scholarly journals A Novel Solar Driven Photocatalyst: Well-Aligned Anodic WO3Nanotubes

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Chin Wei Lai ◽  
Sharifah Bee Abd Hamid ◽  
Srimala Sreekantan
Keyword(s):  
Surface Morphology ◽  
Formation Mechanism ◽  
Tungsten Trioxide ◽  
Average Diameter ◽  
Ammonium Fluoride ◽  
Sodium Sulphate ◽  
Electrochemical Anodization ◽  
Methyl Blue ◽  
Photocatalytic Ability ◽  
Nanotubular Structure

Well-aligned anodic tungsten trioxide (WO3) nanotubes were successfully synthesized by anodization of W foil at 40 V in a bath with electrolyte composed of 1 M of sodium sulphate (Na2SO4) and 0.5 wt% ammonium fluoride (NH4F). The effect of electrochemical anodization times on the formation mechanism of anodic WO3nanotubular structure was investigated. It was found that minimum of 15 min is required for completing transformation from W foil to WO3nanotubular structure with an average diameter of 50 nm and length of 500 nm. The photocatalytic ability of the samples was evaluated by degradation of methyl blue (MB) dye. The results indicate that the surface morphology of anodic WO3affected the photocatalytic MB degradation significantly under solar illumination.

scholarly journals Photocatalysis and Photoelectrochemical Properties of Tungsten Trioxide Nanostructured Films

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Chin Wei Lai
Keyword(s):  
Tungsten Trioxide ◽  
Critical Role ◽  
Solar Spectrum ◽  
Average Diameter ◽  
Active Surface ◽  
Sodium Sulphate ◽  
Electrochemical Anodization ◽  
Active Surface Area ◽  
Fluoride Ions ◽  
Nanotubular Structure

Tungsten trioxide (WO3) possesses a small band gap energy of 2.4–2.8 eV and is responsive to both ultraviolet and visible light irradiation including strong absorption of the solar spectrum and stable physicochemical properties. Thus, controlled growth of one-dimensional (1D) WO3nanotubular structures with desired length, diameter, and wall thickness has gained significant interest. In the present study, 1D WO3nanotubes were successfully synthesized via electrochemical anodization of tungsten (W) foil in an electrolyte composed of 1 M of sodium sulphate (Na2SO4) and ammonium fluoride (NH4F). The influence of NH4F content on the formation mechanism of anodic WO3nanotubular structure was investigated in detail. An optimization of fluoride ions played a critical role in controlling the chemical dissolution reaction in the interface of W/WO3. Based on the results obtained, a minimum of 0.7 wt% of NH4F content was required for completing transformation from W foil to WO3nanotubular structure with an average diameter of 85 nm and length of 250 nm within 15 min of anodization time. In this case, high aspect ratio of WO3nanotubular structure is preferred because larger active surface area will be provided for better photocatalytic and photoelectrochemical (PEC) reactions.

Discovery of WO3/TiO2 Nanostructure Transformation by Controlling Content of NH4F to Enhance Photoelectrochemical Response

2012 ◽  
Vol 620 ◽  
pp. 173-178 ◽  
Author(s):  
Chin Wei Lai ◽  
Srimala Sreekantan
Keyword(s):  
Ammonium Fluoride ◽  
Anodic Oxide ◽  
Photocurrent Density ◽  
Electrochemical Anodization ◽  
Nanoporous Structure ◽  
Nanotubular Structure ◽  
Insufficient Amount ◽  
Photoelectrochemical Response ◽  
Anodization Process ◽  
Anodic Oxide Layer

We report on the effect of the tungsten (W) cathode in controlling the morphology and properties of titanium (Ti) anodic oxide layer via an electrochemical anodization process. The content of ammonium fluoride (NH4F) was varied in ethylene glycol (EG) electrolyte containing hydrogen peroxide (H2O2) in order to obtained the high ordered nanotubular structure. When amount of NH4F was upto 5 wt%, highly ordered WO3-TiO2nanotubes structure was observed. If insufficient amount of NH4F is applied, the nanoporous structure will be favored. Highly ordered WO3-TiO2nanotubes structure exhibited higher photocurrent density ( 0.9 mA/cm2) as compared to the WO3-TiO2nanoporous structure.

