Ammonium Metatungstate Preparing Violet Tungsten Oxide Whisker
Ammonium metatungstate (AMT) is an important compound in tungsten metallurgy industry, an important raw material for preparing tungsten oxide, such as tungsten trioxide (YTO, WO3), violet tungsten oxide (VTO, WO2.72 or W18O49). Violet tungsten oxide whisker is the micro-nano-short fibers which are generated by the high purity violet tungsten oxide, with the mechanical strength equal to the strength of adjacent atoms between the intensity. The highly oriented structure of W18O49 whisker has not only making itself of high strength, modulus and elongation, but also of the properties of electrical, optical, magnetism, dielectricity, conductivity and superconductivity.
It is pointed out that a process for producing violet tungsten oxide whiskers by coaxial electrostatic spinning method with ammonium metatungstate as a raw material is as follows:
1. Mix 2ml saturated ammonium metatungstate solution and 12% PVA solution in a certain proportion, to prepare spinning solution;
2. Inject the best electrospinning solution into 10ml syringe, and install it in the syringe pump to carry out a single tube electrospinning experiment. In the spinning process, solvent will volatilize partly in the air and form ammonium metatungstate/PVA composite fiber;
3. Calcine the obtained ammonium metatungstate / PVA composite fiber in the air to remove the solvent and the matrix PVA, and the ammonium metatungstate is decomposed by heating to obtain WO3 one-dimensional nanofibers at the same time;
4. The WO3 one-dimensional nanofibers is transformed to some specific crystal type and appearance by a certain heat treatment process, thereby to get W18O49 whisker.
The results showed that 800 ℃ is the optimum temperature for the formation of violet tungsten oxide whisker, and the W18O49 whisker nanorods are different in length. In addition, from the transmission electron microscopy (TEM), SEM, XRD and SAED patterns, we can observe that W18O49 whiskers are growing independently of each other with the smooth surface, with nano-level diameter and micron-length, large aspect ratio, and the is diameter mainly among 170nm-250nm, the length is mainly between 2-3μm, long diameter ratio mainly among 10-17, thus to be with some unique properties.
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