Development Of Biodegradable Mg-Znha Composite Via Mechanical Alloying

• Main Author: Salleh, Emee Marina
• Format: Thesis
• Language: English
• Published: 2016
• Subjects: T Technology; TA404 Composite materials
• Online Access: http://eprints.usm.my/41775/1/Development_Of_Biodegradable_Mg-Znha_Composite_Via_Mechanical_Alloying.pdf; http://eprints.usm.my/41775/
• Institution: Universiti Sains Malaysia

Kajian ini bertujuan untuk membangunkan bahan logam biodegradasi menggunakan pengaloian mekanikal (MA). Magnesium (Mg) adalah calon yang paling menjadi tumpuan bagi aplikasi bioperubatan berdasarkan kelebihan sifat-sifatnya berbanding bahan bio yang lain. Tetapi kadar degradasi yang cepat dalam persekitaran fisiologi menghadkan prestasinya. Oleh itu, Mg telah dialoikan dengan zink (Zn) bagi meningkatkan kerintangan kakisan dan mengekalkan integritimekanikal. Dalam mencapai sasaran ini, bahan bio berasaskan Mg telah difabrikasi melalui MA diikuti dengan pemadatan di bawah 400 MPa dan pensinteran pada 350°C. Empat parameter MA iaitu masa pengisaran, kelajuan pengisaran, nisbah berat bola kepada serbuk (BPR) dan kandungan Zn telah disiasat. Ketumpatan 1.80 hingga 1.99 g/cm3 yang setara dengan tulang manusia dan kekerasan mikro yang lebih baik daripada Mg tulen (39.30 HV) iaitu antara 53.76 hingga 94.37 HV telah diperolehi. Berdasarkan rekabentuk faktorial pecahan (FFD), keadaan MA optimum dalam menghasilkan aloi Mg-Zn dicapai dengan menambah 6.5 wt% Zn yang dikisar selama 5 jam pada 200 rpm dengan 7: 1 BPR. Kekuatan mampatan yang lebih tinggi (249.28 MPa) dan kadar kakisan yang lebih rendah (1.13 x10-2 mm/y) daripada Mg tulen (178.04 MPa dan 13.77 x10-2 mm/y) telah diperolehi. Penambahbaikan sifat-sifat tersebut telah dicapai dengan menambah 10 wt% HA ke dalam aloi Mg-6.5wt%Zn. Kekuatan mampatan (292.33 MPa) dan kadar degradasi (0.72 x10-2 mm/y) yang bagus diperolehi. Komposit Mg-Zn/HA memberikan bioaktiviti paling tinggi dengan nisbah Ca:P sebanyak 1:1.46 diikuti oleh aloi Mg-Zn 1:1.29 memenuhi keperluan pemineralan awal tulang iaitu 1:1 kepada 1:1.67. ________________________________________________________________________________________________________________________ This work aims to develop biodegradable metallic material using mechanical alloying (MA). Magnesium (Mg) is the most highlighted candidate for biomedical applications because of its advantageous properties as compared with other biomaterials. But a rapid degradation rate in physiological environment limits its performance. Hence, Mg was alloyed with zinc (Zn) in order to improve its corrosion resistance and sustain its mechanical integrity. In achieving the target, Mg based biomaterials were fabricated using MA followed by compaction under 400 MPa and sintering at 350 °C. Four MA parameters namely milling time, milling speed, ball-to-powder-weight ratio (BPR) and Zn content were investigated. The density of 1.80 to 1.99 g/cm3 which is comparable to human bone and improved microhardness of 53.76 to 94.37 HV as compared to pure Mg (39.30 HV) were attained. By fractional factorial design (FFD), an optimized MA condition in producing Mg-Zn alloy was achieved by adding 6.5 wt% Zn and milled for 5 hours at 200 rpm with 7:1 BPR. A higher compressive strength (249.28 MPa) and lower corrosion rate (1.13x10-2 mm/y) than pure Mg (178.04 MPa and 13.77 x10-2 mm/y) were acquired. A further improvement of those properties was attained by incorporating 10 wt% HA into optimized Mg-6.5wt%Zn alloy. An enhanced compressive strength (292.33 MPa) and degradation rate (0.72 x10-2 mm/y) was attained. Mg-Zn/HA composite provided the highest bioactivity due to highest Ca:P ratio of 1:1.46 followed by Mg-Zn alloy of 1:1.29 which is in agreement with the required Ca:P ratio of 1:1 to 1:1.67 for initial bone mineralization.