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T a k a sh i H a sh im o t o , 1 M .S .; S h i g e h i t o D ek i , D . Sc .; a n dY u k i o K a n a j i , 2 D .E n g .

D i s c r im i n a tio n o f C e r a m i c s S t u d y o n t h eM i c r o s t r u c t u r e s o f C e r a m i c s

R E F E R E N C E : Hashimoto , T . , Deki , S . , and Kanaj i , Y. , " D i s c r im i n a t i o n o f C e r a m i c s - -S t u d y o n t h e M i c r o s tr u c t u r e s o f C e r a m i c s ," Journ al o f Forensic Sciences, J F S C A , V o l .39 , No. 3 , May 1994 , pp . 824-838 .A B S T R A C T : A m e t h o d f o r d i s c r i m i n a t i o n o f a l u m i n a c e r a m i c s w a s d e v e l o p e d b a s e d o nt h e o b s e rv a t i o n o f t he s u r f ace mo rp h o l o g y o f e t ch ed s u r f aces , d en s i ty , X - r ay d i f f r ac t i o n li n eprof i l es and gra in s i ze d i s t r ibu t ions .T h e ex p e r i men t a l o b s e rv a t i o n s o f t h e s u r f ace mi c ro s t ru c t u re w ere mad e , u s i n g t h e s can -n i n g e l ec t ro n mi c ro s co p y (SE M ) , o n s ev e ra l d i f f e r en t a l u mi n a ce rami cs w i t h h i g h (> 9 9 % ) ,mi d d l e (9 6 t o 9 8 % ) an d l o w ( ap p ro x i ma t e l y 9 2 % ) a l u mi n a co n t en t i n o rd e r to i d en t i fy t h em.T h e s amp l es w ere p r ep a red w i t h a s u l fu r i c ac i d (4 . 5 mo l / L ) e t ch i n g me t h o d p e r fo rmed a t1 5 0 ~ 2 0 0 ~ fo r 2 h o n l o w an d mi d d l e p u r i t y a l u mi n a ce rami cs an d fo r 4 h o n h i g h p u r i t ya l u mi n a ce rami cs .T h e r e s u l t s i n d i ca t e t h a t t h e SE M o b s e rv a t i o n co u p l ed w i t h co mp u t e r i zed i mag e an a l y s i st o d e t e rmi n e g ra i n s i ze d i s t r i b u t i o n i s a p o w er fu l t o o l t o d i s c r i mi n a t e amo n g a l u mi n a ce -ramics tha t exh ib i t s imi lar morpholog ica l charac ter i s t i cs .The X-ray d i f f rac t ion l ine p rof i l e s tudy i s sugges ted as an add i t ional usefu l index for thed e t e rmi n a t i o n o f m i c ro c ry s t a l l in e s t ru c t u re .K E Y W O R D S : f o re n s ic s ci en c e , c e ra m i c s

C e r a m i c s a r e s y n t h e t ic m a t e r i a ls , p r o d u c e d f r o m n o n m e t a l l i c i n o r g a n i c s o l id b o u n dt o g e t h e r b y s i n t e ri n g a t h ig h t e m p e r a t u r e . S i n c e t h e y p o s s e s s s e v e r a l u s e f u l c h a r a c t e ri s t ic ss u c h a s h e a t - r e si s t a n c e , c o r r o s i o n - r e s i s ta n c e , r e a s o n a b l e s t re n g t h , i n s u la t io n , o r s e m i c o n -d u c t i v i t y , f i n e c e r a m i c s h a v e b e c o m e w i d e l y e m p l o y e d a s i n d u s t r i a l m a t e r i a l s . T h e s eu s e s i n c l u d e a l u m i n a c e r a m i c s a s I C s u b s tr a te s , t r a n s lu c e n t a l u m i n a a s o p t i c a l m a t e r ia l s ,z i r c o n i a c e r a m i c s a s e d g e t o o l s a n d s i l ic o n c a r b i d e a n d s i l i c o n n i tr i d e a s a h e a t - r e s is t i n gm a t e r i a ls . S a p p h i r e ( a l u m i n a s i n g l e c r y s ta l ) a n d h y d r o x y a p a t it e , w h i c h e x h i b i t h ig hs t re n g t h , a r e r e f e r r e d t o a s b i o c e r a m i c s a n d a r e u s e d a s a r t if i c ia l t e e th o r b o n e s [ 1 - 3 ] .T h e e v e r g r o w i n g u s e o f c e r a m i c s h a s r e s u l t e d i n t h e s e m a t e r i a l s o r a r t ic l e s c o m p o s e do f c e r a m i c s b e in g e n c o u n t e r e d m o r e c o m m o n l y a s p h y s i c a l e v i d e n c e i n c ri m i n a l c as e s[4,5], i n o n e c a s e a f r a g m e n t o f t h e d e n t a l p o r c e l a i n ( a r t i f ic i a l t o o t h ) f o u n d i n t h e m u r d e rs i te w a s i d e n t i f i e d th e a r t i f ic i a l t o o t h o f t h e s u s p e c t i n a m u r d e r c a s e , a n d i n a n o t h e r c a s et h e m a n u f a c t u r e r w a s d e t e r m i n e d f r o m a m i n u t e f r a g m e n t o f a z i r c o n i a c e r a m i c c u t l e r ie s

