분말사출성형한 W-15 wt%Cu 나노복합분말의 고상소결에 미치는 잔류불순물의 영향

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(1)Journal of Korean Powder Metallurgy Institute Vol. 9, No. 4, 2002. ªöÒÂW; W-15 wt%Cu ¾ªö~ ç²Öö ~º º~®Bb~ 'Ë. J~ÁÒWÁJ* ·&v .³Òò", *ÆÊ. "²Ò Effect of Residual Impurities on Solid State Sintering of the Powder Injection Molded W-15 wt%Cu Nanocomposite Powder Eui-Sik Yoon, Jai-Sung Lee and Tae-Sik Yoon* Department of Metallurgy and Materials Science, Hanyang University, Ansan 425-791 Korea *Bestner, Inc., Seoul 135-280, Korea (Received July 30, 2002 ; Accepted form August 14, 2002). Abstract The effects of residual impurities on solid state sintering of the powder injection molded (PIMed) W15wt%Cu nanocomposite powder were investigated. The W-Cu nanocomposite powder was produced by the mechano-chemical process consisting of high energy ball-milling and hydrogen reduction of W blue powder-CuO mixture. Solid state sintering of the powder compacts was conducted at 1050oC for 2~10 h in hydrogen atmosphere. The densification of PIM specimen was slightly larger than that of PM(conventional PM specimen), being due to fast coalescence of aggregate in the PIM. The only difference between PIM and PM specimens was the amount of residual impurities. The carbon as a strong reduction agent effectively reduced residual W oxide in the PIM specimen. The H2O formed by H2 reduction of oxide disintegrated W-Cu aggregates during removal process, on the contrary to this, micropore volume rapidly decreased due to coalescence of the disintegrated W-Cu aggregates during evolution of CO. It can be concluded that the higher densification was due to the earlier occurred Cu phase spreading that was induced by effective removal of residual oxides by carbon. Keywords: Nanocomposite W-Cu, Powder injection molding, Solid state sintering, Residual impurity. 1.. B . ^ ® . 6, ²;Ç;ç~ &ö; NÊæ¢ B ~V * W;&VFº ªöÒÂW;VF Î"' O»b rJ^® . ;öBº FV ÖB Bê £ 50%~ ôf V º~~V r ^ö ç^ jÏê W-Cu ªö ç²Ö ¢~² >»~ j*~&z>V¦ Ö Ú[ . Ni, Cof ?f B3ö²¢ 1 wt% ~ ²ïÎ&~ ~&z¢ Fê~º W²ÖO» BB : ® b¾, ãÖ Î&>º B3ö²º Cu Væç" ÏÚ 6º .³* zbj ;W~ *êê & ~¢ .¾ . V¢B, ²ÖWB~ Î&ì Ô f Cu W~ W-Cu ªö~ j*~&z¢ Fê~º © ç' .. " Î*¶Öë~ /³ B*" þ WÒòº ÂK ÷'²~ OÒ òB '7j A ® . Fº *~ W~ Òòº ^¢ V6ö çw~º ccê>(6~7 ppm/K) f ¸f *êê(210~230 W/mÁK)¢ ¾æÚV r ^ . ¢>'b W-Cu Òòº Ï»b BB . ¾, Ï;f Cu çb jòî W Ï& j* BV(open pore)j ;W¢~ V r^ö Cu Wö B£j Aº . V¢B, ¢>' ç²Ö; Ôf Cu W~ W-10~15 wt%Cu .j B > ®º F~ ~&z;b rJ 10~15 wt%Cu. 1,2). 3). 4-7). 8). 235.

