Nurulhuda Bashirom - Academia.edu (original) (raw)

Papers by Nurulhuda Bashirom

Jurnal Teknologi, 2012

This paper presents a study on the effect of milling time on the synthesis of Cu-WC nanocomposite... more This paper presents a study on the effect of milling time on the synthesis of Cu-WC nanocomposites by mechanical alloying (MA). The Cu-WC nanocomposite with a nominal composition of 25 vol.% of WC was produced in-situ via MA from elemental powders of copper (Cu), tungsten (W), and graphite (C). These powders were milled in the high-energy “Pulverisette 6” planetary ball mill according to the composition Cu-34.90 wt.% W-2.28 wt.% C. The powders were milled in the different milling times; 16 hours, 32 hours, and 48 hours at rotational speed of 600 rpm. The milling process was conducted under argon atmosphere by using a stainless steel vial and 10 mm diameter of stainless steel balls, with ball-to-powder weight ratio (BPR) 10:1. The as-milled powders were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). XRD result indicated the formation of WC after milling for 32 hours, and the peak broadening was observed at higher milling time. From SEM observations, ...

Materials Chemistry and Physics, 2011

In present study, effect of conventional heating (CH) and microwave heating (MH) on Maillard reac... more In present study, effect of conventional heating (CH) and microwave heating (MH) on Maillard reaction (MR) progression and structural, functional and antioxidant properties of glycated protein was investigated. The glycation process was carried out at 90 ºC, in bovine serum albumin-maltodextrin system. The extent of glycation was assessed by ortho-phthaldialdehyde, absorbance at 420 nm. Afterwards, K-means clustering was applied to classify all treatments into three levels of glycation (low, medium, high). Subsequently, SDS-PAGE, structural (surface hydrophobicity and circular dichroism), functional and antioxidant (DPPH radical scavenging) properties were measured within these clusters. Results showed that MH was more effective on

Materials Science Forum, 2020

In this paper, visible-light-active monoclinic WO3 powders were synthesized by thermal oxidation ... more In this paper, visible-light-active monoclinic WO3 powders were synthesized by thermal oxidation of W powders at 200 – 1000 °C in air atmosphere. Morphology and crystal structure of annealed W powders were characterized by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD), respectively. Based on SEM and XRD results, a spherical orthorhombic-W3O8 obtained at 200 °C was transformed into a dendritic monoclinic WO2 + tetragonal WO3 + monoclinic WO3 structures at 400 °C accompanied by a color transition from grey into green. At 600 °C, yellow monoclinic WO3 + monoclinic WO2.96 powder was produced that ascribed to oxygen vacancies. Photocatalytic activity of annealed W powders demonstrated 70.7% Cr (VI) removal after 150 min on sample annealed at 1000 °C. This ascribed to high photoactivity of monoclinic WO3. Nevertheless, the dendritic monoclinic WO2 + tetragonal WO3 + monoclinic WO3 obtained at 400 °C exhibited the lowest Cr (VI) photoreduction i.e. 45.2% implies less photo...

Journal of Materials Research and Technology

Nanostructured Anodic Metal Oxides, 2020

Abstract Research focused on synthesis, characterization, and applications of nanomaterials has r... more Abstract Research focused on synthesis, characterization, and applications of nanomaterials has resulted in nanomaterials with advanced morphologies suitable for the use in environmental remedies either as adsorbent or catalysts to remove pollutions. Among various nanostructures, nanotubular materials are known to have unique properties considering their high surface-to-area ratio and high surface curvature, rendering them to have high surface energy and active sites for absorption and catalytic reaction to ensue. Nanotubes can be produced by anodic process on suitable metal surfaces. For instance, when zirconium or titanium foil is anodized in fluoride electrolyte, the resulting anodic film is often found to consist of ZrO2 or TiO2 nanotube arrays. Anodization is an electrochemical oxidation process that relies on the migration of ions across a solid film for oxide growth to happen. To convert such a barrier-type film to nanotubular arrays, modification of the anodizing electrolyte with fluoride ions is essential. The alignment and aspect ratio of the nanotubes on the other hand are dependent on various other parameters including voltage applied. In this study, several aspects regarding the growth of oxide nanotube arrays on Ti, Zr, and Zr–Ti alloys are presented. Then, the possible applications of the nanotubular anodic film (TiO2, ZrO2, and ZrTiO4) grown on these substrates are described. One application discussed in this chapter is the removal of heavy metal ions, specifically chromium(VI), Cr(VI), by these oxides. Cr(VI) ions have high solubility in aquatic environments, and they can be easily absorbed by aquatic organisms. They are however toxic and carcinogenic; thus their exposure to the environment must be minimized. One way to achieve this is by reducing Cr(VI) to a more benign chromium(III), Cr(III), via a photocatalytic process on illuminated TiO2, ZrO2, and ZrTiO4 nanotubes at point of discharged [as a treatment for wastewater concentrated with Cr(VI) from industrial establishment].

