Sains Malaysiana 46(9)(2017): 1635–1640

http://dx.doi.org/10.17576/jsm-2017-4609-36

 

Sinteran Hidroksiapatit dalam Atmosfera Nitrogen untuk Peningkatan Sifat Mikrokekerasan

(Sintering of Hydroxyapatite under Nitrogen Atmosphere for Improved Microhardness)

 

LEONG CHEE HUAN^1*, ANDANASTUTI MUCHTAR¹, TAN CHOU YONG², MASFUEH RAZALI³ & CHIN CHUIN HAO¹

 

¹Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan

Malaysia

 

²Department of Mechanical Engineering, Faculty of Engineering, Universiti Malaya, 50603 Kuala Lumpur, Wilayah Persekutuan, Malaysia

 

³Periodontology Department, Faculty of Dentistry, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Wilayah Persekutuan, Malaysia

 

Received: 17 November 2016/Accepted: 10 June 2017

 

ABSTRAK

Hidroksiapatit (HA) adalah sejenis kalsium fosfat yang merupakan komposisi kepada kebanyakan fasa mineral tulang dan enamel gigi. HA bersifat bioserasi dan berkonduksi osteo selain mempunyai afiniti biologi dan kimia yang bagus untuk tisu tulang. Dengan ciri tersebut, HA diguna secara luas sebagai graf tulang dan bahan salut bagi implan tisu keras manusia. Walau bagaimanapun, kerapuhan dan keliatan patah yang rendah HA tersinter menghadkan penggunaannya dalam aplikasi bebanan yang tinggi. Kajian ini tertumpu kepada mengenal pasti kesan atmosfera sinteran dengan gas nitrogen (N₂) ke atas sifat mekanik HA untuk aplikasi pergigian. Serbuk nano HA dicirikan dengan menggunakan mikroskop elektron pancaran. Cakera silinder HA dihasilkan dengan kaedah penekanan ekapaksi. Kemudian, cakera silinder HA dikenakan tekanan isostatik sejuk dan disinter dalam dua atmosfera sinteran yang berbeza iaitu sinteran dalam gas N₂ dan sinteran dalam udara pada suhu 1300°C. Ketumpatan, mikrostruktur, kestabilan fasa dan mikrokekerasan HA tersinter dicirikan. Secara keseluruhan, sinteran dengan menggunakan gas N₂ menyebabkan pertumbuhan saiz butiran yang lebih besar dengan ketumpatan relatif dan mikrokekerasan yang lebih tinggi jika dibandingkan dengan atmosfera sinteran dalam udara. Dalam kajian ini, HA yang disinter dengan menggunakan gas N₂ pada suhu 1300°C menunjukkan mikrostruktur yang lebih tumpat, ketumpatan relatif (94%) dan mikrokekerasan (4.07 GPa) yang lebih tinggi jika berbanding dengan sinteran dalam udara tanpa penguraian HA. Kesimpulannya, penggunaan atmosfera sinteran dengan menggunakan gas N₂ pada suhu 1300°C dapat meningkatkan sifat kekerasan Vickers nanokomposit HA dengan mikrostruktur yang padat.

 

Kata kunci: Atmosfera sinteran; hidroksiapatit; sinteran dengan gas nitrogen

 

ABSTRACT

Hydroxyapatite (HA) is a type of calcium phosphate which constitutes most of the mineral phase of bones and tooth enamel. HA is biocompatible and osteoconductive; it also exhibits excellent chemical and biological affinity with bone tissues. With these characteristics, HA has been widely used as bone graft and coating material for human hard tissue implants. However, the brittleness and low fracture toughness of sintered HA limit its capability in load-bearing applications. This study focuses on determining the effect of sintering in nitrogen gas (N₂) atmosphere on the mechanical properties of HA. HA nanopowders were characterised using a transmission electron microscope. Next, HA powders were uniaxially pressed into pellets. The pellets were then isostatically cold-pressed and sintered in two types of atmospheres, namely, sintering in N₂ and sintering in air at 1300°C. The density, microstructure, phase stability and microhardness of sintered HA were characterised. Overall, sintering in N₂ led to the formation of larger grains with higher relative density and microhardness than sintering in air. In this study, HA sintered in N₂ at 1300°C exhibited more compact microstructure with higher relative density (94%) and microhardness (4.07 GPa) without decomposition in comparison to sintering in air. In conclusion, N₂ sintering at 1300°C improves the Vickers hardness of HA by yielding a more compact microstructure.

 

Keywords: Hydroxyapatite; sintering atmosphere; sintering in nitrogen gas

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*Corresponding author; email: cheehuan@hotmail.my