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Preparation and Oxidation Resistance of BN-MgAlON Composites by Hot-pressing Sintering
JOURNALOFIRON ANDSTEELRESEARCH,INTERNATIONAL２ ０ １ ５,２ ２( ５):４ ２ ３ Ｇ ４ ３ ０
Pr e r a t i onandOx i da t i onRe s i s t anc eo fBNＧMgAlONCompo s i t e sby pa Ho t Ｇ e s s i ngS i n t e r i ng pr １２ RanLIU１ ２ , Xi n Ｇ ng Ｇ uan WANG１ ２ , Ya ＧnaQIE１ ２ , yuanZHANG , Xi j １, ２ １, ２ Qi ngLÜ , FuGAO ,
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( １．KeyLabo r a t o r o rAdvanc ed Me t a l l u r chno l ogyo fMi n i s t r fEduc a t i on,Hebe iUn i t edUn i ve r s i t yf gyTe yo y,Tangshan , , , ０６３００９,He b e i,Ch i n a; ２．Co l l e eo fM e t a l l u r n dE n e r H e b e iU n i t e dU n i v e r s i t T a n s h a n０ ６ ３ ０ ０ ９ H e b e i,Ch i n a) g gya gy y g Ab s t r a c t:BNＧMgAlONc ompo s i t e swe r ep r epa r edbyho t Ｇp r e s s i ngs i n t e r i ngunde rn i t r ogena tmo sphe r ewi t hBNＧMg Ｇ , AlONc ompo s i t epowde r sa sr aw ma t e r i a landY２O３a ss i n t e r i ngadd i t i ve． Ba s edont he rmodynami cana l s i s t h eo x i Ｇ y da t i onr e s i s t anc eo fBNＧMgAlONc ompo s i t e swa si nve s t i t edandt hedynami c so fox i da t i onp r o c e s swa sa l s oana Ｇ ga l z ed．Theox i da t i onp r o c e s sandt hemi c r o Ｇmo r l ogyo ft hes amp l e sbe f o r eanda f t e rox i da t i onwe r echa r a c t e r i z ed y pho byXＧ r ayd i f f r a c t i onands c ann i nge l e c t r on mi c r o s c opy．Thedynami c so fox i da t i onr e s i s t anc eo ft heBNＧMgAlON c ompo s i t e swa si nve s t i t edv i at heana l s i so ft hec ons t an tt empe r a t u r eox i da t i on ma s sga i ncu r ve s．Ther e su l t s ga y showt ha tt hema i nc omponen t so ft hema t e r i a la r eMgAlON,S i a l on,BNandCaYAl３O７a t１６５０－１７５０ ℃ ,andt he c on t en to fCaYAl３O７ de c r e a s e sa st hes i n t e r i ngt empe r a t u r ei nc r e a s e s．TheBNＧMgAlON c ompo s i t e sp r epa r eda t １７５０ ℃i sun i f o rmandc ompa c twi t ht heba l anc edd i s t r i bu t i onso fAl,Mg,O,andN．Theox i da t i onp r o c e s so fBNＧ MgAlONc ompo s i t e si na i rma i n l ons i s t so fMgAlON,S i a l onandBNox i da t i on．Thes e c t i ona f t e rbe i ngox i d i z eda t yc １０００－１３００ ℃i nvo l ve st hr e el aye r s,name l heou t e rl aye r,t hemi dd l el aye randt hei nne rl aye r．Theox i da t i on y,t /mo r o c e s sf o l l owst hepa r abo l amode l．Theappa r en ta c t i va t i onene r ft heox i da t i onp r o c e s si s２ １３×１０５ J land p gyo ６ t hef r e a c t o ri s４ ６６×１０ ． quencyf Ke r d s:bo r on Ｇ r i chs l ag;c a r bo t he rma lr educ t i on;n i t r i da t i on;ho t Ｇp r e s s i ngs i n t e r i ng;BNＧMgAlONc ompo s i t e; ywo ox i da t i onr e s i s t anc e
Ludwi i t ea c c oun t sf o rabou t５８％ o fbo r onr e Ｇ g , s ou r c e si nCh i na．Howeve ri ti sd i f f i cu l tt oa ch i eve i n t eg r a t edu t i l i z a t i onbe c aus eo fi t sl ow g r ade ( B２O３ ７ ２３％ ,TFe３０％ ),c omp l ex i t fmi ne r a ls t ruc t u r e yo [ １] a nd mi nu t e n e s so fi n f i l t r a t i ng g r a nu l a r i t r ough y ．Th t hepr oc e s so fpy r ome t a l l u r os epa r a t el udwi i t e, gyt g t heva l uab l ec omponen t so fbo r on,magne s i um and [] s oon c an bec onc en t r a t edi n t o bo r on Ｇ r i ch s l ag２ ． The ma i nchemi c a lc ompo s i t i onso fbo r on Ｇ r i chs l ag a r eox i de sl i keMgO,S iO２ ,B２O３ ,CaO,Al２O３ and s oon,amongwh i cht her a t i o so fMgOandB２O３a r e r e spe c t i ve l r et han３５％ and１２％． I ft het r ad i Ｇ y mo t i ona ll e a ch i ng me t hodsa r eus edt ode a lwi t hbo r on Ｇ r i chs l ag,t hec ons equenc ewi l lbeo fpoo re c onomi c bene f i t s,env i r onmen tpo l l u t i on,t hr oughpu tl imi t a Ｇ t i onandl owadd i t i ona lva l ueo ft hep r oduc t s．HowＧ
eve r,c a rbo t he rma lr educ t i onand n i t r i da t i oni san e f f e c t i vewayt o makecomp r ehens i veus eo fbo r on Ｇ r i chs l ag． I nt hes l ag,MgOand Al２O３ a r et her aw ma t e r i a l st os t he s i z et headvanc eds t ruc t ur a lc e Ｇ yn r ami c s;B２O３i st r ans f e r r edi n t oBNbyc a rbo t he rma l r educ t i onand n i t r i da t i onand S iO２ and Al２O３ i n t o S i a l on,andcons equen t l hecompos i t epowde r so f yt BNＧMgAlON a r ef o rmed．MgAlON c e r ami ci t s e l f s e s s e st hef an t a s t i cqua l i t i e so fh i empe r a t ur e pos ght r e s i s t anc e,t he rma lshockr e s i s t anc eandco r r os i on [ ] r e s i s t anc e３Ｇ５ ．Mo r eove r,BNha st hewonde r f u lox i Ｇ da t i onr e s i s t anc e,t he rma lshock pe r f o rmanc eand [ ] ma ch i n i ngpe r f o rmanc e６Ｇ９ ,t oge t he r wi t hS i a l on ′s no rma landh i empe r a t ur es t r eng t handexc e l l en t ght [ , ] chemi c a ls t ab i l i t th i empe r a t ur e１０ １１ ．The r e Ｇ ya ght f o r e,t heove r a l lpe r f o rmanc eo fBNＧMgAlONcomＧ
Founda t i onI t em: I t em Spons o r edbyNa t i ona lNa t ur a lSc i enc eFounda t i ono fCh i na ( ５０９０４０２２);Educ a t i onDepa r tmen to fHebe iPr ov i nc e Ou t s t and i ngYou t hFundPr o e c to fCh i na ( Y２０１１１１６) j B i o r aphy: RanLIU,Do c t o r,As s o c i a t ePr o f e s s o r; E Ｇma i l: I r ８１９＠１６３ c om; Re c e i v e dDa t e:Ju l y１,２０１４ g
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J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２２
s i t e si sg r e a t l ovedandi ti sexpe c t edt obe po yimpr us eda sadvanc edc e r ami c s,f unc t i ona lc e r ami c sand r e f r a c t o r t e r i a l swi t hh i r f o rmanc e． y ma ghpe I nadd i t i on,f o rc e r ami c ma t e r i a l s,be s i de st he , e r f o r m a n c eo f o w d e r i t s e l f s i n t e r i n r o c e s sa l s o p p gp l aysanimpo r t an tr o l ei nt he pe r f o rmanc eo ft he p ma t e r i a l． I ti ss imp l eando fl owc o s tt os i n t e runde r , o r d i na r r e s s u r e ． H o w e v e r b e c a u s em o r ea d d i t i v e s yp havet obeaddedi n t ot hema t e r i a ldu r i ngt heope r a Ｇ t i on,wh i ch wi l ll e ad t oh i rc on t en to fg l a s s ghe s ei nt heu l t ima t es i n t e r i ng ma t e r i a l．The r e f o r e, pha t hepe r f o rmanc ea th i empe r a t u r ei spoo randt he ght s amp l e sa r ee a s ode f o rm．Ho t Ｇ r e s s i ngs i n t e r i ng yt p t e chno l ogyi st o dens i f he mo l di nt he he a t i ng yt r o c e s st hr oughun i d i r e c t i ona lme chan i c a lp r e s su r e． p Be c aus et heex t e rna lpr e s su r emake sg r a i nbounda r y , andl a t t i c eo ft hema t e r i a ld i f f us ef a s t e rt hedens e r s amp l e sc anbeob t a i neda tl owe rt empe r a t u r eand sho r t e rhe a tpr e s e r va t i ont ime． I no rde rt of u r t he ri nve s t i t et hena t u r eo fBNＧ ga MgAlON,ho t Ｇ e s s i ngs i n t e r i ngi sus edi nt hes i n Ｇ pr t e r i ngo ft heBNＧMgAlON powde r s wh i cha r ep r e Ｇ r edbyt hebo r on Ｇ r i chs l ag．Thedens i f i c a t i onbe Ｇ pa hav i o ro ft he ma t e r i a li nt he p r o c e s so fs i n t e r i ng, t hechangel aw o ft he pha s ec ompo s i t i on,andt he , mi c r os t ruc t u r ea r ea l s os t ud i ed．Fu r t he rmo r e t he ox i da t i onk i ne t i c sexpe r imen ti sc a r r i edou tt oBNＧ MgAlON compo s i t e sa f t e rs i n t e r i ng;t heox i da t i on ; k i ne t i c s mode li s bu i l t t he ox i da t i on behav i o ro f BNＧMgAlON c ompo s i t e si sexp l o r ed．Al lt he s er e Ｇ s e a r che sa im t o pr ov i det heo r e t i c a lsuppo r tf o rt he s t udyo ft heimpr ovemen to fox i da t i onr e s i s t anc eo f BNＧMgAlONc ompo s i t e s．
１ Exp e r imen t
１ １ Pr e r a t i ono fBNＧMgAlONc ompo s i t e s pa Theexpe r imen t a l ma t e r i a l sa r e BNＧMgAlON c ompos i t epowde r sands i n t e r i ngadd i t i veY２O３powＧ de r s．Thema i nr aw ma t e r i a l so fBNＧMgAlONc omＧ , ( ) s i t epowde r sa r ebo r on Ｇ r i chs l ag Al OH ３ and po c onduc t ex．Thepowde r sa r emadeunde rt heexpe r i Ｇ men t a lcond i t i ono fs i n t e r i ngt empe r a t u r e１４８０ ℃ , equ i va l en tchemi c a ldo s age wi t hc a rbon,x ＝４ ５ ( Al２３O２７N５ xMgO),c ons t an tt empe r a t u r el a s t i ng f o r８handN２f l owr a t eo f４００ mL/mi n．XRD pa t Ｇ t e rno f MgAlON c ompo s i t e powde r si sshowni n F i １,wh i chi l l us t r a t e st hema i ni ng r ed i en t so fBNＧ g MgAlONcompo s i t epowde r sa r e MgAlON,S i a l on, CaAl４O７ and BN．The pu r i t f Y２O３ powde r si s yo ９９ ９ ma s s％ andt he i rave r age pa r t i c l es i z ei sl e s s t han１μm．
F i １ XRDpa t t e rno fMgAlONc ompo s i t epowd e rby g c a r bo t h e rma lr odu c t i onandn i t r i da t i on
