Zulkifli Mohd Rosli

Corrosion behavior of AZ91 Mg-Alloy coated with AlN and TiN in NaCl and Hank’s solution

Magnesium alloys create increasing interest in structural application where weight reduction is vast concern. However, its low corrosion resistance especially in atmosphere environment restricts their wide application. In this study, AlN and TiN were coated on AZ91 Mg alloy using PVD magnetron sputtering. AlN and TiN existence is confirmed via grazing angle x-ray diffraction (GA-XRD). The corrosion behaviors of uncoated and coated AZ91 Mg alloy in3.5% NaCl and Hanks solutions were investigated using a potentiostat during electrochemical corrosion test. AlN and TiN coated samples showed better performance in Hanks solution with TiN coated samples have the least corrosion rate (penetration rate=0.040mm/yr and mass loss rate=0.191g/m2d) in Hanks solution. These create interest to further works on exploring the potential of coated AZ91 Mg alloy in biomaterial application.

Characterization of TiAlBN Nanocomposite Coating Deposited via Radio Frequency Magnetron Sputtering Using Single Hot-Pressed Target

TiAlBN coatings have been deposited at varying bias voltage of 0, -60, and-150 V by radio frequency (RF) magnetron sputtering technique. A single hot-pressed Ti-Al-BN target was used for the deposition process. With glancing angle X-ray diffraction analysis (GAXRD), the nanocrystalline (nc-) (Ti,Al)N phase was identified. In addition, the existence of BN and TiB2 amorphous (a-) phase were detected by X-ray photoelectron spectroscopy (XPS) analysis. Thus, the deposited TiAlBN coatings were confirmed as nc-(Ti,Al)N/a-BN/a-TiB2 nanocomposite. On the other hand, it was found that optimum bias voltage used in present study is-60 V where the deposited TiAlBN coating exhibits an excellent adhesion quality. The adhesion quality of the coatings deposited at-60V bias voltage is classified as HF 1 evaluated using the Rockwell-C adhesion test method (developed by the Union of German Engineers).

Effect of PEG Molecular Weight on the TiO2 Particle Structure and TiO2 Thin Films Properties

This research, deals with modification of sol gel process for the synthesis of porous TiO2-PEG thin films with good structural integrity for environmental self-cleaning applications. Relatively, by adding the PEG with various molecular weights (300, 400, and 600) could influence the formation of TiO2 films structure and adhesion. Moreover, the formation of porous TiO2 associated with larger pores will accelerate the mass transfer of the treated contaminants in the larger pore channels. The advantages of the unique structures of as-prepared TiO2₂ films in the application of environmental self-cleaning systems are extensively studied by characterizing the produced films using various advanced characterization tools. Adhesion of TiO2 thin films become smooth and better surface with increasing the coating layers. The X-ray Diffraction spectrum of prepared coating shows present of anatase phase as major phase.

Transmission of Microwave Signal through Metal-Oxide Thin Film of Energy Saving Glass Using Different Shape of Frequency Selective Structure

Metal oxide thin films are widely used for energy saving glass coating. This coating has the ability of blocking the infrared signal while being transparent to other visible part of the spectrum. However, there is one critical disadvantage of this metal oxide coating which it attenuates useful radio frequency and microwave signal such as GSM mobile signal, personal communication, GPS signal through them. These important microwave signals are fall within the range of 800 MHz to 2200 MHz. Frequency selective structure has been applied to solve the attenuation of microwave signal. With the adding of frequency selective structure, it can bring huge improvement of the transmission loss through it. Computer simulation using CST software is used to investigate the transmission loss through the metal oxide coated glass. The frequency selective structure will be etched out from the metallic oxide coated on the glass. Results showed that different shape of the structure will have different peak transmission loss through the glass. When cross dipole and circle shape been simulated using CST software, it can clearly see that the transmission lost and peak frequency had changed drastically. Then, triangle and pentagon shape also have different transmission through it. In addition, conductivity and electrical properties of coated metal oxide thin film is also very important. The transmission through the different ohmic sheet resistance of metal oxide thin film was also investigated. The sheet resistance value was obtained from the reported experimental results. Simulated results showed that full width half maximum, maximum transmission loss and peak frequency loss was very much dependent on the metal oxide sheet resistance. Therefore, the control of the thickness and oxygen content in metal oxide thin film are very much important to optimize the transmission loss through it for energy saving glass applications.

