Use of Secondary Ion Mass Spectrometry to Study Surface Chemistry

14 Use of Secondary Ion Mass Spectrometry to Study Surface Chemistry of Adhesive Bonding Materials W. L. Baun Mechanics and Surface Interactions Branch, Air Force Wright Aeronautical Laboratories,

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AFWAL/MLBM,Wright-PattersonAir Force Base, OH 45433

Secondary Ion Mass Spectrometry used as a solo instrument or in concert with other methods has proven to be an excellent technique for studying the surface chemistry of adhesive bonding materials. The application of SIMS is shown in relation to pretreatments of metals and alloys, chemistry and structure of adhesives, and locus of failure of debonded specimens. The i d e a o f b u i l d i n g s t r u c t u r e s w h i c h a r e s t r o n g e r a n d m o r e d u r a b l e w h i l e a t t h e same t i m e l i g h t e r i n w e i g h t w o u l d a p p e a r c o n t r a d i c t i v e , but has been accomplished u s i n g adhesive bonding and composite materials. Such n o v e l c o n s t r u c t i o n and m a t e r i a l s a r e used e x t e n s i v e l y i n the aerospace and automotive i n d u s t r i e s . Since these s t r u c t u r e s depend on t h e i n t e r a c t i o n o f s u r f a c e s and t h e f o r m a t i o n o f i n t e r f a c e s , i t i s n e c e s s a r y t o d e v e l o p methods o f p h y s i c a l and chemical c h a r a c t e r i z a t i o n which are a p p l i c a b l e to such types of materials. S e c o n d a r y i o n mass s p e c t r o m e t r y , u s e d e i t h e r a s a s t a n d a l o n e i n s t r u m e n t , o r as a complement t o o t h e r t e c h n i q u e s , h a s p r o v e n of value f o r c h a r a c t e r i z a t i o n o f o r i g i n a l m a t e r i a l s and f a i l u r e surfaces f o l l o w i n g use or accelerated t e s t . Since these proceedings c o n t a i n d e t a i l e d d e s c r i p t i o n s o f t h e SIMS t e c h n i q u e a n d i t s v a r i a t i o n s , e m p h a s i s w i l l be p l a c e d i n t h i s a c c o u n t o n a p p l i c a t i o n o f t h e method t o s u r f a c e p r e p a r a t i o n a n d a d h e s i v e b o n d i n g . T h e o r e t i c a l and p r a c t i c a l o p e r a t i o n a l a s p e c t s o f SIMS w i l l b e c o n s i d e r e d o n l y i n s o f a r as they p e r t a i n t o adhesive bonding r e s e a r c h . Discussion In d e c i d i n g which surface chemistry t o o l s to use f o r the broad area o f a d h e s i o n a n d f o r a d h e s i v e b o n d i n g i n p a r t i c u l a r , a number o f a s p e c t s must be c o n s i d e r e d . More o f t e n t h a n n o t , a c o m b i n a t i o n o f i n s t r u m e n t s must be u s e d t o t a k e a d v a n t a g e o f t h e u n i q u e i n f o r m a t i o n provided by each method. T a b l e 1 s h o w s some o f t h e i m p o r t a n t a s p e c t s o f a d h e s i v e b o n d i n g a n d some o f t h e c h a r a c t e r i z a t i o n m e t h o d s which are a p p l i c a b l e i n these areas

.

The acronyms a r e t h o s e

2 in

t h e r e v i e w by P o w e l l ' .