Isolasi Dan Karakterisasi Bentonit Alam Menjadi Nanopartikel Monmorillonit

2018 ◽  
Vol 3 (1) ◽  
pp. 12 ◽  
Author(s):  
Zaimahwati Zaimahwati ◽  
Yuniati Yuniati ◽  
Ramzi Jalal ◽  
Syahman Zhafiri ◽  
Yuli Yetri
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Particle Size ◽  
Surface Morphology ◽  
Average Diameter ◽  
Particle Size Analyzer ◽  
Ft Ir ◽  
Scanning Electron ◽  
Sedimentation Processes

<p>Pada penelitian ini telah dilakukan isolasi dan karakterisasi bentonit alam menjadi nanopartikel montmorillonit. Bentonit alam yang digunakan diambil dari desa Blangdalam, Kecamatan Nisam Kabupaten Aceh Utara.  Proses isolasi meliputi proses pelarutan dengan aquades, ultrasonic dan proses sedimentasi. Untuk mengetahui karakterisasi montmorillonit dilakukan uji FT-IR, X-RD dan uji morfologi permukaan dengan Scanning Electron Microscopy (SEM). Partikel size analyzer untuk menganalisis dan menentukan ukuran nanopartikel dari isolasi bentonit alam. Dari hasil penelitian didapat ukuran nanopartikel montmorillonit hasil isolasi dari bentonit alam diperoleh berdiameter rata-rata 82,15 nm.</p><p><em>In this research we have isolated and characterized natural bentonite into montmorillonite nanoparticles. Natural bentonite used was taken from Blangdalam village, Nisam sub-district, North Aceh district. The isolation process includes dissolving process with aquades, ultrasonic and sedimentation processes.  The characterization of montmorillonite, FT-IR, X-RD and surface morphology test by Scanning Electron Microscopy (SEM). Particle size analyzer to analyze and determine the size of nanoparticles from natural bentonite insulation. From the research results obtained the size of montmorillonite nanoparticles isolated from natural bentonite obtained an average diameter of 82.15 nm.</em></p>

Synthesis and Structure of Titania Nanotubes For Hydrogen Generation

2013 ◽  
Vol 741 ◽  
pp. 84-89 ◽  
Author(s):  
Sangworn Wantawee ◽  
Pacharee Krongkitsiri ◽  
Tippawan Saipin ◽  
Buagun Samran ◽  
Udom Tipparach
Keyword(s):  
Oxalic Acid ◽  
Hydrogen Generation ◽  
Ammonium Fluoride ◽  
Photocurrent Density ◽  
Sodium Sulphate ◽  
Titania Nanotubes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dc Power ◽  
Anodic Voltage

Titania nanotubes (TiO2NTs) working electrodes for hydrogen production by photoelectrocatalytic water splitting were synthesized by means of anodization method. The electrolytes were the mixtures of oxalic acid (H2C2O4), ammonium fluoride (NH4F), and sodium sulphate (VI) (Na2SO4) with different pHs. A constant dc power supply at 20 V was used as anodic voltage. The samples were annealed at 450 °C for 2 hrs. Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) were used to characterized TiO2NTs microstructure. TiO2NTs with diameter of 100 nm were obtained when pH 3 electrolyte consisting of 0.08 M oxalic acid, 0.5 wt% NH4F, and 1.0 wt% Na2SO4was used. Without external applied potential, the maximum photocurrent density was 2.8 mA/cm2under illumination of 100 mW/cm2. Hydrogen was generated at an overall photoconversion efficiency of 3.4 %.

Nanopores and nanosheets of α-Fe2O3 synthetized by electrochemical anodization and analysed by Raman spectroscopy

MRS Advances ◽  
2019 ◽  
Vol 4 (53) ◽  
pp. 2863-2871
Author(s):  
L.M.C. Pérez-Pérez ◽  
A. Báez-Rodríguez ◽  
L. García-González ◽  
J. Hernández-Torres ◽  
O. Velázquez-Camilo ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Crystalline Structure ◽  
Room Temperature ◽  
Ammonium Fluoride ◽  
Deionized Water ◽  
Electrochemical Anodization ◽  
Vibration Modes ◽  
Spectroscopy Technique ◽  
Temperature Scanning ◽  
Static Conditions

