1.
 Influence of Reaction Temperature and Pressure in the Barium Ferrite Synthesis by Supercritical Water Crystallization






 

      

   

* ^†

 

* 

(2001 2 22 , 2001 5 30 )

Influence of Reaction Temperature and Pressure in the Barium Ferrite Synthesis by Supercritical Water Crystallization

Sung Chan Nam, Gun Joong Kim* and Sangdo Park^†

Korea Institute of Energy Research, Daejeon 305-600, Korea

*Department of Chemical Engineering, Inha University, Incheon 402-751, Korea (Received 22 February 2001; accepted 30 May 2001)



  Ba(NO3)₂, Fe(NO₃)₃9H2O KOH      

 !"# $%&  '()*+. , - ./ 01, 2345 67 89 : ;<=


>? $%5@ ABC D  E*FG, H >? IJ@ 8KL E@ MFN OPQ+. RSO !"# $%

&  TU- <V 01, 2345 89 : >? IJ WX 2Y, 67 89 :Z@ [

>? IJ \% ]*+. :Z, TU- <VZ@ 2345 2367 ^ >? IJ_ '`K@ ab \

" cdKe+. fg, hi # 67 40 MPa, j(MP2) 45_ 200^oC, 23kl 45@ 400^oC, imno 100

!N Ke p ;<= >? qr@ stuB vwB cd)*FG, >?IJ@ 0.1-0.2µmN ^xy zw >?

{_ OPl*+.

Abstract−BaO
6Fe2O₃ was produced by hydrothermal treatment of barium nitrite, ferric nitrite and potassium hydroxide under supercritical water conditions. The crystallinity and size of the barium hexaferrite particles were enhanced by increasing the reaction temperature and pressure in the batch system. In the continuous synthesis process, the particle size was decreased by increasing the reaction temperature but was not changed when the reaction pressure was increased. The reaction tempera- ture is a major operational variable for the control of particle size in this process. In particular, 0.1-0.2µm fine particles were synthesized at a pressure of 40 MPa, mixing point(MP2) temperature of 200^oC, tubular reactor temperature of 400^oC and residence time of 100 sec. The particle size distribution was very narrow.

Key words: Supercritical Water Crystallization, Hydrothermal Treatment, Barium Ferrite

†E-mail: sdopark@kier.re.kr

1.  

(BaO 6Fe2O₃)    , 

      !" #$%  "& '(

)*+ ,$-. ./, 01 23$), 45 6+ 7" 8 9 :"; <= '( >: ?@ AB CDE  F : G FH, IJK HDTV L# tapeM, NO@ =P >: QRST UV )*+ " "& WX . Y" "& WX Z[\) F-.

]^M, )*+ " "& WX #$" _`a b c d e

" ,// f), d e" gh ijk $, l"m K/ g

n+ ojk /- p, qr s-t" 89 uvw xyzT {

|/ z }  E  ~, 'a € q z x

‚!) F-[1-3]. )*+ ""&#
ƒ } $ „ 3 „…zT l5 †3z ‡ ˆ } z p ‰Š!H F-.

„…zV 6+, ‹+, ŒŽ+, m‘ „’ z ‡ “Œ qr

' ”• e" –/ — \" 89, ”• e" ˜

 {|$ ™, ] e" gh ./ š-. l5 †3z ›œ, d e" gh |/ ”•ƒ } E  F- :GV FM,

ž" Œm‘ )6a #ŸQ k $, ¡ ¢ -Q ˆ£5 T3

 ¤¥k $" 89 ¦ D§¨ ©), n Jª p «1¬ £ nm‘  $" _$­ ²Ž³ #´ . µ^5ƒ mT ¶·

 39 4 2001 8

ˆ £5$­ g` / nm …¸Q¹ "º, „3

°»$) b m †3‘ ‡ |  œ/ ¼ ½¾¿ F-. ]

^M, ˆ} z ÀQ Œ Q; Á, ˆ £5T3 Âgw

Ã!" 89 bn  ÄV 9G ) F-.