１ ma s s％ Y２O３ c an b ea dd e di n BNＧMgAlON r st of o rmt he mi x t ur e．Theadd i t i ono fsu i t Ｇ powde ab l eamoun to fs i n t e r i ngadd i t i veY２O３ c anp r omo t e t hes i n t e r i ng,t huss i i f i c an t l r ov i ngt he mi Ｇ gn yimp , c r os t ruc t ur eo fs i n t e r edp r oduc t s r educ i ngt hepo Ｇ r os i t nc r e a s i ngt hedens i t ft he men t i oned yandi yo [ , ] r oduc t s１２ １３ ．The mi x t ur eandco rundum g r i nd i ng p , ba l la r epu ti n t oba l l mi l lpo t andt he mi x t ur ei s t akenou ta f t e rg r i nd i ngf o r２４hi nt her o l l i ngba l l , , mi l l．Then,a f t e rd r i n r i n d i n a n ds i e v i n t h e y g g g g mi x t ur ei senc l os edi n t og r aph i t emou l dcoa t edwi t h BN．Ho t Ｇ r e s s i ngs i n t e r i ngi sope r a t edi nt heva cu Ｇ p um ho t Ｇ r e s s i n s i n t e r i n f u r n a c eo ft h eZ G YM １ ０ ０ p g g t i ng t he p r oc e s s, h i i t i t r ogen ype．Dur gh pur yn ( ９９ ９９％ )i si nsu f f l a t edf o rp r o t e c t i on．Thet empe r Ｇ a t ur egoe supt o１４００ ℃ by ２０ ℃/mi nandt hen r e s sur ebeg i nst oi nc r e a s e．Me anwh i l e,he a t i ngr a t e p de c r e a s e sg r adua l l tt hespe edo f５－１０ ℃/mi n． ya Whent het empe r a t ur er e a che s１７５０ ℃ ,t he p r e s Ｇ sur ewi l lr e a cht hemax imumo f３０ MPa．Af t e rhe a t r e s e r va t i onf o r１ h,t het empe r a t ur er educ e st o p １４００ ℃ a tt hespe edo f５－１０ ℃/mi n．Att he mo Ｇ , men tt hep r e s sur ebeg i nst ode c r e a s eg r adua l l yand t he t empe r a t ur e r e s t o r e st o r oom t empe r a t ur e t hr oughna t ur a lcoo l i ng．Schema t i cd i ag r am o fho t Ｇ r e s s i ngs i n t e r i ngi sshowni nF i ２． p g
F i ２ S ch ema t i cd i a r amo fho t Ｇp r e s s i ngs i n t e r i ng g g
I s sue５ Pr epa r a t i onandOx i da t i onRe s i s t anc eo fBNＧMgAlON Compo s i t e sbyHo t Ｇp r e s s i ngS i n t e r i ng
１ ２ Pe r f o rmanc et e s t Af t e rcu t t i ng,g r i nd i ng,andpo l i sh i ngf o rmi r Ｇ , r o rsur f a c e s i n t e r i ng b l o cks wi l lbeunde rt he mi Ｇ c r o s t ruc t ur eobs e r va t i ono ft hesu r f a c e．The pha s e c ompos i t i ono fpr oduc t si sme a su r edbyX Ｇ r a i f f r a c Ｇ yd ( , ) t i on XRD D ＧMAX２２００ ．Th ea c c e l e r a t i onvo l t ageo f Cut a r ti s４０kV,cu r r en ti n t ens i t s３０ mA,and ge yi /mi t hes c ann i ng spe edi s５( °) n．Du r i ng obs e r v i ng , t hemi c r os cop i cmo r l ogyo ft hep r oduc t al aye r pho o fgo l dabou t１０３ nmshou l dbep l a t edwi t hanSBC Ｇ ２ s amp l esur f a c et r e a t i ng ma ch i nef i r s t l he y．Thent s amp l ewi l lber ep r e s en t edbys c ann i nge l e c t r on mi Ｇ c r o s c opy ( SEM,SSXＧ ５５０ SHIMADZU)．Thei s o Ｇ t he rma lox i da t i onexpe r imen ti sc onduc t edonac omＧ r ehens i vet he rma la n a l z e r( STA４４９C,NETZSCH p y Comp any),w i t ht h eamoun to f１０－７ g．Be f o r eox i da Ｇ , t i onexpe r imen tb l o cks amp l e shavebe enf u l l r yd y． Pu tt hes amp l e si n t oc o rundumc ruc i b l e,t henp l a c e t hec ruc i b l ewi t hs amp l e si nt hes amp l ef r ameo ft h e t h e rma la n a l z e r． Th ea i rwa si n t r o du c e da taf l owr a t eo f y ５ ０mL/mi n,f o l l owedbyhe a t i ngupf r omr oomt emＧ r a t ur et ot her e a c t i ont empe r a t u r ea tt her a t eo f１０ pe / , ℃ mi n andke ep i ngc ons t an tt empe r a t u r ef o r３h． Ane l e c t r on i cba l anc ei sus edt or e c o r dt hequa l i t y change．Thent hesu r f a c eandc r o s s Ｇ s e c t i ono fs amＧ l e sa f t e rox i da t i ona r eunde rmi c r o s c op i cmo r l o Ｇ p pho e r va t edbyXＧ r ayd i f f r a c t i onands c ann i nge l e c Ｇ gyobs t r onmi c r os c opy．
２ Re s u l t sandAna l s i s y
２ １ Cha r a c t e r i z a t i onandana l s i so fBNＧMgAlON y c ompo s i t e st hr oughho tpr e s s i ngs t he s i s yn F i ３showst heXRD pa t t e rnso fho t Ｇ r e s s i ng g p s i n t e r i ng ma t e r i a l sa td i f f e r en tt empe r a t u r e s． I tc an bes e ent ha tt hes i n t e r i ng ma t e r i a l sa te a cht empe r a Ｇ t u r econ t a i ns MgAlON,S i a l on,BNandCaYAl３O７ s e．And wi t hi nc r e a s i ng s i n t e r i ngt empe r a t u r e, pha t hec on t en to fCaYAl３O７ pha s er educ e s,MgAlON i nc r e a s e sg r adua l l i a l onandBN r ema i nun Ｇ y,andS c h a ng e db a s i c a l l i n t e r i ngi st h ep r o c e s so f y．MgAlONs l i i d pha s es i n t e r i ng．The g r a i ng r owt hi nl i i d qu qu s ei sgene r a l l omp l e t edbyd i s s o l u t i onandp r e Ｇ pha yc , c i i t a t i on． I nt hepr o c e s so fs i n t e r i ng BNi sno ti n Ｇ p vo l vedi nt her e a c t i on;t he r e f o r e,i t sc on t en tr e Ｇ ma i nst hes ame．Wh e nt h et emp e r a t u r ei s１６５０ ℃ ,t he s o l i dso l u t i onr e a c t i ono c cu r si nt headd i t i ve sY２O３ andCaAl４O７ ,gene r a t i ngl ow me l t i ngeu t e c t i cph a s e CaYAl O ． T h e d i s a e a r a n c e o fC a A l O s h o w s t h a t i t pp ３ ７ ４ ７ ha st hecomp l e t es o l i ds o l u t i on wi t h Y２O３ ．When t het empe r a t u r er i s e st o１７００ ℃ ,CaYAl３O７c on t en t , de c r e a s e sr ap i d l w h i c hs h o w st h a ta tc e r t a i nt e m Ｇ y
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e r a t u r e s, CaYAl nd t he g r a i n bound a r l a s s p yg ３O７ a ( ) , h a s e M Ｇ S i Ｇ A l Ｇ O Ｇ N e n e r a t en e w M A l O N a n di t p g g g c anbecon f i rmeda sd i f f r a c t i on pe ak g r adua l l Ｇ y en hanc e swi t hi nc r e a s i ngt het empe r a t ur e．
F i ３ XRDpa t t e rn so fho t Ｇp r e s s e dma t e r i a l sa t g d i f f e r en tt emp e r a t u r e s
F i ４showsSEM mi c r og r aphsande l emen t s g s e c t i ond i s t r i bu t i ono fpo l i shedsur f a c ef o rs amp l e s s i n t e r eda t１７５０ ℃f o r１h． I ti ss e ent ha tt hes t ruc Ｇ t ur eo ft heBNＧMgAlONcompos i t e sa f t e rho t Ｇ r e s s Ｇ p i ngs i n t e r i ngi s we l l Ｇ d i s t r i bu t edandcompa c t．The s i z eo ft hesur f a c e po r ei s２－５ μm i nd i ame t e r, , , wh i chi sno tb i ． A l M O a n d N a r er e l a t i v e l g g y , we l l Ｇ d i s t r i bu t edi nt hema t e r i a l among wh i ch Ali s t heh i s tandNi st hel owe s t．Thr oughus i ngho t Ｇ ghe , r e s s i n s i n t e r i n t h e s t r e s s c a n r o m t t h em u t u a l p g g p p con t a c tbe twe ent hepa r t i c l e sandt hed i s so l u t i onand d i f f us i ono ft hesubs t anc e,sot hesur f a c es t ruc t ur e o ft hema t e r i a l si swe l l Ｇ d i s t r i bu t edandcompa c t．
２ ２ Ox i da t i onr e s i s t anc eo fBNＧMgAlONc ompo s i t e s t hr oughho tpr e s s i ngs n t h e s i s y MgAlON c e r ami ci so fpoo rox i da t i onr e s i s t Ｇ anc e．Theox i da t i onr e a c t i onwi l lbes eve r e re s e c i a l l p y [ ] a th i emp e r a t u r e sabov e１０００ ℃ １４ ．Manys c ho l a r s ght haves t ud i edt heox i da t i onr e s i s t anc eo f MgAlON, andf oundt ha tadd i ngBNi n t ot heMgAlON ma t e r i Ｇ [, , ] a lc animp r ovei t s ox i da t i on r e s i s t anc e６ １５ １６ ．By [ , ] s t udy i ngt hean t i ox i dan tme chan i smo fBN １７ １８ ,t he
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J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２２
( a)SEM mi c r og r aph; ( b)Se c t i ond i s t r i bu t i ono fAl; ( c)Se c t i ond i s t r i bu t i ono fMg; ( d)Se c t i ond i s t r i bu t i ono fO; ( e)Se c t i ond i s t r i bu t i ono fN．
F i ４ SEM mi c r o r aphande l emen ts e c t i ond i s t r i bu t i ono fpo l i s h e ds u r f a c ef o rs amp l es i n t e r e da t１７５０ ℃ f o r１h g g
r e su l t si nd i c a t et ha tBN ha sexc e l l en tox i da t i onr e Ｇ BN．Theox i da t i onr e a c t i onsr e spe c t i ve l r e: ya s i s t a n c ea t９００ ℃ a ndi tw i l lb eox i d i z e da bo v e９００ ℃． ４Al２３O２７N５ xMgO＋１５O２ ＝４６Al２O３ ( １) B２O３l i i dpha s ei sgene r a t eda th i empe r a t u r e; xMgO＋１０N２ qu ght θ / , Δ G ＝－７ ０ ９ ９ ３＋０ ０ ７ ４ T k J m o l t hust he ma t e r i a l s ′ po r e s wi l lbes e a l ed b l o ck i ng æ １０ ö t hechanne l sf o roxygend i f f us i on,andox i da t i onna Ｇ çP N２ ÷ /mo ΔG ＝ΔGθ＋RTl nçç １５ ÷÷ kJ l t u r eo fMgAlONt u rnst obep r o t e c t i ve,s i i f i c an t l gn y èP O２ ø /mo de c r e a s i ngt heox i da t i ondeg r e e．Howeve r,a tp r e s Ｇ ΔG ＝－７０９ ９３＋０ ２４８T kJ l en t,t her epo r tabou tt heBNＧMgAlONc ompo s i t e s ′ S i１７Al０３N１３O１７ ＋１ ２７５O２ ＝１ ７S iO２ ＋ [, , ] ( ox i da t i onr e s i s t anc ei sr a r e．Zhang５ １９ ２０ ando t he r s ０ １５Al２O３ ＋０ ８５N ２) θ / made BNＧMgAlON c ompo s i t e s by t he me t hod o f ΔG ＝－１１６４ ４５＋０ ２１５T kJ mo l ０ ８５ ö æ ho t Ｇ e s s edb l o ck．Theyhavec a r r i edou tde t a i l edr e Ｇ P pr N ç ÷ ２ /mo ΔG ＝ΔGθ＋RTl nçç １２７５ ÷÷ kJ l s e a r ch on t he rmodynami c p r ope r t chan i c a l y, me èP O２ ø /mo r ope r t he rma lc onduc t i v i t o r r o s i onr e s i s t Ｇ p y,t yandc ４５＋０ ２２９T kJ l ΔG ＝－１１６４ ( anc eandsoon,andpo i n t edou tt ha tgoodpe r f o rmＧ BN＋０ ７５O２ ＝０ ５B２O３ ＋０ ５N２ ３) θ / anc eo ft he rma lsho ckandc o r r o s i onr e s i s t anc ei sbe Ｇ ８３＋０ ０３４T kJ mo l ΔG ＝－３７５ ０ ５ ö æ s t owedont hema t e r i a l．