THE MICRO FABRICATING PROCESS AND ELECTRO- MAGNETIC PROPERTIES OF TWO KINDS OF Fe POWDERS WITH DIFFERENT GRAIN SIZES AND INTERNAL STRAINS

Ý 4 Ý «Vol.4 No. Ü Ò Ý 97 972 ACTA METALLURGICA SINICA Aug. pp.97 972 Ð Ü Î Ý 2 Fe Å ÑÏÆË ß Ø Å «( Àº¾ºÎ Ç Õ Þ ß¼, 430070) Ì 2 Õ Å Å Å ² Fe ÕØл ± ÅØ ÎµØ., Fe, ÅÕ Å, Å Å Fe Õ± Å «, ² h ØлºØÔÑ Fe ; ØлºĐ (t) h, Õ Õ, ; Áµ t=24 h, Fe Û», Å Ç Ì Fe. Fe º¾ Î Å Û Ã, Ƶ Á È»ÏÕ ÃÛ %, Ì Û 1.5 mm º ³ db Û.2 GHz, Û ³ Û. db. É Fe, Øл, Î Ã, µø ÁÃ Í TB3 ÓÖ A Ó Í 04 191()0 097 0 THE MICRO FABRICATING PROCESS AND ELECTRO- MAGNETIC PROPERTIES OF TWO KINDS OF Fe POWDERS WITH DIFFERENT GRAIN SIZES AND INTERNAL STRAINS ZHOU Jing, WANG Wei, SUN Zhigang, GUAN Jianguo State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 Correspondent: GUAN Jianguo, professor, Tel: (027)7232, E-mail: guanjg@whut.edu.cn Supported by National High Technology Research and Development Program of China (No.0AA03A9) and Young Teachers from Fok Ying Tung Education Foundation (No.49) Manuscript received 03, in revised form 05 13 ABSTRACT The micro fabricating process and electromagnetic properties of two kinds of Fe powders with different grain sizes and internal strains were studied. The results show that the homemade Fe powders with smaller grain size, larger internal strain and surface roughness than the carbonyl Fe powders, evolve into big and thin Fe flakes by micro fabricating for h with the help of the process control agent (PCA). When micro fabrication for t= h, these Fe flakes will fracture and their average width will reduce due to strong internal strain. When t is further prolonged to 24 h, these Fe flakes become thinner, finally, those with larger aspect ratio and smaller width can be obtained, which show high permeability and low permittivity. The epoxy resin-based microwave absorbing materials containing such Fe flakes of % (volume fraction) exhibit a reflection loss less than db in the 9.4 17.9 GHz frequency range with a minimal peak of. db, whose average thickness is 1.5 mm. KEY WORDS Fe flake, micro fabrication, electromagnetic parameter, microwave absorbing properties * ß Ö ÚÙ Ó 0AA03A9 Å Î Ý ¹ Ó 49 ÑÅ : 03, Ñ : 05 13 ºÝ : µ, ß, 19 Ý, È DOI:.3724/SP.J.37.117 Ï µø«æï ÆÜØÆÓÇ, Ì Æ Ü Ø Ø ¹. Ï Æ Ø² Ë, Öµ È Snoek «, ÕµØÏÐ. Walser Ú [1] Á ², Ö 1 GHz ÚÖ, ÆØ Í Ö 00