žÅÆa } V | Çb T 7V Th+ƒ "ž

$) F, Th+ È& d e" fjÉ-. ÊË, žÅ Æ Ìa 6+Í ÎÏ ”J/ Ð `a+ ˆÀ01 ‘

‡ m‘¸Ñ Ò  #$Ó qÔE  F" 89 C1 qra T h+ Õ ' nm~ µme" dƒ Ö  F, 

#´ ‹+, X×Q; p qyÐ ` †3 : , †3

, d  ‡ d e" ghƒ ØÓ HE  F-. ./, X

×Q; Ù" 89 ڎw } „3 ,$­ bn ÛÜ 7|

 F, ÝÞ Œ"ƒ #$% Bß:àƒ ;†$Ó fE

 F-[4].

žÅÆ †3z /
 ڎw } „3a d ÌM e" Ð K/ ¬V áâ!H F ™ã ' ä ڂ „3Ð _Z Ã!å, } qrV ˆ} z qr

 ' †3$æ-. œç Âgw Œ"ƒ #$­ žÅÆ qr

a Zx ŒÐ¬ Œ6+ ‡ ÎÏ ]5) ½è5 ‹+é p Ð

 ' b !
 Ò  gê$æ), Âgw „3

a ÖV †Tƒ ëK ڎw } „3 €¸$­ 8 b c b m d, e"Í g p K$­ )ì$æ-.

2.   

2-1.
    

QíV îï×(non-pulse) )Îðñ(PUS-11, GL SCIENCE Co.)ƒ 

#$­ Œ" ò ƒ #$Ó ó$" _` m K/ #`+

œ$) :à ôw + é“1 fV Qí¬ Ba(NO3)₂(Junsei, 98.5%), Fe(NO₃)₃ 9H2O(Showa, 98%), KOH(õn, 85%)ƒ ö6  #`

$­ #$æ,  #´V Fe(NO3)₃ 9H2O ‹+ƒ Âgw

›œ 0.05 M, ڎw ›œ 0.02 M )3$), Ba(NO3)₂ ‡ KOH

$­ q$æ-[5].

Fe/Ba mole ratio = [Fe(NO₃)₃]/[Ba(NO₃)₂] (1)

Alkali mole ratio(R) = (2)

b c Q Õ× Jª/ ¢, rq"(60^oC)a 24Q; rq

$­, XRD(Rigaku, CuKα radiation) g gê$æ, SEM(Philips, XL-30) gê ÷$­ b m  ‡ d e"ƒ ø3$æ-.

2-2.  

žÅƃ Œ WX $­
ƒ } $ Bß

Ã$" _/ Âgw Bß:à ‰ù+ƒ Fig. 1 +Q$æ-. Âg w Bß:à )Î Œ", ˆq(molten salt bath), ¡q(water bath)

 eÓ ‚gE  F-.

 2.57 cm, 7.6 cm òô #¨V 35 cm³-. Œ" òô 6+ƒ

ø3$" _$­ K- ˆ¸Kƒ #$æ), ÎÏV NOSHOK(Germany) ÎÏÆ ‡ pressure transducer(9368612, XPRO Co.)ƒ #, û <ü

$­ ø3$æ-.

Œ"ò ÎÏ 40 MPa $æ 8 ý6Q; '( 6+Ѓ

Fig. 2 +Q$æ-. Fig. 2a <Q
Í U 400^oCs ý6!

? Dx! Q;V 100ž”þ –ÿ
( ý6Ž+ƒ Mò)

F, ] ¢ |3/ 6+ƒ l$) F-. ]5), Œ ’

ÿ †Q¹" _` ¡qa Œ"ƒ ’¡$æ 8 ¡Q

;V 20g $æ-.