1-Dimensional Metal Oxide Nanostructures, 2018

1-Dimensional Metal Oxide Nanostructures, 2018

Catalysts, 2021

In this paper, titanium–dioxide (TiO2) nanotubes (TNTs) are formed by anodic oxidation with a flu... more In this paper, titanium–dioxide (TiO2) nanotubes (TNTs) are formed by anodic oxidation with a fluorinated glycerol–water (85% and 15%, respectively) electrolyte to examine the effect of fluoride ion concentration, time, and applied voltage on TNT morphologies and dimensions. For fluoride ion concentration, the surface etching increases when the amount of ammonium fluoride added to the electrolyte solution increases, forming nanotube arrays with a clear pore structure. At a constant voltage of 20 V, TNTs with an average length of ~2 µm are obtained after anodization for 180 min. A prolonged anodization time only results in a marginal length increment. The TNT diameter is voltage dependent and increases from approximately 30 nm at 10 V to 310 nm at 60 V. At 80 V, the structure is destroyed. TNTs formed at 20 V for 180 min are annealed to induce the TiO2 anatase phase in either air or nitrogen. When ethylenediaminetetraacetic acid is added as a hole scavenger, 100% hexavalent chromium ...

Materials Research Express, 2020

This paper presents the fabrication of self-organized ZrO2, TiO2, and α-Fe2O3 nanotube arrays by ... more This paper presents the fabrication of self-organized ZrO2, TiO2, and α-Fe2O3 nanotube arrays by anodization of Zr, Ti, and Fe foils, respectively in fluoride-containing EG electrolyte at 40 V for 20 min. The as-anodized nanotubes were annealed in a tube furnace at 400 °C for 3 h to induce the crystallization of the oxide film. Morphology, crystal structure, surface properties, and optical properties of the anodic ZrO2 nanotubes (ZNTs), TiO2 nanotubes (TNTs), and α-Fe2O3 nanotubes (FNTs) were characterized by Field-Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), x-ray Diffraction (XRD), Fourier-Transform Infrared (FTIR) spectroscopy, Photoluminescence (PL) spectroscopy, and UV–visible Near-Infrared Diffuse Reflectance Spectra (UV–vis NIR DRS) spectroscopy, respectively. Based on the FESEM and TEM micrographs, ZNTs possessed the longest nanotubes (i.e. 9.6 μm) compared with TNTs and FNTs under the same anodization condition. The aspect ratio of ...

AIP Conference Proceedings, 2018

Self-organized TiO2 nanotube (TNT) arrays were fabricated by anodic oxidation of titanium foil in... more Self-organized TiO2 nanotube (TNT) arrays were fabricated by anodic oxidation of titanium foil in three different fluoride electrolytes: ethylene glycol (EG), glycerol, and sodium sulfate (Na2SO4) at different voltage and anodization time. In these electrolytes, the TNTs were produced in ~ 2 μm long, but at the different diameter. The size of inner diameter can be arranged from the largest to the smallest value in the order of glycerol > EG > Na2SO4. Crystallization of the TNTs by annealing was led to the formation of anatase-TiO2. The sample can be activated under natural sunlight for reduction of hexavalent chromium, Cr(VI) into trivalent chromium, Cr(III). The reduction was thought to occur via synergistic reactions between adsorption and photoreduction. The result demonstrates 100 % of Cr(VI) removal efficiency over the TNTs grown in EG after 120 min. Whereas, only 48 % and 45 % of Cr(VI) can be removed over the TNTs fabricated in glycerol and Na2SO4, respectively. High photocatalytic activity of the TNTs-EG can be attributed to high crystallinity of anatase phase, enhanced Cr(VI) adsorption, and less electron-hole recombination due to smoother tube walls.

Journal of Physics: Conference Series, 2019

Silver nanoparticles (AgNPs) were synthesized by green biological technique utilising kyllinga br... more Silver nanoparticles (AgNPs) were synthesized by green biological technique utilising kyllinga brevifolia extract (KBE) as reducing agents. The KBE was also found to be a good capping as well as stabilizing agent. The size, shape and dispersion of AgNPs were evaluated and compared with the results from the literature survey. The TEM image showed that KBE-driven AgNPs have quasi-spherical shape are highly dispersed with an average particle size ~17.64 nm. The catalytic activity of KBE-driven AgNPs on reduction of methylene blue (MB) using sodium borohydride (SB) was analysed using UV-vis spectroscopy. The MB removal was achieved 100% at pH 8-10. The efficient removal is proposed to be due to the process of reduction via electron relay effect.

