Nanopowders is solid powder of nanoparticles, containing nano-sized nanoparticle agglomerates. These agglomerates can be re-dispersed using, for example, ultrasonic processing, capping agents etc. Nanoparticle dispersions are suspensions of nanoparticles in water or organic solvents. These dispersions can be used as-is, or diluted with suitable (compatible) solvents.
These dispersions tend to settle down on storage and thus have to be mixed sometimes before using. Some surface-functionalized nanoparticles (for example silver, gold, tungsten etc.) are available as solutions in water or organic solvents and thus are called “true” solutions, which do not settle down or exhibit, phase separation upon proper storage.
Tungsten is a greyish-white lustrous metal, which is solid at room temperature. Tungsten Nanoparticles containing multi-metal oxides can be used as pigments. These Nano-Particles are smaller than the visible wavelengths of light, thus causing visible wavelengths to interact in unusual ways as compared to macro particles. Tungsten nano-compounds are ideally suited for creating colour and making superior pigments since with inorganic pigments there is homogenous lattice level mixing of elements.
Tungsten nanoparticles are used in coatings, plastics, nanowires, nano-fibres and in microelectronics films since tungsten nanoparticles have the highest melting point among metallic elements. Tungsten nanoparticles have high surface area, which can lower the sintering temperatures, low vapour pressure, unusual quantum confinement and grain boundary effects.
Highly pure Sodium tungsten oxide nanoparticles are useful in biochemical analysis. Tungsten nanoparticles in metallic form are useful in the analysis of carbon and sulphur by combustion in an induction furnace. The high surface areas of nanoparticles comprising tungsten, having particle size less than 100 nanometres make them useful in these applications. Tungsten nanoparticles may also be used to form stronger polymer composites.
Tungsten nanoparticles offer several unusual benefits as electron emitters as the small size of nanoparticles can enable the formation of very thin film devices, lower the sintering temperatures and sintering times, exhibit inherently low vapour pressure even at high temperatures. They also offer novel compositions for chemical, mechanical polishing applications and electrical contacts.
Nano-device having electrodes, chemical sensors, biomedical sensors, phosphors and anti-static coatings can be prepared from nanoscale powders comprising tungsten, thus Photocopiers, facsimile machines, laser printers and air cleaners can benefit from charger wires prepared from tungsten comprising nanomaterials.
Nanomaterials comprising tungsten are particularly useful as direct heated cathode or heater coils for indirectly heated cathodes in cathode ray tubes, displays, x-ray tubes, X-ray device anodes, klystrons, magnetrons for microwave ovens and electron tubes. Multi-metal nanomaterials comprising tungsten include those based on rare earths minerals and thorium used in high intensity discharge lamps and welding equipment.
The unusual combination of vapour pressure, electrical conductivity and electronic properties make nanomaterials comprising tungsten useful as substrate for high power semiconductor rectifying devices, high voltage breakers, incandescent lamps such as household lamps, automotive lamps, and reflector lamps for floodlight or projector applications, audio-visual projectors, fibre-optical systems, video camera lights, airport runway markers, photo printers, medical and scientific instruments.
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