ˆq(molten salt bath) Œ" òô 6+ ‡ ÎÏ ’Žÿ  ýQ¹), ./ Œ6+ƒ |3$Ó l$" _$­ #! ¼,

 ‡ J Á  40 cm, 30 cm)  30 cm  ô 36 l-.

ˆ WX KNO3Í Ca(NO3)₂ 4H2Oƒ 1 : 1 éÜ }$­

#ŸQ , heater #¨V 5 kW), ˆq 6+ PID(/—, DX9) 6+ qÔ" qÔ$æ-.

/, Œ" ò 6+ ‡ ˆq ò 6+ƒ |3$Ó l$" _

$­ Œ"ƒ 250 rpm “Œ$æ, ¡ 6 m(25^oC)

 #$æ-. Œ" ‡ “Œ" Âgw :à ñÅ )3!H F, ˆq ‡ ¡q lÎw BÊ ` $ ), Œ

 †c ¢ Œ"ƒ ˆqa òH ¡q {V mover

ƒ #$­ { f{$Ó Æ!H F-.

2-3.  

BßB ᧠ڎw Bß:à ‰ù+ Fig. 3 Mòå-. B ß:à  #´ Zd _/ ðñÍ ˆ", Œ" ‡ b m [KOH]

3 Fe NO[ ( ₃)₃]+2 Ba NO[ ( ₃)₂]

( )

---

Fig. 1. Schematic diagram of the batch apparatus.

1. Reactor 4. T, P indicator

2. Molten salt bath 5. Shaker

3. Water bath 6. Mover

Fig. 2. Reactor temperature as a function of time at pressure of 44.01 MPa.

 Â :à ‚ !H F-.

ðñ  #´ 23/ Zd _$­ îï× )Îðñƒ #

$æ, =V 1/4" SUS 316 tubeÍ )Î# tube fitting(Swagelok)

#$æ-. ˆ #/ Õ×Í ö6 K" „" h¶

!H F nD m #$) F% ƒ ¤$" _` 4- channel degasser(Jour Research, X-ActTM)ƒ #$æ, ¼

ô@ Œ ŠbE  F ôŒm b  $æ-.

ˆ" ˆT Œ" <6 _$­ PID 6+ H"(Propor- tional Integral Differential, /—, DX9)ƒ :/ = ¸"(electric furnace, |H, 15 kW)Í IR heating chamber(E4-10(SS),  A$e, 8 kW)ƒ #$æ,  ôg 6+ K- ˆ¸K

ø3$æ-.

ڎw } „3 €¸$" ¸ Bß6+ ‡ ÎÏ K/ 3/

<3 _` pressure transducerÍ ˆ¸K ‡ 6+ qÔ"(Model Hy- P100)ƒ signal generator(Model 6500, GLA Elettronica)ƒ #$­ zero

pointƒ  #$æ-. 8 ¸"ƒ ¤¥ M6 ˆ 6+ 

36+Í 6+I ±1^oCò 3$æ-.

žÅÆ̃ l$) F Œ"a öŒ ÉÃc ¢ Œ

" ‚ b m Œ ’Ž$Ó Q¹" _$­ 2 =

ˆ“ "ƒ ô$­ Ž$Ó ¡$æ-. Œ" ”5 ˆc ˆ

Í  #´ }Gaô@ ˆ“ " d‚s, Œ" Á

ƒ qÔ¶! X× Q; H$æ-. Œ"  =(vertical tube reactor) SUS316 tube(103 MPa, Á 600 cm, ò› 0.32 cm, ô 48.2 cm³) f!å-.

Œ"òa }´ X×Q;(τ)V w (3)T U "Qc-.