Characterisation and Properties of Sintered Glass-Ceramics Produced from Recycling Glass by Using Pressure-Less Method

The aim of this research is to develop glass ceramic produced from recycling glass. Waste glass (e.g. container and bottles) of soda lime silica (SLS) glasses is utilised as main raw materials for the formulation of glass ceramic batch composition with the addition of ball clay. The ball clay was added in order to favour shaping. The recycled glass powder are then mixed with the ball clay according to the ratio of SLSG to ball clay of 95:5 wt.%, 90:10 wt.% and 85:15 wt.%. Differential Thermal Analyses (DTA) was carried out in order to determine the thermal characteristic glass powder prior to the batch formulation. The glass was then crushed, milled and sieved to < 75µm and mixed with the ball clay before it was pressed to a pellet by pressure-less method. This pressure-less route is conducted as an approach to a simple fabrication route of the glass-ceramic samples. The green samples are then sintered at different temperature. The dense and strong glass ceramic samples were obtaining at 850oC, with holding time of one hour and morphological characterized with X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) analyses. Results shown that glass ceramic samples produced at this optimized sintering profile had high density and microhardness value with low porosity and negligible water absorption. Overall results indicates that glass ceramic samples have good mechanical properties (e.g. microhardness exceeding 700Hv) and physical properties (e.g. water absorption, density, porosity making them attractive to the structural application. These results are also utilised as a comparison to a glass ceramic samples produced via Cold Isostatic Press (CIP) from the same batch composition formulation and sintering profiles for the purpose of optimizing the waste glass utilization.

Development and characterization of charcoal filled glass-composite materials made from SLS waste glass

Glass-composite materials were prepared from the soda lime silicate (SLS) waste glass, ball clay and charcoal powder at various carbon content, of 1wt. % C, 5wt.% C and 10 wt.% C, fired to temperature of 850 °C as an alternative method for land site disposal method as well as effort for recycling waster glass. The effect of charcoal powder on the porosity, water absorption and hardness properties were studied. Phase analysis studies revealed the present of quartz (ICDD: 00001-0649, 2θ = 25.6° and 35.6°), cristobalite (ICDD 00004-0379, 2θ = 22.0° and 38.4°) and wollastonite (ICDD 00002-0689, 2θ = 30.1° and 26.9°). The results showed that the composite prepared from the mixture of 84 wt.% SLS, 1 wt.% of charcoal and 15 wt.% ball clay containing average pore size of 10 µm has projected optimized physical and mechanical properties. It is observed this batch has projected lowest water absorption percentage of 0.76 %, lowest porosity percentage of 1.76 %, highest 4.6 GPa for Vickers Microhardness.

The Influence of the Microwave Plasma Nitrided Ti6Al4V Substrate Properties to the Duplex Coating Performance

