Arman Shah Abdullah

Wear on Co-Cr-Mo biomedical implants is still a major issue especially for applications in articulation joints like in total ankle, knee and hip arthroplasty. Generation of excessive wear particles can coagulate in body tissues which later cause inflammation, bone loss and necrosis. Modification of implant surfaces is a common technique for increasing the hardness and thus minimizing these effects. In this study, thermal oxidation method was carried out on the Co-Cr-Mo to investigate the effects of different pretreatment processes and surface roughness on the hardness of oxide layer formed. Prior to oxidation process, all samples were annealed and pickled to remove residual stress and oxide scales respectively. The oxidation process was done inside furnace under atmospheric condition for 3 hours at 1160 °C. The metallic compositions, surface morphology and hardness of the oxide layer formed on the substrate were verified using X-ray diffraction (XRD), scanning electron microscope and micro-Vickers hardness analysis respectively. It is found that mechanical pretreatment provides oxide/carbide layer with higher hardness than chemical pretreatment method. It is believed that remnants of polishing diamond pastes trapped in roughness valleys react with metal matrix and later transform into carbides during oxidation process. In contrast, initial surface roughness of the substrate has no significant effect on the hardness of oxide/carbide layer.

Wear debris and metal ion release generated during application of biomedical devices would cause adverse cellular response, inflammation and pain in the human body. Modifying of implant surface with rutile structure is one of the methods to reduce these problems. In the present study, an attempt was made to evaluate the effect of thermal oxidation temperature on surface morphology and structure of the Ti13Nb13Zr biomedical material. The substrates were heated at varied temperatures of 550°C, 700°C and 850°C for 9 hours and cooled inside muffle furnace at a constant rate of 5oC/min. Scanning electron microscopy and x-ray diffractive were employed to evaluate the surface morphology and analyze the structure of the oxidized substrates respectively. All thermally oxidized samples exhibit the presence of oxides without spallation regardless of the thermal oxidation temperatures. Surface morphology of oxidized substrates changes from smooth to nodular particles-like shape when the oxidation temperature increases from low to high. Rutile structure dominants the surface area when the substrate is thermally oxidized at 850 °C.

Bare biomedical grade of titanium alloys are prone to undergo degradation in body fluid
environment. Surface coating such as Physical Vapor Deposition (PVD) can serve as one of the
alternatives to minimize this issue. In the past studies, effect of bias on corrosion resistance has
received well attention but mostly on steel based implant materials. Similar study on the coated
titanium based alloy is hardly found in the literature. In the present work, the effect of bias voltage
(-50V to -200V) on PVD-TiN coated Ti13Zr13Nb biomedical alloy was studied. Scanning electron
microscopy (SEM) and X-Ray Diffraction (XRD) were used to evaluate surface morphology and
crystal phase of the TiN coating respectively. Image analysis software was employed to quantify
microdroplets counts. In addition, the corrosion behaviour was also evaluated using electrochemical
test under the presence of Kokubo solution. Results show that the samples coated with -125V bias
voltage provides the least number of microdroplets and results in highest corrosion resistance. It is
also revealed that the presence of microdroplets on the coated substrate provides adverse effect to
the coating performance by increasing their corrosion rates.

The releases of harmful ions from cobalt based alloy to host tissues have raised significant health concerns. Carbon contents in this alloy may influence ions release but has yet investigated. It is hypothesized that carbon contents in this alloy will help the formation of oxide layer during thermal oxidation process and hence reducing the release of Co/Cr ions after implantation. In this study, Co-Cr-Mo alloy with carbon concentrations of 0.03% and 0.24% were oxidized at 1050°C for 3 hours under atmospheric condition. The oxidized substrates were characterized under FESEM and subjected to circulating immersion test in simulated body fluid (SBF) for 21 days. Metal ions release was measured using inductively coupled plasma-mass spectrometry (ICP-MS) at day 0, 7, 14 and 21. Oxidized high carbon samples show denser and a more uniform oxide layer than samples with low carbon contents. It is found that compact oxide structure promotes less metal ions release during immersion.