(3)

­"a, V: reactor volume, F: mass flow rate

­"a, ρ: density of the reaction mixture

Œ´V ¡ ¢, in-line filter(Swagelok, SS-8F-K4-05)ƒ ¤àa, d e" # b m ­T/ ¢, ŒÆ òô ÎÏ qÔ _ / $Î%Þ(back pressure regulator, Tescom, 26-1722-24)ƒ ÷$­ &

'´ Â$æ-. ¸X ڎw } „3 ÎÏV pressure trans- ducer(XPRO, 9368612)Í Heise gauge(CMM-010485)ƒ #$­ ø3

$æ-.

3.   

 } „3 #$­ Œ6+Í ÎÏ ‡ ½è5 ‹+

é Ð '( žÅÆ †3Œ Ò  ()<*-. ‚X1¬

BßV i) Fig. 1 Âgw :àƒ #$­ Œ6+, ÎÏT ½è5 ‹ +éƒ ÐQ  8, } c b m g ‡  Ѓ )ì$æ ), ii) Fig. 3 ڎw } „3 #$­ }G MP2a b c 1

°Æ ;b m žÅÆ Ì Œ6+Í ÎÏÐ ' }G MP3Í Œ"ò #´ ÷TQ  8,  c C 2°Æ † 3b m gT d Ì p )ì$­ 13 b qr +

$) $æ-. iii) Âgw :àƒ #/ B߆Tô@ žÅÆ † 3 Œ Œ,-. áâ$æ), ڎw } „3 #$­

}G MP3Í Œ"a 6+Í ÎÏÐ '( 2°Æ †3b m Œ,-.  + é“$æ-.

3-1.  

|Œ1¬ ˆ} zM žÅÆ †3z #/ ”• q

„3a BaO 6Fe2O₃ƒ b $ ŒV -ã w (4)Í UV 0

Œw "&c-.

Ba(OH)₂+12Fe(OH)₃
BaO 6Fe2O₃+19H₂O (4) ]^M,
T / 001é Zd$ ›œ α-Fe₂O₃°|

b !, T¨
 Zd$­k BaO 6Fe2O₃ b ! é01 1 0 Œ ½¾¿ F-. ]5) |Œ1 ˆ} za

Fe/Ba ‹+é Õ¶ ' d e" $D¶ 2  F-. 

^/ &V [OH⁻] 6T [Fe³⁺] ‡ [Ba²⁺] 6 Œ Ž+ "¬

$ ¼ °!, |Œ1¬ ˆ} „3a [OH⁻] 6 ‹ + Õ¶ ' d e" fj, b m 0 Õ/- &T |à$) F-[6].

'a, ä ڂa žÅÆÌa Œ6+ Ð ' b c d Ò  ”à — K` +$" _` Fe/Ba ‹+éƒ 2

 ŒQ; 60g R3 4 )3$) Bß Ã$æ-. Œ

6+ƒ 300, 350, 400^oC ÐQ4 ' } c d q ‡  Ì K/ gê†Tƒ Fig. 4Í 5 XRD 56T SEM É  + Q$æ-. b c d Ò  ()< Fig. 4a <
Í U

τ V_ρ ---F

=

Fig. 3. Schematic diagram of the continuous synthesis apparatus.

 39 4 2001 8

§7 —Àa °|
  b !åM, Fig. 5

SEM Éa ÄV 6+a b c d e" fã 2  F

M †3 V 8H ¼ M9-. ]5), 300^oCa b c d j  :;$Ó ±«H ™*ã 2  F, j ü

¸/ †3°Æ +Ñ$ ™V ¼ bc-.

350^oCa b c d ./ 300^oCa b c d<- e"

Õ$æM j ¼ ./ ü¸/ †3 ±«) F ™, 400^oC

a b c d+ †3‘ œ$ <$M ¸Œ1 6+ Õ

¶ ' d †3  Õ$ ¼ ¬E  Få-. ^/

` uê Ž+ =¾" 89 > †3 : ?$" 89

†3‘ œ/ dƒ Ö" _`a Ê ©V ŒQ; @x/ ¼

 °c-.