9 ½ Ý 4», Ï ÐÏÌ Ø µ, ÏÐ È µ 0. ÆØ«Ù ¼ [2 4] Ñ [5 7] À []. Ù ¼ ¼É, Ê «Æ µú Æ ¾. ¹, Ï Ù ¼» (t) Ø, Ø Í Ù, ÆÖÙ Ï Ð Ø» Æ Ù Đ Ä, ߳à [3,4]. ÜÍ«Ü Đ Ä, Þ Ü ÛÍ [9] Ê Á [] Ã É [11 13] Ú«, ß Í Ï, ÌÆÖ«Ü Đ ÄØ» «ÜÏÐ, Ì Þ Æ µ Ù. Å ¹Í 2 Ö Æ Æ Æ ³ Ø Fe ÖÙ ¼ À ز Ñ Ù ĐÏ Ä Ø, à ÆÅ µ Û ÆµÖ Æ Ø Á«Í Ø Fe, Æ ÕÍÏÐ µ Đ ÄÜ, Ù ËØ Ø. 1 ÛÂÀ ¾ Ü: Fe (Carbonyl iron powders, CI), ½É, Æ 1 5 µm; ±«Fe (Homemade iron powders, HI), ¾ ±«; ÆÇË, Ì, Ð Ø ½É. Fe Ø «ÀÜ: Å g CI, 150 ml ÆÇË (² «Ø) 1 kg Ü 5 mm ØÑ Â QHJM Å Ñ, Đ Ü 5 Hz, Ö Ù ¼³» (t) Î, Ï Ð Fe, Î ± ² h, ÕÒ Fe A.»ÜÅ, Å CI ± HI ²À¾ ÕÒ Fe B. à Á D/Max III A X Å (XRD) Å Fe ³ Æ, ¼» Ä:, ¾ Cu K α, Đ Ü 35 kv, Đ Ü 30 ma, 2, Ë Ü min 1. à S 400 Đ (SEM) ų» «Ø Fe ³ ², ÊÁ e ruler Ë Ú SEM Ø ÆÍ. Å Fe 30% Â É Ó, ¼«Ò 7.0 mm Ö 3.0 mm ÍÑ 3.5 mm Ø. à ËÖ Å (VNA, Agilent N5230A) Ë Fe Ö 2 GHz ÚÖØ ÏÐ (µ r ) Æ Đ Ä (ε r ). Fe Â Ø Ø RL ÚÍ [] : RL = lg Z in Z 0 (1) Z in + Z 0 Z in = Z 0 (µ r /ε r ) 1/2 tanh (j 2πfd(µ rε r ) 1/2 ) c (2), f ÜĐÏ Ø, d Ü ØÍ, c Ü Ë, Z 0 Ü, Z in Ü Ø. 2 Û ÊÞ 2.1 È Đ 1 Ü Fe CI HI Ø XRD Å., 2 Fe Ö 2θ=44., 5.0 Æ 2.3 Ê È Í ÆØ α Fe Ø. ½ Hall Williamson, Æà (D) ÆÖ (ε) Ø Ü βcos θ=2εsin θ+kλ/d( X λ=0.154 nm, k Ü Scherrer Ä, θ Ü Bragg, β Ü µ ). È βcosθ/(kλ) ܳ¼, sinθ/(kλ) Ü˼»,» ÛÉ, Ø Ü 2ε, Ö³¼ ²Ø Ü 1/D. ÚÍÕÒ CI Æ HI Ø ε Ü 0.% Æ 0.5%, D Ü 41.4 Æ 15.0 nm. 2 Ü CI Æ HI Ø SEM., CI Ø ²,, Æ Ö 1 5 µm, Intensity, a.u. HI CI 1 1 0 0 211 211 30 40 50 0 70 0 90 2, deg Ð 1 Ï Fe CI HI XRD Fig.1 XRD patterns of raw Fe powders CI and HI Ð 2 Ï Fe CI Å HI SEM Fig.2 SEM images of raw Fe powders CI (a) and HI (b)

y (u : "LJ_LpW % r 2 Æ Fe rs.dfd}u(s 99 P C Q 4 (i 2a). HI DF & 4, N+ ( & e & x &, W! t t 9 >, t r 1.5 µm, f CI, g [ u ~, " Fe A N B t U 9. j t e/, * H (i 2b). Fe B t 9U A t 9U, Ok HI r u~ 2.2 nxot> Es v7lp 0FH t \!H CI B. {:Tx zt$n i 3 xu~0'e/ (t) t Fe A N, $N \u )T*, _K \. e/, HI B t SEM, D f U t gv 9 i 4. >, CI t g [, \ n - (O e, T X ~0/ R yo r NOSt/[, + e*t Fe 'Fu~0V, r m, DR k0 & Ce ;N, {A ' [15] l 3 t}/&d. s Fe A M B s SEM Fig.3 SEM images of Fe flakes A (a d) and B (e h) obtained by micro fabricating for t=7.5 h (a, e), h (b, f), h (c, g) and 24 h (d, h) (the irregularly shaped Fe flakes are shown in the white circles in Fig.3f)

