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This invention relates to a process of preparation of nanosized metal tungstate particles.
BACKGROUND OF THE INVENTION
Previously, fuel based nano particles was synthesized by using hydrazine based pyrophoric chemicals. The method of the prior art had several disadvantages, like toxicity of the reagents and difficulty in controlling high exothermic process and homogeneity of the multicomponent mixture.
OBJECTS OF THE INVENTION
An object of this invention is to propose a novel process, of preparation of nanosized tungstate particles.
Another object of this invention is to propose a process whose rate of reaction can be smoothly controlled for getting desired
morphology of the particles.
Yet another object of this invention is to propose a cheaper
process for the preparation of nanosized metal tungstate
particles.
Yet another object of this invention is to propose an environment
friendly process.
Other objects and advantages of the invention will be apparent
from the ensuing description.
DETAILED DESCRIPTION OF THE INVENTION
According to this invention is provided a process for the prepa-
ration of nanosized metal tungstate particles comprising
refluxing a pure compound of metal tungstate with EDTA-salt of
amines in aqueous medium to make a homogeneous solution;
mixing the said homogeneous solution with fuel and minor amount

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of polyvinyl alcohol to obtain a homogeneous mixture in aqueous medium;
drying or spray drying the said homogenous mixture by simple evaporation to obtain fluffy carbonaceous mass;
calcinating the said carbonaceous mass at a suitable temperature range depending on the chemical nature of the system to produce the dried nanosized product.
In accordance with this invention, the metal tungstate is refluxed with an EDTA--salt of amine in aqueous medium to make a homogeneous solution. The molar ratio of metal tungstate, EDTA and organic amine is 1:1 to 4:1-4. The homogeneous solution is further mixed with fuel and minor amount of polyvinyl alcohol (PVA) to obtain a homogeneous mixture. The homogeneous mixture comprises metal tungstate, fuel and PVA (with respect to monomer unit) in a molar ratio of 1:1 to 4 = 0.05 to 4. When the fuel used is hydrolysed starch, the formula weight is taken as C6H12O6 .

The homogeneous mixture is dried or spray dried at a temperature of 120 to 200° C to obtain a fluffy carbonaceous mass, which is
calcined at a temperature of 350 to 500° C to give the dried nano-sized metal tungstate particles.
The pure metal tungstate compounds used for the preparation of the nanosized metal tungstate particles are selected from magnesium tungstate, calcium tungstate, strontium tungstate, barium tungstate, zinc tungstate copper tungstate, nickel tungstate, cobalt tungstate iron tungstate chromium tungstate, yttrium tungstate, aluminium tungstate, tungstates of the lanthanide elements, singly or in mixtures.

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Further, the fuel used in the present invention is selected from
xylose, glucose, fructose, sucrose, hydrolyzed starch, sorbitol
and manitol.
The metal tungstate nanosized particles have a size in the range
of 30 to 120 nm.
The following nanosized tungstates can be prepared by the afore-
said process :
i. Metal tungstates
a. [AMO4] , (where A= Mg, Ca Sr, Ba, Zn, Cu, Ni, Co and
mixtures);particle size 30 to 120 nm.
b. B2(SO4)3 , (where B =Fe,Cr,Y,Lanthanides , Al); particle

size 30-120 nm.
EXAMPLE 1 - CaHO4
Freshly prepared 1 mole CaNO4 was dissolved in a mixture of 1-2
mole ethylene diamine tetraacetic acid and 3 mole of diethylene
triamine in aqueous medium and the total volume was 1.5 ltr. In
this mixture, 1 mole sucrose was added and water was added so
that the total volume became 2 Itrs.. In this mixture, 0.05 mole
PVA (with respect to monomer unit) was added as 10% w/w aqueous
solution. The resulting solution were then evaporated at 150° C by
heating on a hot plate. At the time of evaporation, the nitrates
were decomposed and brown fumes of nitrogen dioxide gas was
evolved. After complete evaporations, a voluminous fluffy organic
based precursor powder was resulted. This precursor
powder on calcination at 500°C for 2 hrs. produced CaMO4 powder
with average particle size less than 50 nm.

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WE CLAIM:
1. A process for the preparation of nanosized metal tungstate
particles comprising
refluxing a pure compound of metal tungstate with EDTA - salt of
amines in aqueous medium to make a homogeneous solution;
missing the said homogeneous solution with fuel and minor amount
of polyvinyl alcohol to obtain a homogeneous mixture in aqueous
medium;
drying or spray drying the said homogeneous mixture by simple
evaporation to obtain fluffy carbonaceous mass;
calcinating the said carbonaceous mass at a suitable temperature
range depending on the chemical nature of the system to produce
the dried nanosized product.
2. The process as claimed in claim 1 wherein the molar ratio of
metal tungstate, EDTA and amine in the homogeneous solution is
1:1 to 4:1 to 4.
3- The process as claimed in claim 1 wherein the molar ratio of
metal tungstate, fuel and PVA with respect to monomer unit) in
the homogeneous mixture is 1:1 to 4: 0.05 to 4.
4. The process as claimed in claim 1 wherein said homogeneous
mixture is dried or spray dried at a temperature in the range of
120 to 200° C.
5. The process as claimed in claim 1 where in said carbonaceous
mass is calcined at a temperature of 350 to 500° C.
6. The process as claimed in claim 1 wherein the pure metal tung
state compound is selected from magnesium tungstate, calcium
tungstate, stromtium tungstate, barium tungstate, zinc tungstate,

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copper tungstate, nickel tungstate, cobalt tungstate,iron
tungstate, chromium tungstate yttrium tungstate, aluminium tungstate, tungstates of the lanthanide elements, singly or in mixtures.
7 The process as claimed in claim 1 wherein the fuel is selected from xylose, glucose, fructose, sucrose, hydrolyzed starch, sorbitol and manitol.
8. The process as claimed in claim 1 wherein said nanosized metal
tungstate particles have a size in the range of 30 to 120 nm.
Dated this 16th day of DECEMBER, 1999.
A process for the preparation of nanosized metal tungstate
particles comprising
refluxing a pure compound of metal tungstate with EDTA - salt of
amines in aqueous medium to make a homogeneous solution;
missing the said homogeneous solution with fuel and minor amount
of polyvinyl alcohol to obtain a homogeneous mixture in aqueous
medium;
drying or spray drying the said homogeneous mixture by simple
evaporation to obtain fluffy carbonaceous mass;
calcinating the said carbonaceous mass at a suitable temperature
range depending on the chemical nature of the system to produce
the dried nanosized product.