Abstract:Nanoparticles and nanopores of iron oxide were synthesized by electrochemical anodization, in an electrolytic medium of ammonium fluoride (NH4F), deionized water and ethylene glycol. After anodization, the Fe foils were annealed at 450 °C for 2 hours. Different anodization times and two concentrations of NH4F (0.1 M and 1.2 M) were evaluated, under static conditions at room temperature. Scanning Electron Microscopy showed nanopores (0.1 M) and nanoparticles (1.2 M). Eight vibration modes characteristic of α-Fe2O3 were found with Raman spectroscopy technique. Relationship between the modes Eu(LO) and 2Eu(LO) was found, therefore, their association with the disorder in the crystalline structure can be determined and it was also found that 2Eu(LO) intensity mode at a concentration of 1.2 M is larger than 0.1 M nanostructures, the FWHM of the A1g mode at 227 cm-1 corresponding to the Fe3+ ions and the Eg at 293 cm-1 mode caused by the O2- ions was also analyzed and founded that the crystalline structure of hematite can be determined by the A1g mode at 227 cm-1.

The Effect of Ultrasonic Treatment on the Morphology and Microstructure of TiO2 Nanotubes Prepared by DC Anodization

2016 ◽  
Vol 860 ◽  
pp. 17-20
Author(s):  
Buagun Samran ◽  
Emmanuel Nyambod Timah ◽  
Udom Tipparach
Keyword(s):  
Surface Morphology ◽  
Ethylene Glycol ◽  
Ultrasonic Treatment ◽  
Room Temperature ◽  
Ammonium Fluoride ◽  
Deionized Water ◽  
Dc Voltage ◽  
Anodization Method

This paper presents the effect of ultrasonic treatment on the morphology and microstructure of TiO2 nanotubes prepared by DC anodization method. The TiO2 nanotubes were grown by one-face anodization at room temperature on titanium sheets of 0.25 mm thickness and 99.7% purity. The electrolyte was composed of ethylene glycol (EG), ammonium fluoride (0.3% wt NH4F) and deionized water (2% V H2O). A constant DC voltage of 50 V was applied during anodization for 2 hours. The samples were ultrasonically cleansed in ethanol for different extended periods of time: 0, 10, 30 and 50 minutes respectively. The samples were annealed at 450 °C for 2 hours. The surface morphology and microstructure of the TiO2 nanotubes formed were studied by XRD and SEM. The best result was obtained when the sampleswere ultrasonicated for 30 minutes.

Magnetron Sputtering Deposition of Calcium Phosphate Films with Nanoscale Grain Morphology in their Surface

2006 ◽  
Vol 975 ◽  
Author(s):  
Wilfredo Otaño ◽  
Víctor M. Pantojas ◽  
Juan M. Figueroa ◽  
Darimar Hernández ◽  
Alejandro Rodríguez-Navarro
Keyword(s):  
Calcium Phosphate ◽  
Surface Morphology ◽  
Magnetron Sputtering ◽  
Deposition Time ◽  
Grain Morphology ◽  
Average Diameter ◽  
Deposition Process ◽  
Medical Implants ◽  
Sputtering Deposition ◽  
Coated Implant

ABSTRACTHydroxyapatite (HA) is a calcium phosphate mineral analogous to the mineral part of bone. This similarity makes this material bioactive and suitable to coat medical implants. However, at present, there is not a coating technique which gives the coated implant the desired properties and long life required for medical implants.In an effort to produce HA coatings with improved properties, calcium phosphate films were prepared using magnetron sputtering deposition on a silicon substrate at 600°C. Initial efforts resulted in the deposition of amorphous films with a distinctive grain-like surface morphology. The morphological grain size was studied using SEM and found that it was possible to control the average diameter value of the round shaped grains by adjusting the deposition time. Increasing the deposition time increases the mean grain diameter. EDS spectra showed the unintentional addition of carbon, iron and nickel to the samples during deposition. After eliminating the impurities, it was possible to prepare calcium phosphate films in the HA phase but without the grain-like surface morphology. These results suggested that the impurities prevented the formation of the calcium phosphate HA phase while acting as nuclei for the heterogeneous nucleation of the grains. This is an important result where the deposition process parameters can be controlled to functionalize the films in order to produce distinctive nanoscale features in the surface morphology.