Wha tl imi t si t sdeve l opmen t P N ÷ ç ２ /mo kJ l ΔG ＝ΔGθ＋RTl nçç ０７５ ÷÷ r edomi nan t l st hesus c ep t i b i l i t oox i da t i onand p yi yt èP O２ ø /mo t hel ow me chan i c a ls t r eng t h．Bu tt heox i da t i onr e Ｇ ΔG ＝－３７５ ８３＋０ ０４３T kJ l s i s t anc eo ft he ma t e r i a li s no ts t ud i edi n de t a i l． whe r e,ΔG and ΔGθ a r e Gi bbsf r e eene r c h a nge gy ; The r e f o r e,t he r e s e a r ch abou tt he BNＧMgAlON ands t anda rd Gi bbsf r e eene r s ga s gy change R i c ompos i t e s ′ox i da t i onsus c ep t i b i l i t t i ox i dan t cons yandan t an t;T i st empe r a t ur e;and PN２ and PO２ a r e me a sur e sunde rbo r on Ｇ r i chs l agandc a rbo t he rma lr e Ｇ pa r t i a lpr e s sur eo fN２ and O２ ,r e spe c t i ve l l a t ed y．Re [ ２１ Ｇ ２５] duc t i onandn i t r i da t i onpr epa r a t i onha sr e a l i s t i cs i Ｇ t g he rmodynami cda t ar e f e rt ol i t e r a t ur e s ． n i f i c anc ef o ri t sdeve l opmen tandp r a c t i c a lus e． Und e rs t and a r ds t a t eanda tmo s r i cc ond i t i on s phe ５ ５ ( , ) , ２ ２ １ The rmodynami cana l i sof BNＧMgAlON ys PO２ ＝０ ２１×１０ Pa PN２ ＝０ ７８×１０ Pa t hec hang e c ompo s i t e s o ft heG i bb sf r e ee n e r nt heabov et h r e er e a c t i on sa t gyi XRD p a t t e r ns howst h a tt h ema i nph a s ec ompo s i Ｇ d i f f e r e n tt emp e r a t u r e si ss howni nF i ５．Ast hep i c t u r e g t i on so fma t e r i a ls s t ema r e MgAlON,S i a l ona ndBN, s y hows,unde rt heexpe r imen t a lcond i t i ons,ΔGi nt he a nde v e r s ed i s t r i bu t i oni sno tun i f o rm．Ea c hg r a i n abovet ypha h r e er e a c t i on si sf a rl e s st hanz e r o,wh i c hme an s w i l lbeexpos edt oa i rand may beox i d i z eda tt he t ha tBN,MgAlONandS i a l onma eox i d i z e d． Be c au s e yb s amet ime．Theox i da t i ono fma t e r i a l sa c t ua l l a nb e o yc fr e a c t i onk i n e t i c s,t her e a c t i ons e e di sv e r l owa t p ys ( r e a r d e da st h eox i d a t i onc omb i n a t i ono fMgAlON Th e l g owt emp e r a t u r e,wh i l et heox i d a t i onr e a c t i oni sr a i da t p a s s ume df o rmu l ai sAl i a l onand h i emp e r a t u r edu et ot he rma la c t i v a t i on． gO),S ２３ O２７ N５ xM ght
I s sue５ Pr epa r a t i onandOx i da t i onRe s i s t anc eo fBNＧMgAlON Compo s i t e sbyHo t Ｇp r e s s i ngS i n t e r i ng
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F i ５ Re l a t i on s h i ft emp e r a t u r ewi t hΔG i n g po r e a c t i on s( １)t o( ３)
２ ２ ２ Ox i da t i o npr o c e s sandc ha r a c t e r i s t i c sana l s i s y Ox i d a t i onb e h a v i o ro fma t e r i a l swa ss t ud i e da ndt h e t emp e r a t u r e swe r ema i n t a i nedf o r３ha t１０００,１１００, １２００and１３００ ℃ ,r e spe c t i ve l i ６showsXＧ r ay y．F g
d i f f r a c t i onpa t t e rnso fs amp l e sa f t e rox i da t i oni na i r a t１３００ ℃．Compa r edwi t ht heXRDpa t t e rnsbe f o r e ox i da t i ono fBNＧMgAlON,d i f f r a c t i onpe akso fMg Ｇ AlONandBNi nt hes amp l e shavec omp l e t e l i s ap Ｇ yd a r ed,p r oduc i ng magne s i uma l umi n i umsp i ne land pe c o rundum．Wi t hou tBNo rB２O３i nt hep r oduc t, i ti s i nd i c a t edt ha tB２O３ ont hesu r f a c ei sen t i r e l Ｇ yevapo r a t eda f t e rox i da t i on．The ma i npha s e so ft hes amＧ r eCaAl２S i２O６ ,CaAl４O７ , l e sa f t e rt heox i da t i ona p Al２O３ and MgAl２O４ ． F i ７s howsBNＧMgAlON′ sSEM mi c r og r aphso f g
F i ６ X Ｇ r a i f f r a c t i onpa t t e rn so fs amp l e s g yd a f t e rox i da t i oni na i r
sur f a c e so ft hes amp l e sox i d i z edi na i ra t１０００－ １３００ ℃ f o r３h． I tshowst ha twhent heox i da t i on t empe r a t ur ei s１０００ ℃ ,t he s amp l e ′ssur f a c ei s smoo t handsh i ny．Anox i del aye rf o rmsa f t e rox i da Ｇ , t i on a l ong wi t hsma l lho l e sgene r a t edt hr ought he ove r f l owi ngo fN２ ．At１０００ ℃ ,t hed r i v i ngf o r c eo f ox i da t i onr e a c t i oni sl ow,sot heox i da t i on oc cur s f i r s ti nt heg r a i nbounda r rde f e c tpos i t i ons．Wi t h yo t hei nc r e a s eo ft empe r a t ur e,t he mo l t enox i def i lm r adua l l o rmsont hesur f a c eo f ma t e r i a l,wh i ch g yf , c anr ap i d l a lt hepo r e sandmi c r oc r a cks t he r eby yhe e f f e c t i ve l r even t i ngt hef ur t he re r o s i ono foxyg e nt o yp
( a)１０００ ℃ ,３h; ( b)１１００ ℃ ,３h; ( c)１２００ ℃ ,３h; ( d)１３００ ℃ ,３h．
F i ７ SEM mi c r o r aph so fs u r f a c e so fs amp l e sox i d i z e di na i r g g
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J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２２
t hema t e r i a l． F i ８s c r og r a so ft h ec r o s ss e c t i on g howsSEM mi ph o fBNＧMgAlON a f t e rox i da t i ona t１０００－１３００ ℃ f o r３h． I tshowst ha t,a f t e rox i da t i ona t１０００ ℃ ,
t hesubs t r a t ema t e r i a l so fBNＧMgAlONa r ei ngood , c ond i t i onandi nt hec r o s ss e c t i on ox i del aye rdoe s no tappe a robv i ous l h i ss t age,t heox i da t i on y．Att i nc r e a s ei sve r l ow andt heox i da t i on p r o c e s si s ys ma i n l t r o l l ed by t he ox i da t i on r e a c t i on．Wi t h y con t hei nc r e a s eo ft empe r a t u r e,t he po r e si nc r e a s ea t １１００ ℃ andt hes amp l eox i da t i oni sbe t t e rpene t r a Ｇ t edt hant ha ta t１０００ ℃．Ox i d i z eds amp l e sa r ed i v i d Ｇ edi n t otwol aye r s．Theou t e rl aye ri st heox i del aye r , madeupo fox i de s sucha sAl２O３ andCaAl２S i２O８ , wh i l et hei nne rl aye ri st hesubs t r a t ema t e r i a l．The r e i snoobv i oust r ans i t i onl aye ri nt he mi dd l eandt he ox i da t i ono fs amp l ei son l t h i nt hes c opeo faf ew ywi
mi c r ome t e r sont hesur f a c e．Theox i da t i onf i lm p r e Ｇ ven t soxygenf r omf ur t he rpene t r a t i ngi n t ot he ma Ｇ , t e r i a lsubs t r a t e sot heox i da t i oni nc r e a s ei sr e l a t i ve Ｇ l l ow．Af t e rox i da t i ona t１２００ ℃ f o r３h,t heox Ｇ ys i def i lm wi l lbe comeacompa r a t i ve l h i ckdens el ay Ｇ yt e r．The s amp l es e c t i on i s obv i ous l i v i ded i n t o yd t hr e el aye r s:ox i da t i onl aye r,t r ans i t i onl aye rand subs t r a t ema t e r i a l．Theou t e rmos tl aye ri st hewe l l Ｇ , d i s t r i bu t ed and compa c t ox i de l aye r wh i ch c an maket hepo r e sc l os ed,e f f e c t i ve l t opp i ngt heoxy Ｇ ys i f f us i ont ot hei ns i des amp l eandi nh i b i t i ngt he gend ox i da t i onr e a c t i on．Whent het empe r a t ur er i s e st o １３００ ℃ ,t heox i del aye ri sr e l a t i ve l oos ecompa r ed yl wi t ht ha to f１２００ ℃．Thepo r e sa r epene t r a t edand i n t eg r a t edandt heox i da t i ono ft hes amp l e sa r ef a r de epe r．Att he momen t,t heox i del aye ri spo r ous, wi t ht het h i ckne s so fabou t１００μm．Thee f f e c tt op r o Ｇ
( a)１０００ ℃ ; ( b)１１００ ℃ ; ( c)１２００ ℃ ; ( d)１３００ ℃．
F i ８ SEM mi c r o r aph so ft h ec r o s ss e c t i ono fBNＧMgAlONox i d i z e d g g
t e c tt hei n t e rna lsubs t r a t ei sr e l a t i ve l akened． y we Ac co rd i ngt oSEM r e su l t so ft heBNＧMgAlON c ompos i t e sa f t e rox i da t i on,whent heox i da t i ont emＧ , e r a t u r e i sh i h e rt h a n１ ０ ０ ０ ℃ t h eB N Ｇ M A l p g g ON , c ompos i t e swi l lbeox i d i z edi na i r gene r a t i ng mag Ｇ ne s i um a l umi na t esp i ne l,who s ec on t en to fa l umi n Ｇ ( i umox i d ei sf a rh i h e rt h a nt h et h e o r e t i c a lv a l u e a l u Ｇ g mi n ai nt hes up e r s a t u r a t e ds t a t e)a tt h i s po i n t．The sp i ne li si nt heme t a s t ab l es t a t e．Whent heox i da t i on t empe r a t ur er e a che s１３００ ℃ ,α ＧAl２O３ wi l lp r e c i i Ｇ p
t a t ef r omt hesp i ne li nt he me t a s t ab l es t a t e．Then, t heα ＧAl２O３ a f t e rde so l ven t i z i ng wi l lbed i s t r i bu t ed a r oundt hesp i ne l．The s et i nyg r a i nso fα ＧAl２O３g r ow r adua l l th i empe r a t ur e, wh i l et he sp i ne l g ya gh t r a i nsbe comesma l l e r．Thes e r i e so fs t ruc t ur echan Ｇ g swi t h i nt hema t e r i a l swi l lgene r a t eac e r t a i nvo l Ｇ ge umee f f e c t,c aus i ngt hel oos ene s so ft hes t ruc t ur eo f , t heox i del aye r．The r e f o r ei tc anbes e ent ha tt he ox i d a t i onme c han i smo ft heBNＧMgAlONc ompo s i t e si s [ ２６] b a s i c a l l i d e n t i c a lw i t ht h a t o f r e v i o u sw o r k ． y p
I s sue５ Pr epa r a t i onandOx i da t i onRe s i s t anc eo fBNＧMgAlON Compo s i t e sbyHo t Ｇp r e s s i ngS i n t e r i ng