This chapter not subject to U.S. copyright. Published 1985, American Chemical Society

In Desorption Mass Spectrometry; Lyon, P.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

used

228

DESORPTION MASS

SPECTROMETRY

It i s seen i n Table 1 that SINS i s applicable to several areas of investigation i n adhesive bonding. SIMS may be used i n a variety of ways including species imaging of the surface (SUMS) which may be e s p e c i a l l y useful f o r c l a r i f y i n g mixed mode f a i l u r e surfaces. ο

The main features of SIMS are shown i n Table ΙΓ"\


Chemistry of Adherends A determination of the chemistry cf metallic adherends presents problems of each of the areas discussed here. Many of the surface chemical techniques are applicable to the analysis of adherends, and because of the s t a b i l i t y and good conductivity, decomposition and surface charging are not problems. Surface chemical analysis i s usually devoted to (1) determining the amount and d i s t r i b u t i o n of elements purposely placed on the surface to impart a desirable property, and (2) detection and monitoring of impurity elements which may be deleterious to the adhesive bond. Many chemical etching and oxidizing treatments are used on metal and a l l o y s to enhance adhesive bonding of the surface. Enhancement cones about by roughening of the surface and by changing the surface chemistry. In addition, some thermal treatments, such as the bond cure i n adhesive bonding, may a f f e c t the composition of the surface, either by introducing impurities or by increasing or decreasing a concen t r a t i o n of a l l o y i n g elements at the surface. McDevitt and co-work4 5 6 ers ' used SIMS and other modern surface analysis tools to analyze several aluminum a l l o y s following chemical treatment f o r adhesive bonding. They found a number of i n t e r e s t i n g phenomena, including the formation of an i n t e r f a c i a l region r i c h i n copper on the s t r u c t u r a l a l l o y 2024 aluminum. The concentration and width of t h i s p o t e n t i a l weak boundary layer was found to vary depending on the etching conditions of the s u l f u r i c acid-sodium dichromate solution. This solution i s related to the surface preparation method known as the FPL etch. Similar results were obtained more recently by Sun and Co-workers^. The formation of such potential weak boundary layers may influence both the i n i t i a l bondability and the long time d u r a b i l i t y of the adhesive bond. Baun et a l used Ion Scattering Spectrometry (ISS), Secondary Ion Mass Spectrometry (SIMS) and Auger Electron Spectrometry (AES) to analyze a v a r i e t y of metal and a l l o y adherends. These authors also used several surface treatments on titanium and titanium a l l o y s and analyzed them by 9

9,

1 0

1 1

surface techniques such as ISS, SIMS, AES and SEM ' . Large differences i n chemistry were observed on titanium and i t s a l l o y s depending on the surface treatments. Some possible steps i n the surface preparation of titanium a l l o y s f o r adhesive bonding are 12 shown i n Table I I I .


Table I Aspectsôf methods

adhesive

bonding and a p p l i c a b l e s u r f a c e

Adherend chemistry AEAPS, AEM,A E S , A P S , B I S , C I S , C L , EM, E S , EXAFS, I S , I S S , D I P , P E S , R B S , S I M S , S X A P S , SXES Adherend s t r u c t u r e AEM,

229

Surface Chemistry of Adhesive Bonding Materials

14. BAUN

E L L , E M , HEED,

characterization

IIRS,

IIXS,

IMMA,

and morphology IMMA, L E E D ,

SEM, S U M S ,

S R S , STEM,

T E M , X E M , XRD


Adhesive chemistry A E S , A I M , ASW, A T R , E S R , H A , 1 R S , I S S , L S , P E S , S I M S , U P S , XPS A d h e s i v e s t r u c t u r e and morphology A T R , I R , U V , R A M A N , SEM I n t e r a c t i o n of polymers w i t h metals A E S , A I M , ASW, C P D , E L L , E E L S , E S D I , ESDN, F D , F D S , H A , 1 R S , I R , I S S , I S D , L E E D , L S , P D , S C , S I M S , U P S , X P S , RAMAN Failure surfaces (locus of f a i l u r e ) AES, ATR, E L L , I S S , SIMS, PES, X P S , SEM, SXES,