(2) J~ÁÒWÁJ. 236. f W-Cu~ ~&zf &NB ^B¢ ² îbB W-Cu ¾ªöj Ï~ Ö~&. . W 5 Cu Özbj ªê/bê >²~ö ~ B W-Cu ¾ªöf ²ÖWB~ Î &ì 1200 C ~~ jv' Ôf NêöB j*~ &zö ê~º Ö> ²ÖßWj <º . Ö> ²ÖßWb W-Cu ¾ªöf ªöÒ ÂW;VFö 'Ï~ê j*~&zö ê > ® î . VB ß *çf ªöÒÂW; W-Cu ªöW;Ú& ¢>ªö¢.»b B W;Ú . ôf ç~&zNj ¾æÚî º 6 . * Ö" ö V, W-Cu ¾ªö~ ç²Öf ê³>º ç²Ö ~&zN &~f ®¢ >» j ¢V~, z×, B®B ~>~ ;&êö k 'Ëj > ® . V¢B ªöÒÂW;Ú~ ç ²Öÿf '~ W-Cu Òò¢ B~V * B ;{~² >Ú¢ . J f *Ö"öB ÖB¦V º~~º ê ² 5 Ö²& B>º ";öB W-Cu ¾ª ö~ .V²Ö"; /ê>î º Ö"¢ ~&. . ¾, º~®Bb B>º ";öB WCu ¾ªö~ ç²Öÿö ÚÆ 'Ëj " îºæ& *® ~^6b Îj® . V¢B, öBº º~®Bb Bf W-15 wt%Cu ¾ ªö~ .V²Öÿ"~ ç^&ê¢ Ò~& . ¢ *B b& W-Cu ¾ªöÚ º~®Bb. ~ z' ;f Bÿj ªC~&, " ;öB W-Cu ¾ªö~ ^ æz¢ Ò ~& . þÖ"¦V W-Cu ¾ªö ~ ç²Öÿö ~º º~®Bb~ j «~¶ ~& . Lee. 9-11). o. 12). 13). 14). 2.. þ O». ¾ªöf W blue powder(WO2.9, f Özb(CuO, 1~2 µm)j attritoröB 1 * ÿn Û&çj ê, 2ê >²~ö(200 C/1 h, 800 C/1 h)~ B~& . ªöÒÂW;j * ªö" ÖB~ bj * Wª ÖB(45% Paraffin Wax-15% Bees Wax-30% Polyethylene-10% Stearic Acid(7ï%))¢ ÒÏ~ W-Cu ªö" 60:40 ~ ¦bb 125 CöB 1* ÿn b~& . ² W-15 wt%Cu 30 µm) Cu. o. o. 15). o. Journal of Korean Powder Metallurgy Institute. Fig. 1. Schematic diagram of debinding process.. Ö þj * ÒÂW;Ú~ B·f bÚ¢ 110 C öB 12.5 MPa~ {Kb çã 10 mm~ öÛ;b W;~º *7' O»b &j~& . ÖB º wicking" ª»b >²ª*VöB â 1 ~ 4ê N¾Ò ;b B~ ªöÒÂW ; Þ(PIM)j &j~& . r wick Òò ï «ê 50 nm V~ α-Al O ªöj ÒÏ~& . 6 , bö ÒÏB W-15 wt%Cu ¾ªöj î æW;Ú~ &êf & &² 12.5 MPa~ {K b W; ê, â 1~ ¾Ò¢ ~ jvÞj &j~& . êº Þj PIM Þ" ª~ PM Þ¢ £ . ÖB B¾Òêö PIM (brown part)" PM Þ~ ç&&êº '' &ê~ 36%, 40%& . ²Öf 1050 CöB 2~10* ¯~&, ' Þ~ Z², çã" ¸¢ G;~ ²Ö&ê¢ êÖ~&. . ªö" ²ÖÞ~ ^º 7*ã" "Ò*¶*ãb &V~& . ê²f Ö²~ ï æzº 'F >»" ®WVÚ Ï»j ÒÏ ~ ªC~&, ®Bb ~ çf îæW; Ú~ ö & X-ray photoelectron spectroscopy(XPS) ªC~ Ò~& . ÒÏB photoelectronf Al Kα 1486.6 eV &b, Öö.æ~ b*~º C1s~ b*~(284.3 eV)¢ Ï~ ;~& . º~®Bb~ Bÿj Ò~V* î æW;Ú¢ >²ª*VöB 50 C/min~ ³ê 1050 C ræ ßN~B OÂ>º VÚ H O, CO 5 CH ~ ³êæz¢ '' hygrometryf quadrupole mass spectrometry(QMS)¢ ÒÏ~ *b ª o. 2 3. o. o. o. 4. 2.