1-Dimensional Metal Oxide Nanostructures, 2018

IEEE Transactions on Nanotechnology, 2018

Heterogeneous photocatalysis based on semiconductor oxide is a promising technology for treating ... more Heterogeneous photocatalysis based on semiconductor oxide is a promising technology for treating polluted industrial waste water. Cr(VI) is an example of toxic and mobile water pollutant originated mainly from industrial processes like steel industry and electroplating. The removal of Cr(VI) can be done by photoreduction on a surface of photocatalysts like TiO2 nanotubes (TNTs). Here we describe a fast-rate formation of highly ordered TNTs via two steps anodization processes in an aged electrolyte containing fluoride-ethylene glycol. First step anodization was done for template formation as well as for saturating the electrolyte with TiF62– and second anodization was done to grow TNTs. The template was formed by removing initial anodic layer through sonication. Anodization voltage was kept constant at 60 V. After an hour of anodization, 22.70 μm long TNTs were formed with the rate of ∼350 nm/min. The as-anodized TNTs were then annealed in N2 gas at different temperatures. The annealed TNTs were then used as photocatalyst for the photoreduction of Cr(VI) under sunlight in a parabolic trough reflector. The TNTs annealed at 450 °C in nitrogen show the best photoreduction activity with ∼80% Cr(VI) removal after 5 h exposure to sunlight. This is due to the presence of anatase TiO2 as well as a possibility of nitrogen insertion, which may have narrowed the band gap of the oxide.

Nanotechnology, Jan 14, 2018

Visible-light-active freestanding zirconia (ZrO2) nanotube (FSZNT) arrays were fabricated by a fa... more Visible-light-active freestanding zirconia (ZrO2) nanotube (FSZNT) arrays were fabricated by a facile electrochemical anodization method in fluoride containing ethylene glycol electrolyte added to it 1 vol.% of potassium carbonate (K2CO3) at 60 V for 1 h. Poor adhesion at metal|oxide interface was induced by K2CO3 leading to formation of the FSZNT flakes. The effect of crystal structures of FSZNTs e.g., amorphous, amorphous/tetragonal, and tetragonal/monoclinic was investigated towards the photocatalytic reduction of 10 ppm hexavalent chromium, Cr(VI) at pH 2 under sunlight. The results demonstrate the amorphous FSZNTs exhibited the highest Cr(VI) removal efficiency than the crystalline FSZNTs (95 % versus 33 % after 5 h). The high photocatalytic activity of the amorphous FSZNTs can be attributed to enhanced Cr(VI) adsorption, high visible light absorption, and better charge carriers separation. The low photocatalytic activity of the crystalline FSZNTs annealed at 500 °C was mainly ...

Surface and Coatings Technology, 2017

The influence of K 2 CO 3 on the morphology of anodic zirconia (ZrO 2) nanotubes array were inves... more The influence of K 2 CO 3 on the morphology of anodic zirconia (ZrO 2) nanotubes array were investigated by anodizing zirconium (Zr) foil at 60 V in fluorinated ethylene glycol (EG) electrolyte added to it varying amount of K 2 CO 3 : 0.5 vol.%, 1 vol.%, 2 vol.% and 3 vol.%. The adhesion of ZrO 2 on Zr is affected by the volume of K 2 CO 3 added whereby at lower volume, i.e. 0.5 vol.% and 1 vol.%, poor adhesion of anodic film was observed leading to the formation of loose ZrO 2 flakes. At higher 2 vol.% and 3 vol.% addition the adhesion was improved. All anodic films are comprised of nanotubes with length increases when more K 2 CO 3 was added in EG. Nanotubes grown in 3 vol.% K 2 CO 3 are 9.4 µm long with 48.8 nm outer diameter and 9.1 nm wall thickness. Reducing the applied potential to 20 V resulted in compact oxide and at 40 V, nanotubes with smaller diameter of < 50 nm were produced. Crystallization of the ZrO 2 nanotubes was achieved by annealing at 400 °C. The crystalline ZrO 2 nanotubes (mostly in monoclinic and tetragonal phasess) grown in 3 vol.% K 2 CO 3 exhibits the highest photocurrent density (0.12 mA/cm-2) and rapid methyl orange (MO) degradation under ultraviolet (UV) radiation. This is attributed to the good adhesion of ZrO 2 on Zr, longer length of the tubes and perhaps from the effect of adsorbed carbonate ions on the surface of the oxide.

Solid State Phenomena, 2017

Anodisation of zirconium, Zr at 40 V for 60 min in 0.1 wt.% NH4F/ethylene glycol (EG) added to it... more Anodisation of zirconium, Zr at 40 V for 60 min in 0.1 wt.% NH4F/ethylene glycol (EG) added to it 1 ml, 2 ml or 3 ml of water resulted in the formation of self-aligned ZrO2 nanotube (ZNT) arrays. Water content did not affect the length and diameter of the ZNTs but was influencing surface etching whereby better surface etching was observed for sample anodised in 3 ml-water/NH4F/EG. From transmission electron microcopy (TEM) image, the ZNTs were found to have an outer diameter of ~ 40 nm and wall thickness of 10 nm. Annealing at 400 °C was resulted in monoclinic (M-ZrO2) and tetragonal (T-ZrO2) formation, but at 600 °C M-ZrO2 dominates. Cr(VI) reduction is higher for ZNTs annealed at 400 °C compared to 600 °C sample.