２ ２ ３ Dynami c sana l i sofoxida t i onpr o c e s s ys F i ９ s h o w si s o t h e r m a lo x i d a t i o n m a s s i n g ga , , cu r ve so fBNＧMgAlON a t１０００ １１００ １２００ and １３００ ℃． I tshowst ha tox i da t i on ma s sga i no fBNＧ MgAlONi nc r e a s e s wi t ht her i s i ng o ft empe r a t u r e． Theox i da t i onma s sga i no ft hes amp l ei sve r i t t l e yl a t１０００－１１００ ℃．Att hei n i t i a ls t ageo fc ons t an t t empe r a t ur eo f１２００ ℃ ,ox i da t i onr a t ei sa c c e l e r a t ed andox i da t i onma s sga i no fun i ta r e ashowst het end Ｇ enc f obv i ousi nc r e a s e．Wi t ht he ex t ens i on o f yo , t ime ox i da t i on ma s s ga i no ft hes amp l e be c ome s s l ow,be c aus et het h i ckne s so ft hec ompa c tox i de l aye ri nc r e a s e s,en l a r i ng t he ox i da t i on r e s i s t anc e g ande f f e c t i ve l r even t i ngt hei n t e rna ld i f f us i on o f yp oxygent ot hes amp l e．At１３００ ℃ ,t heox i da t i on ma s sga i n i ngi nc r e a s e ss i i f i c an t l spe c i a l l r Ｇ gn y,e ydu i ngt he p r e l imi na r t ageo fox i da t i on．Be c aus eα Ｇ ys Al２O３ p r e c i i t a t e sf r omt hesp i ne li nt heme t a s t ab l e p s t a t eandt heox i del aye rbe c ome sl oo s e,t hef unc t i on t oi s o l a t eoxygenaba t e s．Bu twi t ht heex t ens i ono f t ime,t heox i da t i onspe edwi l lg r adua l l l owdown． ys
F i ９ I s o t h e rma lox i da t i onma s sg a i nc u r v e so f g BNＧMgAlONa td i f f e r en tt emp e r a t u r e s
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F i １０ Ox i d i z i ngk i n e t i cc u r v e so fBNＧMgAlON g T a b l e１ Ox i d a t i o nr a t ec o n s t a n ta ndc o r r e l a t i o nc o e f f i c i e n t Ra td i f f e r en tt emp e r a t u r e so fBNＧMgAlON /℃ Tempe r a t ur e
k
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１１００ １３００
０ ０２４００ ０ ３９０９８
０ ９７８１２ ０ ９８０５９
r v e sa r el i n e a r,i nd i c a t i ngt ha tt he ma t e r i a l ′sox i d a t i on k i ne t i c sf o l l owst hel awso fpa r abo l awonde r f u l l y． Ther e l a t i onsh i twe en pa r abo l i cox i da t i on p be o l l ows r a t econs t an tandox i d i z i ngt empe r a t ur eT f t hef o rmu l aAr rhen i usl n k＝l nA －E/RT ( Ei st he /mo a c t i va t i ono fchemi c a lr e a c t i on,J l;A i sf r e Ｇ / ) kv s． １ T cur vei sas t r a i tl i ne, a c t o r． l n quenc yf gh a sshowni nF i １１．Thes l opeo ft hes t r a i tl i nei s g gh －E/R andt hei n t e r c ep ti st hel nA i nF i １１,and g t husappa r en ta c t i va t i onene r hef r equenc gyE andt y anbec a l cu l a t ed． E ,A andR o ft hel i ne a r f a c t o rA c r eg r e s s i ona r el i s t edi nTab l e２．
Wh i l eS i３N４c e r ami c si si nt hep r o c e s so fox i da Ｇ t i on,i ti sgene r a l l c o n s i d e r e dt h a tt h e r o w t ho f y g ox i del aye ri sc on t r o l l edbyd i f f us i on．Thep r o c e s so f ox i da t i onk i ne t i c si so f t eni n t e r r e t eda spa r abo l a, p f o l l owi ngt heru l e so fpa r abo l i cr a t e: ２ ( / ) ( Δm S ＝k t＋C ４) whe r e,Δm i sga i n i ng ma s so ft hes amp l e;Si ssu r Ｇ sox i da t i onr a t ec ons t an t; ti s f a c eo ft hes amp l e;ki ox i da t i ont ime;andCi sc ons t an t．
F i １０showst ha tt her e l a t i onsh i twe ent he g pbe squa r eo ft heox i da t i on ma s sva l ueandt ime．The l i ne a rs l opei st heox i da t i onr a t ec ons t an ta td i f f e r en t t empe r a t ur e s．Tab l e１g i ve st heox i da t i onr a t ec on Ｇ s t an tandt hel i ne a rr eg r e s s i onc o r r e l a t i onc o e f f i c i e n t a td i f f e r e n tt emp e r a t u r e s． F i １０showst ha ta l lt hecu Ｇ g
F i １１ l n kv s． １/T c u r v eo fBNＧMgAlON g Tab l e２ Ox i da t i onk i n e t i cpa r ame t e r so fBNＧMgAlON E/( Jmo l－１) ２ １３×１０５
A
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４３０
J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２２
３ Conc l u s i on s ( １)Th e r ea r e MgAlON,S i a l ona ndBN ph a s e s bo t hb e f o r ea nda f t e rho t Ｇ r e s s i ngs i n t e r i ng．CaAl p ４O７ w i l ld i s a e a ra f t e rs i n t e r i ng,wh i l eal i t t l eCaYAl pp ３O７ , r a t e s wh i ch de c r e a s e sg r adua l l t ht hei n Ｇ gene y wi c r e a s eo fs i n t e r i ng t empe r a t u r e．The s t ruc t u r eo f BNＧMgAlONc ompo s i t e sa f t e rs i n t e r i ngs n t h e s i s i s y we l l Ｇ d i s t r i bu t edandc ompa c t,wi t ht hepo r ed i ame Ｇ t e ro fabou t２－５μm．Al,Mg,OandNa r er e l a t i ve Ｇ , l l l Ｇ d i s t r i bu t edi nt hema t e r i a l wi t ht heh i s t ywe ghe Alandt hel owe s tN． ( ２)Thema i npha s e so fBNＧMgAlONc ompo s Ｇ , , i t e sa r eCaAl i CaAl Al nd MgAl ２S ２O６ ４O７ ２O３ a ２O４ ． Af t e rox i da t i ona t１０００ ℃ f o r３ h,t hesubs t r a t e ma t e r i a li si ngoodc ond i t i onandox i da t i onma s sga i n i nc r e a s e ss l owl t e rox i da t i on a t１１００ ℃ ,t he y．Af s amp l ei sd i v i dedi n t otwol aye r s．Theou t e rl aye ri s t heox i del aye rmak i ngupo fox i de s,sucha sAl２O３ andCaAl２S i２O８ ,wh i l et hei nne rl aye ri st hesub Ｇ s t r a t ema t e r i a l．The r ei snoobv i oust r ans i t i onl aye r i nt hemi dd l e．Thes amp l ea f t e rox i da t i ona t１２００ ℃ c anbeobv i ous l i v i dedi n t ot hr e el aye r s:ox i da t i on yd l aye r,t r ans i t i onl aye randsubs t r a t e ma t e r i a l s．The ou t e rmos tl aye ri swe l l Ｇ d i s t r i bu t edandc ompa c t,e f Ｇ f e c t i ve l r even t i ngoxygenf r omd i f f us i ngt ot hei n Ｇ yp t e rna ls amp l eandi nh i b i t i ngt heox i da t i onr e a c t i on． ( ３)Af t e rox i da t i ona t１３００ ℃ ,t het h i ckne s s o fox i del aye ri nc r e a s e sobv i ous l hes t ruc t u r e yandt i sl oo s eandpo r ous．Th i si sc aus edbyt hesupe r s a t u Ｇ r a t eda l umi n i um ox i de de s o l ven t i z i ng f r om sp i ne l． Att h i spo i n t,t hepr o t e c t i ono ft heox i da t i onl aye r t ot hema t e r i a lde c r e a s e ss i i f i c an t l gn y． ( ４)Theox i da t i on p r o c e s so ft he ma t e r i a la t ２ ＝ １０００－１３００ ℃f o l l owst h ep a r a bo l i cr u l e:( Δm/S) k t＋C ．Theox i da t i onr a t ec ons t an t sa t１０００,１１００, １２００and１３００ ℃ a r er e s e c t i v e l ０１０２５,０ ０２４００, p y０ ０ １６６０４and０ ３９０９８．Theappa r en ta c t i va t i onene r Ｇ /mo fox i da t i onp r o c e s si s２ １３×１０５ J landt he gyo f r equenc a c t o ri s４ ６６×１０６ ． yf Re f e r enc e s:
[ １] YG．Di ng,J S．Wang,G．Wang,S．Ma,QG．Xue,J． I r on
S t e e lRe s． I n t． １９ ( ２０１２)No ６,９ Ｇ １３． [ L．L i u,Z F．L i,X X．Xue,J． I r onS t e e lRe s． ２] Z D．Yang,S I n t． １４ ( ２００７)No ６,３２ Ｇ ３６． [ ３] C J．Deng,YR．Hong,X C．Zhong,J L．Sun,J．Un i v．Sc i． Te chno l．Be i i ng７ ( ２０００)９６ Ｇ ９８． j [ ４] B W．Duan,Re s e a r chand App l i c a t i ono f MgAlON Compo s Ｇ i t e s,Ti en t s i nUn i ve r s i t an i n,２００８． y,Ti j [ ５] Z T．Zhang,Syn t he s i sand Cha r a c t e r i z a t i ono f MgAlONＧBN Re f r a c t o r i e s,KTH Schoo l,S t o ckho lm,２００６． [ /Bo /Co ６] S． Zhao,Magne s i um Al umi num Oxyn i t r i de r onNi t r i de Ｇ r undum Como s i t eRe f r a c t o r i ve r s i t fSc i enc eand y,WuhanUn yo Te chno l ogy,Wuhan,２００４． [ ７] T．Wi d ema n,L G． Sn e ddon,Ch em．Ma t e r． ８( １９９６)No １,３ Ｇ ５． [ ８] B．Tour e l e,D．Co r nu,H．Vi nc en t,J．Bou i x,Adv． y,P．Mi Func．Ma t e r． １２ (２００２)２２８ Ｇ ２３４． [ ９] W． Zhang,HJ．Wang,Z H． J i n,Or dnanc e Ma t e r．Sc i．Eng． ２７ ( ２００４)No ５,５８ Ｇ ６３． [ i,NF．L i,Ce r ami cS t ud i e sJ our na l１１ １０] HQ．Zhang,Y．Da ( １９９６)No ２,８３ Ｇ ８７． [ f r a c t o r i e s４１ ( ２００７)No １,３７ Ｇ ４０． １１] X S．Wang,F．Cao,Re [ １２] X R．Guo,S t udyonFabr i c a t i on,Pr ope r t i e sand Mi c r o s t r uc Ｇ t ur eo f Al２O３—Baux i t e Ｇ ba s ed MgAlON Compo s i t e,Zheng Ｇ zhouUn i ve r s i t zhou,２００４． y,Zheng [ １３] B． L i u,C Q． Peng,R C．Wang,X F．Wang,T T． L i,Z Y． i n． J．Non Ｇ f e r r ousMe t． ２２ ( ２０１２)２３０２ Ｇ ２３１０． Wang,Ch [ L．Sun,Y R．Hong, ng,J G．Zh a ng,HZ．Wa １４] X T．Wa ng,B Re f r a c t o r i e s３８ ( ２００４)６６ Ｇ ６９． [ L． Sun,Ch i n． J．Non Ｇ C． Zhong,J R．Hong,X １５] C J．De ng,Y f e r r ous．Me t． １０ ( ２０００)Supp l． １０,３９ Ｇ ４１． [ L． Sun,Re f r a c t o r i e s C． Zhong,J １６] C J．Deng,YR．Hong,X ３５ ( ２００１)No １,４ Ｇ ７． [ １７] J C．Labbe,A． J e anne,G．Rou l t,Ce r ami c sI n t e r na t i ona l１８ ( １９９２)No ２,８１ Ｇ ８４． [ s． I r onandS t e e l１２ ( ２００１)No ６,１ Ｇ ５,１４． １８] X C． Zhong,Re [ i,J our na lo ft heEur ope an D．Teng,WC．L １９] Z T． Zhang,L Ce r ami cSo c i e t ２００７)３１９ Ｇ ３２６． y２７ ( [ ２０] Z T． Zh a ng,S． S e e t h a r ama n,WC． L i,Me t a l l．Ma t e r．T r a n s． B． ３７ ( ２００６)６１５ Ｇ ６２１． [ r am．So c． ２１] G D．Qu i nn,N D．Co r b i n,J W．McCa u l e y,Am．Ce Bu l l． ６３ ( １９８４)７２３ Ｇ ７２９． [ ２２] HF．L i,Fabr i c a t i onandPr ope r t i e so fMgAlONandCompo s Ｇ i t eRe f r a c t o r i e s,Wuhan Un i ve r s i t fSc i enc eand Te chno l o Ｇ yo gy,Wuhan,２００２． [ ２３] A．Yamaguch i,Pr a c t i c a lThe rmodynami c sandI t sApp l i c a t i on i n Hi r a t ur eCe r ami c s,WuhanI ndus t r i a lUn i ve r s i t ghTempe y Pr e s s,Wuhan,１９９３． [ ２４] Q． Zhen,WC．L i,Ch i n． J．Ma t e r．Re s． １４ ( ２０００)２７ Ｇ ３１． [ ２５] Y J．L i a ng,Y C．Ch e,Th e rmo dyn ami cDa t aHa ndbo oko fI no r Ｇ a n i cCompound s,No r t he a s t e r n Un i ve r i t e s s,Shenyang, g y Pr １９９３． [ ２６] HX．Zhang,S t udyonFundamen t a l so fSyn t he s i sandPr op Ｇ e r t i e so fS i ng l e Pha s e MgAlON,Un i ve r s i t fSc i enc eand yo Te chno l ogyBe i i ng,Be i i ng,２００３． j j