Titanium alloys, especially TI6Al4V has been used in many industries such as aerospace applications, medical application and automotive applications. This is because it has beneficial properties such as low density, high strength to weight ratio, low modulus elasticity, excellent corrosion resistance and etc. However, titanium and its alloys have limited use in mechanical engineering applications involving sliding wear or abrasion due to poor wear resistance. Therefore, the duplex coating concept was introduced with the intention of the surface modification process as a pre-treatment of the substrate prior to the deposition of hardcoating process. In this study, plasma nitriding of the Ti6Al4V was performed using a microwave plasma technique at 600°C and 700°C for 1 hour, 3 hours and 5 hours, then followed by deposition of chromium nitrate (CrN) on plasma nitrided samples for duplex coating purposes. Microstructural analysis and mirohardness measurement revealed that formation of Ti2N and TiN phase indicating the formation of the compound layer was observed for substrate nitrided at temperature as low as 600°C for 1 hour and a substantial increase on the case depth obtained on plasma nitrided Ti6Al4V was observed with an increase of process temperature and time. The duplex coating obtained in this study has superior surface hardness property and improved load carrying capacity of the coating – substrate system compared to CrN coatings deposited on as received Ti6Al4V which was observed in the penetration depth analysis.

Chemical Composition Analysis of TiAlBN Nanocomposite Coating Deposited via RF Magnetron Sputtering

TiAlBN nanocomposite coating have been successfully deposited on AISI 316 substrate via RF magnetron sputtering by varying nitrogen-to-total flow ratio (RN) of 5, 15, 20, 25%, as well as varying substrate temperature of 100, 200, 300, and 400 oC; using single Ti-Al-BN hot-pressed target. Chemical compositions of the coatings were analysed using X-ray photoelectron spectroscopy (XPS). XPS results showed that the TiAlBN nanocomposite coating reaches a nitride saturated state at higher RN (e.g 15, 20, and 25%) and boron concentration was found to be approximately 9 at.%. However, as the concentration of nitrogen decreases at lower RN (5%), boron concentration was found to increase to 16.17 at. %. This is due to the increase of TiB2 phase in the coating. Variations of substrate temperatures were found to give no significant effect on the chemical composition of the deposited TiAlBN nanocomposite coating.

Ti6Al4V Surface Hardness Improvement by Duplex Coating

Ti6Al4V alloy are among the most widely used materials in engineering applications. This is because their relatively beneficial properties. However, inadequate wear properties of Ti6Al4V alloy have largely constrained the application for this material. In this study, Plasma nitriding of the Ti6Al4V was performed using microwave plasma technique at 600°C for 1hour, 3 hours and 5 hours then followed with deposition of CrN on plasma nitrided samples for duplex coating purposes. Microstructural analysis and hardness measurement revealed that formation of Ti2N and TiN phases indicating the formation of compound layer is observed for substrate nitrided at temperature as low as 600°C 1 hour and a substantial increase on the surface hardness of plasma nitrided Ti6Al4V is observed with an increase of process time. The duplex coating obtained in this study has significant surface hardness property and superior as compared with CrN coatings deposited on as received Ti6Al4V.

Optimization of Transmission Lost for Energy Saving Glass with Different Sheet Resistance Values

Recently, energy saving glass is commonly applied in the modern engineered building. This is due to its advantages of keeping the heat inside the building in winter while rejecting the heat when in summer. The typical energy saving glass is made by applying a very thin metallic oxide such as silver oxide or tin oxide on one side of the float glass. But at the same time, it has the disadvantages of attenuates useful microwave frequencies that ranging from 0.8 2.2 GHz. The examples of the microwave frequency at this range are GSM mobile signal, GPS and personal communication. Frequency selective surface (FSS) has been introduced to overcome this drawback of energy saving glass. In this study, the transmission of the microwave signal is observed through the simulation using Computer Simulation Technology Microwave Studio. Bandpass frequency selective surface of cross dipole shape is used for the simulation. In the simulation, conductivity and electrical properties of glass and metal oxide thin film are important. The microwave transmission was evaluated at various sheet resistance of metal oxide thin film. The results show that the minimum transmission lost increased with the ohmic resistance increased. On the other hand, the peak frequency at various sheet resistance shows constant value at around 1.25-1.30 GHz. The full width half maximum of the microwave transmission increases with the sheet resistance value. The results suggest that FSS structured metal oxide thin film with lowest sheet resistance transmits more signal in the range for GSM phone signal.