Hasan Zuhudi Abdullah

Preparation and Characterisation of TiO2 Thick Films Fabricated by Anodic Oxidation

Anodic oxidation has been used to make well adhered and porous (≤1 μm pore diameter) thin films of anatase on titanium using electrolytic solutions with combinations of H2SO4, H3PO4, and H2O2. The crystallinity, film thickness, and pore size and number increase with time and voltage. The voltage is limited to ~180 V by electrolysis and/or breakdown and the film thickness is ≤3 μm.

Coating methods for self-cleaning thick films of titania

Abstract The present work provides a brief but wide ranging survey of the different methods that may be used to apply thick films of titanium dioxide for self-cleaning building materials. This survey is preceded by a general description of the photocatalytic applications of TiO2, a tabulated list of some relevant properties of the three naturally occurring polymorphs of TiO2 and a tabulated survey of world market shares and resources of TiO2. The survey of coating technologies consists of succinct coverage of twenty potential periodic and continuous routes for the application of liquid borne suspensions of TiO2 to building units. This coverage consists mainly of an illustration accompanied by relevant comments concerning the advantages and disadvantages of each method.

Preparation and Characterisation of TiO2 Thick Films by Gel Oxidation

Titanium foils were subjected to soaking in NaOH aqueous solutions in the concentration range 0.1 M to 10.0 M, followed by oxidation in the range 400°C to 800°C. The samples were characterised by glancing angle X-ray diffraction and Raman microspectroscopy. The results showed that the corrosion by NaOH solution resulted in: • Partial dissolution of the anatase passive oxidation layer • Partial dissolution of the underlying titanium foil • Formation of a TiO2-rich sodium titanate hydrogel (Na2O·mTiO2·nH2O) The subsequent oxidation of the hydrogel on the titanium substrate resulted in: • Recrystallisation of sodium titanate (Na2O·5TiO2) • Recrystallisation of the rutile polymorph of TiO2 The concentration of the NaOH solution was important in that it affected the dissolution or retention of the anatase passive oxidation layer, where lower concentrations (0.5 M and 1.0 M NaOH) resulted in a lower degree of dissolution in comparison to where higher concentrations (5.0 M and 10.0 M NaOH) were used.

Preparation and Characterisation of TiO2 Thick Films Fabricated by Electrophoretic Deposition

Rutile nano-powders were suspended in a solution of acetylacetone and iodine. The suspensions were electrophoretically deposited on titanium foil at a voltage range of 5-30 V over times of 5-120 s. The dried tapes then were sintered at 800°C for 2 h in flowing argon. Both the green and fired tapes were examined by field emission scanning electron microscopy, optical microscopy, X-ray diffraction, and Raman microspectroscopy. The thickness of the films depended on the voltage and the time of deposition. The sintered microstructures depended significantly on the thickness of the film, which was a function the proximity to the Ti/TiO2 interface. The interface is critical to the microstructure because it acts as the source of defect formation, which enhances sintering, grain growth, and grain facetting.

Effect of zeta potential of stanum oxide (SnO2) on electrophoretic deposition (EPD) on porous alumina

Zeta potential analysis of stanum oxide (SnO2) aqueous suspensions (pH7 to pH11) was performed prior to the electrophoretic deposition (EPD) of SnO2. Deposition of SnO2 on porous alumina was obtained by applying the EPD technique carried out by applying voltage of 18V for duration of four minutes. It was found that the depositions SnO2 suspended at pH 7 to pH 11 were successful. The relation between the SnO2 deposition with SnO2 pH and zeta potential values was established in which increased value of pH causes decreased value of zeta potential and decreased SnO2 deposition through EPD technique.