Table I I Main features Positive

-

Negative

o f SIMS a s

a surface

analysis

SXAPS,

S R S , UPS

method

Information depth i n the "monolayer range" D e t e c t i o n of a l l elements i n c l u d i n g hydrogen D e t e c t i o n o f c h e m i c a l compounds Isotope separation E x t r e m e l y h i g h s e n s i t i v i t y f o r many e l e m e n t s a n d

compounds (^10 ^ m o n o l a y e r s ) - Quantitative analysis after calibration - N e g l i g i b l e d e s t r u c t i o n o f t h e s u r f a c e ( S t a t i c SIMS) - E l e m e n t a l p r o f i l i n g (Dynamic SIMS) - E l e m e n t a l and C l u s t e r Imaging - Large differences i n s e n s i t i v i t y for d i f f e r e n t "surface s t r u c t u r e s " ( f a c t o r 1000) - Problems i n q u a n t i t a t i v e i n t e r p r e t a t i o n of molecular spectra - Ion induced surface reactions - Surface Charging i n Insulators


230

DESORPTION MASS SPECTROMETRY

Table I I I Surface Preparations 1 Clean

2 Etch

Solvent

Acids

for Adhesive Bonding

4 Modify

3 Convert Chemical

B o i l i n g HÔ

Phosphates,

Boiling H

± ±

Liquid

HF,

2.

Vapor

H S0 , 4

Fluorides,

Dry

H P0

4

etc.

Heat + H u m i d i t y

Anodization

Absorption

2

3

HN0 ,

12

1.

Abrasion


of Titanium Alloys

3

Alkaline

Combinations

Combinations

Alkaline

dense

Abrasive

porous

Slurry

UV,

Combinations

2

Q

Heat

Ions,

Corona,

etc «

The s u r f a c e c h e m i s t r y o f T i t a n i u m a l l o y s v a r i e s w i t h e a c h physical or chemical treatment. An example o f ISS/SIMS r e s u l t s from a t y p i c a l c h e m i c a l p r e t r e a t m e n t f o r T i - 6 A 1 - 4 V i s s e e n i n F i g u r e 1. H e r e t h e s a m p l e was d e g r e a s e d , e t c h e d i n KNO^/HF a n d c o n v e r t e d w i t h a m i x t u r e o f H F , NaF a n d Na^PO^ i n aqueous s o l u t i o n . S p e c t r a from t h i s s u r f a c e shows t h a t i t i s f a r f r o m b e i n g a s i m p l e o x i d e . An ISS s p e c t r u m f r o m a t y p i c a l T i O ^ s u r f a c e i s shown i n t h e i n s e t f o r comparison.

Note i n the

SIMS d a t a t h e

appearance o f the

molecular

+

i o n T i F , w h i c h s u g g e s t s the c o m b i n a t i o n o f f l u o r i n e and t i t a n i u m . I t i s a l s o i n t e r e s t i n g t h a t s o d i u m a n d f l u o r i n e d o n o t seem t o b e a s s o c i a t e d even though a p p r e c i a b l e amounts o f each o c c u r on the surface. SIMS d a t a i n F i g u r e 2 A f o r a t y p i c a l a n o d i z e d o x i d e f o r m e d i n a n e u t r a l N a „ I I P 0 , + H P 0 . s o l u t i o n a t 50 v o l t s s h o w s a s p e c t r u m o