Surface and Coatings Technology, 2017

13.6 µm long ZrO 2 nanotubes were fabricated by anodization in fluoride ethylene glycol added to ... more 13.6 µm long ZrO 2 nanotubes were fabricated by anodization in fluoride ethylene glycol added to it K 2 CO 3. The addition of K 2 CO 3 in the electrolyte was found to weaken the adherence of the anodic film from the underlying Zr. This produced freestanding ZrO 2 nanotubes in a form of loose flakes. The as-anodized ZrO 2 nanotubes were amorphous with surface area of 25.3 m 2 /g. The amorphous ZrO 2 nanotubes were then used to adsorb and reduce Cr(VI) in aqueous solution under visible light illumination. The presence of hydroxyl and carbonate groups on the surface of the nanotubes may have improved the adsorbent property of the nanotubes. Once the Cr(VI) ions were adsorbed on the oxide, they were reduced by photoelectrons generated when ZrO 2 was illuminated. High concentration of oxygen vacancies and Zr 3+ defects, as well as the incorporation of carbon atoms into the ZrO 2 lattice may have influence the formation of free electrons for photoreduction process to occur.

Freestanding ZrO2 nanotubes (ZNTs) were produced using a simple anodization method in fluorinated... more Freestanding ZrO2 nanotubes (ZNTs) were produced using a simple anodization method in fluorinated ethylene glycol electrolyte containing 1 ml 1 M K2CO3. The pH of the bath was kept constant at 8. The potassium carbonate (K2CO3) was added into electrolyte to promote the detachment of anodic ZrO2 film from the underlying zirconium (Zr) substrate. The poor adherence of ZNTs layer was due to generation of CO2 gas that was thought to occur between metal|oxide interfaces. The effect of anodization voltages towards the detachment of ZNTs layer was systematically studied at 20 V, 40 V, 50 V and 60 V for 1 hour. The formation of CO2 gas is a function of anodization voltage, in which at 60 V, a good anodic film separation seen due to higher formation of CO2 gas. A preliminary study shown the capability of ZNTs in removing 5 ppm of Cr(VI) aqueous solution under illumination of UV light.

Procedia Chemistry, 2016

0.3 wt % ammonium fluoride (NH 4 F) or ammonium chloride (NH 4 Cl) was added to ethylene glycol (... more 0.3 wt % ammonium fluoride (NH 4 F) or ammonium chloride (NH 4 Cl) was added to ethylene glycol (EG) as an active ingredient for the formation of anodic oxide comprising of ZrO 2 nanotubes (ZNTs) by anodic oxidation of zirconium (Zr) at 20 V for 10 min. It was observed that nanotubes were successfully grown in EG/NH 4 F/H 2 O with aspect ratio of 144.3. Shorter tubes were formed in EG/NH 4 F/H 2 O 2. This could be due to higher excessive chemical etching at the tip of the tubes. When fluoride was replaced by chloride in both electrolytes, multilayered oxide resembling pyramids was observed. The pyramids have width at the bottom of 3-4 µm and the top is 1-2 µm with 10.7 µm height. Oxidation of Zr in EG/NH 4 Cl/H 2 O 2 was rater rapid. The multilayered structure is thought to have formed due to the re-deposition of ZrO 2 or hydrated ZrO 2 on the foil inside pores formed within the oxide layer. XRD result revealed an amorphous structure for as-anodized samples regardless of the electrolytes used for this work.

Applied Surface Science, 2016

Abstract Thermal oxidation of iron foil was done at 400 °C and 500 °C in for 2 h to form multilay... more Abstract Thermal oxidation of iron foil was done at 400 °C and 500 °C in for 2 h to form multilayered oxide scale with outer oxide layer of α-Fe2O3 comprising of nanowires and nanosheets respectively. Iron oxidized at 300 °C formed a rather compact film with no noticeable nanostructures. The morphologies of oxide formed in different oxidation environment (water vapour or dry air) were compared; densely packed nanostructures were produced in water vapour compared to dry air. Time variation study indicated rapid growth of nanostructure whereby for 1 min at 500 °C dense nanowires with some noticeable nanosheets were already observed. The nanowires and nanosheets were used to adsorb Cr(VI) from aqueous solution. Adsorption of 10 ppm of Cr(VI) on the nanowires and nanosheets was found to be successful with much faster removal efficiency for the nanosheets. Both samples displayed complete adsorption for less than 1 h.