JOURNALOFIRON ANDSTEELRESEARCH,INTERNATIONAL２ ０ １ ５,２ ２( ５):４ ２ ３ Ｇ ４ ３ ０
Pr e r a t i onandOx i da t i onRe s i s t anc eo fBNＧMgAlONCompo s i t e sby pa Ho t Ｇ e s s i ngS i n t e r i ng pr １２ RanLIU１ ２ , Xi n Ｇ ng Ｇ uan WANG１ ２ , Ya ＧnaQIE１ ２ , yuanZHANG , Xi j １, ２ １, ２ Qi ngLÜ , FuGAO ,
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( １．KeyLabo r a t o r o rAdvanc ed Me t a l l u r chno l ogyo fMi n i s t r fEduc a t i on,Hebe iUn i t edUn i ve r s i t yf gyTe yo y,Tangshan , , , ０６３００９,He b e i,Ch i n a; ２．Co l l e eo fM e t a l l u r n dE n e r H e b e iU n i t e dU n i v e r s i t T a n s h a n０ ６ ３ ０ ０ ９ H e b e i,Ch i n a) g gya gy y g Ab s t r a c t:BNＧMgAlONc ompo s i t e swe r ep r epa r edbyho t Ｇp r e s s i ngs i n t e r i ngunde rn i t r ogena tmo sphe r ewi t hBNＧMg Ｇ , AlONc ompo s i t epowde r sa sr aw ma t e r i a landY２O３a ss i n t e r i ngadd i t i ve． Ba s edont he rmodynami cana l s i s t h eo x i Ｇ y da t i onr e s i s t anc eo fBNＧMgAlONc ompo s i t e swa si nve s t i t edandt hedynami c so fox i da t i onp r o c e s swa sa l s oana Ｇ ga l z ed．Theox i da t i onp r o c e s sandt hemi c r o Ｇmo r l ogyo ft hes amp l e sbe f o r eanda f t e rox i da t i onwe r echa r a c t e r i z ed y pho byXＧ r ayd i f f r a c t i onands c ann i nge l e c t r on mi c r o s c opy．Thedynami c so fox i da t i onr e s i s t anc eo ft heBNＧMgAlON c ompo s i t e swa si nve s t i t edv i at heana l s i so ft hec ons t an tt empe r a t u r eox i da t i on ma s sga i ncu r ve s．Ther e su l t s ga y showt ha tt hema i nc omponen t so ft hema t e r i a la r eMgAlON,S i a l on,BNandCaYAl３O７a t１６５０－１７５０ ℃ ,andt he c on t en to fCaYAl３O７ de c r e a s e sa st hes i n t e r i ngt empe r a t u r ei nc r e a s e s．TheBNＧMgAlON c ompo s i t e sp r epa r eda t １７５０ ℃i sun i f o rmandc ompa c twi t ht heba l anc edd i s t r i bu t i onso fAl,Mg,O,andN．Theox i da t i onp r o c e s so fBNＧ MgAlONc ompo s i t e si na i rma i n l ons i s t so fMgAlON,S i a l onandBNox i da t i on．Thes e c t i ona f t e rbe i ngox i d i z eda t yc １０００－１３００ ℃i nvo l ve st hr e el aye r s,name l heou t e rl aye r,t hemi dd l el aye randt hei nne rl aye r．Theox i da t i on y,t /mo r o c e s sf o l l owst hepa r abo l amode l．Theappa r en ta c t i va t i onene r ft heox i da t i onp r o c e s si s２ １３×１０５ J land p gyo ６ t hef r e a c t o ri s４ ６６×１０ ． quencyf Ke r d s:bo r on Ｇ r i chs l ag;c a r bo t he rma lr educ t i on;n i t r i da t i on;ho t Ｇp r e s s i ngs i n t e r i ng;BNＧMgAlONc ompo s i t e; ywo ox i da t i onr e s i s t anc e
Ludwi i t ea c c oun t sf o rabou t５８％ o fbo r onr e Ｇ g , s ou r c e si nCh i na．Howeve ri ti sd i f f i cu l tt oa ch i eve i n t eg r a t edu t i l i z a t i onbe c aus eo fi t sl ow g r ade ( B２O３ ７ ２３％ ,TFe３０％ ),c omp l ex i t fmi ne r a ls t ruc t u r e yo [ １] a nd mi nu t e n e s so fi n f i l t r a t i ng g r a nu l a r i t r ough y ．Th t hepr oc e s so fpy r ome t a l l u r os epa r a t el udwi i t e, gyt g t heva l uab l ec omponen t so fbo r on,magne s i um and [] s oon c an bec onc en t r a t edi n t o bo r on Ｇ r i ch s l ag２ ． The ma i nchemi c a lc ompo s i t i onso fbo r on Ｇ r i chs l ag a r eox i de sl i keMgO,S iO２ ,B２O３ ,CaO,Al２O３ and s oon,amongwh i cht her a t i o so fMgOandB２O３a r e r e spe c t i ve l r et han３５％ and１２％． I ft het r ad i Ｇ y mo t i ona ll e a ch i ng me t hodsa r eus edt ode a lwi t hbo r on Ｇ r i chs l ag,t hec ons equenc ewi l lbeo fpoo re c onomi c bene f i t s,env i r onmen tpo l l u t i on,t hr oughpu tl imi t a Ｇ t i onandl owadd i t i ona lva l ueo ft hep r oduc t s．HowＧ
eve r,c a rbo t he rma lr educ t i onand n i t r i da t i oni san e f f e c t i vewayt o makecomp r ehens i veus eo fbo r on Ｇ r i chs l ag． I nt hes l ag,MgOand Al２O３ a r et her aw ma t e r i a l st os t he s i z et headvanc eds t ruc t ur a lc e Ｇ yn r ami c s;B２O３i st r ans f e r r edi n t oBNbyc a rbo t he rma l r educ t i onand n i t r i da t i onand S iO２ and Al２O３ i n t o S i a l on,andcons equen t l hecompos i t epowde r so f yt BNＧMgAlON a r ef o rmed．MgAlON c e r ami ci t s e l f s e s s e st hef an t a s t i cqua l i t i e so fh i empe r a t ur e pos ght r e s i s t anc e,t he rma lshockr e s i s t anc eandco r r os i on [ ] r e s i s t anc e３Ｇ５ ．Mo r eove r,BNha st hewonde r f u lox i Ｇ da t i onr e s i s t anc e,t he rma lshock pe r f o rmanc eand [ ] ma ch i n i ngpe r f o rmanc e６Ｇ９ ,t oge t he r wi t hS i a l on ′s no rma landh i empe r a t ur es t r eng t handexc e l l en t ght [ , ] chemi c a ls t ab i l i t th i empe r a t ur e１０ １１ ．The r e Ｇ ya ght f o r e,t heove r a l lpe r f o rmanc eo fBNＧMgAlONcomＧ
Founda t i onI t em: I t em Spons o r edbyNa t i ona lNa t ur a lSc i enc eFounda t i ono fCh i na ( ５０９０４０２２);Educ a t i onDepa r tmen to fHebe iPr ov i nc e Ou t s t and i ngYou t hFundPr o e c to fCh i na ( Y２０１１１１６) j B i o r aphy: RanLIU,Do c t o r,As s o c i a t ePr o f e s s o r; E Ｇma i l: I r ８１９＠１６３ c om; Re c e i v e dDa t e:Ju l y１,２０１４ g
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J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２２
s i t e si sg r e a t l ovedandi ti sexpe c t edt obe po yimpr us eda sadvanc edc e r ami c s,f unc t i ona lc e r ami c sand r e f r a c t o r t e r i a l swi t hh i r f o rmanc e． y ma ghpe I nadd i t i on,f o rc e r ami c ma t e r i a l s,be s i de st he , e r f o r m a n c eo f o w d e r i t s e l f s i n t e r i n r o c e s sa l s o p p gp l aysanimpo r t an tr o l ei nt he pe r f o rmanc eo ft he p ma t e r i a l． I ti ss imp l eando fl owc o s tt os i n t e runde r , o r d i na r r e s s u r e ． H o w e v e r b e c a u s em o r ea d d i t i v e s yp havet obeaddedi n t ot hema t e r i a ldu r i ngt heope r a Ｇ t i on,wh i ch wi l ll e ad t oh i rc on t en to fg l a s s ghe s ei nt heu l t ima t es i n t e r i ng ma t e r i a l．The r e f o r e, pha t hepe r f o rmanc ea th i empe r a t u r ei spoo randt he ght s amp l e sa r ee a s ode f o rm．Ho t Ｇ r e s s i ngs i n t e r i ng yt p t e chno l ogyi st o dens i f he mo l di nt he he a t i ng yt r o c e s st hr oughun i d i r e c t i ona lme chan i c a lp r e s su r e． p Be c aus et heex t e rna lpr e s su r emake sg r a i nbounda r y , andl a t t i c eo ft hema t e r i a ld i f f us ef a s t e rt hedens e r s amp l e sc anbeob t a i neda tl owe rt empe r a t u r eand sho r t e rhe a tpr e s e r va t i ont ime． I no rde rt of u r t he ri nve s t i t et hena t u r eo fBNＧ ga MgAlON,ho t Ｇ e s s i ngs i n t e r i ngi sus edi nt hes i n Ｇ pr t e r i ngo ft heBNＧMgAlON powde r s wh i cha r ep r e Ｇ r edbyt hebo r on Ｇ r i chs l ag．Thedens i f i c a t i onbe Ｇ pa hav i o ro ft he ma t e r i a li nt he p r o c e s so fs i n t e r i ng, t hechangel aw o ft he pha s ec ompo s i t i on,andt he , mi c r os t ruc t u r ea r ea l s os t ud i ed．Fu r t he rmo r e t he ox i da t i onk i ne t i c sexpe r imen ti sc a r r i edou tt oBNＧ MgAlON compo s i t e sa f t e rs i n t e r i ng;t heox i da t i on ; k i ne t i c s mode li s bu i l t t he ox i da t i on behav i o ro f BNＧMgAlON c ompo s i t e si sexp l o r ed．Al lt he s er e Ｇ s e a r che sa im t o pr ov i det heo r e t i c a lsuppo r tf o rt he s t udyo ft heimpr ovemen to fox i da t i onr e s i s t anc eo f BNＧMgAlONc ompo s i t e s．
１ Exp e r imen t
１ １ Pr e r a t i ono fBNＧMgAlONc ompo s i t e s pa Theexpe r imen t a l ma t e r i a l sa r e BNＧMgAlON c ompos i t epowde r sands i n t e r i ngadd i t i veY２O３powＧ de r s．Thema i nr aw ma t e r i a l so fBNＧMgAlONc omＧ , ( ) s i t epowde r sa r ebo r on Ｇ r i chs l ag Al OH ３ and po c onduc t ex．Thepowde r sa r emadeunde rt heexpe r i Ｇ men t a lcond i t i ono fs i n t e r i ngt empe r a t u r e１４８０ ℃ , equ i va l en tchemi c a ldo s age wi t hc a rbon,x ＝４ ５ ( Al２３O２７N５ xMgO),c ons t an tt empe r a t u r el a s t i ng f o r８handN２f l owr a t eo f４００ mL/mi n．XRD pa t Ｇ t e rno f MgAlON c ompo s i t e powde r si sshowni n F i １,wh i chi l l us t r a t e st hema i ni ng r ed i en t so fBNＧ g MgAlONcompo s i t epowde r sa r e MgAlON,S i a l on, CaAl４O７ and BN．The pu r i t f Y２O３ powde r si s yo ９９ ９ ma s s％ andt he i rave r age pa r t i c l es i z ei sl e s s t han１μm．
F i １ XRDpa t t e rno fMgAlONc ompo s i t epowd e rby g c a r bo t h e rma lr odu c t i onandn i t r i da t i on
