambient temperature if the bath composition leads to an alloy which contains at least 15% of _Loms of the metalloid in the case of phosphorous, and 20% of atoms with boron. The upper limits are, respectively, 25 and 35%. It does not seem possible to obtain a bigger quantity of metalloid with these two methods. The local order can be represented by an assembly of clusters in which chemical bonds exist between the metal and metalloid atoms. Every cluster is surrounded by a domain where atomic position is distributed following a Gaussian function. Beyond that the material is completely amorphous.

INTRODUCTION The of

usual

small

variable turning films for

methods

area

homogeneity cylinder

deposited

example,

and

metallic

by evaporation composition

glasses

lead to either

on a cold support realised

by

1.11

thin films

, or ribbons of

an ultra-rapid

quench

on

a

12 1 . We have tried to obtain some metallic glasses as thin on an insulator

coppir

which give suitable

0254-0584/84/$3.00

of preparing

obtained

l-4-61

[3] and as thick layers formed on a conductor,

, by some rapid processes

reproducible

of relatively

small

cost

samples.

0 ElsevierSequoia/Printedin The Netherlands

454 prepared

by homogeneous

oxidoreduction

the layers by heterogeneous

The films were

oxidoreduction

or electrolysis.

We systematically selves

to

threw

those

having

away all the crystallized a structure

presenting

in the liquid phase,

deposits

only

and we limited our-

local

order,

as shown

by

X-ray analysis. n

The

film

thickness

generally

varied

from

: that of the layers

500 to 5000 A

from 1 to 100 urn. We

studied

four

metalloid. although

binary

Table

1

couples

defines

its composition

Table 1. Percentage NiP

observed

metalloid.

the

domain

of Metalloid

in which

by

alloy

a metal

remains

and a

amorphous

types

a higher

in Amorphous

Sample

COB

of behaviour

closely

dependent

The boron atom is lighter and smaller

tly, we obtained

formed

the

(in Atoms) Present

COP

two

glasses

varies.

NiB

We

of metallic

percentage

with

on the nature

than phosphorus

this element

of the

and consequen-

in the amorphous

alloy

than with phosphorus. We have examined

:

successively

- the deposits obtained, - their characteristics, - the evolution

METHODS

It has

phosphide

been

known

the structure

which

or

metallic

protection plating

indeed

We have been are

is a metallic

examining

formed

level,

electroless

in the year 1947, the amorphous

tions

for more a nickel

than 50 years

with

a

glass

Brenner

method lead

to

formed

on the

these materials nickel

or

since

cobalt

salt

large

and

at that time. 181 discovered

surfaces.

Chemical

of

'Kanigen

production

and phosphorus.

any fundamental

1956 [3]

in

171.

and Riddel

by nickel

state did not provoke

that

salt and sodium hypo-

of the formed deposit was not studied

on an industrial

important

nickel-plating

chemistry

or palladium,

and this was used by Feigh and Frankel

this reaction most

in analytical

traces of platinum

are needed

Of course,

Nickel'

on heating

oxidoreduction

order to detect

the

resistivity

OF PREPARATION

Homogeneous

Using

of the electrical

But

research.

. The retained solu-

sodium

hypophosphite

or

potassium

hydroboride

generally

complexed

of this salt and its great reducing The

bath

compositions

For example,

vary

with

ammonia,

power in aqueous

as

a function

of

given

the instability

media.

the

purpose

of

the

deposit.

:

we used

l/2 1 of solution contains -2 .?t long NL with 40 g/l; i.e. 2 x 10 -2 atg P with 40 g/l; i.e. 4.82 x 10

1) In the case of nickel-phosphorus:

:

125 cm3 of Ni(CH3C00)2.4H20 125 cm3 of NaH2P02.H20 250 cm3 of NaCH3COO

with 40 g/l (buffer)

a few drops of PdC12 with 0.096 g/l; i.e. 54 X low5 iong Pd

2) In the case of nickel-boron: 400 cm3 of Ni(CH3C00)2.4H20 200 cm3 of NH40H

1 1 of solution

2+

contains

:

obtained

in the same manner.

with 65 g/l

to 29 volumes

4 g of KBH4 dissolved

in 50 cm3 of NH40H

10 cm3 of PdC12 with 0.5 g/l; 340 cm3 of water. Cobalt-boron

and cobalt-phosphorus

Object-slides, film

was

suitably

formed

The reaction

on

them

mechanism

ned. We can write,

B1-l;+ 3H20 + H2B03-

same

described

the purely

the

time

as

bath.

a powder

A bright

formed

the same whatever

the metalloid

in the case of the nickel-boron

4Nio + H2BO-3

metallic

in the liquid. concer-

alloy:

+ 5H20

+ 4H2

baths

of

were

chemical

for

technique

The

efficiency

The metalloid

the

leads

alloy

way,

in the

was

previously

Indeed, we have observed precipitate

such as palladium

the homogeneous formed

oxidoreduction

oxidoreduction.

similar.

to a metallic

catalyst

same

can provoke

preceding.

