Sains Malaysiana 43(1)(2014): 129–136

 

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 Serbuk Mikro)

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

 

Received: 10 April 2012/Accepted: 21 June 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