similar

to

the

crystalline

oxide,

rutile. +

These

thin

anodized +

s p e c i m e n s show l a r g e amounts o f T i O i n r e l a t i o n t o T i . I t i s i n t e r e s t i n g t h a t the a l l o y i n g element vanadium i s n e a r l y absent i n the oxide l a y e r . The s u r f a c e c h e m i s t r y o f p o r o u s a n o d i z e d o x i d e s a r e m u c h d i f f e r e n t a s s e e n i n F i g u r e 2B w h e r e t h e SIMS s p e c t r u m i s s h o w n f o r a t h i c k o x i d e f o r m e d i n t h e same e l e c t r o l y t e a s A , b u t a t 13 100V w h i c h i s n e a r t h e b r e a k d o w n v o l t a g e f o r t h i s e l e c t r o l y t e and titanium. SIMS d a t a s h o w h y d r o c a r b o n s , a l k a l i e l e m e n t s , c a l c i u m , and most i m p o r t a n t l y e v i d e n c e o f phosphorus ( p r o b a b l y p h o s p h a t e i o n ) i n the porous f i l m . AES e l e m e n t a l p r o f i l e s show t h a t phosphorus c o n c e n t r a t i o n s are h i g h a t the s u r f a c e and c o n t i n u e on i n t o the film. I n i t i a l b o n d a b i l i t y o f a n o d i z e d s u r f a c e s was t e s t e d i n t h e l a p s h e a r c o n f i g u r a t i o n u s i n g numerous c o m m e r c i a l epoxy a d h e s i v e s . With o n e e x c e p t i o n , a l l s u r f a c e s p r o v e d t o be b o n d a b l e a n d g a v e a c c e p t able lap shear values. T h a t e x c e p t i o n was an a n o d i z e d f i l m f o r m e d


14.

Β AU Ν


2500 V

197-7

SIMS

231

ISS


,Na* Af 10*

JHS. 20 30 H mmm 40 50 m\mmmm m mnn n m rmi rr-t I lit 11

atomic mass units

Figure

1.

ISS/SIMS Data f o r T1-6A1-4V A l l o y Etched w i t h HF/HNO. and Converted w i t h HF/NaF/Na^PO^. Inset shows t y p i c a l I S S S p e c t r u m f r o m T i 0 . o

SIMS

Na*

C H ;

PO: > 10 A 4

10

20

30

40

50

60

10

20

30

40

Atomic Mass

50

60

Units

Atomic Mass U n i t s Figure. 2 .

SIMS D a t a f o r T 1 - 6 A 1 - 4 V A l l o y . A. Specimen Anodized i n Na HPO, + H P0, a t 50 V o l t s . B. Specimen A n o d i z e d i n Na-HPO, + H~P0, a t 100 V o l t s ( B r e a k d o w n ^ 0

Â

Q

4

J

(pH » 7)

f

(pH = 7 )


232

DESORPTION MASS

SPECTROMETRY

i n any e l e c t r o l y t e containing f l u o r i n e ions. The r e s u l t was rather unexpected since a commercial patent c a l l s f o r the addition of f l u o r i n e ions to a solution to increase the current density and subsequently the porosity of the anodized f i l m f o r adhesive bonding. The adhesive showed good adhesion to the oxide f i l m i n these cases. F a i l u r e often occurred i n t e r f a c i a l l y at the oxide/metal interface even using lap shear specimens. Uhen a test i n which pure shear was placed at the interface, as i n the three-point-bend method, then f a i l u r e always took place i n t e r f a c i a l l y at the oxide/metal i n t e r face. Peel tests on anodized films i n which f l u o r i n e was present also showed i n t e r f a c i a l f a i l u r e i n most t e s t s . Peel strength i n the anodized regions was v i r t u a l l y zero. SIMS spectra showed f l u o r i n e to be present on these surfaces (both on the adhesive and adherend). Downloaded by UNIV OF SYDNEY on May 29, 2013 | http://pubs.acs.org Publication Date: October 17, 1985 | doi: 10.1021/bk-1985-0291.ch014