１ ma s s％ Y２O３ c an b ea dd e di n BNＧMgAlON r st of o rmt he mi x t ur e．Theadd i t i ono fsu i t Ｇ powde ab l eamoun to fs i n t e r i ngadd i t i veY２O３ c anp r omo t e t hes i n t e r i ng,t huss i i f i c an t l r ov i ngt he mi Ｇ gn yimp , c r os t ruc t ur eo fs i n t e r edp r oduc t s r educ i ngt hepo Ｇ r os i t nc r e a s i ngt hedens i t ft he men t i oned yandi yo [ , ] r oduc t s１２ １３ ．The mi x t ur eandco rundum g r i nd i ng p , ba l la r epu ti n t oba l l mi l lpo t andt he mi x t ur ei s t akenou ta f t e rg r i nd i ngf o r２４hi nt her o l l i ngba l l , , mi l l．Then,a f t e rd r i n r i n d i n a n ds i e v i n t h e y g g g g mi x t ur ei senc l os edi n t og r aph i t emou l dcoa t edwi t h BN．Ho t Ｇ r e s s i ngs i n t e r i ngi sope r a t edi nt heva cu Ｇ p um ho t Ｇ r e s s i n s i n t e r i n f u r n a c eo ft h eZ G YM １ ０ ０ p g g t i ng t he p r oc e s s, h i i t i t r ogen ype．Dur gh pur yn ( ９９ ９９％ )i si nsu f f l a t edf o rp r o t e c t i on．Thet empe r Ｇ a t ur egoe supt o１４００ ℃ by ２０ ℃/mi nandt hen r e s sur ebeg i nst oi nc r e a s e．Me anwh i l e,he a t i ngr a t e p de c r e a s e sg r adua l l tt hespe edo f５－１０ ℃/mi n． ya Whent het empe r a t ur er e a che s１７５０ ℃ ,t he p r e s Ｇ sur ewi l lr e a cht hemax imumo f３０ MPa．Af t e rhe a t r e s e r va t i onf o r１ h,t het empe r a t ur er educ e st o p １４００ ℃ a tt hespe edo f５－１０ ℃/mi n．Att he mo Ｇ , men tt hep r e s sur ebeg i nst ode c r e a s eg r adua l l yand t he t empe r a t ur e r e s t o r e st o r oom t empe r a t ur e t hr oughna t ur a lcoo l i ng．Schema t i cd i ag r am o fho t Ｇ r e s s i ngs i n t e r i ngi sshowni nF i ２． p g
F i ２ S ch ema t i cd i a r amo fho t Ｇp r e s s i ngs i n t e r i ng g g
I s sue５ Pr epa r a t i onandOx i da t i onRe s i s t anc eo fBNＧMgAlON Compo s i t e sbyHo t Ｇp r e s s i ngS i n t e r i ng
１ ２ Pe r f o rmanc et e s t Af t e rcu t t i ng,g r i nd i ng,andpo l i sh i ngf o rmi r Ｇ , r o rsur f a c e s i n t e r i ng b l o cks wi l lbeunde rt he mi Ｇ c r o s t ruc t ur eobs e r va t i ono ft hesu r f a c e．The pha s e c ompos i t i ono fpr oduc t si sme a su r edbyX Ｇ r a i f f r a c Ｇ yd ( , ) t i on XRD D ＧMAX２２００ ．Th ea c c e l e r a t i onvo l t ageo f Cut a r ti s４０kV,cu r r en ti n t ens i t s３０ mA,and ge yi /mi t hes c ann i ng spe edi s５( °) n．Du r i ng obs e r v i ng , t hemi c r os cop i cmo r l ogyo ft hep r oduc t al aye r pho o fgo l dabou t１０３ nmshou l dbep l a t edwi t hanSBC Ｇ ２ s amp l esur f a c et r e a t i ng ma ch i nef i r s t l he y．Thent s amp l ewi l lber ep r e s en t edbys c ann i nge l e c t r on mi Ｇ c r o s c opy ( SEM,SSXＧ ５５０ SHIMADZU)．Thei s o Ｇ t he rma lox i da t i onexpe r imen ti sc onduc t edonac omＧ r ehens i vet he rma la n a l z e r( STA４４９C,NETZSCH p y Comp any),w i t ht h eamoun to f１０－７ g．Be f o r eox i da Ｇ , t i onexpe r imen tb l o cks amp l e shavebe enf u l l r yd y． Pu tt hes amp l e si n t oc o rundumc ruc i b l e,t henp l a c e t hec ruc i b l ewi t hs amp l e si nt hes amp l ef r ameo ft h e t h e rma la n a l z e r． Th ea i rwa si n t r o du c e da taf l owr a t eo f y ５ ０mL/mi n,f o l l owedbyhe a t i ngupf r omr oomt emＧ r a t ur et ot her e a c t i ont empe r a t u r ea tt her a t eo f１０ pe / , ℃ mi n andke ep i ngc ons t an tt empe r a t u r ef o r３h． Ane l e c t r on i cba l anc ei sus edt or e c o r dt hequa l i t y change．Thent hesu r f a c eandc r o s s Ｇ s e c t i ono fs amＧ l e sa f t e rox i da t i ona r eunde rmi c r o s c op i cmo r l o Ｇ p pho e r va t edbyXＧ r ayd i f f r a c t i onands c ann i nge l e c Ｇ gyobs t r onmi c r os c opy．
２ Re s u l t sandAna l s i s y
２ １ Cha r a c t e r i z a t i onandana l s i so fBNＧMgAlON y c ompo s i t e st hr oughho tpr e s s i ngs t he s i s yn F i ３showst heXRD pa t t e rnso fho t Ｇ r e s s i ng g p s i n t e r i ng ma t e r i a l sa td i f f e r en tt empe r a t u r e s． I tc an bes e ent ha tt hes i n t e r i ng ma t e r i a l sa te a cht empe r a Ｇ t u r econ t a i ns MgAlON,S i a l on,BNandCaYAl３O７ s e．And wi t hi nc r e a s i ng s i n t e r i ngt empe r a t u r e, pha t hec on t en to fCaYAl３O７ pha s er educ e s,MgAlON i nc r e a s e sg r adua l l i a l onandBN r ema i nun Ｇ y,andS c h a ng e db a s i c a l l i n t e r i ngi st h ep r o c e s so f y．MgAlONs l i i d pha s es i n t e r i ng．The g r a i ng r owt hi nl i i d qu qu s ei sgene r a l l omp l e t edbyd i s s o l u t i onandp r e Ｇ pha yc , c i i t a t i on． I nt hepr o c e s so fs i n t e r i ng BNi sno ti n Ｇ p vo l vedi nt her e a c t i on;t he r e f o r e,i t sc on t en tr e Ｇ ma i nst hes ame．Wh e nt h et emp e r a t u r ei s１６５０ ℃ ,t he s o l i dso l u t i onr e a c t i ono c cu r si nt headd i t i ve sY２O３ andCaAl４O７ ,gene r a t i ngl ow me l t i ngeu t e c t i cph a s e CaYAl O ． T h e d i s a e a r a n c e o fC a A l O s h o w s t h a t i t pp ３ ７ ４ ７ ha st hecomp l e t es o l i ds o l u t i on wi t h Y２O３ ．When t het empe r a t u r er i s e st o１７００ ℃ ,CaYAl３O７c on t en t , de c r e a s e sr ap i d l w h i c hs h o w st h a ta tc e r t a i nt e m Ｇ y
４２５
e r a t u r e s, CaYAl nd t he g r a i n bound a r l a s s p yg ３O７ a ( ) , h a s e M Ｇ S i Ｇ A l Ｇ O Ｇ N e n e r a t en e w M A l O N a n di t p g g g c anbecon f i rmeda sd i f f r a c t i on pe ak g r adua l l Ｇ y en hanc e swi t hi nc r e a s i ngt het empe r a t ur e．
F i ３ XRDpa t t e rn so fho t Ｇp r e s s e dma t e r i a l sa t g d i f f e r en tt emp e r a t u r e s
F i ４showsSEM mi c r og r aphsande l emen t s g s e c t i ond i s t r i bu t i ono fpo l i shedsur f a c ef o rs amp l e s s i n t e r eda t１７５０ ℃f o r１h． I ti ss e ent ha tt hes t ruc Ｇ t ur eo ft heBNＧMgAlONcompos i t e sa f t e rho t Ｇ r e s s Ｇ p i ngs i n t e r i ngi s we l l Ｇ d i s t r i bu t edandcompa c t．The s i z eo ft hesur f a c e po r ei s２－５ μm i nd i ame t e r, , , wh i chi sno tb i ． A l M O a n d N a r er e l a t i v e l g g y , we l l Ｇ d i s t r i bu t edi nt hema t e r i a l among wh i ch Ali s t heh i s tandNi st hel owe s t．Thr oughus i ngho t Ｇ ghe , r e s s i n s i n t e r i n t h e s t r e s s c a n r o m t t h em u t u a l p g g p p con t a c tbe twe ent hepa r t i c l e sandt hed i s so l u t i onand d i f f us i ono ft hesubs t anc e,sot hesur f a c es t ruc t ur e o ft hema t e r i a l si swe l l Ｇ d i s t r i bu t edandcompa c t．
２ ２ Ox i da t i onr e s i s t anc eo fBNＧMgAlONc ompo s i t e s t hr oughho tpr e s s i ngs n t h e s i s y MgAlON c e r ami ci so fpoo rox i da t i onr e s i s t Ｇ anc e．Theox i da t i onr e a c t i onwi l lbes eve r e re s e c i a l l p y [ ] a th i emp e r a t u r e sabov e１０００ ℃ １４ ．Manys c ho l a r s ght haves t ud i edt heox i da t i onr e s i s t anc eo f MgAlON, andf oundt ha tadd i ngBNi n t ot heMgAlON ma t e r i Ｇ [, , ] a lc animp r ovei t s ox i da t i on r e s i s t anc e６ １５ １６ ．By [ , ] s t udy i ngt hean t i ox i dan tme chan i smo fBN １７ １８ ,t he
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J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２２
( a)SEM mi c r og r aph; ( b)Se c t i ond i s t r i bu t i ono fAl; ( c)Se c t i ond i s t r i bu t i ono fMg; ( d)Se c t i ond i s t r i bu t i ono fO; ( e)Se c t i ond i s t r i bu t i ono fN．
F i ４ SEM mi c r o r aphande l emen ts e c t i ond i s t r i bu t i ono fpo l i s h e ds u r f a c ef o rs amp l es i n t e r e da t１７５０ ℃ f o r１h g g
r e su l t si nd i c a t et ha tBN ha sexc e l l en tox i da t i onr e Ｇ BN．Theox i da t i onr e a c t i onsr e spe c t i ve l r e: ya s i s t a n c ea t９００ ℃ a ndi tw i l lb eox i d i z e da bo v e９００ ℃． ４Al２３O２７N５ xMgO＋１５O２ ＝４６Al２O３ ( １) B２O３l i i dpha s ei sgene r a t eda th i empe r a t u r e; xMgO＋１０N２ qu ght θ / , Δ G ＝－７ ０ ９ ９ ３＋０ ０ ７ ４ T k J m o l t hust he ma t e r i a l s ′ po r e s wi l lbes e a l ed b l o ck i ng æ １０ ö t hechanne l sf o roxygend i f f us i on,andox i da t i onna Ｇ çP N２ ÷ /mo ΔG ＝ΔGθ＋RTl nçç １５ ÷÷ kJ l t u r eo fMgAlONt u rnst obep r o t e c t i ve,s i i f i c an t l gn y èP O２ ø /mo de c r e a s i ngt heox i da t i ondeg r e e．Howeve r,a tp r e s Ｇ ΔG ＝－７０９ ９３＋０ ２４８T kJ l en t,t her epo r tabou tt heBNＧMgAlONc ompo s i t e s ′ S i１７Al０３N１３O１７ ＋１ ２７５O２ ＝１ ７S iO２ ＋ [, , ] ( ox i da t i onr e s i s t anc ei sr a r e．Zhang５ １９ ２０ ando t he r s ０ １５Al２O３ ＋０ ８５N ２) θ / made BNＧMgAlON c ompo s i t e s by t he me t hod o f ΔG ＝－１１６４ ４５＋０ ２１５T kJ mo l ０ ８５ ö æ ho t Ｇ e s s edb l o ck．Theyhavec a r r i edou tde t a i l edr e Ｇ P pr N ç ÷ ２ /mo ΔG ＝ΔGθ＋RTl nçç １２７５ ÷÷ kJ l s e a r ch on t he rmodynami c p r ope r t chan i c a l y, me èP O２ ø /mo r ope r t he rma lc onduc t i v i t o r r o s i onr e s i s t Ｇ p y,t yandc ４５＋０ ２２９T kJ l ΔG ＝－１１６４ ( anc eandsoon,andpo i n t edou tt ha tgoodpe r f o rmＧ BN＋０ ７５O２ ＝０ ５B２O３ ＋０ ５N２ ３) θ / anc eo ft he rma lsho ckandc o r r o s i onr e s i s t anc ei sbe Ｇ ８３＋０ ０３４T kJ mo l ΔG ＝－３７５ ０ ５ ö æ s t owedont hema t e r i a l．