970 ½ Ý 4 Width, m; aspect ratio Width, m; aspect ratio (a) Width Thickness Aspect ratio 1. 1.2 0. 0.4 4 2 24 2 Time, h (b) 1. 1.2 0. 0.4 4 2 24 2 Time, h Ð 4 Fe A Å B Ì Å Ì Thickness, m Thickness, m Fig.4 Curves of average width, thickness and aspect ratio of Fe flakes A (a) and B (b) vs micro fabricating time Í ØÑ Ø ÏĐ ÙËØà µ, Õ À []. Fe A Ø Ï t Ø Ù ; Æ Fe B Ø Ö h ÖÙ, h» Æ, Ð Ø ( 3f Ñ ). ßÇ HI ÖÙ ¼ À È Í. ß Ø Ì È Ü HI µøö Æ, ÊÐ ² Ø. t Â Ò 24 h, ÍØ Fe B ܼ, Í Ù, Fe B Πà ʵ, Ì ÙÖ Ø» Å Ø Í. t h», Fe A Ø Fe B Ø, t > h», Fe A Ø Fe B Ø, ÞØ Ð¹ Ø, ß Â Ç HI ÖÙ ¼ À ² Ø Fe È Í, Æ CI ² È Í, ÅÁÍ ÅÔĐØ. 5 ÜÙ ¼³» «Ø Fe A Æ B Ø Đ Ä¾ (ε ) (f) Ø., Ï t Ø, Fe A Ø ε Ù, ÌÜ Fe Ù»Ù,» Ã Ö É ² Ö, ĐÐ µ [17]. f=2 GHz», Ï t Ø, ε 9 ¹ Ù Ò, Ù Ñ %; Æ t h», ε Ù Ò, Ù Ò 0%. ßÇ CI Ø À Ö t h Î, ß 4a Ø Í Ä (a) 0 h 7.5 h h h 24 h (b) Ð 5 Fe A Å B ý (ε ) (f) Fig.5 Dependence of real part of permittvity (ε ) for Fe flakes A (a) and B (b) on frequence (f) ½Â, h» Í Ü 4.92, Æ 24 h» Í 15.. 3a c, CI Ö t h» Æ Æ. CI ØÆ ³ Â, ÆØ Í «Ò À Î, Ñ ½ ÙÖĐ À Ò Ø ÆÅ. Å HI, Ï t Ø, ε Ù, Î «, Î Ü ¼Ù, ß Fe ( 4b) Â. Ö t= h»«ø Fe B Ø ε t= h Ø, ß ÌÜ Fe B Ö Í, «ÜÍ Fe Ø. f=2 GHz, t h», ε ² Ò, Ù 0%, Fe A Ø ε ØÙ µè 90%,» Í Æ 11.95, Fe A Ø 2.4, Ç HI CI ¹ÀØ ¼Ì, µø. t h», ε Ù Ò, Ù Ò 33%,» Í Ù Ò.5, Ç Î Ã µ. 2.3 Ò Ù ÄÔ ÜÅ Fe Ù ¼ 24 h Î«Ø Fe A Æ B ØÙ ĐÏ Ä Ø., Fe B ÜØ Đ Ä, ¾ (ε ) «ÜÑ % ( a), º (ε ) «ÜÑ 30% ( b); ÆÏÐ ¾ (µ ) ƺ (µ ) ÅÁ³, ¾ Ü Ä ( c Æ d). Fe B Ø Đ Ä ÌÜ ÆÃ

Ý «Ù : Ä ÄÔÏ ±Ö 2 Æ Fe Ö º ÐÍ 971 (a) Sample A Sample B 1.5 (b) 1.0 0.5-0.5 4.5 4.0 3.5 3.0 2.5 1.5 1.0 0.5 (c) -1.0 2.5 1.5 1.0 0.5 (d) Ð t=24 h ºÅ Fe A Å B Ø Î Ã Fig. Curves of real part (a) and imaginary part (b) of permittivity, real part (c) and imaginary part (d) of permeability vs frequency f for Fe flakes A and B obtained by micro fabricating for t=24 h, Ù«, ÆÐ Đ µ [3],» Fe B Ø, Ã Đ Ä«Ü. ÏÐ Ø Í Æ ÏÐ. HI µø Ö Æ, Î Æ, ³Ã ÏÐ Ø µ [9], Ì Ò Fe B Ø Í, Ï Ð ³. Ï Â Đ Â ± ¾ Ö ÚÌÊ. HI Ö ØÖ, Ä ÆÏ»ØÔ Ú, ÆÖÏ» Ø À ¹ Ò ÂĐÏ ÙË, Ï ÂÙ, Â, Fe B Ø Í, ± ¾ Í Ø Â, Í Fe A, Đ Â, ÈÖßÔ ÌÊزÉ, Ï Â ³, ² Ë Ø¾ Ü Ä [1]. Ȳ, HI ÖÙ ¼ À ØÙ ĐÏ Ù Ø Ö Ø Æà ƵØÖ Æ. ÆÅ ÚÌÊ À, ÊÕÒ Æ Ø, Ò» Î, Ö Ø», Ð Ø,»Ã ÙÅÁµØ Æ Í. È CI Ü Ù ¼«Ø Fe A, HI Ü Ù ¼«Ø Fe B ÜØ Đ ÄÆ ØÏÐ, Ã, µ Ù. Reflection loss, db 0-5 - -15 Sample A Sample B Ð 7 t=24 h ºÅ Fe A Å B Á µ Ø»Ï ³ Á Fig.7 Curves of reflection loss vs frequency for epoxy resin based microwave absorbing materials containing % volume fraction Fe flakes A or B obtained by micro fabricating for t=24 h (the thickness is 1.5 mm) 2.4 Õ Ù ÄÔ 7 Ü t=24 h»«ø Fe A Æ B  ØÙ ¼ Ø Ï Ø (Fe ÄÜ %)., t=24 h»«ø Fe A, Fe B Ø ¼ Ø

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