Tin oxide particles

Details Tin oxide particles Tin oxide particles

1998-03-13

2001-03-13

Krynski, William (Department: 1774)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Physical dimension specified

C204S157220, C204S157500, C423S618000, C423S592100, C257S449000, C428S702000

Reexamination Certificate

active

06200674

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to tin oxide particles with average diameters on a nanometer scale. The invention further relates to the production of nanoscale tin oxide particles using laser pyrolysis and to transparent electrodes incorporating nanoscale tin oxide particles.
BACKGROUND OF THE INVENTION
Tin oxide can exist with various stoichiometries. In particular, tin oxide exists commonly as SnO or SnO
2
. SnO
2
is an n-type semiconductor with significant conduction at room temperature. Because of its semiconducting property and its relatively high transparency of visible light, SnO
2
has been an important component for transparent electrodes in flat-panel displays, generally in combination with indium oxide to form indium tin oxide (ITO). SnO
2
has also been useful for producing gas sensors, catalysts, electrostatic charge protection coatings, and other devices. Solution based methods generally are used for the production of small tin oxide particles. These solution based synthesis methods can produce fine powders but are limited with respect to obtainable particle size uniformity.
SUMMARY OF THE INVENTION
Crystalline particles of tin oxide have been produced on a nanometer scale with extremely high particle size uniformity. In particular, the particle size distribution drops off sharply such that there are effectively no particles with diameters substantially smaller or larger than the average diameter. The basis for the synthesis is laser pyrolysis in which radiation pyrolyzes a reactant stream. Additional processing can be used to modify the properties of the particles produced by laser pyrolysis. Different stoichiometric forms of the tin oxide can be produced either directly or with additional processing. The extremely uniform particles are particularly valuable for producing highly transparent electrodes. The small particle size and uniformity yield especially high levels of transparency. The methods of particle production are efficient and provide for the production of large quantities of materials.
In a first aspect, the invention features a collection of particles comprising crystalline tin oxide, the collection of particles having an average diameter of about 500 nm or less, wherein at least about 95 percent of the nanoparticles have a diameter greater than about 50 percent of the average diameter and less than about 150 percent of the average diameter. The collection of particles preferably have an average diameter of about 100 nm or less and more preferably an average diameter from about 5 nm to about 50 nm. The tin oxide nanoparticles can have a stoichiometry of SnO
2
. Preferably, at least about 99 percent of the nanoparticles have a diameter greater than about 50 percent of the average diameter and less than about 150 percent of the average diameter. Preferably, about 95 percent of the nanoparticles have a diameter greater than about 60 percent of the average diameter and less than about 160 percent of the average diameter. The particles generally are roughly spherical in appearance and have a single crystalline phase.
The invention also features devices including a coating where the coating has tin oxide nanoparticle having an average diameter of about 500 nm or less, wherein at least about 95 percent of the nanoparticles have a diameter greater than about 50 percent of the average diameter and less than about 150 percent of the average diameter. The device can be a gas sensor. The device can include a display wherein the coating functions as a transparent electrode.
In another aspect, the invention features a method of producing tin oxide nanoparticles comprising pyrolyzing a molecular stream in a reaction chamber, the molecular stream including a tin precursor, an oxidizing gas and a radiation absorbing gas. The pyrolysis preferably is driven by heat absorbed from a laser beam such as a CO
2
laser. The tin oxide nanoparticles preferably have an average diameter from about 5 nm to about 100 nm. The tin precursor can be SnCl
4
, and the oxidizing gas can be O
2
.
In another aspect the invention features an apparatus comprising:
(a) a reaction chamber isolated from the ambient atmosphere;
(b) a reactant gas inlet defining a path of a molecular stream, the inlet being connected to sources of tin precursor, oxygen contributing reagent and a laser absorbing gas;
(c) a laser beam path intersecting the path of the molecular stream; and
(d) a product outlet.
The tin precursor can be SnCl
4
, and the oxygen contributing reactant can be O
2
. The reactant gas inlet preferably is elongated in one dimension. The apparatus preferably further includes a CO
2
laser aligned to produce a laser beam along the laser beam path. The apparatus can further include a carrier gas in fluid communication with the source of tin precursor.
In another aspect, the invention features, a collection of crystalline tin oxide particles yielding a diffraction spectrum with peak positions indicated in FIG.
9
.
Other features and advantages of the invention will be apparent from the following detailed description of the invention and from the claims.


REFERENCES:
patent: 1119547 (1914-12-01), Spitz
patent: 1237840 (1917-08-01), Terwelp
patent: 1362237 (1920-12-01), De Ros
patent: 3486913 (1969-12-01), Zirngibl et al.
patent: 4246143 (1981-01-01), Sonoda et al.
patent: 4323480 (1982-04-01), Dines et al.
patent: 4478812 (1984-10-01), Lane
patent: 4548798 (1985-10-01), Rice
patent: 4588575 (1986-05-01), David
patent: 4647404 (1987-03-01), Morimoto et al.
patent: 4649037 (1987-03-01), Marsh et al.
patent: 4861572 (1989-08-01), Sugoh et al.
patent: 4960324 (1990-10-01), Brown
patent: 5013706 (1991-05-01), Schramm et al.
patent: 5014646 (1991-05-01), Ito et al.
patent: 5062936 (1991-11-01), Beaty et al.
patent: 5116468 (1992-05-01), Giersburg et al.
patent: 5158705 (1992-10-01), Swank
patent: 5221352 (1993-06-01), Terneu et al.
patent: 5246623 (1993-09-01), Giersberg et al.
patent: 5304783 (1994-04-01), Clough et al.
patent: 5330833 (1994-07-01), Yamashita et al.
patent: 5401441 (1995-03-01), Robert et al.
patent: 5494652 (1996-02-01), Robert
patent: 5569412 (1996-10-01), Feist et al.
patent: 5635154 (1997-06-01), Arai et al.
patent: 5705098 (1998-01-01), Okuda et al.
patent: 5719016 (1998-02-01), Christian et al.
“Laser synthesis of vanadium-titanium oxide catalysts”, M. Musci et al. J. Mater. Res., vol. 7, No. 10, (1992) pp. 2846-2852.
“Synthesis of ultrafine TiO2powders by a CW CO2laser”, F. Curcio et al. Applied Surface Scince 46 (1990) pp. 225-229.

Affiliated with

Also associated with

Rating

Tin oxide particles does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Tin oxide particles, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tin oxide particles will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2443794