FORMATION MECHANISM AND SURFACE EVOLUTION OF SILVER FILMS SPUTTERING DEPOSITED ON SILICONE OIL SUBSTRATES

2008 ◽  
Vol 15 (05) ◽  
pp. 525-530 ◽  
Author(s):  
SEN-JIANG YU ◽  
YONG-JU ZHANG
Keyword(s):  
Surface Morphology ◽  
Formation Mechanism ◽  
Silver Film ◽  
Silicone Oil ◽  
Dc Magnetron Sputtering ◽  
Continuous Film ◽  
Silver Films ◽  
Surface Evolution ◽  
Physical Mechanisms ◽  
Silver Atoms

The formation mechanism and surface evolution of thin silver films deposited on silicone oil substrates by a DC-magnetron sputtering method are reported. As the film thickness increases, the deposited silver atoms first form compact clusters, then transfer to ramified aggregates and finally form a continuous film on the liquid substrate. After deposition, the surface morphology of the silver film is susceptible to evolve successively in the atmosphere condition, resulting in the formation of broad cracks and straight-sided (or worm-like) wrinkles. The evolution behaviors and underlying physical mechanisms of the cracks and wrinkles are presented and discussed in detail.

Effect of Hydrogen Dilution on Structure and Electronic Properties of Ge:H and GeYSi1-Y Films Deposited by Low Frequency Plasma

2006 ◽  
Vol 910 ◽  
Author(s):  
Andrey Kosarev ◽  
L. Sanchez ◽  
A. Torres ◽  
T. Felter ◽  
A. Ilinskii ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Surface Morphology ◽  
Low Frequency ◽  
Average Diameter ◽  
Gas Flows ◽  
Average Height ◽  
Optical And Electrical Properties ◽  
Hydrogen Dilution ◽  
Frequency Plasma

AbstractWe report on a systematical study of growth rate, surface morphology, hydrogen and oxygen incorporation, optical and electrical properties in Ge:H and GeYSi1-Y:H, Y> 0.85 films, deposited in a capacitive reactor by low frequency PE CVD. Silane and germane were used as feed gases diluted by hydrogen. Hydrogen dilution characterized by R= QH2/[QSiH4+QGeH4], where QH2, QSiH4, and QGeH4 are gas flows of hydrogen, silane and germane, respectively. The flow was varied in the range of R=20 to 80. Composition of the films was characterized by SIMS profiling. We did not observed a significant change of the deposition rate Vd in GeYSi1-Y:H films in all the range of R, while for Ge:H films Vd was significantly reduced after R=50. AFM characterization of the surface morphology demonstrated that at R=50 average height <H>(R) reached maximum in both Ge:H and GeYSi1-Y:H films, while average diameter <D>(R) had a minimum in GeYSi1-Y:H films and maximum in Ge:H films. Both Ge:H and GeYSi1-Y:H films demonstrated change of E04 in the studied range of R, and a minimum clearly appeared in &#61508;E at R=50-60 suggesting significant reduction in weak bonds of these films. The activation energy of conductivity Ea slightly increases with R in Ge:H films and shows no definitive trend in GeYSi1-Y:H: films. Both FTIR and SIMS data show a general trend of reducing hydrogen and oxygen content with R. These two types of films showed different behavior and correlations between surface morphology and optical and electrical properties.

Effect of Electrochemical Reaction Enviroment on the Surface Morphology and Photoluminescence of Porous Silicon

2013 ◽  
Vol 737 ◽  
pp. 60-66
Author(s):  
Ali Syari’ati ◽  
Veinardi Suendo
Keyword(s):  
Porous Silicon ◽  
Surface Morphology ◽  
Silicon Oxide ◽  
Quantum Confinement Effect ◽  
Etching Rate ◽  
Green Emission ◽  
Wet Etching ◽  
Electrochemical Anodization ◽  
Etching Method ◽  
Silicon Based

Porous silicon (p-Si) is a well-known silicon based material that can emit visible light at room temperature. The radiative recombination that originated from quantum confinement effect shows photoluminescence (PL) in red, while the defect on silicon oxide at the surface of p-Si shows in blue-green region. Porous silicon can be synthesized through two methods; wet-etching and electrochemical anodization using hydrofluoric acid as the main electrolyte. The electrochemical anodization is more favorable due to faster etching rate at the surface than the conventional wet-etching method. The objective of this research is to show that both of porous silicons can be synthesized using the same main electrolyte but by varying the reaction environment during anodization/etching process. Here, we shows the wet-etching method that enhanced by polarization concentration will produce porous silicon with silicon oxide defects by means blue-green emission, while direct electrochemical anodization will produce samples that emit red PL signal. The effect of introducing KOH into the electrolyte was also studied in the case of enhanced-wet-etching method. Surface morphology of porous silicon and their photoluminescence were observed by Scanning Electron Microscope and PL spectroscopy, respectively.

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