Re ce i v ed fo r p u b l i ca t i o n 1 5 J u n e 1 9 93 ; r ev i s ed man u s c r i p t r ece i v ed 3 0 A u g . an d 1 2 N o v . 1 9 9 3 ;accep ted fo r pub l i ca t ion 15 Nov. 1993 .~Fo ren s i c Ch emi s t , Fo ren s i c Sc i en ce L ab o ra t o ry , H y o g o P re f . Po l i ce D ep a r t men t , K o b e , J ap an .2Ass is tan t Profe ssor and Professor , respect ive ly , Dept . o f Chem ical Scienc e and Enginee r ing ,Fac . o f E n g i n ee r i n g , K o b e U n i v e r s i t y , K o b e , J ap an .824

Copyright 1994 by ASTM International

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HASHIMOTO ET AL. 9 MICROSTRUCTURES OF CERAMICS 825b y m e a n s o f s c a n n i n g m i c r o p h o t o g r a p h y . E s ta b l i sh m e n t o f f o re n s i c s c ie n c e m e t h o d s f o rd i s t i n g u i s h in g t h e c h a r a c t e r i s ti c s o f th e s e m a te r ia l s i s n e e d e d f o r c r im in a l i n v e s t i g a t io n s .

T h e s c a n n i n g e l e c t r o n m i c r o s c o p e ( S E M ) i s w e l l s u i t e d f o r t h e o b s e r v a t i o n o f t h em ic r o s t r u c tu r e o f c e r a m ic s m a t e r ia l s . I t i s we l l k n o w n th a t s iz e a n d s h a p e o f g r a in s o fs i n t e r e d p o ly c r y s t a l l i n e c e r a m ic s a r e a f f e c t e d b y t h e c o n d i t i o n o f t h e s i n t e r in g p r o c e s sa n d n a t u r e o f t h e o r i g in a l c e r a m i c p o w d e r [ 6 - 1 2 ] 9I n t h i s s t u d y , t h e a im wa s t o c l a s s i f y c e r a m ic s f r o m d i f f e r e n t s o u r c e s b y S E M -o b s e r v a t i o n o f t h e i r m ic r o s c o p i c a l s u r f a c e c h a r a c t e r i s t i c s wh ic h wa s c l e a r e d b y a c id o rt h e r m a l e t c h i n g m e t h o d .M a t e r i a ls a n d M e t h o d sM a t e r i a l s

N i n e t e e n a l u m i n a c e r a m i c s a m p l e s m a n u f a c t u r e d b y n i ne c e r a m i c c o m p a n i e s i n J a p a nwe r e c o l l e c t e d . T h e i r a l u m in a c o n t e n t v a r i e d a n d wa s d iv id e d i n to t h r e e g r o u p s a c c o r d in gt o a l u m i n a c o n t e n t ( l o w p u r i t y a p p r o x i m a t e l y 9 2 % , m e d i u m p u r i t y 9 6 t o 9 8 % a n d h i g hp u r i t y m o r e t h a n 9 9 % , s e e T a b l e 1 ) .M e a s u r e m e n t

Re c t a n g u l a r s o l i d s a m p le s a p p r o x im a te ly 1 2 c m a n d 0 .5 c m th i c k we r e p r e p a r e db y c u t t i n g t h e m f r o m t h e e x h i b i t s w i t h a d i a m o n d s a w .A f t e r t h e m e a s u r e m e n t o f t h e d e n s i ty o f s a m p l e s b y A r c h i m e d i a n m e t h o d , t h e s am p l e s

w e r e g r o u n d i n t u r n o n # 6 0 0 0 d i a m o n d p a d , w i t h # 4 0 0 0 S i C p o w d e r a n d # 6 0 0 0 a l u m i n ap o wd e r . T h i s p o l i s h in g p r o c e s s i s e s s e n ti a l t o m a k e t h e g r a in b o u n d a r y s t r u c tu r e o f th es a m p le c l e a r , b e c a u s e t h e i r r e g u l a r o r i g in a l s u r f a c e ( wh e th e r f r o m c u t s u r f a c e , p o l i s h e ds u r f a c e o r b r o k e n s u r f a c e ) o b s c u r e s t h e m o r p h o lo g y o f m ic r o s t r u c tu r e s ( F ig . 1 ).