+

An i n t e r e s t i n g r e s u l t was the appearance of F i n the residual gas analysis when the electron beam i n AES was placed on the sample, suggesting easy desorption and a very unstable surface. In f a c t , when electron beam currents were not minimized, the fluorine f r e quently was desorbed completely, and did not appear i n the Auger spectrum. SIMS spectra from simple etching processes also showed i n t e r esting r e s u l t s . Figure 3 shows the high a c t i v i t y of etched surfaces, and tendency to react with elements found i n tap water. Note that the calcium from the water appears to combine with f l u o r i n e l e f t on the surface by the h y d r o f l u o s i l i c i c a c i d , but there i s l i t t l e suggestion of any reaction between f l u o r i n e and titanium to form a compound. Also of i n t e r e s t i s the very low concentration of the a l l o y i n g element aluminum on these surfaces i n view of the high secondary ion y i e l d from aluminum. Vanadium, which was not observed i n the anodized specimens, appears prominently on most acid etched surfaces. Aluminum a l l o y s show equally i n t e r e s t i n g surface chemist r y changes with processing. Many aluminum a l l o y s following processing including hot r o l l i n g and heat treatment, show surface elemental concentrations f a r d i f f e r e n t from true bulk composition. Even following cleaning such as degreasing and a l k a l i n e bath, appreciable differences are seen between surface and bulk as shown i n Figure 4. Here SIMS and ISS spectra are shown f o r a degreased and l i g h t l y a l k a l i n e cleaned 2024 a l l o y . SIMS shows a large amount of Mg on the surface and the ISS r a t i o of 0 to Mg-Al i s about that MgO. One advantage of SIMS showing i t s complementary nature i s seen here where Mg and A l cannot be resolved i n ISS but i s e a s i l y separated i n the SIMS spectrum. When the surface i s etched i n a stronger a l k a l i n e solution, the SIMS spectrum ( B ) shows a much smaller r a t i o of Mg to A l , much more i n l i n e with the magnesium content of approximately 1.5%. Other surface treatments which etch away the surface s t i l l leave the surface composition much d i f f e r e n t from the bulk. Figure 5 shows the ISS/SIMS spectra f o r 2024 aluminum a l l o y etched i n a mixture of n i t r i c and hydrofluoric acids. As i s seen i n both spectra, copper i s prominent on the surface. This i s a very mild case of surface smutting . Surface smut i s observed i n many mate-' r i a l s which are heavily etched i n acid or a l k a l i n e media. Smut on 1

stainless s t e e l has been studied by ISS/SIMS ^. An example of such spectra on a smutted 304 stainless s t e e l surface i s seen i n Figure 6



BAUN

TÎ-6AI-4V hydrofluosilicic acid etch

I || jj

A. deionized H 0 rinse 2


+

10

!; !;

S I M S

20

30

40

50

60

atomic mass units Figure 3.

SIMS D a t a f r o m T 1 - 6 A 1 - 4 V A l l o y . A. Etched i n H y d r o f l u o s i l i c i c A c i d , Rinse B. Etched i n H y d r o f l u o s i l i c i c A c i d ,

Deionized H 0 2

T a p HÔ R i n s e

Mg

2024 AI Na

A. 10

20 3 0 4 0 5 0

+ SIMS

m.--

— .1—

_i .3S

Figure 4.

I S S / S I M S D a t a From 2024 Aluminum A l l o y , D e g r e a s e d and G e n t l e A l k a l i n e C l e a n . I n s e t s h o w s SIMS Spectrum from B u l k A l l o y .




234

Figure

6.

ISS/SIMS Data

From Smutted S t a i n l e s s

Steel


Β AU Ν

14.


235

a n d i s f o u n d t o be m o s t l y s i l i c o n and o x y g e n . Even when t h e s u r f a c e i s v i s i b l y desmutted, o f t e n t r a c e s r e m a i n w h i c h a r e measurable by ISS/SIMS. Smutted and d e - s m u t t e d s u r f a c e s were examined by s e v e r a l a n a l y t i c a l techniques. The r e s u l t s o f w h i c h a r e s u m m a r i z e d i n T a b l e IV.