Adhesion strength between the coating and the substrate is considered as a significant factor, which may help determine both the successful implantation and the long-term stability of any coated implant. A weakly adhered coating on a medical implant may delaminate after the process of implantation, which in turn may severely limit the effectiveness along with the life of the implant itself. Related previous studies have shown that process parameters may have a direct influence on the quality of TiN coating. In the present work, the effect of substrate temperature on adhesion strength of TiN coating on Ti–13Zr–13Nb biomedical grade alloy was investigated. The coating parameter, which varied in this study, was the substrate temperature (i.e., 100, 200 and \(300\,^{\circ }\hbox {C}\)). The adhesion strength of TiN coating was examined by means of scratch testing method. In addition, calibrated optical images were also used to verify the total coating failures on the scratched coated samples. Results indicated that an increase observed in the substrate temperature may have resulted in a decrease in the microdroplet form on TiN coating. In contrast, the adhesion strength of TiN coating was observed to equally increase when substrate temperature increased. It is believed that the higher mobility of atom at a higher substrate temperature (i.e., \(300\,^{\circ }\hbox {C}\)) filling up the defect appears on the surface to provide a mechanical interlock and thus providing better adhesion strength.

The design of current talus implant are focusing too much on mechanical simplicity and usually based on certain population which tends to ignore the anatomically difference between populations. An anatomically talus implant design is known can reduce the contact pressure but one of the constraints for designing implant anatomically is to get bone parameters. This is due to the difficulty to get enough volunteers in getting bone parameters using hazardous method (X-ray or CT scan) .Thus, the talus implant (TI) for particular population was developed based on artificial neural network (ANN) prediction. By using Finite Element Method (FEM), numerical models that include mainly the talus bone and the talus implants are created to compare the contact pressure distribution of the newly develop talus implant with the three different kind of current talus implant designs (BOX, STAR & TNK). For FEM results, only BOX and the newly develop talus implant exceeded the contact stress recommended for the superior articular surface compared to the others. The results also showed that the stress increased near the resected surface. Thus, it is agreed that excessive bone resection may not support the force at the ankle which consequently may contribute to early loosening and subsidence of the talus implant. It is concluded that the excessive bone resection can be avoided by perfectly match talus implant which only can be achieved by designing talus implant for a particular population.

Surface modification of metallic implants is often required to facilitate positive interaction between the implant and the surrounding hard tissue. In the present study, an oxide layer (Cr 2 O 3 ) was successfully created on a Co-Cr-Mo alloys substrate by using thermal oxidation technique in atmospheric condition. The effect of different carbon content (0.03% and 0.24%) of oxidized Co-Cr-Mo alloys was investigated in terms of its corrosion behavior using electrochemical impedance spectroscopy techniques that immersed in simulated body fluid. The corrosion tests were repeated for five times for each of sample condition. The results demonstrated that thermal oxidation and carbon content have correlation in influencing the corrosion performance in Co-Cr-Mo alloys. A high carbon content sample generates a lower corrosion-rate compared to low carbon content sample even though all samples were treated at similar oxidation temperature and time duration. Observation also showed that less diffusion of cobalt released in high carbon sample which is believed has effects in creating the uniformity and dense oxide layer without any presence of microcracks and delamination. This phenomenon can be concluded that carbon content in Co-Cr-Mo alloy have influenced in controlling the reaction of metal elements during thermal oxidation which is beneficial in formation of oxide layer. The uniformity and compact oxide layer substantially have enhanced the corrosion resistance of high carbon Co-Cr-Mo alloy.