Wha tl imi t si t sdeve l opmen t P N ÷ ç ２ /mo kJ l ΔG ＝ΔGθ＋RTl nçç ０７５ ÷÷ r edomi nan t l st hesus c ep t i b i l i t oox i da t i onand p yi yt èP O２ ø /mo t hel ow me chan i c a ls t r eng t h．Bu tt heox i da t i onr e Ｇ ΔG ＝－３７５ ８３＋０ ０４３T kJ l s i s t anc eo ft he ma t e r i a li s no ts t ud i edi n de t a i l． whe r e,ΔG and ΔGθ a r e Gi bbsf r e eene r c h a nge gy ; The r e f o r e,t he r e s e a r ch abou tt he BNＧMgAlON ands t anda rd Gi bbsf r e eene r s ga s gy change R i c ompos i t e s ′ox i da t i onsus c ep t i b i l i t t i ox i dan t cons yandan t an t;T i st empe r a t ur e;and PN２ and PO２ a r e me a sur e sunde rbo r on Ｇ r i chs l agandc a rbo t he rma lr e Ｇ pa r t i a lpr e s sur eo fN２ and O２ ,r e spe c t i ve l l a t ed y．Re [ ２１ Ｇ ２５] duc t i onandn i t r i da t i onpr epa r a t i onha sr e a l i s t i cs i Ｇ t g he rmodynami cda t ar e f e rt ol i t e r a t ur e s ． n i f i c anc ef o ri t sdeve l opmen tandp r a c t i c a lus e． Und e rs t and a r ds t a t eanda tmo s r i cc ond i t i on s phe ５ ５ ( , ) , ２ ２ １ The rmodynami cana l i sof BNＧMgAlON ys PO２ ＝０ ２１×１０ Pa PN２ ＝０ ７８×１０ Pa t hec hang e c ompo s i t e s o ft heG i bb sf r e ee n e r nt heabov et h r e er e a c t i on sa t gyi XRD p a t t e r ns howst h a tt h ema i nph a s ec ompo s i Ｇ d i f f e r e n tt emp e r a t u r e si ss howni nF i ５．Ast hep i c t u r e g t i on so fma t e r i a ls s t ema r e MgAlON,S i a l ona ndBN, s y hows,unde rt heexpe r imen t a lcond i t i ons,ΔGi nt he a nde v e r s ed i s t r i bu t i oni sno tun i f o rm．Ea c hg r a i n abovet ypha h r e er e a c t i on si sf a rl e s st hanz e r o,wh i c hme an s w i l lbeexpos edt oa i rand may beox i d i z eda tt he t ha tBN,MgAlONandS i a l onma eox i d i z e d． Be c au s e yb s amet ime．Theox i da t i ono fma t e r i a l sa c t ua l l a nb e o yc fr e a c t i onk i n e t i c s,t her e a c t i ons e e di sv e r l owa t p ys ( r e a r d e da st h eox i d a t i onc omb i n a t i ono fMgAlON Th e l g owt emp e r a t u r e,wh i l et heox i d a t i onr e a c t i oni sr a i da t p a s s ume df o rmu l ai sAl i a l onand h i emp e r a t u r edu et ot he rma la c t i v a t i on． gO),S ２３ O２７ N５ xM ght
I s sue５ Pr epa r a t i onandOx i da t i onRe s i s t anc eo fBNＧMgAlON Compo s i t e sbyHo t Ｇp r e s s i ngS i n t e r i ng
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F i ５ Re l a t i on s h i ft emp e r a t u r ewi t hΔG i n g po r e a c t i on s( １)t o( ３)
２ ２ ２ Ox i da t i o npr o c e s sandc ha r a c t e r i s t i c sana l s i s y Ox i d a t i onb e h a v i o ro fma t e r i a l swa ss t ud i e da ndt h e t emp e r a t u r e swe r ema i n t a i nedf o r３ha t１０００,１１００, １２００and１３００ ℃ ,r e spe c t i ve l i ６showsXＧ r ay y．F g
d i f f r a c t i onpa t t e rnso fs amp l e sa f t e rox i da t i oni na i r a t１３００ ℃．Compa r edwi t ht heXRDpa t t e rnsbe f o r e ox i da t i ono fBNＧMgAlON,d i f f r a c t i onpe akso fMg Ｇ AlONandBNi nt hes amp l e shavec omp l e t e l i s ap Ｇ yd a r ed,p r oduc i ng magne s i uma l umi n i umsp i ne land pe c o rundum．Wi t hou tBNo rB２O３i nt hep r oduc t, i ti s i nd i c a t edt ha tB２O３ ont hesu r f a c ei sen t i r e l Ｇ yevapo r a t eda f t e rox i da t i on．The ma i npha s e so ft hes amＧ r eCaAl２S i２O６ ,CaAl４O７ , l e sa f t e rt heox i da t i ona p Al２O３ and MgAl２O４ ． F i ７s howsBNＧMgAlON′ sSEM mi c r og r aphso f g
F i ６ X Ｇ r a i f f r a c t i onpa t t e rn so fs amp l e s g yd a f t e rox i da t i oni na i r
sur f a c e so ft hes amp l e sox i d i z edi na i ra t１０００－ １３００ ℃ f o r３h． I tshowst ha twhent heox i da t i on t empe r a t ur ei s１０００ ℃ ,t he s amp l e ′ssur f a c ei s smoo t handsh i ny．Anox i del aye rf o rmsa f t e rox i da Ｇ , t i on a l ong wi t hsma l lho l e sgene r a t edt hr ought he ove r f l owi ngo fN２ ．At１０００ ℃ ,t hed r i v i ngf o r c eo f ox i da t i onr e a c t i oni sl ow,sot heox i da t i on oc cur s f i r s ti nt heg r a i nbounda r rde f e c tpos i t i ons．Wi t h yo t hei nc r e a s eo ft empe r a t ur e,t he mo l t enox i def i lm r adua l l o rmsont hesur f a c eo f ma t e r i a l,wh i ch g yf , c anr ap i d l a lt hepo r e sandmi c r oc r a cks t he r eby yhe e f f e c t i ve l r even t i ngt hef ur t he re r o s i ono foxyg e nt o yp
( a)１０００ ℃ ,３h; ( b)１１００ ℃ ,３h; ( c)１２００ ℃ ,３h; ( d)１３００ ℃ ,３h．
F i ７ SEM mi c r o r aph so fs u r f a c e so fs amp l e sox i d i z e di na i r g g
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J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２２
t hema t e r i a l． F i ８s c r og r a so ft h ec r o s ss e c t i on g howsSEM mi ph o fBNＧMgAlON a f t e rox i da t i ona t１０００－１３００ ℃ f o r３h． I tshowst ha t,a f t e rox i da t i ona t１０００ ℃ ,
t hesubs t r a t ema t e r i a l so fBNＧMgAlONa r ei ngood , c ond i t i onandi nt hec r o s ss e c t i on ox i del aye rdoe s no tappe a robv i ous l h i ss t age,t heox i da t i on y．Att i nc r e a s ei sve r l ow andt heox i da t i on p r o c e s si s ys ma i n l t r o l l ed by t he ox i da t i on r e a c t i on．Wi t h y con t hei nc r e a s eo ft empe r a t u r e,t he po r e si nc r e a s ea t １１００ ℃ andt hes amp l eox i da t i oni sbe t t e rpene t r a Ｇ t edt hant ha ta t１０００ ℃．Ox i d i z eds amp l e sa r ed i v i d Ｇ edi n t otwol aye r s．Theou t e rl aye ri st heox i del aye r , madeupo fox i de s sucha sAl２O３ andCaAl２S i２O８ , wh i l et hei nne rl aye ri st hesubs t r a t ema t e r i a l．The r e i snoobv i oust r ans i t i onl aye ri nt he mi dd l eandt he ox i da t i ono fs amp l ei son l t h i nt hes c opeo faf ew ywi
mi c r ome t e r sont hesur f a c e．Theox i da t i onf i lm p r e Ｇ ven t soxygenf r omf ur t he rpene t r a t i ngi n t ot he ma Ｇ , t e r i a lsubs t r a t e sot heox i da t i oni nc r e a s ei sr e l a t i ve Ｇ l l ow．Af t e rox i da t i ona t１２００ ℃ f o r３h,t heox Ｇ ys i def i lm wi l lbe comeacompa r a t i ve l h i ckdens el ay Ｇ yt e r．The s amp l es e c t i on i s obv i ous l i v i ded i n t o yd t hr e el aye r s:ox i da t i onl aye r,t r ans i t i onl aye rand subs t r a t ema t e r i a l．Theou t e rmos tl aye ri st hewe l l Ｇ , d i s t r i bu t ed and compa c t ox i de l aye r wh i ch c an maket hepo r e sc l os ed,e f f e c t i ve l t opp i ngt heoxy Ｇ ys i f f us i ont ot hei ns i des amp l eandi nh i b i t i ngt he gend ox i da t i onr e a c t i on．Whent het empe r a t ur er i s e st o １３００ ℃ ,t heox i del aye ri sr e l a t i ve l oos ecompa r ed yl wi t ht ha to f１２００ ℃．Thepo r e sa r epene t r a t edand i n t eg r a t edandt heox i da t i ono ft hes amp l e sa r ef a r de epe r．Att he momen t,t heox i del aye ri spo r ous, wi t ht het h i ckne s so fabou t１００μm．Thee f f e c tt op r o Ｇ
( a)１０００ ℃ ; ( b)１１００ ℃ ; ( c)１２００ ℃ ; ( d)１３００ ℃．
F i ８ SEM mi c r o r aph so ft h ec r o s ss e c t i ono fBNＧMgAlONox i d i z e d g g
t e c tt hei n t e rna lsubs t r a t ei sr e l a t i ve l akened． y we Ac co rd i ngt oSEM r e su l t so ft heBNＧMgAlON c ompos i t e sa f t e rox i da t i on,whent heox i da t i ont emＧ , e r a t u r e i sh i h e rt h a n１ ０ ０ ０ ℃ t h eB N Ｇ M A l p g g ON , c ompos i t e swi l lbeox i d i z edi na i r gene r a t i ng mag Ｇ ne s i um a l umi na t esp i ne l,who s ec on t en to fa l umi n Ｇ ( i umox i d ei sf a rh i h e rt h a nt h et h e o r e t i c a lv a l u e a l u Ｇ g mi n ai nt hes up e r s a t u r a t e ds t a t e)a tt h i s po i n t．The sp i ne li si nt heme t a s t ab l es t a t e．Whent heox i da t i on t empe r a t ur er e a che s１３００ ℃ ,α ＧAl２O３ wi l lp r e c i i Ｇ p
t a t ef r omt hesp i ne li nt he me t a s t ab l es t a t e．Then, t heα ＧAl２O３ a f t e rde so l ven t i z i ng wi l lbed i s t r i bu t ed a r oundt hesp i ne l．The s et i nyg r a i nso fα ＧAl２O３g r ow r adua l l th i empe r a t ur e, wh i l et he sp i ne l g ya gh t r a i nsbe comesma l l e r．Thes e r i e so fs t ruc t ur echan Ｇ g swi t h i nt hema t e r i a l swi l lgene r a t eac e r t a i nvo l Ｇ ge umee f f e c t,c aus i ngt hel oos ene s so ft hes t ruc t ur eo f , t heox i del aye r．The r e f o r ei tc anbes e ent ha tt he ox i d a t i onme c han i smo ft heBNＧMgAlONc ompo s i t e si s [ ２６] b a s i c a l l i d e n t i c a lw i t ht h a t o f r e v i o u sw o r k ． y p
I s sue５ Pr epa r a t i onandOx i da t i onRe s i s t anc eo fBNＧMgAlON Compo s i t e sbyHo t Ｇp r e s s i ngS i n t e r i ng