Table IV S p e c i e s f o u n d o n 304 s t a i n l e s s


Technique Smutted i n

steel

by s u r f a c e

De-smutted

H S0^ 2

AES

Si ,

0,

C l , C, Cu, Fe, C r , N i

0,

ISS

Si

0,

C, Cu, Fe, Cr

0,

+SIMS

Si" , N a , S i 0 , S i O H , + + + Fe' , C r , N i , C u

+

+

analysis

+

+

C u , CH ,

C , S,

Fe, Cr, N i

+

+

9

n

,

CH

C H η η , 0 , OH , S 1 0 ~ , S i 0 ~ , S i O> ~, S i F ~ , S i 0 F ~ , S i 0 F , F e 0 " 2

3

HÔ^-CrO^

Na, Fe, Cr + + + N a , K ' S i , S , OH , II

-SIMS

in

techniques

2

2

C H

Fe , C r , N i __

__

_

n >

C 0 ~ , FeO Fe0 C rrO0 ~ , C C rr O 2

G

C ,

0,

S,

S i

b

, N , Cu, Fe, Cr, N i

_

0",0H",Cl"",Si0 CrO" ( g r e a t l y reduced) n

C, 0,

3

2

Fe, Cr, N i

XPS

More t h a n Oxide

one

form.

form.

C h e m i s t r y and S t r u c t u r e

of Adhcsives

SIMS i s v e r y s e n s i t i v e t o s u r f a c e m o l e c u l a r s t r u c t u r e , s h o w i n g f r a g m e n t a t i o n p a t t e r n c h a n g e s e v e n o n t h e same m a t e r i a l b u t g i v e n different treatment. F i g u r e 7 s h o w s SIMS d a t a f o r a c o m m e r c i a l t w c - p a r t e p o x y m i x e d u n d e r t h e same c o n d i t i o n s a n d t h e n d i v i d e d i n t o two p o r t i o n s , o n e c u r e d 24 h o u r s a t r o o m t e m p e r a t u r e a n d t h e o t h e r c u r e d one h o u r a t 2 5 0 ° F . A s c a n be s e e n , some l a r g e r f r a g m e n t s a r e s e e n i n t h e s a m p l e h e l d at e l e v a t e d t e m p e r a t u r e , and sodium has s e g r e g a t e d t o the surface. S u c h s e g r e g a t i o n i s v e r y common i n h i g h t e m p e r a t u r e c u r e d specimens, where sodium i s o f t e n found at the f a i l u r e s u r f a c e i n an a d h e s i v e f a i l u r e mode. ISS/SIMS data from the adhesive s i d e of a t i t a n i u m - e p o x y f a i l u r e i n t e r f a c e from a t e n s i l e t e s t specimen are shewn i n F i g u r e 8. The f r a g m e n t a t i o n p a t t e r n i s d i f f e r e n t ( c o m p a r e d t o t h e two p a r t epoxy) from t h i s t e m p e r a t u r e s e n s i t i v e tape epoxy and sodium i s seen at the f a i l u r e i n t e r f a c e . S o d i u m was a l s o o b s e r v e d o n t h e matching t i t a n i u m side o f the specimen.


236


+ SIMS


RT

10

20

30

40

cure

50

60

atomic mass units

I H I I I H 1 1 H H I I I 1 I H I U l i l l l l U U l l l l l l J M I ! I ! I I1 1 1 1 1 J 1 1 1 1 I I I U l l l 10

Figure

7.

2

0

30

AO

M)

atomic m ass units

60

SIMS D a t a F r o m Two P a r t E p o x y C u r e d a t Room T e m p e r a t u r e f o r 24 H o u r s a n d a t 2 5 0 ° F f o r One Hour.


14.

