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Moldability Characteristics of 3 mol% Yttria Stabilized Zirconia Feedstock for Micro-powder Injection Molding Process (Ciri Kebolehacuanan Bahan
Suapan 3 mol% Yttria Zirconia Terstabil bagi Proses Pengacuanan
Suntikan Mikro Serbuk) HAFIZAWATI ZAKARIA1*, NORHAMIDI MUHAMAD1, ABU BAKAR
SULONG1, MOHD HALIM
IRWAN IBRAHIM2& FARHANA FOUDZI1
1Department of Mechanical & Material
Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan
Malaysia, 43600 UKM, Bangi, Selangor, Malaysia
2Faculty of Mechanical and Manufacturing
Engineering, Universiti Tun Hussein Onn Malaysia 86400 Batu Pahat, Johor, Malaysia
Diserahkan: 10 April 2012/Diterima: 21 Jun
2012
ABSTRACT
Micro-powder injection molding (μPIM) is a promising process that
may satisfy the demand on miniaturization parts to micro domain
in mass production with low manufacturing cost. Three mol% yttria
stabilized zirconia (YSZ) with nano-sized powder and binder
system consists of polyethylene glycol (PEG),
polymethyl methacrylate (PMMA) and
stearic acid (SA) were
used. Nano-size powders with higher surface area generally require
more binder to form a feedstock. As such, determination of the optimum
powder loading of the feedstock for μPIM process
is important. The rheological characteristics of different YSZ
feedstocks with powder loading of 52 53 and 54 vol.
% were investigated in terms of flow behavior as a function of viscosity
and shear rate. Fairly low values of flow behavior exponent ranging
from 0.25 to 0.39 (n<1) resulted in pseudoplastic flow behavior
of the examined YSZ feedstock.
The 52 vol.% feedstock exhibited the lowest viscosity resulting
in highest activation energy and lowest moldability index of 1.862×10-6, while the 54 vol.% feedstock
regardless to its high viscosity, yielded a low activation energy
of 4.14 kJ/mol and high moldability index of 4.59×10-6.
Based on rheological properties obtained, a powder loading of 54
vol.% has desirable feedstock characteristics for μPIM
process and exhibited molding ability for micro-detail
filling. The relationship between the optimum rheological properties
obtained and the actual injection process was also determined. The
results showed that the green parts were able to be injected without
defects such as short shot or flashing.
Keywords: Feedstock; micro-powder injection
molding; rheological properties
ABSTRAK
Permintaan ke arah pengecilan komponen
kecil kepada mikro saiz dalam bentuk pengeluaran secara besar-besaran
dengan kos pemprosesan yang rendah telah membuatkan pengacuanan
suntikan mikro serbuk merupakan satu proses yang sesuai digunakan.
Bahan yang digunakan dalam proses ini ialah serbuk 3 mol% yttria
zirconia terstabil (YSZ)
bersaiz nano dan sistem bahan pengikat yang terdiri daripada polietilena
glikol (PEG), polimetil metakrilat (PMMA) dan asid sterik. Walau bagaimanapun,
serbuk bersaiz nano menyumbang ke arah luas permukaan yang lebih
tinggi dengan lebih banyak bahan pengikat diperlukan, oleh itu,
ia menyebabkan bahan suapan yang terhasil mempunyai pembebanan serbuk
yang lebih rendah. Ini menunjukkan betapa pentingnya untuk menentukan
pembebanan serbuk bagi bahan suapan untuk proses pengacuanan suntikan
mikro serbuk. Ciri reologi bagi pembebanan serbuk yang berbeza iaitu
52, 53 dan 54 vol. % bagi bahan suapan YSZ dikaji daripada aspek sifat aliran
dalam fungsi kelikatan dan kadar ricih. Nilai sifat aliran yang
terhasil daripada kajian ini adalah agak rendah iaitu dalam julat
0.25~0.39 (n<1) menunjukkan bahan suapan YSZ
yang dikaji mempunyai sifat aliran pseudoplastik diperhatikan.
Bahan suapan 52 vol.% seperti yang telah dijangkakan telah mempamerkan
kelikatan yang paling rendah manakala bagi bahan suapan 54 vol.%,
berbanding dengan kelikatannya yang tinggi, telah menghasilkan tenaga
pengaktifan yang paling rendah iaitu 4.14 kJ/mol dan nilai indeks
kebolehacuanan yang tinggi iaitu 4.59×10-6. Berdasarkan
kepada sifat reologi ini, boleh disimpulkan bahawa bahan suapan
pada pembebanan serbuk 54 vol.% memiliki ciri bahan suapan yang
dikehendaki dalam proses pengacuanan suntikan mikro serbuk. Ia juga
menunjukkan keupayaan diacuankan bagi mengisi penuh perincian acuan
mikro. Penghubungkaitan sifat reologi kepada proses suntikan sebenar
telah dibuktikan dengan jasad hijau telah berjaya disuntikkan tanpa
mengalami sebarang kecacatan seperti tembakan pendek atau percitan.
Kata
kunci: Bahan suapan; pengacuanan suntikan mikro serbuk; sifat reologi
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*Corresponding author; email: hafizawati@unimap.edu.my
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