Fig. 6V Œ6+ƒ 400^oC Fe/Ba ‹+é ‡ R3  2Í 4

|3$Ó )3$) Œ"ò ÎÏÐ ' b c d q  MA XRD 56-. Fig. 6a <
Í U ŒQ; 60g

 $æ 8, ŒÎÏ 28.27 MPa a 231 °|

 b B ¬E  FåM, 22.06T 27.03 MPa

a JCPDS CD "&! ™V EB/ e MF ¬

E  Få-. ^/ l 3$Ó GH ™*þ Œ ;

b m øc-. ]5), Fig. 7V Fig. 6T IJ Œ6+ƒ

400^oC $) ÎÏÐ ' b c
d SEM

É +Q/ ¼-. ŒÎÏ Õ¶ ' d e" Õ

$) F), †3‘V !) Fã ¬E  Få, ÎÏ

28.27 MPaa d e"Í †3+ : 0û/


 d b !åã ¬E  Få-. ^/ ÎÏÐ K/

 d Ò Ð žÅÆ  m Ð ' > ž ÅÆ 7V l¸ÜT l{  ²Žnm K` H= 3+ #

+ . ÎÏ qÔ¶! eÓ ÐQL  F-. 'a, ^/

Ò Kô@  #´ò /M
 #`+M nÆ I Fig. 4. XRD patterns of products at reaction time of 60 min with var-

ious reaction temperature(44.01 MPa, Fe/Ba ratio 2, R ratio 4).

Fig. 5. SEM micrographs of products at reaction time of 60 min with various reaction temperature.

Fig. 6. XRD patterns of products at reaction time of 60 min with var- ious pressure(400^oC, Fe/Ba ratio 2, R ratio 4).

Fig. 7. SEM micrographs of barium ferrite at reaction time of 60 min with various pressure.

 / ŒŽ+ I 89¬ ¼ °c-[4, 11].

-ãV ½è5 ‹+é¬ R3 — K$­ b c gM  ‡

 )ì$" _$­ Bß6+ 400^oC, ÎÏV 44.01 MPa(24 ml charge)a Bß Ã$æ-. Fig. 8 XRD gê†Tƒ ()< R

 b B ½  Få-. |Œ1 Fe(OH)3 pH 7

a …¸ NH, Ba(OH)2 13a …¸ Šb$Ó c -[7]. 'a, R3 0.5a
 b ! ™V ¼V

 #´ R3 ÄV †T ¬$­ Ba(OH)2 …¸ Šb$

<$%, Fe(OH)3 Ba(OH)2Í Œ$ <$) hematite O

¸  NHPã ½  F-.

Sada p[8] †T $ R3 ÕE& d e" $D/

å), R3 Ä& d †3‘V B 2  Få, 

K/ B߆Tƒ Fig. 9 SEMÉ Mòå-.

ä Âgw :àƒ #/ ڂa Ataie p[9] Q9 Š"c BaO Fe2O₃M Kiyama[10] BaO 4.5Fe2O₃p ; b mV R

! ™*-. ^/ l ¸ ڂK Ã/ Âgw(autoclave)

 #/ ˆ} za 4-5^oC/nib ý6!" 89 Œ"ò

 m‘¬ Fe(NO3)₃ . Fe(OH)3 #´ = ý6Ž+ `

;b m α-Fe₂O₃Í UV 23/ m‘K ¸ c S


m‘ »;1 ý6Q¹" 89 α-Fe2O₃Í UV 23/ n

m b !" ¸ FeOOHÍ U
6T Œ  œ/ m

‘ ¸ c S T

gM b !" 89¬ ¼

°c-.

3-2.  