(3) ªöÒÂW; W-15 wt%Cu ¾ªö~ ç²Öö ~º º~®Bb~ 'Ë. C~& . ²Ö";öB ^Væzº BET¢ Ï~ î² /îONFj G;~ Ò~& .. 3.. 237. Ö" 5 V. ç²Öÿ â 2f ö ÒÏB W-15 wt%Cu ¾ ªö~ ^¢ & . â 2(a)öB ¾ªöf 500 nm ~~ «¶ Ú ^ ®î . â 2(b)º «¶ f ~¾~ « ¶& jò «¶ oöê aggregate ªj " ® . aggregateº Özb ªêê > ²~ö~ B W-Cu ¾ªö~ *;' ;çb W" Cu «¶ Ú^ ®r WªC b {>î . Aggregate~ ¢¦ªj TEMj Û {& &V Ö", â 2(c)öB º:f ? aggregate f 30~50 nm V~ W-Cu«¶ Ú^ ®rj r > ® . â 3f ²Ö* PM(a)" PIM(b) Þ~ 2 ^¢ SEMb &V Ö" . SEM &VÖ ", ÖB Bê v Þ*~ ^öº N 3.1.. 16). Fig. 2. Oa, b) SEM and (c) TEM micrographs of the W-15 wt%Cu nanocomposite powder.. Fig. 3. SEM micrographs of the (a) PM and (b) PIM specimens after debinding. Vol. 9, No. 4, 2002.

(4) J~ÁÒWÁJ. 238. Fig. 4. Densification process of W-15 wt%Cu nanocomposite powders at 1050oC in H2 atmosphere.. ¢ &V > ì . â 4º >²ª*V 1050 C öB N²Ö~º ÿn PIM Þ" PM Þ~ ç &&ê æz¢ ¾æÞ . 5* ²Öê ç&&ê& /Ï® Ã&~º ©j " > ® . Ú ©f, PIM Þ~ ²Ö* ç&&ê& PM Þ Ô~r öê ®~ 10* ²Öê z ôf ç~&zN j ¾æÚî º 6 . ß®, 5* Fæ~º ÿn PIM~ *ö & ç&&êæzN PM ©j r > ® . º PIM ÞöB ¾æÂ ¸f ~&zNf .V ç²Ö³êö V ©ª j ~ . â 5º 1050 CöB 2~10* ÿn ²Ö PM (a, c, e)" PIM(b, d, f) Þ~ ^ . WCu aggregate 66 WË~º *;' ç²Ö ÿö V¢ ~&z& ê¯>º ©j r > ® . â 4~ Ö"öB ç&'b ¸f ~&zNj ¾æ Þ PIM Þf aggregate V¢ ¾æÚ ® . Ö"¦V PIM Þ ¸f ~&z Nj ¾æÞ ©f *;' ç²Ö"; ² ¢ÚÒV r^ªj r > ® . Lee ö V , W-Cu~ ç²Öf Cu& W b {Öj ~ {ÖB Cu b ï~ Cu& ¢æB W-Cu aggregate& ;W> &æB network ¢ ;W~æ ªö~ >»j Fê >î . f ?f ç²Ö";f Ö PIM Þ öB Cu {Ö" ¢ö ¢ÚÒ º ©j ~ . PM Þ" PIM Þ~ ÂBªö" ¾ Ò ";f ÿ¢~, v Þ*~ Nº ÒÂW;ö o. o. 17). Journal of Korean Powder Metallurgy Institute. Fig. 5. SEM and OM micrographs of the W-15 wt%Cu nanocomposite powders sintered at 1050oC for (a, b) 2, (c, d) 5 and (e, f) 10 h.. ÒÏB FVÖB& B>B PIM Þö ê² 5 Ö²& º~ º 6 . ÖB~ ª ê º~~º ®Bb f «¶ ~ activityö 'Ëj * > ® . 6, ¢>'b ê² 5 Ö²º {Ö ö & Ob j . &6öB, PIM ÞöB º~®Bb ~'Ëj .ç > ® . 3.2. º~®Bb~ ; 5 B â 6f 1050 CöB N²Ö7 PIM Þ" PM Þ~ ê² (a) 5 Ö²ï (b) æz¢ ¾æÚº Ö" . ²Ö* PIM" PM Þ~ º~Ö²ïf N¢ ¾æÚæ p~ . >, PIM Þ~ º~ ê²ïf 0.16 wt%, PM Þ~ ãÖ 0.04 wt%, PIM Þö 4V ôf ê²& º~~ ® . Ú ©f º~®Bb 2* ²Öê &¦ ª B>î º 6 . 6, â 4~ Ö"öB f ?, PIM Þf 9% z ôf &êÃ&¢ ¾æ Úî . º PIM Þf º~ ®Bb , ß® º~ o.