TABLE 1 - - A l u m i n a c e r a m i c s .Manufacturer Grade name Purity (%)S A-392

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HASHIMOTO ET AL. 9 MICROS TRUCTUR ES OF CERAMICS 827Af te r c l e a n in g i n a n u l t r a s o n i c c l e a n e r , e a c h s a m p le wa s t r e a t e d t o m a k e g r a in b o u n d -

a r y c o n s p i c u o u s b y a c id o r t h e r m a l e t c h in g p r o c e d u r e ( F ig . 2 ) .E a c h p r e p a r e d s a m p l e w a s s p u tt e r c o a te d w i t h P t - A u a n d o b s e r v e d w i t h H i t a c h i $ 2 5 0 0

S E M ; s e c o n d a r y e l e c t r o n i m a g e o p e r a t i n g a t 2 5 k V .T h e im a g e p r o c e s s in g f o r d e t e r m in a t i o n o f t h e a r e a d is t r ib u t i o n s o f th e m ic r o g r a ins t r u c tu r e wa s p e r f o r m e d b y t h e m ic r o g r a in s t r u c tu r e a n a ly s i s p r o g r a m p r e v io u s ly d e v e l -o p e d f o r m e t a l c r y s t a l s s u p p l i e d b y t h e I r o n a n d S t e e l I n s t it u t e o f J a p a n [13].

T h e X - r a y d i f f r a c t i o n ( X R D ) m e a s u r e m e n t s w e r e m a d e b y u s i n g a S h i m a z u X D - D 1( X- r a y d i f f r a c tm e te r ) w i th Cu - k a s o u r c e o p e r a t i n g a t 4 0 k V - 3 0 m A, s c a n n in g ra t e is 0 .1 2 5d e g /m in a n d a n i n t e g l a t i n g t im e i s 4 s [14-16] . F o r t h i s m e a s u r e m e n t , s a m p le s we r e c u tt o b e a re c t a n g u l a r s o l i d s p e c im e n a p p r o x im a te ly 1 2 c m a n d 0 .5 c m th i c k f i x e d o nt h e h o l d e r w i t h a c l a y c o m p o u n d .Et c h i n g Pr o c e d u r e

T wo k in d s o f c h e m ic a l e t c h in g a n d t h e r m a l e t c h in g we r e e v a lu a t e d f o r t h e i r u s e f u ln e s sin e lu c id a t i n g m o r p h o lo g i c a l s t r u c tu r e .P h o s p h o r i c a c i d e t c h i n g w a s e v a l u a t e d b y d i p p i n g s a m p l e s o n 6 0 % a n d 8 0 % b o i l i n gp h o s p h o r i c a c id u n d e r s t a n d a r d a tm o s p h e r i c p r e s s u r e f o r s e v e r a l m in u t e s . T y p i c a l S E M

m ic r o g r a p h s a r e s h o wn in F ig . 3 a a n d 3 b .Co n t r o l o f t h e e t c h in g t im e a n d t e m p e r a tu r e o f t hi s p h o s p h o r i c a c id e t c h in g p r o c e d u r e

wa s f o u n d t o b e t o o d i f f i c u l t t o o b t a in r e p r o d u c ib l e r e s u l t s . E i t h e r i n c r e a s in g t h e a c ids t re n g t h f r o m 6 0 t o 8 0 % o r e x t e n d in g o f e tc h i n g t i m e f r o m 5 t o 1 5 m i n c a u s e d a ne x c e s s i v e a m o u n t o f g r ai n b o u n d a r y e t c h in g ( F i g . 3 a ,3 b ) .F o r t h e t h e r m a l e t c h in g , s a m p le s we r e h e a t e d at 1 4 0 0 ~ f o r 1 0 m in . T h e t e m p e r a tu r ei s 1 0 0 ~ l o w e r t h a n t h e s i n t e r in g t e m p e r a tu r e , T a m m a n t e m p e r a tu r e , o f a l u m in a c e r a m ic s .

