Arman Shah

Graphical abstract Abstract The effects of oxide interlayer on cobalt-chromium-molybdenum substrate were investigated in order to improve the quality of hydroxyapatite (HA) coating as well as enhance the cell responses. Substrates were oxidized at temperature of 850 °C and 1050 °C for 3 hours. Oxidized substrates were then coated with HA slurry using dip coating technique. Analysis of surface morphology, thickness and chemical composition of oxide interlayer prior to HA coating were performed using field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy and grazing X-ray diffraction respectively. It seems that rough surface of oxide interlayer provides better mechanical interlocking of HA particles to the substrate surface with no visible micro-cracks. In addition, the HA coated substrates with oxide interlayer also demonstrate strong attachment and better proliferation of cells compared to HA coated substrates without oxide interlayer. The results also demonstrates that cells were spread out more actively as earlier as day 7 and have greater extensions of filopodium on HA coated substrates with oxide interlayer. It is concluded that the introduction of an intermediate oxide layer on Co-Cr-Mo substrate prior to HA coating has shown a positive effect in terms of improving the quality of HA coating as well as cell bioactivity performance. Abstrak Kesan lapisan oxida ke atas substrat kobalt-kromium-molibdenum dikaji dengan tujuan mempertingkatkan kualiti salutan hidrosiapatit (HA) sekaligus mempergiatkan tindakbalas sel. Substrat dioksidakan pada suhu 850 °C dan 1050 °C selama 3 jam. Substrat yang telah teroksida kemudian disalut dengan HA menggunakan teknik salutan bercelup. Analisis ke atas permukaan morfologi, ketebalan dan komposisi kimia bagi lapisan oxida sebelum salutan HA dijalankan menggunakan mikroskop imbasan pelepasan elektron, serakan tenaga X-ray spektroskopi dan ragutan X-ray pembelauan. Ia seolah-olah permukaan kasar lapisan oksida telah menyediakan pautan mekanikal yang lebih baik kepada partikal HA ke atas permukaan substrat tanpa ada mikro-retak yang boleh dilihat. Tambahan lagi, salutan HA substrat dengan lapisan oksida juga menunjukkan lekatan

Surface modification is often required in order to improve the biological and tribological properties of metallic implants. In the present study, Co-Cr-Mo alloy was oxidized in atmospheric condition to create oxide interlayer (Cr 2 O 3) prior to hydroxyapatite (HA) coating. The effect of oxide interlayer on the adhesion strength of HA coating on oxidized Co-Cr-Mo substrate was investigated. The surface of oxide interlayer was rough and contained abundant of pores, which helps in providing better mechanical interlocking to HA coating. Scanning electron microscopy and X-ray diffraction techniques were used to characterize the surface morphology of the HA coating whilst a Revetest scratch test was used to measure the adhesion strength of HA coating on oxidized substrates. The oxide interlayer on the substrate was able to prevent severe cracks while maintaining the porosity of the coated layer. Scratch test results showed that adhesion strength of the HA coating on substrates with interlayer was significantly higher than those without interlayer (1.40 N Vs 1.04 N; p<0.05). Increasing sintering temperature increases adhesion strength proportionally. These findings suggest that the porous oxide interlayer provides better anchorage whilst minimizing surface cracks of HA on Co-Cr-Mo substrates.

The unmanageable agricultural waste comprises of structural polymers, cellulose, hemicellulose and lignin can be led to pollutions, thus it can be used as a mushroom substrate. Lignocellulosic materials are most favorable feedstock as renewable and natural resource. Forestry and agricultural practices generated a large amount of ligncelluosic waste and promoted to serious problematic environmental pollution. It can be easily broken down by lignocellulotic enzymes. In this study, an attempt was made to evaluate the effect of various substrates on cultivation of Pleurotus sajor-caju. The substrates used in this study were tissue paper, rice husk ash and rubber sawdust. All of the substrates were added with rice bran and calcium carbonate (CaCO 3). Then, the mixtures were transferred into plastic sized 8 cm × 4.5 cm and were pasteurized in the steamer for 1 hour at 60 °C-100 °C. After that they were cooled overnight at 25 °C-30 °C. The spawn were inoculated into the bag and incubated in incubation room. The media bags were incubated until mycelium fully colonized and watering was done twice a day. The parameters studies were included spawn running, number of fruit body, total of stipe length, weight of fruit body and biological efficiency. Results showed that the fastest spawn running and highest number of fruits body, total of stipe length, weight of fruit body and biological efficiency are found using tissue paper substrates. In contrast the rubber sawdust showed the lowest values of spawn running, total of stipe length, weight of fruit body and biological efficiency. It can be concluded that the tissue paper is one of promising substrate which can be used in growing of Pleurotus sajor-caju due to lower cost and easy to purchase as compared to other substrates.

