Jariah Mohamad Juoi

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.

Nanocomposite TiAlBN Coatings as a Corrosion Protection Layer for AZ91 Mg Alloy Substrate in NaCl

Magnesium alloys create increasing interest in structural application where weight reduction is vast concern. However, one of magnesium drawback in various applications is low corrosion resistance. In general, a hard coating can be applied on metal to combat such a problem. AlN and TiN coatings are most widely utilized in manufacturing area i.e for structural application due to its high hardness, high chemical stability, and excellent adhesion to substrates. Most recent, TiAlBN coating catch many attentions due to its superior properties than other most studied hard coating. The incorporation of aluminium in the cubic face centered TiN structure on Ti sites leads to deformation and strengthening of the crystal structure of the coating together. Moreover, incorporation of BN in this coating should improve and enhanced the corrosion resistance of Mg alloy. Therefore, in this study, TiAlBN coating have been chosen to be deposited on Mg alloy using reactive magnetron sputtering together with AlN and TiN coatings for comparison study. During depositions, target power, working pressure and bias voltage are optimized for each coating. Analysis on the effect of AlN, TiN and TiAlBN coatings on Mg alloy substrate include thickness measurement and microstructure by scanning electron microscope (SEM). Coatings phase were analysed using glancing angle X-ray diffraction analysis (GAXRD) and corrosion properties were evaluated using potentiodynamic polarization in NaCl solution. TiAlBN shows better performance of corrosion protection with the least corrosion rate (penetration rate = 0.20 mm/yr; mass loss rate=0.97g/m2d) in sodium chloride (NaCl) solution although having the lowest coating thickness (412 nm).

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.

Rheological Properties of Urea-CaLS Mixture for Urea Fertilizer Granulation

The rheological properties of feedstock for granulation process are important in controlling the parameters throughout the process. This study identifies the type of fluid that mixtures of Urea and Calcium Lignosulfonates (CaLS) possessed through the viscosity profiles using a parallel plate rheometer. The viscosity behavior of mixtures with varied weight percentages (wt %) of CaLS in urea solution were analysed. Results identified that the mixtures show shear thickening behavior of non-Newtonian fluid. It is also observed that the increases of CaLS content increase the viscosity of the mixtures. Moreover, the mixture with 50 % CaLS addition is found not suitable for further investigation as its viscosity is too high (3.450-6.773 Pa.s at zero shear rate) compared to molten urea (0.002 Pa.s).

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.

Influence of Sol-Gel pH and Soaking Time on the Morphology, Phases and Grain Size of TiO 2 Coating

Titanium oxide, (TiO2), can exist in three distinct crystallographic phases known as anatase, rutile, and brookite. Brookite, however, is the least known TiO2 phases and usually exists as byproduct during synthesising rutile or anatase. Therefore, in this study, the influence of sol-gel pH and soaking time on surface morphology, phases and grain size of TiO2 coating were investigated in an attempt to develop brookite thin film. Titanium (IV) isopropoxide (TTiP) is used as precursor for preparing TiO2 sols. Prior to heating, TiO2 layers were deposited on a glass slide by dipping it five times into TiO2 sols. The TiO2 layers were then heated at 450°C and soaked for 1 and 3 hours to form TiO2 coating. Analysis on the phases and grain size were carried out using X-ray diffraction (XRD). The TiO2 surface morphology was investigated using Scanning Electron Microscope (SEM). Results showed that brookite phase with grain size of 27.40 nm successfully deposited on glass slide from sols with pH12. Conversely, the TiO2 coatings deposited from sols of pH1 and pH7 are amorphous. The effect of soaking time on phases and grain size is insignificant but enhances coatings uniformity as the soaking time increased. Thus, it can be concluded that sol-gel pH affect TiO2 crystallinity and phases. Brookite film is develop only when the TiO2 sols is in bases condition or at higher pH value.

Effect of Degussa P25 on the Morphology, Thickness and Crystallinity of Sol-Gel TiO 2 Coating

The deposition of titanium dioxide, TiO2, films on various substrates was studied in order to take benefit of its antimicrobial properties for suitable application in related fields. In this paper, the effect of Degussa P25 (a commercial TiO2 nanoparticles additive in the sol) on the morphology, thickness and crystallinity of the deposited TiO2 was investigated. TiO2 films, without and with Degussa P25, were deposited on glass slides and unglazed ceramic tiles via sol-gel process. Films were deposited ten times using dip coating technique and heat treated at 500°C for 1 hour. The coating morphologies and thickness were analyzed using Scanning electron microscope (SEM), while the crystalline phases were characterized using Glancing angle X-ray Diffraction (GAXRD). Results show that the addition of Degussa P25 produces coating with homogeneous morphology and less cracks, thicker film and promotes the presence of anatase and rutile phases. It was also observed that the deposition of TiO2 with Degussa P25 on unglazed ceramic tile produced thicker film (~120mm) as compared to the film deposited on glass slide (~7mm). Thus, it can be concluded that the addition of Degussa P25 affect the morphology, thickness and crystallinity of the TiO2 coatings, whereas the type of substrate only affects the coating morphology and thickness, but not the crystallization of the TiO2 coating.

Characterization of TiO 2 Coating Deposited on Ceramic Substrate

The deposition of titanium dioxide, TiO2, films on ceramic tiles was studied in order to take benefit of its antimicrobial properties for suitable application in related fields. In this paper, the characteristics of TiO2 coating deposited on unglazed ceramic substrates with high surface roughness were investigated. TiO2 films were deposited several times via dip coating sol-gel technique and heat treated at 500oC for 1 hour. The coating morphologies and thickness were analyzed using Scanning electron microscope (SEM), while the crystalline phases were characterized using Glancing angle X-ray Diffraction (GAXRD). Results show that it produces coating with homogeneous morphology, thicker film and with the presence of anatase and rutile phases. It was also observed that one dipping time is sufficient to produce a continuous coating with thickness of ~ 12 μm on average.

Influence of Catalyst in Synthesizing Brookite Thin Film Coating

Brookite is the least known titanium dioxide (TiO2) crystallographic phases compare to anatase and rutile. In a sol-gel process, very few works are devoted on synthesizing pure brookite as a thin film coating and usually brookite co-exist with anatase and rutile as a byproduct. This study is performed as an attempt to produce brookite thin film coating via sol-gel dipping method. In this study, the influence of catalyst type on TiO2 phases, morphology and grain size were investigated. Hydrochloric acid (HCl) is used for an acid catalyst and sodium hydroxide (NaOH) is used as base catalyst. All of the TiO2 films were deposited on a glass substrate and heated at four different temperatures of 400°C, 450°C, 500°C and 550°C for 3 hours. X-ray diffraction (XRD) is employed to analyze the phases and the grain size acquired. Images on the surface morphology are obtained with Scanning Electron Microscope (SEM). Results showed that brookite phase exist only for base catalyst with a grain size of 27.40 nm for all of the selected temperatures except at 550°C. SEM results revealed that the surface morphology of the deposited TiO2 film with base catalyst comprised of agglomerated particle networks. In contrast, the surface morphology of the deposited TiO2 film with acid catalyst seems more compact and uniform with an XRD pattern of amorphous-like characteristic having grain size of less than 3 nm.