A l o n g t i m e - - h a l f a d a y - - w a s n e e d e d f o r h e a ti n g a n d c o o l i n g o f t h e sa m p l e . T h ise t c h in g t r e a tm e n t g a v e a d e s i r a b l e r e s u l t f o r t h e p u r p o s e , h o we v e r s l i g h t g r a in g r o wthd u e t o t h e h e a t i n g wa s o b s e r v e d ( F ig . 3 c ) .Ac c o r d in g t o t h e s e r e s u l t s , i t wa s c o n c lu d e d t h a t b o th p h o s p h o r i c a c id e t c h in g a n dth e r m a l e t c h in g we r e n o t s u i t a b le f o r th e o b s e r v a t i o n o f t h e m ic r o s t r u c tu r e o f s u r fa c e s

in the p resen t s tudy .S u l f u r i c a c id e t c h in g p r o d u c e d f a v o r a b l e r e s u l t s f o r g r a in s t r u c tu r e a n a ly s i s b y S E M .T o e v a lu a t e s u l f u r i c a c id e t c h in g , sa m p le s we r e im m e r s e d i n 4 .5 m o l / L o r 6 m o l /L

su l fu r ic ac id in a te f lon capsu le , sea led in a s ta in less s tee l p ressu re vesse l and hea ted tob e tw e e n 1 5 0 a n d 2 0 0 ~ f o r 2 t o 4 h. E t c h in g w i th 4 .5 m o l /L s u l fu r i c a c id a t 2 0 0 ~ f o r2 h g e n e r a t e d g o o d g r a in b o u n d a r y e t c h in g , wh i l e t h e i n c r e a s e o f a c id c o n c e n t r a t i o n t o6 m o l /L r e s u l t e d i n a t t a c k o f t h e i n t e rn a l p o r t i o n s o f g r a in s ( F ig . 4 ) .

E x p e r im e n t s w i th h ig h t e m p e r a tu r e s u l f u r i c a c id e n c h a n t s r e s u l t e d i n t h e a d o p t i o n o f4 .5 m o l /L s u lf u r i c a c id a t 1 5 0 t o 2 0 0 ~ a s th e b e s t a l t e rn a t iv e . T h e d e g r e e o f e t c h in gd e p e n d e d o n t h e A12 03 p u r i t y o f c e r a m ic s . T w o h o u r t r e a tm e n t s f o r l o w a lu m in a s a m p le ss e e m e d a d e q u a t e , wh i l e u p t o f o u r h o u r s we r e r e q u i r e d f o r t h e h ig h a lu m in a m a te r i a l s(F ig . 5 ) .

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HASHIMOTO ET AL. 9 MICROS TRUCTU RES OF CERAMICS 831T h e s e r e s u l ts s u g g e s t t h a t e t c h in g f o r l o n g t im e m a k e s i t d i f fi c u l t t o i d e n t i f y g r a inb o u n d a r y , a n d h ig h c o n c e n t r a t i o n s o f s u l f u r i c a c id i s n o t s u i ta b l e f o r a l u m in a c e r a m ic s

e tch ing .Ba s e d o n t h e s e r e s u l t s , t h e m o s t s u i t a b l e c o n d i t i o n s f o r c h e m ic a l e t c h in g o f a l u m in ac e r a m ic s wa s d e t e r m in e d ; t o b e , s u l f u r i c a c id ( 4 .5 t o o l /L ) a t a t e m p e r a tu r e r a n g e i s o f1 5 0 t o 2 0 0 ~ c a r r i e d o n f o r 2 h o n l o w p u r i t y a l u m in a c e r a m ic s a n d f o r 4 h o n h ig h

p u r i t y a l u m in a c e r a m ic s .T h e r e f o r e , i t is a p p a r e n t t h a t f o r s a m p le o f u n k n o w n c o n t e n t o f A lu m in a , s u i t a b l ee t c h in g c o n d i t i o n s m u s t b e e s t a b l i s h e d .