(5) ªöÒÂW; W-15 wt%Cu ¾ªö~ ç²Öö ~º º~®Bb~ 'Ë. 239. ê²& B>º ";öB ç²Öj /ê® º © j z~º Ö" . â 7f îæW;Ú~ ö & XPS~ survey(a) 5 core level spectra(b-d) NZ . îæW;Ú~ öB W 5 Cu ç ö Ö²f ê²ö & b & ¾æ¾ ® . ®Bb '' W-Cu «¶f ÚÆ z' Öj ~ ®ºæº â 7(a)öB ¾æ¾º bö & core level spectra ªCÖ"¦V r > ® . Ö"öB r > ®, Ö²º W 5 Cu ç" &æ Özbj ;W~ ®b, ê²º ëã'b Ò~ ® . 7, W «¶~ öº ¢ Özb jò WO , WO , WO ~ ^&æ Özb ;W>Ú ®rj r > ® . Özb ¾Ò ";öB Úá² B >ºæf ";öB W-Cu ¾ªö~ ç² Ö~ >²ª*VöB Özb" ê²f ?f ®Bb. ~ B";j Ò~V *~ >², Özb, ê ²& >w~ W > ®º H O, CO, CH & Ê~ OÂj ªC~& . â 8f >²ª*VöB &~º ÿn îæW;ÚöB OÂ>º H O(a)f 2. 2.72. Fig. 6. Variations of (a) carbon and (b) oxygen contents during isotermal sintering at 1050oC.. 3. 2. 4. 2. Fig. 7. XPS analysis results of the brown part; (a) survey spectra, core level spectra of (b) tungsten, (c) copper and (d) carbon. Vol. 9, No. 4, 2002.

(6) J~ÁÒWÁJ. 240. . 6, >²fº Ò ê²º ÚB W-Cu « ¶~ ö º~~, 7/~ ®º W Özbj ~öÎ . V¢B ê²º Î"'b W «¶ b Cu& {Ö > ®º ~ãj ò Ú& . Ö" 'b, PIM Þ PM Þö j z ôf ç ~&zNj ¾æÞ ©f ê²ö ~ º~Özb~ ~öö V ©ªj r > ® . 3.3. ²Ö"; â 9º º~®Bb B>º ßN";7 î æW;Ú~ &êæz¢ ¾æÞ Ö" . 1020 C r æ ßN~º ";öB W;Ú~ &êæzº ìº © j r > ® . öB, ®Bb VÚçb B>º ÿn &êæzº ¢Ú¾æ p~ . â 10 f îæW;Ú (a)f H O ò OÂ>º 550 C(b), CO& OÂ>º 700 C(c), &¦ª~ º~®Bb B B 1020 C(d)ræ ßN~ /ï Þ~ ^ . â 9~ Ö"öB &êæz& ì, ^ ç~ Vêö N¢ ¾æÚæ pº ©j r > ® . ¾, W-Cu aggregate~ ;çf Nê& Ã&ö V¢ æ~º © &VB . ß®, 700 Cö Bº aggregate~ V& £* Ã& >, 1020 C öBº J®J V& 6² ©j r > ® . aggregate ^~ æz¢ ;ï'b ªC~V *~ BET~ î² /îO ªC»j Ï ~ ^Væz¢ Ò~& . â 11f â 10~ Þ ö &B î²~ ç&{Kö V î² /îO ¦b¢ ¾æÞ F . VB Pº OB î²~ {K, P º &V{ 760 Torr o. o. 2. o. o. Fig. 8. The results of gas evolution analyses by (a) hygro metry and (b) QMS, in-situ conducted during heat-up sintering to 1050oC in H2.. ~ &Ê³êæz¢ hygrometryf QMS ¢ Ï~ ªC Ö" . H Of CO &Ê~ OÂ 1020 Cræ ßN~º ";öB «ò~º © j r > ® . º &¦ª~ º~Özb" ê²& ßN";7 BB º ©j ~ . º~Özbf >²f ê²ö ~ ~ö>Ú B>, CH ¢ W ~º >²ö ~ ê²~ Bº Z ;ê& . H