Β AU Ν


Failure


237

Surfaces

SIMS a n d t h e o t h e r c o m p l e m e n t a r y s u r f a c e s p e c t r o s c o p i e s are e x t r e m e l y u s e f u l i n d e t e r m i n i n g j u s t where a n a d h e s i v e bonded s t r u c ture a c t u a l l y separated. Following f a i l u r e during service or test, i t i s n o t always o b v i o u s j u s t where the f a i l u r e took p l a c e . Often a f a i l u r e i s termed " a d h e s i v e " or i n t e r f a c i a l j u s t because the a d h e r e n d a p p e a r s t o be " c l e a n " (no a d h e s i v e ) . In a c t u a l i t y the f a i l u r e may h a v e o c c u r r e d i n a w e a k b o u n d a r y l a y e r v e r y n e a r a n interface. A f a i l u r e may a l s o b e i n i t i a t e d i n o n e a r e a a n d p r o g r e s s I n t o another weaker a r e a . F i g u r e 9 shows a m o d e l o f an a d h e s i v e b o n d a n d some o f t h e f e a t u r e s c o n t r i b u t i n g t o a f i n g e r p r i n t s p e c t r u m which p i n p o i n t s the exact locus of f a i l u r e . Examples o f these c h e m i c a l " f i n g e r p r i n t s " w e r e shown e a r l i e r i n I S S / S I M S s p e c t r a from a l l o y s u r f a c e s i n w h i c h a l l o y i n g and i m p u r i t y element d i s t r i b u t i o n s were f a r d i f f e r e n t from b u l k v a l u e s . I n a d d i t i o n , some o f t h e i n t e r f a c i a l r e g i o n s show v e r y c h a r a c t e r i s t i c s p e c t r a d e p e n d i n g on p a s t h i s t o r y or p u r p o s e l y added e l e m e n t s . F o r example, as mentioned e a r l i e r , b o n d s on m e t a l s o r a l l o y s w h i c h h a v e b e e n h e a t e d f o l l o w i n g e t c h i n g o r d u r i n g p r o c e s s i n g o f t e n show weak b o u n d a r y l a y e r f a i l u r e s i n w h i c h l a r g e q u a n t i t i e s o f a l k a l i elements have m i g r a t e d to the interface. Such a f a i l u r e s u r f a c e a l o n g w i t h the o r i g i n a l T1-6A1-4V e t c h e d s u r f a c e s h o w n i n F i g u r e 10 o r i g i n a t e d w i t h r e s e a r c h o n modeling of gold adhesion to t i t a n i u m a l l o y s . F o l l o w i n g easy p e e l o f t h e g o l d , t h e s u r f a c e was f o u n d t o p r o d u c e a h i g h s o d i u m s i g n a l I n t h e SIMS s p e c t r a w h i c h h a d n o t b e e n o b s e r v e d i n t h e o r i g i n a l surface. The g o l d s i d e o f t h e f a i l u r e a l s o c o n t a i n e d a l a r g e a m o u n t of sodium. P u r p o s e l y added l o c u s o f f a i l u r e as

elements

also often

help to

i l l u s t r a t e d i n Figure 11.

shown t o h a v e o c c u r r e d n e a r

the

indicated

spectra

b y SIMS a n d o t h e r

p i n p o i n t an

priner-aluminum a l l o y on the

S i m i l a r w o r k u s i n g SIMS h a s

i n f e r environmental

and t o d e t e r m i n e

thickness

failure

of

c o r r o s i o n i n h i b i t o r ( s t r o n t i u m chromate) sion resistance

is

interface

w h i c h showed e l e m e n t s

been used t o

exact

Here a f a i l u r e

as

the

surfaces. corro

of t h i n s i l a n i z e d

surfaces^

SUMMARY I o n beams p r o v i d e u s e f u l i n f o r m a t i o n e i t h e r a s a d i a g n o s t i c t o o l o r as a p r e c i s i o n e t c h i n g method i n a d h e s i v e b o n d i n g r e s e a r c h . The c o m b i n a t i o n o f SIMS w i t h c o m p l e m e n t a r y methods s u c h a s I S S o r AES p r o v i d e s a p o w e r f u l t o o l f o r e l e m e n t a l and l i m i t e d s t r u c t u r a l c h a r a c t e r i z a t i o n o f m e t a l s , a l l o y s and a d h e s i v e s . The r e s u l t s shown here i n d i c a t e t h a t s u r f a c e c h e m i s t r y (and i n t e r f a c e c h e m i s t r y ) can be d e c i d e d l y d i f f e r e n t f r o m b u l k c h e m i s t r y . Often i t i s t h i s c h e m i s t r y w h i c h governs the q u a l i t y and d u r a b i l i t y o f an a d h e s i v e bond. T h e s e same s u r f a c e t e c h n i q u e s a l s o a l l o w a n a n a l y s i s o f t h e l o c u s o f f a i l u r e o f bonded m a t e r i a l s w h i c h f a i l i n s e r v i c e o r t e s t .