R e s u l t s a n d D i s c u s s io n

Observation of Grain MorphologyP h o t o m i c r o g r a p h s o f l o w a l u m i n a c o n t e n t c e r a m i c s s a m p l e s (9 2 % ) m a n u f a c t u r e d b yth r e e c o m p a n i e s ( O , N , S ) a r e s h o wn in F ig . 6 . I n t h e m th e o n e f r o m c o m p a n y S wa sd i s c ri m i n a t ed f r o m o t h e r m a k e r s t h r o u g h f e a t ur e o f g r ai n m o r p h o l o g y .T h e s u r f a c e m o r p h o l o g y o f m i d d l e p u r i ty a lu m i n a c e r a m i c s s a m p l e s ( 9 6 - 9 7 % ) m a n -u f a c tu r e d b y f i v e c o m p a n i e s ( S , O , N , I , T ) a r e s h o wn in F ig . 7 . D i s t i n c t d i f f e r e n c e s o f

g r a i n m o r p h o l o g y w e r e o b s e r v e d a m o n g m a k e r s .P i t s i n t h e g r a in b r o u g h t f r o m th e g r a in g r o wth we r e o b s e r v e d f o r t h e s a m p le f r o mc o m p a n y T .T h e e x i s t e n c e o f p i ts e n a b l e d d i s c r im in a t i o n b e tw e e n s a m p le s f r o m T a n d O , a l t h o u g h

th o s e h a d s im i l a r a s p e c t s i n t h e i r g r a in m o r p h o lo g y .P h o t o m i c r o g r a p h s o f h i g h a lu m i n a c o n t e n t c e ra m i c s a m p l e s ( > 9 9 % ) m a n u f a c t u r e d b ys ix com pan ies (N, N T, I , O, T , S ) are show n in F ig . 8 . The la rge s ize o f g ra ins in thes a m p l e f r o m c o m p a n y I w a s s i m i l a r t o t h a t f r o m t h e c o m p a n y T .T h e s a m p le f r o m c o m p a n y I , h o we v e r , c o n t a in e d s o m e s m a l l s i z e g r a in s , a n d i t i n -d i c a t e d t h a t t he r a w c e r a m ic p o w d e r h a d d i f f e r e n t p a r ti c l e s i z e d i st r ib u t i o n , o r t h e c e r a m ic

wa s s i n t e r e d i n d i f f e r e n t c o n d i t i o n s f r o m o th e r s . A l th o u g h t h e g r a in s i z e d i s t r i b u t i o n i ns a m p l e f r o m c o m p a n y N T w a s s i m i l a r t o t h a t f r o m c o m p a n y O , s o m e g r a i n g r o w t h i nt h a t f r o m c o m p a n y O r e s u l t e d i n d i s c r i m i n a t i o n b e t w e e n t h e m .T h e m ic r o s t r u c tu r e o f l o w a lu m in a c o n t e n t c e r a m ic s is d i s ti n g u i s h a b l e b y t h e S E M

o b s e r v a t i o n , b e c a u s e o f c l e a r d i f fe r e n c e s i n t h e ir g r a in b o u n d a r y s t r u c tu r e s. I n c r e a s e i nth e a lu m in a c o n t e n t o f t h e c e r a m ic s p r o d u c e s l e s s g r a in b o u n d a r y d i f f e r e n c e s t h e re f o r eid e n t if i c a ti o n o f m ic r o s t r u c tu r e d i f f e r e n c e s o f t h e h ig h a n d m id d l e a l u m in a c o n t e n t c e -r a m ic s we r e p r o b l e m a t i c .Gr a in s i z e b e c o m e s l a r g e a s t h e p u r i t y o f a l u m in a p o wd e r i n c r e a s e s , b e c a u s e t h e l a c ko f im p u r i t i e s a t t h e g r a in b o u n d a r y p r o m o te s l a r g e g r a in g r o wth d u r in g s i n t e r i n g p r o c e s s .Be c a u s e i n c r e a s e i n t h e p u r i t y o f a l u m in a c e r a m ic s p r o d u c e s l e s s g r a in b o u n d a r y e t c h in g ,i d e n t if i c a ti o n o f m ic r o s t r u c tu r e o n h ig h a n d m id d l e p u r i t y o f a l u m in a c e r a m ic s i s m o r ediff icul t .

DensityT a b le 2 s h o ws t h e m e a s u r e d d e n s i t y o f a l u m in a c e r a m ic s . T h e d e n s i t y g e n e r a l l y i n -

c r e a s e d p r o p o r t i o n a l l y w i th t h e i n c r e a s e o f th e p u r i t y o f a l u m in a i n t h e c e r a m ic s . T h eg r a in g r o wth o b s e r v e d i n t h e h ig h a lu m in a c o n t e n t c e r a m ic s d e c r e a s e d t h e p o r o s i t y .T h e s e d e n s i t y m e a s u r e m e n t s s h o we d t h e p o s s ib i l i ty o f g e n e r a t i n g i n f o r m a t io n a b o u tt h e d i f f e r e n t m a n u f a c tu r i n g p r o c e s s e s t h e r e b y l e a d in g t o i d e n t i f i c a t i o n o f t h e s o u r c em a n u f a c tu r e r .