Oº 1020 C ræ ² 3B~ b¢ ¾æÚ O Â>î . * Ö" ö V, Ñ ® bº Cu Özb~ ~öö ~ b, êö ¾æ ¾º b 2Bº W Özb~ ~öö ~ b . Ú ©f >²& º~Özbj ~öÊº ÿ n ê²& 650 C ¦V W Özbj ~öÎ º © . W Özb >²ö ~ ~ö>º ÿn ê² & Özbj ~öÒ > ®º ©f ê²& >². ;K ~öBV r^ . ê²& W Özb j ~ö~ CO &Ê¢ W~B B>º ©f 7º ~¢ <º . ¯, ê²º Özb" ?f { Öö & ObB CO &Ê¢ OÂ~ B> æ v ê²f Özb ÿö BB º 6 CO, CH4(b). 2. o. 4. 2. o. o. o. o. 18). o. 19). Journal of Korean Powder Metallurgy Institute. Fig. 9. Variation of relative density of brown part during heat-up sintering..

(7) ªöÒÂW; W-15 wt%Cu ¾ªö~ ç²Öö ~º º~®Bb~ 'Ë. 241. Fig. 10. SEM micrographs of (a) the brown part and heat-up sintered specimens up to (b) 550oC, (c) 700oC and (d) 1020oC.. . ßN";öB î²~ O ¦bf ;& æ~º ©j r > ® . H O ò OÂ>º 550 C Þ öBº îæW;Úö j £ 4V~ V¦bÃ&& ¢ÚÒb, F~ ;º BV(open pore)~ ¦ bÃ&¢ ¾æÞ . ê³B CO & OÂ>V ·~º 700 CöBº 550 CöB Ã&>î~ BV~ ¦b& /Ï® 6²~B, ^Vï £ 16 cm / göB 7.5 cm /g 6²~& . º~®Bb &¦ª BB 1020 CöBº ^V~ · 6² ©j r > ® . â 12º î²~ OFj Ï~ BJH » b ^V~ Vª¢ Ò Ö". . .V îæW;Úöº " 30 nm ~~ V ;W>Ú ® . 550 C ræ ßN êöº îæW; ÚöB ;W>Ú®~ V~ ·f 6²~ £ 150 nm V~ V~ · Ã& ©j r > ®. . Ã&B Vf â 11öB ¢® BV ; . 700 C ræ ßN êöº 550 CöB Ã& B Vf &¦ª ²B ©j " > ® . VB Ú ©f H Oò OÂ>º 550 CöB 30 nm V ~~ V~ · 6²~B £ 150 nm V~ V ;WB >, H Of þ CO& OÂ> º 700 CöBº £ 150 nm V~ Vf ²>î o. 2. 20). o. o. 3. 3. o. 21). o. o. o. o. 2. 2. o. º 6 . H Oº «¶~ Özb" ¦ F «B >²f~ >wb W>º ©, COº « ¶~ ê²f Özb~ >wb W>º VÚ . «¶öB WB v VÚº «¶ *~ V j Û {Ö~ ¦ OÂ~²B . 6 öB, ßN";öB îæW;ÚöB ¾æÂ Væz º VÚ~ {Ö";öB ¢VB ©b 6B . ¯, 550 CöB ¾æÂ VÃ&º H O~ &Ê{ö ~ V ccB ©b 'B . >ö 700 C öB V >» ©f r" ? J«F > ®. . CO& {Ö~ OÂ > ®º ãº H Oö ~ {>î, çöB ê²º >² f þ º~Özbj Î"'b B~² B . Ö" Cu& {Ö > ®º Ob ê²f Özb ÿö B>B W-Cu ç²Ö ·>îV r^ö V /Ï® >» ©b 'B . J«f W-Cu aggregate~ ;çæz¢ ¶^® & VbB ÝAB . â 13f ßN";7 îæW;Ú(a), 550 C(b), 700 C(c)ræ ßN Þ~ W-Cu aggregate ;çæ z¢ SEMb &V Ö" . Nê& Ã&~B aggregate~ ;ç æ~º ©j «{~² " > ® 2. o. 2 22,23). o. 2. o. o. Vol. 9, No. 4, 2002.