Diamond coating are commonly used in industries especially for application such as cutting tools, biomedical components, optical lenses, microelectronics, engineering, and thermal management systems. The diamond coating quality is strongly depending on substrate preparation prior to diamond coating. Thus, the several process parameters must be studied to obtain optimal parameters which lead high quality diamond coating. In this present work, an attempt was made to optimize pretreatment parameters namely temperature and time on cobalt removal of tungsten carbide. Full factorial experimental designs followed by Response Surface Methodology (RSM) were employed in this study to plan and analyze the experiment. The cobalt removal was the independent response variables. Empirical model was successfully developed to predict amount of cobalt removal on the substrate after single step etching process. Experimental results have shown that the temperature, time and time 2 are found to be the most significant factors for cobalt removal. Whereas for interaction of time and temperature were insignificant factors to influence cobalt removal. According to this study, the minimum cobalt content can be obtained at working temperature from 48 to 50C for 3 minute. Abstrak Salutan berlian biasa digunakan dalam industri terutama untuk aplikasi seperti alat memotong, komponen bioperubatan, kanta optik, mikroelektronik, kejuruteraan, dan sistem pengurusan haba. Kualiti salutan berlian adalah sangat bergantung kepada penyediaan substrat sebelum salutan berlian. Oleh itu, beberapa parameter proses perlu dikaji untuk mendapatkan parameter optimum yang dapat menghasilkan salutan berlian berkualiti tinggi. Dalam kajian ini, percubaan telah dibuat untuk mengoptimumkan parameter rawatan awal iaitu suhu dan masa pada penyingkiran kobalt tungsten karbida. reka bentuk eksperimen faktorial penuh diikuti oleh Metodologi Tindak balas Permukaan (RSM) telah digunakan dalam kajian ini untuk merancang dan menganalisis eksperimen. Penyingkiran kobalt adalah pemboleh ubah tindak balas bebas. model empirikal telah berjaya dibangunkan untuk meramalkan jumlah penyingkiran kobalt pada substrat selepas proses langkah pertama. Keputusan eksperimen telah menunjukkan bahawa suhu, masa dan masa 2 didapati menjadi faktor paling penting bagi penyingkiran kobalt. Manakala bagi interaksi masa dan suhu adalah faktor penting untuk mempengaruhi penyingkiran kobalt. Keputusan menunjukkan kobalt minimum boleh diperolehi pada suhu dari 48 ke 50C selama 3 minit. Kata kunci: Salutan berlian, RSM, reka bentuk faktor penuh, tungsten karbida

Cathodic arc physical vapor deposition (CAPVD) is one of the physical Vapor deposition (PVD) techniques used to coat titanium nitride (TiN) on biomedical implants due to its good adhesion and high evaporation rate. However, this technique emits micro droplets which have can detrimental effect on the coating performance. Previous studies reported that micro droplets can be controlled through proper deposition parameters. In this paper, the PVD coating was performed on the Ti-13Zr-13Nb biomedical alloy with different substrate temperatures. Scanning electron microscopy (SEM) was used to characterized the surface morphology and coating thickness while X-Ray Diffraction (XRD was employed to evaluate the crystal phase of the coated substrates. Image analysis software was used to quantify micro droplets counts. The results show that higher substrate temperature able to decrease a significant amount of micro droplets and concurrently increase the thickness of TiN coating. A mixed crystal planes of (111) and (200) are obtained on the coated substrates at this setting which exhibits denser structure as compared to substrates coated at lower substrate temperature. Abstrak Cathodic arc physical vapor deposition (CAPVD) merupakan salah satu teknikPhysical vapor Depostion (PVD) yang digunakan untuk menyaluttitanium nitrida (TiN) di implan bioperubatan disebabkan kekuatan lekatan yang baik dan kadar sejatan yang tinggi. Walau bagaimanapun, kaedah ini menghasilkan titisan mikro yang mempunyai kesan yang tidak baik ke atas salutan. Kajian lepas menunjukkan bahawa titisan mikro boleh dikawal melalui parameter salutan yang sesuai. Dalam kajian ini , salutan PVD telah dilakukan ke atas aloi bioperubatan Ti-13Zr-13Nb dengan suhu substrat yang berbeza.Mikroskop imbasan elektron (SEM) telah digunakan untuk menilai morfologi permukaan dan ketebalan lapisan manakala fasa kristal salutsubstrat telah diuji dengan menggunakan X-Ray Diffraction (XRD). Perisian analisis imej telah digunakan untuk mengukur bilangan dan saiztitsan mikro. Hasil kajian menunjukkan bahawa suhu substratyang tinggi dapat mengurangkan sejumlah besar titisan mikro dan dapat meningkatkan ketebalan salutan TiN. Permukaan kristal campuran (111) dan (200) diperolehi pada salutan substrat yang dihasilkan pada aliran N2yang tinggiyang mana mempamerkan struktur yang padat dengan kekuatan lekatan yang lebih tinggi berbanding dengan substrat bersalut yang dihasilkan pada kadar aliran gas N2 yang lebih rendah.