Jurnal Teknologi, 2012

This paper presents a study on the effect of milling time on the synthesis of Cu-WC nanocomposite... more This paper presents a study on the effect of milling time on the synthesis of Cu-WC nanocomposites by mechanical alloying (MA). The Cu-WC nanocomposite with a nominal composition of 25 vol.% of WC was produced in-situ via MA from elemental powders of copper (Cu), tungsten (W), and graphite (C). These powders were milled in the high-energy “Pulverisette 6” planetary ball mill according to the composition Cu-34.90 wt.% W-2.28 wt.% C. The powders were milled in the different milling times; 16 hours, 32 hours, and 48 hours at rotational speed of 600 rpm. The milling process was conducted under argon atmosphere by using a stainless steel vial and 10 mm diameter of stainless steel balls, with ball-to-powder weight ratio (BPR) 10:1. The as-milled powders were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). XRD result indicated the formation of WC after milling for 32 hours, and the peak broadening was observed at higher milling time. From SEM observations, ...

Materials Chemistry and Physics, 2011

In present study, effect of conventional heating (CH) and microwave heating (MH) on Maillard reac... more In present study, effect of conventional heating (CH) and microwave heating (MH) on Maillard reaction (MR) progression and structural, functional and antioxidant properties of glycated protein was investigated. The glycation process was carried out at 90 ºC, in bovine serum albumin-maltodextrin system. The extent of glycation was assessed by ortho-phthaldialdehyde, absorbance at 420 nm. Afterwards, K-means clustering was applied to classify all treatments into three levels of glycation (low, medium, high). Subsequently, SDS-PAGE, structural (surface hydrophobicity and circular dichroism), functional and antioxidant (DPPH radical scavenging) properties were measured within these clusters. Results showed that MH was more effective on

Materials Science Forum, 2020

In this paper, visible-light-active monoclinic WO3 powders were synthesized by thermal oxidation ... more In this paper, visible-light-active monoclinic WO3 powders were synthesized by thermal oxidation of W powders at 200 – 1000 °C in air atmosphere. Morphology and crystal structure of annealed W powders were characterized by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD), respectively. Based on SEM and XRD results, a spherical orthorhombic-W3O8 obtained at 200 °C was transformed into a dendritic monoclinic WO2 + tetragonal WO3 + monoclinic WO3 structures at 400 °C accompanied by a color transition from grey into green. At 600 °C, yellow monoclinic WO3 + monoclinic WO2.96 powder was produced that ascribed to oxygen vacancies. Photocatalytic activity of annealed W powders demonstrated 70.7% Cr (VI) removal after 150 min on sample annealed at 1000 °C. This ascribed to high photoactivity of monoclinic WO3. Nevertheless, the dendritic monoclinic WO2 + tetragonal WO3 + monoclinic WO3 obtained at 400 °C exhibited the lowest Cr (VI) photoreduction i.e. 45.2% implies less photo...

Journal of Materials Research and Technology

Nanostructured Anodic Metal Oxides, 2020

Abstract Research focused on synthesis, characterization, and applications of nanomaterials has r... more Abstract Research focused on synthesis, characterization, and applications of nanomaterials has resulted in nanomaterials with advanced morphologies suitable for the use in environmental remedies either as adsorbent or catalysts to remove pollutions. Among various nanostructures, nanotubular materials are known to have unique properties considering their high surface-to-area ratio and high surface curvature, rendering them to have high surface energy and active sites for absorption and catalytic reaction to ensue. Nanotubes can be produced by anodic process on suitable metal surfaces. For instance, when zirconium or titanium foil is anodized in fluoride electrolyte, the resulting anodic film is often found to consist of ZrO2 or TiO2 nanotube arrays. Anodization is an electrochemical oxidation process that relies on the migration of ions across a solid film for oxide growth to happen. To convert such a barrier-type film to nanotubular arrays, modification of the anodizing electrolyte with fluoride ions is essential. The alignment and aspect ratio of the nanotubes on the other hand are dependent on various other parameters including voltage applied. In this study, several aspects regarding the growth of oxide nanotube arrays on Ti, Zr, and Zr–Ti alloys are presented. Then, the possible applications of the nanotubular anodic film (TiO2, ZrO2, and ZrTiO4) grown on these substrates are described. One application discussed in this chapter is the removal of heavy metal ions, specifically chromium(VI), Cr(VI), by these oxides. Cr(VI) ions have high solubility in aquatic environments, and they can be easily absorbed by aquatic organisms. They are however toxic and carcinogenic; thus their exposure to the environment must be minimized. One way to achieve this is by reducing Cr(VI) to a more benign chromium(III), Cr(III), via a photocatalytic process on illuminated TiO2, ZrO2, and ZrTiO4 nanotubes at point of discharged [as a treatment for wastewater concentrated with Cr(VI) from industrial establishment].