(8) J~ÁÒWÁJ. 242. Fig. 11. Nitrogen isotherm curves (a) the brown part and heat-up sintered specimens up to (b) 550oC, (c) 700oC and (d) 1020oC.. Özb~ >²~ö";öB BB H O~ OÂö V VÚ{K r^ ©b 'B . ö > V /Ï® >» 700 C(c)öBº ^ & &VB . v B~ aggregate& Cu ç(zÚ ¦ ª)ö ~ Ö>Ú ®b(A), w÷B aggregate(B)& &VB . Aggregate ~ ¢¦ªj { &B &V Ö"(â 13(d)), ©f Cu ç~ z +ö V ©b {>î . ^º W «¶b Cu ç~ ¢öö ~ ê¯>º W-Cu ~ ç²Ö 700 CöB ¢ÚÒ º ©j ~ . A aggregateº Cu~ ¢öê aggregate~ &z ";ö ®º ©, B aggregateº B~ aggregate& w÷B ç¢ > ® . V¢B, â 12(c)öB ¾æÂ V>»f Cu ¢öö ~ aggregate~ &z ö V ©ªj r > ® . 6, f ? ç² Ö ê¯F > ®î~ ©f º~ê²& W º~Öz bj Î"'b B®V r^¢ 6B . öB, º~ê²ï 4V ôf PIM Þf PM Þ º º~Özb~ B& ² ê¯NbB ç²Ö ² ¢ÚÂ © . ¾, ßN";öB ¢Ú¾º .Vç²Öf W «¶WËöº ' Ëj "æ pf ©b ¾æÒ (â 14). 2. o. o. Fig. 12. Pore size distribution curves of (a) the brown part and heat-up sintered specimens up to (b) 550oC, (c) 700oC and (d) 1020oC.. . .V îæW;Ú~ aggregateº £ 1 µm V~ B~ «¶& w÷B ;çj ~ ® . ö > 550 C ÞöB &V>º aggregateº .V aggregate& ªêB ;çj ~ ® . ªê>Ú ·j ê aggregate *~ VV& 100~200 nm, º .V aggregate& ªê>B & V ;W B © . ªêöf aggregate Ú¦ö Ò~º o. Journal of Korean Powder Metallurgy Institute.

