Preparation of crack-free Al2O3 washcoat on

W-Re metallic wire by electrophoretic deposition

指導教授：王聖璋 副教授報告人：黃俊嘉

目的 :

In this work ， the coated fibres are intended crack-free and high-quality ceramic coatings on W-Re metallic wire .

Try atmosphere, PH and voltage of the alumina coating effects.

Experimental methods

EPD 參數

DC = 40 VW-Re ： cathode distance = 10 mmdeposition time = 1 min dried at room temperature for 24 h and calcined at 800°C in gas for 3 hgas ： 5 ％氫之氬氣

PAA4X10-6 ml/ml

AIP0.054g

γ-Al2O3

-Al2O3

-Al2O3

5wt%

vigorous stirringfor 20 min

ultrasonic bathfor 20 min

W/Re DC

＋

－

EPD

dried and calcined

SEM OM

powder

γ-Al2O3 θ-Al2O3 A16SG

500°C

800°C

500°C

大明500°C 500°C

800°C

800°Cgas

800°C

800°Cgas

800°C

800°Cgas

voltage

PH

Success Failure

進度

Before

Now

OM

OM pictures of the surface of the Al-coated wire. Green(a 、 b and c)and calcined at 800°C in atmosphere (e 、 d

and f).θ-Al2O3(a and d) 、 α-Al2O3-大明 (b and e) 、 A16SG(c and f).

(a) (b) (c)

(d) (e) (f)

SEM α-Al2O3 powder( 大明 )

SEM micrographs of alumina deposits calcined at 800°C in atmosphere of 5%H2/Ar for 3 h.

The experiments were preformed at room temperature and a coating with a deposited thickness of about 600 μm .

OM α-Al2O3 powder( 大明 )

OM pictures of the surface of the Al-coated wire.

Green(a 、 b and c)and calcined at 800°C in atmosphere(e 、 d and f).

pH2(a and d) 、 pH3(b and e) 、 pH4(c and f).

Some pores or defects are found on surface.

(a) (b) (c)

(d) (e) (f)

OM pictures of the surface of the Al-coated wire.

Green (a and b ) and sintered at 800°C in atmosphere of 5%H2/Ar (c and d ).

Electrophoretic voltage in 20V(a and c) 、 10V(b and d).

OM α-Al2O3 powder( 大明 )

(a) (b)

(c) (d)

SEM micrographs of alumina deposits voltage in 20V calcined at 800°C in atmosphere of 5%H2/Ar for 3 h.

The experiments were preformed at room temperature and a

coating with a deposited thickness of about 65 μm

SEM α-Al2O3 powder( 大明 ) in pH2

Conclusions在使用了 γ-Al2O3 、 θ-Al2O3、 α-Al2O3(A16SG和大明 (d=100nm))進行實驗後，發現 α-Al2O3成果最好，但 A16SG的粉末必須在酸性底下，其懸浮性才會好。

使用 α-Al2O3 在 800°C氣氛下進行燒結後，發現大明的粉末有較好的成果，所以決定用大明進行接下來實驗。

將大明懸浮液分散在酸性溶液 (pH2)，並在電壓 20V下進行電泳，燒結後，產生較成功的鍍膜。