238

AI C

5

Figure

8.

ISS/SIHS Data From

F ^ P c i t u

0

.6

.7

.8

From Tape Epoxy A d h e s i v e

.9

Debonded

Titanium

F I L L E R S AND ADDITIVES

ADHESIVE > MOLECULAR STRUCTURE PRIMER

ι 0 R R 0 S I 0 N

OXIDE

RESIDUE

ADHEREND J

9.

Model

FROM

TREATMENTS 'ALLOYING

Figure

CONTROL

ADDITIVES

1

of Adhesive

ELEMENTS

Bond Showing I m p u r i t i e s

and

Additives


1.0



BAUN

10

20 ATOMIC

Figure

10.

30 MASS

40

50

60

UNITS

SIMS D a t a f r o m T i - 6 A 1 - 4 V A l l o y . A. O r i g i n a l Surface o f Titanium A l l o y B. S u r f a c e A f t e r G o l d S t r i p p e d From T i t a n i u m Alloy



240

+ SIMS ΑΓ C H;

Sr*


2

Να

Cr*

X2.

KJ 15

30

45

60

75

i

ATOMIC MASS UNITS Figure

11.

SIMS D a t a F r o m A l u m i n u m A l l o y F a i l u r e Containing Corrosion Control Additive Chromate)

Surface (Strontium


14. BAUN


241

Literature Cited

Baun, W. L.; Appl. Surface Science, 1980, 4, 291. Powell, C. J.; Appl. Surface Science, 1978, 1, 143. Benninghoven, Α.; Surface Science, 1975, 53, 596. McDevitt, N. T.; Baun, W. L.; Solomon, J. S.; J. Electrochem. Soc., 1976, 123, 1058. 5. McDevitt, N. T.; Baun, W. L.; Solomon, J. S.; AFML-TR-76-13, March 1976, Available NTIS. 6. McDevitt, N. T.; Baun, W. L.; Solomon, J. S. AFML-TR-75-122, October 1975, Available NTIS. 7. Sun, T. S.; Chen, J. M.; Venables, J. D.; Hopping, R.; Appl. Surface Science, 1978, 1 202. 8. Baun, W. L.; McDevitt, N. T.; Solomon, J. S. In: "Surface Analysis Methods for Metallurgical Applications"; ASTM STP 596, ASTM, Philadelphia, PA,, 1976, p. 86. 9. Baun, W. L.; AFML-TR-76-29, March 1976, Pt. I, Available NTIS 10. Baun, W. L.; McDevitt, N. T.; AFML-TR-76-29, May 1976, Pt. II, Available NTIS. 11. Baun, W. L.; McDevitt, N. T.; Solomon, J. S.; AFML-TR-76-29, October 1976, Pt. III, Available NTIS. 12. Baun, W. L.; McDevitt, N. T.; J. Vac. Science Technology, 1984, 2(2), 787. 13. Dyer, C. K.; Leach, J. S. L.; J. Electrochem. Soc., 1978, 125, 1032. 14. Baun, W. L.; Surface Technology, 11, 385. 1980. 15. Gettings, M.; Kinloch, A. J.; J. Material Science, 1977, 12, 2511. 16. Ross, M. R.; Evans, J. F.; In: "Proceedings of 7th Midland Macromolecular Symposium"; Leyden, D., Ed.; Gordon and Breach, 1980, pp. 99-123.


1. 2. 3. 4.

RECEIVED

J u n e 4, 1 9 8 5


Use of Secondary Ion Mass Spectrometry to Study Surface Chemistry

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