1-Dimensional Metal Oxide Nanostructures, 2018

1-Dimensional Metal Oxide Nanostructures, 2018

Catalysts, 2021

In this paper, titanium–dioxide (TiO2) nanotubes (TNTs) are formed by anodic oxidation with a flu... more In this paper, titanium–dioxide (TiO2) nanotubes (TNTs) are formed by anodic oxidation with a fluorinated glycerol–water (85% and 15%, respectively) electrolyte to examine the effect of fluoride ion concentration, time, and applied voltage on TNT morphologies and dimensions. For fluoride ion concentration, the surface etching increases when the amount of ammonium fluoride added to the electrolyte solution increases, forming nanotube arrays with a clear pore structure. At a constant voltage of 20 V, TNTs with an average length of ~2 µm are obtained after anodization for 180 min. A prolonged anodization time only results in a marginal length increment. The TNT diameter is voltage dependent and increases from approximately 30 nm at 10 V to 310 nm at 60 V. At 80 V, the structure is destroyed. TNTs formed at 20 V for 180 min are annealed to induce the TiO2 anatase phase in either air or nitrogen. When ethylenediaminetetraacetic acid is added as a hole scavenger, 100% hexavalent chromium ...

Materials Research Express, 2020

This paper presents the fabrication of self-organized ZrO2, TiO2, and α-Fe2O3 nanotube arrays by ... more This paper presents the fabrication of self-organized ZrO2, TiO2, and α-Fe2O3 nanotube arrays by anodization of Zr, Ti, and Fe foils, respectively in fluoride-containing EG electrolyte at 40 V for 20 min. The as-anodized nanotubes were annealed in a tube furnace at 400 °C for 3 h to induce the crystallization of the oxide film. Morphology, crystal structure, surface properties, and optical properties of the anodic ZrO2 nanotubes (ZNTs), TiO2 nanotubes (TNTs), and α-Fe2O3 nanotubes (FNTs) were characterized by Field-Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), x-ray Diffraction (XRD), Fourier-Transform Infrared (FTIR) spectroscopy, Photoluminescence (PL) spectroscopy, and UV–visible Near-Infrared Diffuse Reflectance Spectra (UV–vis NIR DRS) spectroscopy, respectively. Based on the FESEM and TEM micrographs, ZNTs possessed the longest nanotubes (i.e. 9.6 μm) compared with TNTs and FNTs under the same anodization condition. The aspect ratio of ...

AIP Conference Proceedings, 2018

Self-organized TiO2 nanotube (TNT) arrays were fabricated by anodic oxidation of titanium foil in... more Self-organized TiO2 nanotube (TNT) arrays were fabricated by anodic oxidation of titanium foil in three different fluoride electrolytes: ethylene glycol (EG), glycerol, and sodium sulfate (Na2SO4) at different voltage and anodization time. In these electrolytes, the TNTs were produced in ~ 2 μm long, but at the different diameter. The size of inner diameter can be arranged from the largest to the smallest value in the order of glycerol > EG > Na2SO4. Crystallization of the TNTs by annealing was led to the formation of anatase-TiO2. The sample can be activated under natural sunlight for reduction of hexavalent chromium, Cr(VI) into trivalent chromium, Cr(III). The reduction was thought to occur via synergistic reactions between adsorption and photoreduction. The result demonstrates 100 % of Cr(VI) removal efficiency over the TNTs grown in EG after 120 min. Whereas, only 48 % and 45 % of Cr(VI) can be removed over the TNTs fabricated in glycerol and Na2SO4, respectively. High photocatalytic activity of the TNTs-EG can be attributed to high crystallinity of anatase phase, enhanced Cr(VI) adsorption, and less electron-hole recombination due to smoother tube walls.

Journal of Physics: Conference Series, 2019

Silver nanoparticles (AgNPs) were synthesized by green biological technique utilising kyllinga br... more Silver nanoparticles (AgNPs) were synthesized by green biological technique utilising kyllinga brevifolia extract (KBE) as reducing agents. The KBE was also found to be a good capping as well as stabilizing agent. The size, shape and dispersion of AgNPs were evaluated and compared with the results from the literature survey. The TEM image showed that KBE-driven AgNPs have quasi-spherical shape are highly dispersed with an average particle size ~17.64 nm. The catalytic activity of KBE-driven AgNPs on reduction of methylene blue (MB) using sodium borohydride (SB) was analysed using UV-vis spectroscopy. The MB removal was achieved 100% at pH 8-10. The efficient removal is proposed to be due to the process of reduction via electron relay effect.

