Limits...
Formation of tungsten oxide nanostructures by laser pyrolysis: stars, fibres and spheres.

Govender M, Shikwambana L, Mwakikunga BW, Sideras-Haddad E, Erasmus RM, Forbes A - Nanoscale Res Lett (2011)

Bottom Line: In this letter, the production of multi-phase WO3 and WO3-x (where x could vary between 0.1 and 0.3) nanostructures synthesized by CO2-laser pyrolysis technique at varying laser wavelengths (9.22-10.82 mm) and power densities (17-110 W/cm2) is reported.The average spherical particle sizes for the wavelength variation samples ranged between 113 and 560 nm, and the average spherical particle sizes for power density variation samples ranged between 108 and 205 nm.It was found that more concentrated starting precursors result in the growth of hierarchical structures such as stars, whereas dilute starting precursors result in the growth of simpler structures such as wires.

View Article: PubMed Central - HTML - PubMed

Affiliation: CSIR National Laser Centre, P, O, Box 395, Pretoria 0001, South Africa. BMwakikunga@csir.co.za.

ABSTRACT
In this letter, the production of multi-phase WO3 and WO3-x (where x could vary between 0.1 and 0.3) nanostructures synthesized by CO2-laser pyrolysis technique at varying laser wavelengths (9.22-10.82 mm) and power densities (17-110 W/cm2) is reported. The average spherical particle sizes for the wavelength variation samples ranged between 113 and 560 nm, and the average spherical particle sizes for power density variation samples ranged between 108 and 205 nm. Synthesis of W18O49 (= WO2.72) stars by this method is reported for the first time at a power density and wavelength of 2.2 kW/cm2 and 10.6 μm, respectively. It was found that more concentrated starting precursors result in the growth of hierarchical structures such as stars, whereas dilute starting precursors result in the growth of simpler structures such as wires.

No MeSH data available.


Related in: MedlinePlus

Scanning electron micrographs of the post-annealed sample showing the growth of six-sided stars from the agglomerations of the pre-annealed sample depicted in the inset.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211218&req=5

Figure 2: Scanning electron micrographs of the post-annealed sample showing the growth of six-sided stars from the agglomerations of the pre-annealed sample depicted in the inset.

Mentions: When the CO2 laser beam was focused with a 1-m radius of curvature mirror, it produced a minimum beam radius or a beam waist of 1.2 mm, and at a laser power of 50 W on the 10.6-μm emission line, a power density of 2.2 kW/cm2 was achieved. These parameters were consistent with those obtained when synthesizing WO3 nanowires using a very dilute precursor of 27 μM [10]. Laser pyrolysis of the more concentrated 2.5 mM precursor showed many uniform agglomerations composed of nanospheres (40 nm) before annealing, as depicted in the SEM micrograph in the inset of Figure 2. The sample was annealed, and from the agglomerates, stars grew with six points as seen in the SEM micrographs of Figure 2.


Formation of tungsten oxide nanostructures by laser pyrolysis: stars, fibres and spheres.

Govender M, Shikwambana L, Mwakikunga BW, Sideras-Haddad E, Erasmus RM, Forbes A - Nanoscale Res Lett (2011)

Scanning electron micrographs of the post-annealed sample showing the growth of six-sided stars from the agglomerations of the pre-annealed sample depicted in the inset.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211218&req=5

Figure 2: Scanning electron micrographs of the post-annealed sample showing the growth of six-sided stars from the agglomerations of the pre-annealed sample depicted in the inset.
Mentions: When the CO2 laser beam was focused with a 1-m radius of curvature mirror, it produced a minimum beam radius or a beam waist of 1.2 mm, and at a laser power of 50 W on the 10.6-μm emission line, a power density of 2.2 kW/cm2 was achieved. These parameters were consistent with those obtained when synthesizing WO3 nanowires using a very dilute precursor of 27 μM [10]. Laser pyrolysis of the more concentrated 2.5 mM precursor showed many uniform agglomerations composed of nanospheres (40 nm) before annealing, as depicted in the SEM micrograph in the inset of Figure 2. The sample was annealed, and from the agglomerates, stars grew with six points as seen in the SEM micrographs of Figure 2.

Bottom Line: In this letter, the production of multi-phase WO3 and WO3-x (where x could vary between 0.1 and 0.3) nanostructures synthesized by CO2-laser pyrolysis technique at varying laser wavelengths (9.22-10.82 mm) and power densities (17-110 W/cm2) is reported.The average spherical particle sizes for the wavelength variation samples ranged between 113 and 560 nm, and the average spherical particle sizes for power density variation samples ranged between 108 and 205 nm.It was found that more concentrated starting precursors result in the growth of hierarchical structures such as stars, whereas dilute starting precursors result in the growth of simpler structures such as wires.

View Article: PubMed Central - HTML - PubMed

Affiliation: CSIR National Laser Centre, P, O, Box 395, Pretoria 0001, South Africa. BMwakikunga@csir.co.za.

ABSTRACT
In this letter, the production of multi-phase WO3 and WO3-x (where x could vary between 0.1 and 0.3) nanostructures synthesized by CO2-laser pyrolysis technique at varying laser wavelengths (9.22-10.82 mm) and power densities (17-110 W/cm2) is reported. The average spherical particle sizes for the wavelength variation samples ranged between 113 and 560 nm, and the average spherical particle sizes for power density variation samples ranged between 108 and 205 nm. Synthesis of W18O49 (= WO2.72) stars by this method is reported for the first time at a power density and wavelength of 2.2 kW/cm2 and 10.6 μm, respectively. It was found that more concentrated starting precursors result in the growth of hierarchical structures such as stars, whereas dilute starting precursors result in the growth of simpler structures such as wires.

No MeSH data available.


Related in: MedlinePlus