One of the crucial factors which determine the success of coated implantation and stability in the long run is the strength of adhesion between the coating and substrate. After implantation, a weakly adhered coating may delaminate and this might seriously restrict the implant's effectiveness and longevity. Based on past studies, the quality of TiN coating is directly influenced by the process parameters. The objective of this research is to evaluate the effect of N2 gas flow rate on adhesion strength of biomedical grade Ti-13Zr-13Nb alloy. In this research, N2 gas flow rate of 100, 200 and 300 sccm were varied while the other parameters (substrate temperature and bias voltage) were fixed. The scratch testing method was used to examine the adhesion strength of the TiN coating. This research used the calibrated optical images to verify the total coating failures on the scratched coated samples. The results indicated that the micro droplet form on the TiN coating decreases as the flow rate of the N2 gas increases. In contrast, the TiN coating's adhesion strength increases with the increase of N2 gas flow rate. It can be concluded that N2 gas flow rate was significant factor in improving the coating properties of TiN on Ti-13Zr-13Nb alloy. Abstrak Salah satu faktor yang penting dalam menentukan kejayaan salutan implan dan kestabilan untuk jangka masa panjang ialah kekuatan lekatan antara salutan dan substrat. Selepas proses implantasi, lekatan salutan yang lemah mungkin akan tertanggal dan ini akan memendekkan jangka hayat dan keberkesanan implan. Berdasarkan kajian lepas, kualiti salutan titanium nitrida secara langsung akan dipengaruhi oleh proses parameter. Objektif kajian ini ialah untuk menilai keberkesanan kadar aliran gas N2 ke atas kekuatan lekatan gred bio-perubatan aloi Ti-13Zr-13Nb. Dalam kajian ini, kadar aliran gas nitrogen 100, 200 dan 300 sccm telah diubah manakala suhu substrat dan voltage bias telah dikekalkan. Ujian cakaran telah digunakan untuk menilai kekuatan salutan TiN. Selanjutnya, kajian ini menggunakan imej-imej optik ditentukur untuk mengesahkan jumlah kegagalan lapisan pada sampel bersalut yang dicakar. Keputusan kajian menunjukkan bahawa titisan mikro daripada lapisan TiN berkurang apabila kadar aliran gas N2 bertambah. Sebaliknya, kekuatan lekatan salutan TiN akan bertambah dengan bertambahnya kadar aliran gas N2.

Cathodic arc physical vapor deposition (CAPVD) is one of the promising techniques that have a potential to coat titanium nitride (TiN) on biomedical implants due to its good adhesion and high evaporation rate. However, this method emits microdroplets which have the possible detrimental effect on the coating performance. Past studies indicated that micro droplets can be controlled through proper deposition parameters. In the present work, an attempt was made to study the effect of nitrogen gas flow rates (100 to 300 sccm) on TiN coating of the Ti-13Zr-13Nb biomedical alloy. Scanning electron microscopy (SEM) was used to evaluate surface morphology and coating thickness while crystal phase of the coated substrates was determined using X-Ray Diffraction (XRD). Image analysis software was employed to quantify microdroplets counts. Results show that higher nitrogen gas flow rate able to decrease a significant amount of microdroplets and concurrently increase the thickness of TiN coating. A mixed crystal planes of (111) and (220) are obtained on the coated substrates at this setting which exhibits denser structure with higher adhesion strength as compared to substrates coated at the lower N2 gas flow rate. Abstrak Cathodic arc physical vapor deposition (CAPVD) merupakan salah satu teknik yang berpotensi untuk menyalut titanium nitrida (TiN) ke atas implant bioperubatan disebabkan kekuatan lekatan yang baik dan kadar sejatan yang tinggi. Walaubagaimanapun, kaedah ini menghasilkan titisan mikro yang mempunyai kesan yang buruk ke atas salutan. Kajian lepas menunjukkan bahawa titisan mikro boleh dikawal melalui parameter salutan yang sesuai. Dalam kajian ini satu percubaan telah dibuat untuk mengkaji kesan kadar aliran gas nitrogen (100-300 SCCM) pada salutan TiN ke atas aloi bioperubatan Ti-13Zr-13Nb. Mikroskop imbasan elektron (SEM) telah digunakan untuk menilai morfologi permukaan dan ketebalan salutan manakala fasa kristal salut sub strat telah diuji dengan menggunakan X-Ray Diffraction (XRD). Perisian analisis imej telah digunakan untuk mengukur bilangan dan saiz titisan mikro. Hasil kajian menunjukkan bahawa kadar aliran gas nitrogen yang tinggi dapat mengurangkan sejumlah besar titisan mikro dan dapat meningkatkan ketebalan salutan TiN. Permukaan Kristal campuran (111) dan (220) diperolehi pada salutan substrat yang dihasilkan pada aliran N2 yang tinggi yang mana mempamerkan struktur yang padat dengan kekuatan lekatan yang lebih tinggi berbanding dengan substrat bersalut yang dihasilkan pada kadar aliran gas N2 yang lebih rendah.