Micro reactorƒ #/ Âgw :à Ãc Bß ÷$­ žÅÆ

 †3z #/ ˆ} zV " ˆ} z é` Wœ Ù V Œ Q;
ƒ } E  Fã ¬$æ,

^/ †Tƒ ëK ڎw } „3 1#$­ Bß Ã$æ -. ڎw } „3 ›œ, m‘ ”5 Uéc ˆÍ O

} ` žÅÆ Ì ’$Ó ý6B ', " Âgw :à α-Fe2O₃Í UV ôb m

 Šb E  FH ŒQ; ’$Ó °QL  F-[5, 11].

|Œ1¬ nm} a #´ ž" ‹+ — b m Ò  # — Zþ, Œ žÅÆÌa Œ6+Í Î Ï — -( qÔ Ð é` d e" ‡ gh+ --V

— ”W-. 'a, ä ڂa }G MP2a b c 1°Æ

g` b m }G MP3Í Œ"òa X×Q;(τ₂) 100

ž )3Q¹), Œ6+  300, 350, 400, 450^oC, ¸X Æ

ÎÏV 35, 40, 45 MPa qÔ$a C 2°Æ öŒ b m Ö V d g ‡ Ì Ðƒ )ì$æ-.

}G MP2 6+ƒ 200^oC, Œ" ÎÏ 40 MPa ]5) X×Q

; 100ž )3$), }G MP3Í Œ" 6+ƒ  300, 350,

400, 450^oC ÐQ¹a } c b m q V ÂgwT IJ

 §7 —Àa BaO 6Fe2O₃°| b !å-. ]^M, Fig. 10 Fig. 8. XRD patterns of products at reaction time of 60 min with vari-

ous alkali molar ratio(R)(400^oC, 44.01 MPa, Fe/Ba ratio 2).

Fig. 9. SEM micrographs of products at reaction time of 60 min with various alkali molar ratio(R).

Fig. 10. SEM micrograph of the products obtained with various tem- perature at 40 MPa(Fe/Ba ratio 2, R ratio 4).

 39 4 2001 8

 SEM Éa <
Í U 300^oCa } c
 

 ›œ Âgw :àƒ #/ Œ6+ Ð ' } c


   300^oC ¼T l/ ̃ ±) F ¼ ¬E

 Få, 350^oCô@ d †3‘ GG !) F ¼ = ìE  Få-. b c d e" }G MP3Í Œ" 6+

400^oCa b c d 0.1-0.2µm3+ fÓ } !å d

+ œ$æ-. ]^M, 450^oC

6+ ý `
( ŒŽ+ b !åX 0.1-0.2µm e"

”• -Q #` ‡ uê ÉÃ!" 89 °c-.

}G MP3Í Œ"a ˆÍ } $­ žÅÆ q r¬ 400^oC +Ñ$, α-FeOOHÍ Ba(OH)2 0 †} ‡ ö Œ

 / °¨X b T3T °¨X inclusion / †3 : T

 ˆ} a<- K°ÿ e" 89 0 †} V ö Œ

V ¤ {Q |HMÓ !, #WÏ $D¶ ' #`+ $D

¶!, h+ ’ÿ Õ$Ó c-. 'a, žÅÆ †3

|/ Ç b T Th+ Õ & "ž $) F" 89 b

M, Œ6+ ¦î ý$Ó ! b c dK; Z[\+ ’

ÿ Õ$Ó !H ]ÿ¾ -Q #` u†3T3 Šb$Ó !H d gh+ šÓ MM & Šb/-. 'a, 1–/ Œ

6+ 3 } c d e"M gh+ — ”à ZxÐ

 c-.

-ã }G MP2a 6+ƒ 200^oC, }G MP3a 6 +ƒ 400^oC, Œ"ò X×Q;(τ₂) 100ž Bßqr  ) 3Q^ S ÎÏ 35, 40, 45 MPa ÐQ¹a žÅÆ Ìa ÎÏÐ b c d e"M d  H_/ — ”à

 =`a Rë$æ-.

ŒÎÏ ÕM $D / b m gÐ |HM ™V

Œ, Fig. 11a <
Í U ÎÏ Õ¶ ' } c


å-.