1-Dimensional Metal Oxide Nanostructures, 2018

IEEE Transactions on Nanotechnology, 2018

Heterogeneous photocatalysis based on semiconductor oxide is a promising technology for treating ... more Heterogeneous photocatalysis based on semiconductor oxide is a promising technology for treating polluted industrial waste water. Cr(VI) is an example of toxic and mobile water pollutant originated mainly from industrial processes like steel industry and electroplating. The removal of Cr(VI) can be done by photoreduction on a surface of photocatalysts like TiO2 nanotubes (TNTs). Here we describe a fast-rate formation of highly ordered TNTs via two steps anodization processes in an aged electrolyte containing fluoride-ethylene glycol. First step anodization was done for template formation as well as for saturating the electrolyte with TiF62– and second anodization was done to grow TNTs. The template was formed by removing initial anodic layer through sonication. Anodization voltage was kept constant at 60 V. After an hour of anodization, 22.70 μm long TNTs were formed with the rate of ∼350 nm/min. The as-anodized TNTs were then annealed in N2 gas at different temperatures. The annealed TNTs were then used as photocatalyst for the photoreduction of Cr(VI) under sunlight in a parabolic trough reflector. The TNTs annealed at 450 °C in nitrogen show the best photoreduction activity with ∼80% Cr(VI) removal after 5 h exposure to sunlight. This is due to the presence of anatase TiO2 as well as a possibility of nitrogen insertion, which may have narrowed the band gap of the oxide.

Nanotechnology, Jan 14, 2018

Visible-light-active freestanding zirconia (ZrO2) nanotube (FSZNT) arrays were fabricated by a fa... more Visible-light-active freestanding zirconia (ZrO2) nanotube (FSZNT) arrays were fabricated by a facile electrochemical anodization method in fluoride containing ethylene glycol electrolyte added to it 1 vol.% of potassium carbonate (K2CO3) at 60 V for 1 h. Poor adhesion at metal|oxide interface was induced by K2CO3 leading to formation of the FSZNT flakes. The effect of crystal structures of FSZNTs e.g., amorphous, amorphous/tetragonal, and tetragonal/monoclinic was investigated towards the photocatalytic reduction of 10 ppm hexavalent chromium, Cr(VI) at pH 2 under sunlight. The results demonstrate the amorphous FSZNTs exhibited the highest Cr(VI) removal efficiency than the crystalline FSZNTs (95 % versus 33 % after 5 h). The high photocatalytic activity of the amorphous FSZNTs can be attributed to enhanced Cr(VI) adsorption, high visible light absorption, and better charge carriers separation. The low photocatalytic activity of the crystalline FSZNTs annealed at 500 °C was mainly ...

Surface and Coatings Technology, 2017

The influence of K 2 CO 3 on the morphology of anodic zirconia (ZrO 2) nanotubes array were inves... more The influence of K 2 CO 3 on the morphology of anodic zirconia (ZrO 2) nanotubes array were investigated by anodizing zirconium (Zr) foil at 60 V in fluorinated ethylene glycol (EG) electrolyte added to it varying amount of K 2 CO 3 : 0.5 vol.%, 1 vol.%, 2 vol.% and 3 vol.%. The adhesion of ZrO 2 on Zr is affected by the volume of K 2 CO 3 added whereby at lower volume, i.e. 0.5 vol.% and 1 vol.%, poor adhesion of anodic film was observed leading to the formation of loose ZrO 2 flakes. At higher 2 vol.% and 3 vol.% addition the adhesion was improved. All anodic films are comprised of nanotubes with length increases when more K 2 CO 3 was added in EG. Nanotubes grown in 3 vol.% K 2 CO 3 are 9.4 µm long with 48.8 nm outer diameter and 9.1 nm wall thickness. Reducing the applied potential to 20 V resulted in compact oxide and at 40 V, nanotubes with smaller diameter of < 50 nm were produced. Crystallization of the ZrO 2 nanotubes was achieved by annealing at 400 °C. The crystalline ZrO 2 nanotubes (mostly in monoclinic and tetragonal phasess) grown in 3 vol.% K 2 CO 3 exhibits the highest photocurrent density (0.12 mA/cm-2) and rapid methyl orange (MO) degradation under ultraviolet (UV) radiation. This is attributed to the good adhesion of ZrO 2 on Zr, longer length of the tubes and perhaps from the effect of adsorbed carbonate ions on the surface of the oxide.

Solid State Phenomena, 2017

Anodisation of zirconium, Zr at 40 V for 60 min in 0.1 wt.% NH4F/ethylene glycol (EG) added to it... more Anodisation of zirconium, Zr at 40 V for 60 min in 0.1 wt.% NH4F/ethylene glycol (EG) added to it 1 ml, 2 ml or 3 ml of water resulted in the formation of self-aligned ZrO2 nanotube (ZNT) arrays. Water content did not affect the length and diameter of the ZNTs but was influencing surface etching whereby better surface etching was observed for sample anodised in 3 ml-water/NH4F/EG. From transmission electron microcopy (TEM) image, the ZNTs were found to have an outer diameter of ~ 40 nm and wall thickness of 10 nm. Annealing at 400 °C was resulted in monoclinic (M-ZrO2) and tetragonal (T-ZrO2) formation, but at 600 °C M-ZrO2 dominates. Cr(VI) reduction is higher for ZNTs annealed at 400 °C compared to 600 °C sample.