(9) ªöÒÂW; W-15 wt%Cu ¾ªö~ ç²Öö ~º º~®Bb~ 'Ë. 243. Fig. 13. SEM micrographs of (a) the brown part and heat-up sintered specimens up to (b) 550oC, (c) 700oC and (d) aggregate surface of 700oC.. 4.. Ö . öBº ªöÒÂW; W-Cu ¾ª ö~ ç²Öÿö ~º º~®Bb~ 'Ëö & Ò~& . PIM Þf PM Þ ç²Ö /ê>î . ^&VÖ", PIM ÞöBº W-Cu aggregate~ &z& ² ¢ÚÒrj r > ®î . PIM Þ" PM Þ"~ F¢ N 6f º~®Bbïî . PIM Þ" PM Þö º~~º Ö²ïöº N& ìîæò, º~ê² ~ ãÖ, PIM Þö 4V ôf · º~~& . PIM Þ~ º~ê²º >² ;K ~öBB W º~Özbj Î"'b B~& . >²~ ~ö> wö ~ WB H Oº OÂ";öB W-Cu aggregate ¢ ªê~&æò, ê²~ ~ö>wö ~ CO OÂ öº ªê>î~ aggregate ~ w÷*ç ¢Ú ¾B V¦b& /Ï® 6²>î . CO OÂ aggregate w÷*çf W «¶b~ Cu~ ¢ö *çö ~ ¢ÚÂ ©ª ^ &VÖ" C& r . Ö'b, PIM Þ~ º~ê²& º~Öz 2. Fig. 14. The variations of W particle size during heat-up sintering to 1020oC.. bj Î"'b BbB PM Þ W² Ö /êB © .. 6Ò~ & º "VF¦~ 2001j &æ; Ò Vol. 9, No. 4, 2002.

(10) J~ÁÒWÁJ. 244. ëæöö ~~ >¯>îb ö 6Òãî .. ^^ò 1. C. Williams: Ceramic Bulletin, 50 (1991) 714. 2. C. Zweben: Journal of Metals, 7 (1992) 15. 3. R. M. German, K. F. Hens and J. L. Johnson: Intern. J. Powder Metallurgy, 30 (1994) 205. 4. R. Miura, J. Sekikawa, M. Uchida, Y. Owaki, and J. Madarame: J. Japanese Soc. of Powder and Powder Metallurgy, 38 (1991) 801. 5. I. H. Moon and J. S. Lee: Powder Metallurgy, 22 (1979) 5. 6. idem.: Powder Metallurgy International, 9 (1977) 23. 7. J. L. Johnson and R. M. German: Advances in Powder Metallurgy & Particulate Materials, MPIF, Princeton, NJ, 4 (1993) 201. 8. T. W. Kirk, S. G. Caldwell and J. J. Oakes: ibid., 9 (1992) 115. 9. J. S. Lee, T. H. Kim and T. G. Kang: Proc. 1993 Powder Metall. World Congress, Kyoto, Japan, (1993) 365. 10. : 97-1558, 1997, 2. 11. 11. J. S. Lee and T. H. Kim: Nanostr. Matr., 6(1995) 691. 12. I. H. Moon, M. K. Kang, J. S. Lee, J. K. Lee, and J. S.. ÒW Úßî. Journal of Korean Powder Metallurgy Institute. Kang: Proc. of 1994 Powder Metallurgy World Congress, Paris, France 3 (1994) 1807. 13. E. S. Yoon, J. S. Lee, S. T. Oh, and B. K. Kim: Intern. J. Refractory Metals & Hard Mater., 2002 in press. 14. , , : , 5(1998) 258. 15. J. S. Lee and T. H. Kim: Solid State Phenomena, 25&26 (1992) 143. 16. , , : , 4(1997) 304. 17. J. S. Lee, W. A. Kaysser and G. Petzow: Modern Developments in Powder Metallurgy, Eds. E. N. Aqua and C. I. Whitman, MPIF and APMI, 15 (1985) 489. 18. T. H. Kim, J. H. Yu and J. S. Lee: Nanostr. Matr., 9 (1997) 213. 19. D. S. Venables and M. E. Brown: Thermochimica Acta, 285 (1996) 361. 20. L. Jiqiao, Ch. Shaioyi, Z. Zhiqiang, L. Haibo, and H. Baiyan: Intern. J. Refractory Metal & Hard Mater., 17 (1999) 423. 21. E. P. Barrett, L. G. Joyner and P. P. Halenda: J. Amer. Chem. Soc., 73 (1951) 73. 22. Y Sakka: J. Mater. Sci. Lett. 10 (1991) 426. 23. A. Upadhyaya and R. M. German: Int. J. Powder Metall. 34 (1998) 43.. J~ Fæî ÒW ªö¢.²æ J~ Fæî ÒW ªö¢.²æ.

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