２ ２ ３ Dynami c sana l i sofoxida t i onpr o c e s s ys F i ９ s h o w si s o t h e r m a lo x i d a t i o n m a s s i n g ga , , cu r ve so fBNＧMgAlON a t１０００ １１００ １２００ and １３００ ℃． I tshowst ha tox i da t i on ma s sga i no fBNＧ MgAlONi nc r e a s e s wi t ht her i s i ng o ft empe r a t u r e． Theox i da t i onma s sga i no ft hes amp l ei sve r i t t l e yl a t１０００－１１００ ℃．Att hei n i t i a ls t ageo fc ons t an t t empe r a t ur eo f１２００ ℃ ,ox i da t i onr a t ei sa c c e l e r a t ed andox i da t i onma s sga i no fun i ta r e ashowst het end Ｇ enc f obv i ousi nc r e a s e．Wi t ht he ex t ens i on o f yo , t ime ox i da t i on ma s s ga i no ft hes amp l e be c ome s s l ow,be c aus et het h i ckne s so ft hec ompa c tox i de l aye ri nc r e a s e s,en l a r i ng t he ox i da t i on r e s i s t anc e g ande f f e c t i ve l r even t i ngt hei n t e rna ld i f f us i on o f yp oxygent ot hes amp l e．At１３００ ℃ ,t heox i da t i on ma s sga i n i ngi nc r e a s e ss i i f i c an t l spe c i a l l r Ｇ gn y,e ydu i ngt he p r e l imi na r t ageo fox i da t i on．Be c aus eα Ｇ ys Al２O３ p r e c i i t a t e sf r omt hesp i ne li nt heme t a s t ab l e p s t a t eandt heox i del aye rbe c ome sl oo s e,t hef unc t i on t oi s o l a t eoxygenaba t e s．Bu twi t ht heex t ens i ono f t ime,t heox i da t i onspe edwi l lg r adua l l l owdown． ys
F i ９ I s o t h e rma lox i da t i onma s sg a i nc u r v e so f g BNＧMgAlONa td i f f e r en tt emp e r a t u r e s
４２９
F i １０ Ox i d i z i ngk i n e t i cc u r v e so fBNＧMgAlON g T a b l e１ Ox i d a t i o nr a t ec o n s t a n ta ndc o r r e l a t i o nc o e f f i c i e n t Ra td i f f e r en tt emp e r a t u r e so fBNＧMgAlON /℃ Tempe r a t ur e
k
R
１０００
０ ０１０２５
０ ９９４６４
１２００
０ １６６０４
０ ９９９８５
１１００ １３００
０ ０２４００ ０ ３９０９８
０ ９７８１２ ０ ９８０５９
r v e sa r el i n e a r,i nd i c a t i ngt ha tt he ma t e r i a l ′sox i d a t i on k i ne t i c sf o l l owst hel awso fpa r abo l awonde r f u l l y． Ther e l a t i onsh i twe en pa r abo l i cox i da t i on p be o l l ows r a t econs t an tandox i d i z i ngt empe r a t ur eT f t hef o rmu l aAr rhen i usl n k＝l nA －E/RT ( Ei st he /mo a c t i va t i ono fchemi c a lr e a c t i on,J l;A i sf r e Ｇ / ) kv s． １ T cur vei sas t r a i tl i ne, a c t o r． l n quenc yf gh a sshowni nF i １１．Thes l opeo ft hes t r a i tl i nei s g gh －E/R andt hei n t e r c ep ti st hel nA i nF i １１,and g t husappa r en ta c t i va t i onene r hef r equenc gyE andt y anbec a l cu l a t ed． E ,A andR o ft hel i ne a r f a c t o rA c r eg r e s s i ona r el i s t edi nTab l e２．
Wh i l eS i３N４c e r ami c si si nt hep r o c e s so fox i da Ｇ t i on,i ti sgene r a l l c o n s i d e r e dt h a tt h e r o w t ho f y g ox i del aye ri sc on t r o l l edbyd i f f us i on．Thep r o c e s so f ox i da t i onk i ne t i c si so f t eni n t e r r e t eda spa r abo l a, p f o l l owi ngt heru l e so fpa r abo l i cr a t e: ２ ( / ) ( Δm S ＝k t＋C ４) whe r e,Δm i sga i n i ng ma s so ft hes amp l e;Si ssu r Ｇ sox i da t i onr a t ec ons t an t; ti s f a c eo ft hes amp l e;ki ox i da t i ont ime;andCi sc ons t an t．
F i １０showst ha tt her e l a t i onsh i twe ent he g pbe squa r eo ft heox i da t i on ma s sva l ueandt ime．The l i ne a rs l opei st heox i da t i onr a t ec ons t an ta td i f f e r en t t empe r a t ur e s．Tab l e１g i ve st heox i da t i onr a t ec on Ｇ s t an tandt hel i ne a rr eg r e s s i onc o r r e l a t i onc o e f f i c i e n t a td i f f e r e n tt emp e r a t u r e s． F i １０showst ha ta l lt hecu Ｇ g
F i １１ l n kv s． １/T c u r v eo fBNＧMgAlON g Tab l e２ Ox i da t i onk i n e t i cpa r ame t e r so fBNＧMgAlON E/( Jmo l－１) ２ １３×１０５
A
R
４ ６６×１０６
－０ ９８２９２
４３０
J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２２
３ Conc l u s i on s ( １)Th e r ea r e MgAlON,S i a l ona ndBN ph a s e s bo t hb e f o r ea nda f t e rho t Ｇ r e s s i ngs i n t e r i ng．CaAl p ４O７ w i l ld i s a e a ra f t e rs i n t e r i ng,wh i l eal i t t l eCaYAl pp ３O７ , r a t e s wh i ch de c r e a s e sg r adua l l t ht hei n Ｇ gene y wi c r e a s eo fs i n t e r i ng t empe r a t u r e．The s t ruc t u r eo f BNＧMgAlONc ompo s i t e sa f t e rs i n t e r i ngs n t h e s i s i s y we l l Ｇ d i s t r i bu t edandc ompa c t,wi t ht hepo r ed i ame Ｇ t e ro fabou t２－５μm．Al,Mg,OandNa r er e l a t i ve Ｇ , l l l Ｇ d i s t r i bu t edi nt hema t e r i a l wi t ht heh i s t ywe ghe Alandt hel owe s tN． ( ２)Thema i npha s e so fBNＧMgAlONc ompo s Ｇ , , i t e sa r eCaAl i CaAl Al nd MgAl ２S ２O６ ４O７ ２O３ a ２O４ ． Af t e rox i da t i ona t１０００ ℃ f o r３ h,t hesubs t r a t e ma t e r i a li si ngoodc ond i t i onandox i da t i onma s sga i n i nc r e a s e ss l owl t e rox i da t i on a t１１００ ℃ ,t he y．Af s amp l ei sd i v i dedi n t otwol aye r s．Theou t e rl aye ri s t heox i del aye rmak i ngupo fox i de s,sucha sAl２O３ andCaAl２S i２O８ ,wh i l et hei nne rl aye ri st hesub Ｇ s t r a t ema t e r i a l．The r ei snoobv i oust r ans i t i onl aye r i nt hemi dd l e．Thes amp l ea f t e rox i da t i ona t１２００ ℃ c anbeobv i ous l i v i dedi n t ot hr e el aye r s:ox i da t i on yd l aye r,t r ans i t i onl aye randsubs t r a t e ma t e r i a l s．The ou t e rmos tl aye ri swe l l Ｇ d i s t r i bu t edandc ompa c t,e f Ｇ f e c t i ve l r even t i ngoxygenf r omd i f f us i ngt ot hei n Ｇ yp t e rna ls amp l eandi nh i b i t i ngt heox i da t i onr e a c t i on． ( ３)Af t e rox i da t i ona t１３００ ℃ ,t het h i ckne s s o fox i del aye ri nc r e a s e sobv i ous l hes t ruc t u r e yandt i sl oo s eandpo r ous．Th i si sc aus edbyt hesupe r s a t u Ｇ r a t eda l umi n i um ox i de de s o l ven t i z i ng f r om sp i ne l． Att h i spo i n t,t hepr o t e c t i ono ft heox i da t i onl aye r t ot hema t e r i a lde c r e a s e ss i i f i c an t l gn y． ( ４)Theox i da t i on p r o c e s so ft he ma t e r i a la t ２ ＝ １０００－１３００ ℃f o l l owst h ep a r a bo l i cr u l e:( Δm/S) k t＋C ．Theox i da t i onr a t ec ons t an t sa t１０００,１１００, １２００and１３００ ℃ a r er e s e c t i v e l ０１０２５,０ ０２４００, p y０ ０ １６６０４and０ ３９０９８．Theappa r en ta c t i va t i onene r Ｇ /mo fox i da t i onp r o c e s si s２ １３×１０５ J landt he gyo f r equenc a c t o ri s４ ６６×１０６ ． yf Re f e r enc e s:
[ １] YG．Di ng,J S．Wang,G．Wang,S．Ma,QG．Xue,J． I r on
S t e e lRe s． I n t． １９ ( ２０１２)No ６,９ Ｇ １３． [ L．L i u,Z F．L i,X X．Xue,J． I r onS t e e lRe s． ２] Z D．Yang,S I n t． １４ ( ２００７)No ６,３２ Ｇ ３６． [ ３] C J．Deng,YR．Hong,X C．Zhong,J L．Sun,J．Un i v．Sc i． Te chno l．Be i i ng７ ( ２０００)９６ Ｇ ９８． j [ ４] B W．Duan,Re s e a r chand App l i c a t i ono f MgAlON Compo s Ｇ i t e s,Ti en t s i nUn i ve r s i t an i n,２００８． y,Ti j [ ５] Z T．Zhang,Syn t he s i sand Cha r a c t e r i z a t i ono f MgAlONＧBN Re f r a c t o r i e s,KTH Schoo l,S t o ckho lm,２００６． [ /Bo /Co ６] S． Zhao,Magne s i um Al umi num Oxyn i t r i de r onNi t r i de Ｇ r undum Como s i t eRe f r a c t o r i ve r s i t fSc i enc eand y,WuhanUn yo Te chno l ogy,Wuhan,２００４． [ ７] T．Wi d ema n,L G． Sn e ddon,Ch em．Ma t e r． ８( １９９６)No １,３ Ｇ ５． [ ８] B．Tour e l e,D．Co r nu,H．Vi nc en t,J．Bou i x,Adv． y,P．Mi Func．Ma t e r． １２ (２００２)２２８ Ｇ ２３４． [ ９] W． Zhang,HJ．Wang,Z H． J i n,Or dnanc e Ma t e r．Sc i．Eng． ２７ ( ２００４)No ５,５８ Ｇ ６３． [ i,NF．L i,Ce r ami cS t ud i e sJ our na l１１ １０] HQ．Zhang,Y．Da ( １９９６)No ２,８３ Ｇ ８７． [ f r a c t o r i e s４１ ( ２００７)No １,３７ Ｇ ４０． １１] X S．Wang,F．Cao,Re [ １２] X R．Guo,S t udyonFabr i c a t i on,Pr ope r t i e sand Mi c r o s t r uc Ｇ t ur eo f Al２O３—Baux i t e Ｇ ba s ed MgAlON Compo s i t e,Zheng Ｇ zhouUn i ve r s i t zhou,２００４． y,Zheng [ １３] B． L i u,C Q． Peng,R C．Wang,X F．Wang,T T． L i,Z Y． i n． J．Non Ｇ f e r r ousMe t． ２２ ( ２０１２)２３０２ Ｇ ２３１０． Wang,Ch [ L．Sun,Y R．Hong, ng,J G．Zh a ng,HZ．Wa １４] X T．Wa ng,B Re f r a c t o r i e s３８ ( ２００４)６６ Ｇ ６９． [ L． Sun,Ch i n． J．Non Ｇ C． Zhong,J R．Hong,X １５] C J．De ng,Y f e r r ous．Me t． １０ ( ２０００)Supp l． １０,３９ Ｇ ４１． [ L． Sun,Re f r a c t o r i e s C． Zhong,J １６] C J．Deng,YR．Hong,X ３５ ( ２００１)No １,４ Ｇ ７． [ １７] J C．Labbe,A． J e anne,G．Rou l t,Ce r ami c sI n t e r na t i ona l１８ ( １９９２)No ２,８１ Ｇ ８４． [ s． I r onandS t e e l１２ ( ２００１)No ６,１ Ｇ ５,１４． １８] X C． Zhong,Re [ i,J our na lo ft heEur ope an D．Teng,WC．L １９] Z T． Zhang,L Ce r ami cSo c i e t ２００７)３１９ Ｇ ３２６． y２７ ( [ ２０] Z T． Zh a ng,S． S e e t h a r ama n,WC． L i,Me t a l l．Ma t e r．T r a n s． B． ３７ ( ２００６)６１５ Ｇ ６２１． [ r am．So c． ２１] G D．Qu i nn,N D．Co r b i n,J W．McCa u l e y,Am．Ce Bu l l． ６３ ( １９８４)７２３ Ｇ ７２９． [ ２２] HF．L i,Fabr i c a t i onandPr ope r t i e so fMgAlONandCompo s Ｇ i t eRe f r a c t o r i e s,Wuhan Un i ve r s i t fSc i enc eand Te chno l o Ｇ yo gy,Wuhan,２００２． [ ２３] A．Yamaguch i,Pr a c t i c a lThe rmodynami c sandI t sApp l i c a t i on i n Hi r a t ur eCe r ami c s,WuhanI ndus t r i a lUn i ve r s i t ghTempe y Pr e s s,Wuhan,１９９３． [ ２４] Q． Zhen,WC．L i,Ch i n． J．Ma t e r．Re s． １４ ( ２０００)２７ Ｇ ３１． [ ２５] Y J．L i a ng,Y C．Ch e,Th e rmo dyn ami cDa t aHa ndbo oko fI no r Ｇ a n i cCompound s,No r t he a s t e r n Un i ve r i t e s s,Shenyang, g y Pr １９９３． [ ２６] HX．Zhang,S t udyonFundamen t a l so fSyn t he s i sandPr op Ｇ e r t i e so fS i ng l e Pha s e MgAlON,Un i ve r s i t fSc i enc eand yo Te chno l ogyBe i i ng,Be i i ng,２００３． j j