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GO

P c z I 0 'n 'n 02 IT z Iq 7 0m

FG,6Compsoomicoruuoaumincamic9%)romdesueacmpS(bcmpO;ccmpN

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FIG. 7 - - C o m p a r i s o n o f m i c ro s tr u c tu r e o fa l u m i n a c e r a m i c s ( 9 5 - 9 7 % ) f r o m d i f f e r e n tsupplier: (a ) c o m p a n y S ; (b ) c o m p a n y O; (c)c o m p a n y N ; (d ) c om pany I ; ( e ) c om pany Z833

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FIG. 8 - - Co m p ar i so n o f m ic ros t ruc ture o f a lum ina c e ram ic s ( > 9 9 %) f rom d i ff e re n t supp l i er :(a ) c o m p a n y N ; (b ) c o m p a n y N T ; (c ) c o m p a n y I; (d ) c om pany O; ( e ) c om pany T ; ( f ) c om pany S .8 34

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H A S H I M O T O E T A L , 9 M I C R O S T R U C T U R E S O F C E R A M I C S 8 3 5T A B L E 2--Densi~ofa&mina ceramics.

Suppl ier Grade name Pur i ty (%) Densi tyS A-392A-396A-399N K S S A - AS S A - 9 9 9NT KP-990I

N

O

T AL-170AL-197K A-471

92 3.62796 3.73699 3.99792 3.89599 3.90499 3.85996 3.75399.5 3.91192 3.54596 3.76899.8 3.91992 3.61897 3.77099.5 3.92097 3.76799 3.88297 3.686

bnage Ana ly s isF i g u r e 9 s h o w s r e s u l t s o f g r a i n s i z e d i s t r i b u t i o n a n a l y s i s f o r l o w a l u m i n a c o n t e n t

c e r a m i c s f r o m c o m p a n i e s O a n d N , w h i c h i s o n e o f t y p i c a l r e s u l t s d e r i v e d f r o m s o m ea n a l y s i s . T h e y e x h i b i t e d l e s s m o r p h o l o g i c a l d if f e r e n c e s , th e r e f o r e d i s c r i m i n a t i o n b e t w e e nt h e m s e e m e d d i f f i c u l t .

H o w e v e r t h e p a t t e rn o f g r a i n a r e a d i s t r ib u t i o n fo r t h e m w e r e d i f f e re n t a p p a re n t l y . T h es a m p l e f ro m c o m p a n y N h a d h i g h e r p e r c e n t a g e o f l a r g e g r a i n s iz e t h a n th a t f r o m c o m -p a n y O . T h i s r e s u l t i n d i c a t e s th a t t h e a n a l y s i s o f p a r t i c l e a re a d i s t r i b u t i o n is a p o w e r f u lt o o l to s u p p o r t m o r p h o l o g i c a l d i s c r i m i n a t io n o f a l u m i n a c e r a m i c s w i t h t h e s i m i l a r m o r -p h o l o g i c a l c h a r a c t e ri s t ic s .

F o r t h e f u t u r e , d a t a a c c u m u l a t i o n r e g a r d i n g t h e p a t t e r n o f g r a i n a r e a d i s t r i b u t i o n s h o u l db e d e s i r e d f o r a p p l y i n g t h i s m e t h o d t o th e d i s c r i m i n a t i o n o f c e r a m i c s .

X-Ray Dif fract ion Analys isT a b l e 3 s h o w s r e s u l ts o f t h e h a l f w a v e w i d t h , a m e a s u r e o f b a n d b r o a d e n i n g i n X - r a y

d i f f r a c t i o n .B e c a u s e t h e h a l f w a v e w i d t h i s re f l e c t e d m a i n l y b y t h e a v e r a g e c r y s t a l l i te s i ze , t h e

h a l f w a v e w i d t h b y X - r a y d i f f ra c t io n a n a l y s is s e e m s t o b e g o o d i n d e x a l o n g w i t h g r a i no b s e r v a t i o n s t o d i s c r i m i n a t e t h e m i c r o s t r u c t u r e o f a l u m i n a c e r a m i c s .