Surface and Coatings Technology, 2017

13.6 µm long ZrO 2 nanotubes were fabricated by anodization in fluoride ethylene glycol added to ... more 13.6 µm long ZrO 2 nanotubes were fabricated by anodization in fluoride ethylene glycol added to it K 2 CO 3. The addition of K 2 CO 3 in the electrolyte was found to weaken the adherence of the anodic film from the underlying Zr. This produced freestanding ZrO 2 nanotubes in a form of loose flakes. The as-anodized ZrO 2 nanotubes were amorphous with surface area of 25.3 m 2 /g. The amorphous ZrO 2 nanotubes were then used to adsorb and reduce Cr(VI) in aqueous solution under visible light illumination. The presence of hydroxyl and carbonate groups on the surface of the nanotubes may have improved the adsorbent property of the nanotubes. Once the Cr(VI) ions were adsorbed on the oxide, they were reduced by photoelectrons generated when ZrO 2 was illuminated. High concentration of oxygen vacancies and Zr 3+ defects, as well as the incorporation of carbon atoms into the ZrO 2 lattice may have influence the formation of free electrons for photoreduction process to occur.

Freestanding ZrO2 nanotubes (ZNTs) were produced using a simple anodization method in fluorinated... more Freestanding ZrO2 nanotubes (ZNTs) were produced using a simple anodization method in fluorinated ethylene glycol electrolyte containing 1 ml 1 M K2CO3. The pH of the bath was kept constant at 8. The potassium carbonate (K2CO3) was added into electrolyte to promote the detachment of anodic ZrO2 film from the underlying zirconium (Zr) substrate. The poor adherence of ZNTs layer was due to generation of CO2 gas that was thought to occur between metal|oxide interfaces. The effect of anodization voltages towards the detachment of ZNTs layer was systematically studied at 20 V, 40 V, 50 V and 60 V for 1 hour. The formation of CO2 gas is a function of anodization voltage, in which at 60 V, a good anodic film separation seen due to higher formation of CO2 gas. A preliminary study shown the capability of ZNTs in removing 5 ppm of Cr(VI) aqueous solution under illumination of UV light.

Procedia Chemistry, 2016

0.3 wt % ammonium fluoride (NH 4 F) or ammonium chloride (NH 4 Cl) was added to ethylene glycol (... more 0.3 wt % ammonium fluoride (NH 4 F) or ammonium chloride (NH 4 Cl) was added to ethylene glycol (EG) as an active ingredient for the formation of anodic oxide comprising of ZrO 2 nanotubes (ZNTs) by anodic oxidation of zirconium (Zr) at 20 V for 10 min. It was observed that nanotubes were successfully grown in EG/NH 4 F/H 2 O with aspect ratio of 144.3. Shorter tubes were formed in EG/NH 4 F/H 2 O 2. This could be due to higher excessive chemical etching at the tip of the tubes. When fluoride was replaced by chloride in both electrolytes, multilayered oxide resembling pyramids was observed. The pyramids have width at the bottom of 3-4 µm and the top is 1-2 µm with 10.7 µm height. Oxidation of Zr in EG/NH 4 Cl/H 2 O 2 was rater rapid. The multilayered structure is thought to have formed due to the re-deposition of ZrO 2 or hydrated ZrO 2 on the foil inside pores formed within the oxide layer. XRD result revealed an amorphous structure for as-anodized samples regardless of the electrolytes used for this work.

Applied Surface Science, 2016

Abstract Thermal oxidation of iron foil was done at 400 °C and 500 °C in for 2 h to form multilay... more Abstract Thermal oxidation of iron foil was done at 400 °C and 500 °C in for 2 h to form multilayered oxide scale with outer oxide layer of α-Fe2O3 comprising of nanowires and nanosheets respectively. Iron oxidized at 300 °C formed a rather compact film with no noticeable nanostructures. The morphologies of oxide formed in different oxidation environment (water vapour or dry air) were compared; densely packed nanostructures were produced in water vapour compared to dry air. Time variation study indicated rapid growth of nanostructure whereby for 1 min at 500 °C dense nanowires with some noticeable nanosheets were already observed. The nanowires and nanosheets were used to adsorb Cr(VI) from aqueous solution. Adsorption of 10 ppm of Cr(VI) on the nanowires and nanosheets was found to be successful with much faster removal efficiency for the nanosheets. Both samples displayed complete adsorption for less than 1 h.