Anodic Oxidation of Titanium in Mixture of β-Glycerophosphate (β-GP) and Calcium Acetate (CA)

Anodic oxidation is an electrochemical method for the production of a ceramic film on a metallic substrate. It involves the use of an electrical bias at relatively low currents while the substrate is immersed in a weak organic acid bath. The films produced are usually dense and stable, with variable microstructural features. In the present work, ceramic films of the anatase and rutile polymorphs of TiO2 were formed on high-purity Ti foil (50 μm) using mixtures of β-glycerophosphate disodium salt pentahydrate (β-GP) and calcium acetate monohydrate (CA) solutions. The experiments were carried out at varying voltages (150-350 V), times (1-10 min), and current density (10 mA.cm-2) at room temperature. The ceramic films were characterised using digital photography, glancing angle X-ray diffraction (GAXRD), and field emission scanning electron microscopy (FESEM). The thicknesses of the films on Ti were measured using focused ion beam (FIB) milling. The colour, microstructures, and thicknesses of the films were seen to be strongly dependent on the applied voltage. At bias <200 V, single-phase anatase was observed to form on Ti, while at higher bias (250 V), rutile formed due to the arcing process.

Short review of ultrafiltration of polymer membrane as a self-cleaning and antifouling in the wastewater system

This paper focuses on ultrafiltration polymer membrane for wastewater systems as a self-cleaning and antifouling. Fouling is one of the most important problems in almost all membrane processes. In this review, membrane antifouling and self-cleaning properties can be improved by using titanium dioxide (TiO2) particles and UV radiation on membrane structure and surface. Coating TiO2 particles on membrane surface is an advanced method to minimize membrane fouling. Hence, these properties can be improved the membrane performance.

Properties of polyurethane foam/coconut coir fiber as a core material and as a sandwich composites component

This research focuses on the fabrication and characterization of sandwich composite panels using glass fiber composite skin and polyurethane foam reinforced coconut coir fiber core. The main objectives are to characterize the physical and mechanical properties and to elucidate the effect of coconut coir fibers in polyurethane foam cores and sandwich composite panels. Coconut coir fibers were used as reinforcement in polyurethane foams in which later were applied as the core in sandwich composites ranged from 5 wt% to 20 wt%. The physical and mechanical properties found to be significant at 5 wt% coconut coir fiber in polyurethane foam cores as well as in sandwich composites. It was found that composites properties serve better in sandwich composites construction.

Gel oxidation of titanium and effect of UV irradiation on precipitation of hydroxyapatite from simulated body fluid

Sodium titanate gels on the surface of titanium metal have been formed using sodium hydroxide solution and oxidised at 400°-800°C. The reaction sequence for these processes with increasing temperature is Ti → sodium titanate gel → crystalline sodium titanate gel → porous (top) and dense (bottom) anatase → porous (top) and dense (bottom) rutile. These samples subsequently were soaked in simulated body fluid in order to study the precipitation of hydroxyapatite in the absence and presence of long UV radiation, which has not been investigated before. One sample showed greatly enhanced hydroxyapatite deposition, this being the one oxidised at 400°C, consisting of small amounts of crystalline sodium titanate and anatase, and subjected to UV irradiation. More generally, enhancement of hydroxyapatite precipitation is observed in the presence of anatase and/or sodium titanate; suppression of hydroxyapatite precipitation is observed in the presence of gels and rutile. However, UV light with anatase enhanced precipitation while UV light with rutile suppressed it. This is attributed to the morphological effect of the larger grain of rutile compared to the smaller anatase.

Titanium Dioxide (TiO2) Films by Anodic Oxidation in Phosphoric Acid

Anodic oxidation is an electrochemical method for the production of an oxide film on a metallic substrate. It involves the application of an electrical bias at relatively low currents while the substrate is immersed in an acid bath. The films can be very dense and stable, with a variety of microstructural characteristics. In the present work, films of the anatase polymorph of TiO2 were formed on high-purity Ti foil (50 μm thickness) using phosphoric acid (0.3 M H3PO4). The conditions of oxidation involved the application of potentials (5 to 350 V) and current densities (5 to 60 mA.cm-2) for 10 min at room temperature. The films were characterised using a digital photography, laser Raman microspectroscopy, and field emission scanning electron microscopy. The thicknesses of the oxide films on Ti were measured using a thin film analyser based on optical spectroscopy principles. The colours, thicknesses, and microstructures of the films depended strongly on the applied voltage and current density. At bias more than 15 V, single-phase anatase was observed to form on Ti at low (5 mA.cm-2) and higher (up to 60 mA.cm-2) current density.