T h e s a m p l e ( a l u m i n a c o n te n t 9 2 % ) f r o m c o m p a n y N s h o w e d l a r g e h a lf w a v e w i d t ho f t h re e d i f f r a c t i o n p e a k s , i n c o m p a r i s o n w i t h t h a t f r o m c o m p a n y O ( T a b l e 3 ).A l t h o u g h t h e se s a m p l e s s h o w e d a l m o s t t he s a m e m o r p h o l o g y o f g r a i n s tr u c tu r e s o n

S E M o b s e r v a t i o n , th e c r y s t a l li t e s i z e o f a l u m i n a i n th e c e r a m i c s f r o m c o m p a n y N w a st w i c e a s l a rg e a s th a t f ro m c o m p a n y O . X - r a y d i f f r a c t io n g i v e s s o m e i n f o r m a t i o n s a b o u tt h e i n t e r n a l p it s o f th e p a r t i c l e s w h i l e t h e S E M o b s e r v a t i o n s d e a l w i t h t h e s u r fa c e .

F o r t h e s e s a m p l e s , t h e s h i f t o f d - v a l u e s p a c i n g o f l a tt i c e p l a n e , c a u s e d b y a c r y s t a l l i n es t r a i n w a s n o t o b s e r v e d .

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8 3 6 J O U R N A L O F F O R E N S IC S C I E NC E S

F I G . 9-- Par tic le area distribution.

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HASHIMOTO ET AL. 9 MICRO STRUCT URES OF CERAMICS 837T A B L E 3 - - H a l f w a v e w i d th o f t h r e e X - r a y d if fi 'a c ti on p e a k s f o rt wo a lumi na c e ram i c s t ha t sho w s i mi l a r morpho logy o fmicros trac tures . Alumina content: 92%.

Plane Inde x (116) (113) (104)( h k l )Co mp any O 0.125 0.106 0.184Com pany N 0.277 0.267 0.275

C o n c l u s i o nT h e m o r p h o l o g i c a l o b s e r v a t io n o f c e r a m i c s s u r fa c e s w a s p r e f o r m e d t o d i s c r i m i n a te

t h e i r m i c r o s t r u c t u r e . T h e e t c h i n g d u r i n g p r e p a r a t i o n o f s a m p l e s w a s a n i m p o r t a n t f a c t o ri n d e t e r m i n i n g m o r p h o l o g i c a l d if f e re n c e s a m o n g s p e c i m e n s . I m a g e a n a l y s is a n d X - r a yd i f f r a c t i o n a n a l y s i s s u p p o r t e d t h e r e s u l t s o b t a i n e d b y e x a m i n i n g m i c r o s t r u c t u r e . D e n s i t ym e a s u r e m e n t s s u g g e s t e d t h e d e g r e e o f g r a i n g r o w t h , w h i c h w a s r e l a t e d to t h e p u r i t y o fa l u m i n a p o w d e r .

F u r t h e r a n a l y t i c a l d e t e r m i n a t i o n s o f t h e e l e m e n t s w h i c h a r e a d d e d t o c e r a m i c f o r m u -l a t i o n s i n o r d e r t o c o n t r o l t h e g r a i n g r o w t h o n s i n t e r i n g , o r t o i m p r o v e c e r a m i c s ' c h a r -a c t e r i s ti c s m a y b e u s e f u l. S u r f a c e s t u d y w o u l d s u p p o r t t h e d i s c r i m i n a t i o n o f c e r a m i c se s t a b l is h e d b y t h e m o r p h o l o g i c a l o b s e r v a t i o n [ 3 - 6 ] . A n d t h e r e f o r e t h e s e f u r t h e r s t u d i e sa re r e c o m m e n d e d .

A c l o l o w l e d g m e n tW e a r e g r a t e f u l t o b o t h t h e D e p a r t m e n t o f I n d u s t r i a l C h e m i s t r y o f K o b e U n i v e r s i t y

a n d F o r e n s i c S c i e n c e I n s t i t u t e o f t h e N a t i o n a l P o l i c e A g e n c y f o r g i v i n g t h e o p p o r t u n i t yf o r t h i s r e s e a r c h w o r k .

T h e s u p p l y i n g o f c e ra m i c s s p e c i m e n s b y m a n y m a n u f a c t u r e rs i s a l s o a p p r e ci a te d .