Titanium and titanium alloys are widely used in a variety of engineering applications,
where the combination of mechanical and chemical properties is of crucial importance.
Aerospace, chemical and automotive industries as well as the medical device manufacturers
also benefited from the outstanding properties of titanium alloys. The wide spread of its
uses in biomedical implants is mainly due to their well-established corrosion resistance and
biocompatibility. However, not all titanium and its alloys can meet all of the clinical
requirements for biomedical implants. For instance, it is reported that bare titaniumvanadium
alloy has traces of vanadium ion release after long period exposure with body
fluid (López et al., 2010). Excessive metal ions release into the body fluid and causes toxicity
problems to the host body. A new group of titanium alloy such as Ti-Nb and Ti-Zr based are
recently introduced in the market to overcome the toxicity of titanium-vanadium based
alloy (Gutiérrez et al., 2008). Although, these alloys have a high strength to weight ratio and
good corrosion resistance and biocompatible, but it suffers from poor tribological properties
which limits their usefulness to a certain extent especially when they are applied to joint
movements. Wear debris generated from these articulation joints can induce inflammation
problem and toxic effect to the human body. In biomedical point of view, post implantation
is very crucial stage where the interaction between the implanted material surface and the
biological environment in human body is critically evaluated. Either in the short or long run,
the toxic effect becomes an issue to host body. Hence, the implant material surface has a
strong role in the responses to the biological environment. In order to improve the biological
and tribological properties of implant materials, surface modification is often required
(Huang et al., 2006, Kumar et al., 2010b). This chapter embarks on the commonly used
implant biomaterials, followed by general overview on the surface modification techniques
for treating titanium alloy. The basic principles of oxidation, carburization and ion
implantation methods and their developments are discussed in the following sections.

The corrosion phenomena are always give bad impact to any metal products including human implants. This is due to the corrosion impacts are harmful for hard tissues and soft tissues. There are many methods to prevent the process of corrosion on implant materials such as coating with bioceramic materials and modify the implant surface with surface modification techniques. However, until now there is still no gold standard to overcome this problem and it is remain in researching process. Thus, the aim of this research is to investigate the potential and economical surface modification method to reduce the corrosion effects on Cobalt-Chromium-Molybdenum (Co-Cr-Mo) based alloy when insert in human body. The thermal oxidation process was selected to treat Co-Cr-Mo surface substrate. Firstly, Co-Cr-Mo alloy was heated in muffle furnace at constant temperature of 850°C with different duration of heating such as 3 hours and 6 hours in order to analyze the formation of oxide layer. The corrosion behaviours of untreated sample and oxidized sample were investigated utilizing potentiodynamic polarization tests in simulated body fluids (SBF). The Vickers hardness after corrosion testing was measured in order to evaluate the effect of thermal oxidation in reducing corrosion rate. Based on the results obtained it is clearly showed that substrates undergone thermal oxidation with 6 hours duration time performed better than 3 hours duration, with the hardness value 832.2HV vs. 588HV respectively. Dense oxide layer and uniform thickness formed on the oxidized substrates able to help in reducing the corrosion effects on Co-Cr-Mo alloy without degraded its excellent mechanical properties. The microstructures of oxidized substrates before and after corrosion test were also analyzed using FESEM images for better observations. It was determined that corrosion resistance of Co-Cr-Mo substrate can be increased with oxide layer formed on the alloys using thermal oxidation process.

Bare biomedical grade titanium alloys are prone to degradation when in a body fluid environment. Surface coatings such as Physical Vapor Deposition (PVD) can serve as one of the options to minimize this issue. Past reports showed that the PVD coated layer consists of pores, pinholes, and columnar growths which act as channels through which the aggressive medium attacks the substrate. Duplex and multilayer coatings seem able to address this issue to varying extents but at the expense of manufacturing time and cost. In this paper, the effect of an ultrasonic vibration frequency on PVD TiN coated Ti–13Zr–13Nb biomedical alloy was studied. Disk type samples were prepared and coated with TiN at fixed conditions: bias voltage (−125 V), substrate temperature (300 • C), and nitrogen gas flow rate (300 standard cubic centimeters per minute (SCCM)). An ultrasonic vibration was then subsequently applied to the TiN coated samples at frequencies of 8 kHz and 16 kHz for 5 min. All TiN coated samples treated with ultrasonic vibrations exhibited a higher corrosion resistance than the untreated ones. Microstructure analysis under Field Emission Scanning Electron Microscopy (FESEM) confirmed that the coated sample at frequencies of 16 kHz produced the most compact coating. It is believed that the hammering effect of the ultrasonic vibration reduced the micro channels' size in the coating and thus decelerated the corrosion's attack.

Physical Vapour Deposition (PVD) is one of the versatile surface modification method commonly used in the manufacturing of coatings, powders, fibres, and monolithic components. The applications of PVD are cutting tools, decorative, aerospace industries and biomedical application. The main advantages of PVD coating as compared with other surface modification methods is low processing temperature thus can be used on variety of materials. However PVD coating has limitation due to low corrosion resistance especially when it contact with Cl ion in sea water and body fluids. Hence, this review explains the overview of PVD coating on corrosion resistance in body fluids and sea water. The types of PVD coating and parameter commonly used as well as issue related to PVD coating is discussed in this paper.