ŒÎÏ '( de" $D žÅÆ m5 01 Ò  Œ

ÎÏ Õ¶ ' [Ba²⁺]+[OH⁻] [BaOH⁺] Œ #` +

{ ' [BaOH⁺] ‹+ Õ$) >, Ç 0 Õ$­  ¬

` [BaOH<sup>+</sup>] E23/ Fe(OH)3 …` ‡ n / öT3T † 3Œ /
  b  #$Ó !H, f) |/

 É
 ƒ Ö  F" 89¬ ¼ `êc-[4].

^/ žÅÆ †3 Œ,-. ,/ ¼V Âgw Œ"

òô = ý6Ž+Í Ñ5 ”5 Uéc ˆÍ O }

(MP3) ` žÅÆÌ ’$Ó ý6B ', Wœ
( ö

Œ ` b d Ì eÓ Ð$), ²Ž6 Œ Ž+

²Ž6‹+ 1I Ž+w 'a" 89 ÙV X×Q;+ d

  #$" 89-[12]. †T1 jÅÆô@ žÅƗÀ

 Œ ÉÃB ' b ŒŽ+ cd! Âg w :àa b ! ôb m Šb ‡ d e"ƒ CDE  Få-. 'a " Âgw :àƒ #/ ˆ} a


 gM } $" _` 30g-48Q; Dx! ¼T é“E 8 ä ڂ ڎw } „3a 1°Æ g` b mT 2°Æ ö

Œ b m } Q; CD¶! 2gò Œ †!

ŒÒ  Mòå-.

ä ڂ †Ta }G MP2 Œ6+ 200^oCæ 8, }G MP3Í Œ" ›œ 400^oC, 40 MPaæ 8, 2°Æ †3b m

0.1-0.2µm
 °| ÖHd ¬E  Få-.

]5), &u
 gM "1 Ò qÔ ‡ + d

e"ƒ 0.1µm$ q$" _` Co²⁺Í Ti⁴⁺Í UV m‘ à Q   } Q¹ ڂƒ à  F, ¢ js áâ! ™V :à  ôga Šb$ Œ,-. K/ ڂ+ Ž1

ÃE Æe-.

4. 

žÅÆ qra
 b ŒV Wœ
aÓ É Ãc- Âgw B߆Tô@ žÅÆ †3z #/ ڎw } „3+ °| BaO 6Fe2O₃ƒ b E  Få-. ]5), b c d Ò  žÅÆ qr$a Œ6+Í ÎÏ ”J/ Ð

 'a eÓ fœg  Fã ¬$æ-.

Òÿ, žÅÆ †3z / ڎw } „3 ›œ Fe/Ba ‹+

éƒ 2 R3 4 )3/ S }GT Œ"ò Œ6+Í ÎÏ

  400^oC, 40 MPaæ 8, C †3b m 0.1-0.2µm d

ghƒ ± œ/
 °| ÖHP-.

ä Bß ÷$­ žÅÆ qra
( g` ‡ 0 Œ, ]5) ö Œ $­ 2g ò ÙV Œ Q; BaO 6Fe2O₃

ƒ ڎ1 b E  Fã ', " Âgw q „3 é

$­ bn  eÓ QL  Fã ½  Få-.



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J. Am. Ceram. Soc., 81(9), 2461(1998).

6. Seo, S. Y., Rho, S. W. and Park, S. D.: HWAHAK KONGHAK, 38, 75(2000).

Fig. 11. SEM micrograph of the products obtained with various pres- sure at 400^oC(Fe/Ba ratio 2, R ratio 4).

7. Lee, K. H., Lee, B. H. and Yoon, K. J.: J. Korean Ceram. Soc., 22(5), 61(1985).

8. Sada, E., Kumazawa, H. and Cho, H.-M.: Ind. Eng. Chem. Res., 30, 1319(1991).

9. Ataie, A., Piramoon, M. R., Harries, I. R. and Ponton, C. B.: J. Mater.

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