R e f e r e n c e s[1] Soga, N., Bas i c o f C e rami cs , Agune, Tokyo, 1990 (text in Japanese).[2] Yanagida, H., Fi ne C e rami c s , B l ue Bac ks , Kodansha, Tokyo, 1987 (text in Japanese).[3] Japan Chemical Society, Engineerbzg Ceramics , Ch emica l Rev iew No. 37 , Japanese ChemicalSociety Publishing Center , 1982 (text in Japanese).[4] Suzuki, K., Hanaoka, Y., Minaguchi, K., Inoue, M., a,]d Suzuki, H., "Positive Identificationof D en ta l Porce l a in in Case o f M urder , " J a p a n e s e J o u r n a l o f L e g a l M e d i c b w , Vo l. 45, N o.4, 1991, pp. 330-340, ( text in Japanese, abstract in English).[5] Kudoh , M. , "Z i r co n ia Ceramics Cu t l e r i es - -P resum pt ion o f t he C eramics Maker by a M inu teFragment of a Cut t ing Edge," Ac t a C r i mhzo l ogy J apon , Vo l. 54, No. 5, pp. 200-2 09, 1988(text in Japanese, abstract in English).[6] Ting, J. Y. H.-Ming, Lin, R. Y., and Ko, Y. H., "Effect of Powder Characterist ics on MicroStructure and St rength of Sintered Al um ina," Ceramic Bullet in, Vo l. 70, No. 7, 19 91, pp.1167-1172 .[7] Coble , R. L . , "Sin ter ing C rystal l ine Sol ids I I . Exper imental Test of Dif fusion M odels inP o w e r C o m p a c t s ," J o u r n a l o f A p p l ie d P h y s i cs , Vol. 32, No. 5, 1961 , pp. 793 -799 .[8] Pow el l -Dogan, C. A. and Heuer, A . H., "M icrost ructu re of 96% A lum ina Ceramics: I , Char-ac t e ri za tion o f t he As-S in t e r ed Mate r i a l s , " J ou rna l o f t he Ame r i c an C e rami cs Soc ie ty , Vol.73, No. 12, 1990, pp. 3670-36 76.[9] Powe l l -Doga n, C. A. and Heuer, A . H., " M icrost ructure of 96% A lumin a Ceramics: I I , Crys-t a l li za t ion o f High-Manganese Boundary Glass es , " J o u r n a l o f th e A m e r i c a n C er a m ic s S o c i -ety , Vol. 73, No. 12, 1990 , pp. 3 677-3 683.[10] Powel l -Dogan, C. A. and Heuer , A. H. , "Microst ructure of 96% Alumina Ceramics: I I I ,Crys t a l li za t ion o f High-Ca lc i a Boundary Glass es , " J o u r n a l o f th e A m e r i c a n C e r a m ic s S o c i et y ,Vol. 73, No. 12, 19 90, pp. 3684 -36 91.

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8 3 8 J O U R N A L O F F O R E N S I C S C I E N C E S[11] Kwo n , O . H . , an d Mess in g , G . L . , " K in e t i c A n a ly s i s o f So lu t io n -Pr ec ip i ta t i o n Du r in g L iq u id -Ph ase S in t e r in g o f A lu m in a , " Journal o f the Amer ican Ceramics Society , Vol. 73, No. 2,1990, pp. 275-281.[12] Chappel l , J . S . , R ing , T . A. , and B irchal l , J. D. , "P ar t ic le Size D ist r ibu t ion Effec ts on Sin ter ingR a t e s , " Jour na l o f A pp l i ed Phys ics , Vol. 60, No. 1, 1986, pp. 383-391.[13] Imagemeasurement Sof tware Suppl ied by the I ron and Stee l Inst i tu te o f Japan .[14] Culli ty, B. D., Eleme nts o f X-Ray Diffract ion , Ad d i so n - W es ley Pu b l i sh in g C o m p an y I n c .,Reading , MA., 1956.[15] Kato , S ., B as i c C o u rse o f C e r am ics 3 " X- r ay D i f fr ac t io n An a ly s i s , " Uch id a R o k ak u h o Pu b -l i sh ing Co. , Ltd . , Tokyo , 1990 , pp . 246-248 ( tex t in Japanese) .[16] Okashi ta , H. , Uota , A. , and Sato , H. , "Crysta l l i te Size Analysis o f Talc wi th X-ray Dif f rac-tometry , ' " Shimadzu Review, Vol . 48 , No. 1 , 1991 , pp . 23-28 , ( tex t in Japanese , abst rac t inEngl ish) .Address requests fo r repr in ts o r add i t ional in format ion toTak ash i Hash im o toHyogo Pref . Po l ice Dept .Forensic Science Labora tory5 - 4 - 1 , Sh im o y am a ted o r i C h u o - KuKo b e , Jap an