The precision

role in the process.

homogeneous

are probably

a deposit-promoting In

the

or heterogeneous

mechanisms

solutions.

a current

plays an important

used

and electrolysis

the electrolysis to

the same

in the

oxidoreduction

Both process

dilute

were

dipped

is approximately

seem that hydrogen

Heterogeneous

sence

alloys

were

+ H2 + BO +'ZOH- + H20

It would

The

at

for example,

4Ni++ + BH4- + 80H-+

H2BO-3

cleaned,

only in the pre-

chloride

in the very

case of the nickel-boron oxidoreduction

in such

deposit,

which aligns

a quantity

that

that

itself

we observed

1101 above unity.

was assayed

was about

by absorptiometry

one percent,

as allowed

using a few tens of micrograms. by Beer's

law relative

to the

456

absorbed

We

luminous

utilized

monochromatic

carminic

:

flux

acid

in the

1.9 i

., , and phosphomolybdic

case of boron

blue i 3 1 to detect the phosphorus. L. J STRUCTURE The as

metallic

films

a significant

appeared

in

substances with

solution.

using

an X-ray

film

of

thickness

layers thicker

on an insulator

of powders

the

a resolution

The

formed

quantity

This

with

were

the

phenomenon

diffractometer

l/10

degree,

allowed

only

allowed

equipped

a gonlometer a

study

than 30 pm were directly

deposited

with

examined

at the same

same composition us

to characterize

with

these

a step-by-step

and

a scintillation

the

electron

without

time

as the films

device counter.

microscope.

any particular

The

pi‘ecau-

tion.

ilr) 2_

iii) \

P

l_

l-

0

_A_-__

-1

0.5

0

1

1.5

2

2.5

Fig.1. Experimental interference of amorphous Ni 66B34 (powder)

Fig. 1 and 2 indicate bient

temperature

on

and an electrolytic rent

diffusion

diagrams

and

shows

that

the

absence

ground 19,111

of

a powder

68B32 distortion and there

peaks

crystals

peaks

or the borides

then

function

using

chemical

for the gaseous

standardised.

The

relationship

observed

at am-

techniques,

diffusion, similarity

between

the

incoheof both samples.

in which only local order exists characterized and

the presence

of a strong

continuous

back-

. were placed under a classical

appeared.

This

the same condi-,:ions as previously and narrow

obtained

corrected

is a structural

glasses

sharp

interference

of Ni66B34

layer Ni

When both substances of 450°c,

Fig.2. Experimental interference function of amorphous Ni68B3* (layer)

the experimental

They are binary metallic by

function

appear,

identified

is obvious described:

the position

on Fig.

vacuum at the temperature 3 and 4, obtained

the continuous

of which

as Ni 3B , Ni2B, Ni4B3.

background

characterizes

either

under

is lower the metal

Ni3B 0 Ni2B 0

Ni4B3 V

3

25

30

35

i’u

%O

Fig.3. Diagram X of crystallised Ni66B34 powder(XCoKa)

z5

30

35

aa

Fig.4. Diagram X of crystallised Layer(XCoYcx) Ni68B32

The metallic glasses obtained by these methods are somewhat analogous. Compared to the crystallized substances, all the physicochemical properties are different. As

an

example, let us look at the electrical behaviour.

ELECTRICAL PROPERTIES Since an increase in thermal energy modifies their structure, these materials are metas-tableand their electrical conductivity increase at the same time as the matrix

becomes

ordered. Likewise, the average temperature coeffi-

cient of the electric resistance, R 0 ’ varies with the degree of order. In order to show these properties, it suffices to place under vacuum either an amorphous film OF a layer and then to vary its temperature step-by-step from ambient to 450°C, continuously recording its electrical resistance. The duration at a given temperature depends on the isothermal rate of variation of the resistance. When this speed tends towards zero, it suffices to return to ambient temperature to measure R

Successive cycles between 0 and 8 OC revea0 led a relative reversibility as long as we did not exceed the stabilization

level. Fig. 5 shows the compared values of the resistivities at ambient temperature and at 450°C for the chemical Ni66B34 and electrolytic N175Bz5 alloys as a function of the deposit thickness. If we take as c first

approximation,

that the electrical conductivity c expressed, in kinetic theory, the the classical formula:

is

458

where

A = electronic

mean free path and v

F

= electron

velocity

at the Fermi

level.

Fig.5. Compared values of the resistivity (films, ---- layers) We imagine the

electronic

very little, Fig

that

the thermal

mean

free

increases

6 and 7 show, as a function

path

energy and

as a function

creates

as

order

the velocity

until the free enthalpy

for two of these of the annealing

alloys

of the thickness

in the matrix at the Fermi

minimum

is reached.

(film and layer),

temperatures

of successive

p,

to increase level varies

the variation levels.

10-6”c-!

2000 t

1500

20% B

i 1000 24.7% 3

500

,

:i:-,_

/

0 OC C

Fig.G.Variation 0; flo (successive annealings)for films

Fig.7. Variation of R annealings) for layer:

(successive

459

Two points 1) the very

are to be noted: low values

interest

for practical

2) their

sudden

The phonon

increase

to the amorphous

state,

a property

of

at the crystallization. is important

predominance

range order whereas

relative

of R.

applications;

in a medium

it is less in a disordered

where

there

exists

long

matrix.

CONCLUSION The

chemical

of amorphous

ple,

rapid

and electrolytical

alloy and

all classical

of

films

methods

represent

two means

and layers of the metal-metalloid

relatively

physicochemical

low

cost.

studies

The samples

of metallic

obtained

glasses

of preparation

type. They are simcan be used

for

cI 11.!

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1

A.K. Sinha, B.C. Giessen and D.E. Polk, Treatise Vol. 3 1 Ed.by N.B. Hannay, 1976

2

R.E. Maringer, C.E. Mobley and E.W. Callings, Rapidly Quenched Metals, Vo1.23, 1976, p.87

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F.A. Kuhnast, A. Obaida and A. Rashid, DBp6ts J. FlBchon, F. Machizaud, Electrolytiques amorphes de NiB et COP, B. Sot. Chim., 7,8, 1982, 257

7

Feigl and Frankel,

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A. Brenner

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F.A. Kuhnast,

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G. Milazzo,

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