I am synthesizing ceria powders using the combustion technique. But the yield is too low. The real output is only 2 grams even if the expected output is 10 grams. The ceria nanopowders fly off during the combustion process. I use glycine as fuel. What can be done to increase yield? Does anyone who prepare this ceria powders by combustion face the same problem?
Thanks Daniela Mam. But when more fuel is used , the grain size increases. We need to control the combustion reaction and increase the yield without flying off.
Fast cooling of the reaction products will reduce the grain size (stay in the nano-range).
The fly-off may be recovered by a filtering or cyclone technique.
Would it be possible to use a water column through which you lead the fly-off? Afterwards you can recover the reaction products from the water by centrifuge or drying technique.
Thanks for the suggestion Erik Sir. We do combustion in beaker. Fast cooling induces thermal stress and cracks the beaker. We usually close the beaker with aluminium foil with some pin holes. But still the powders fly off, since the foil couldn't withstand the thrust of the combustion. What chemical or experimental modification could be done to increase the yield of ceria powders?
The thrust of the combustion process probably is due to the large heat developed. I presume that no gaseous reactants are formed.
At high temperature many substances become gaseous and expand. Also the air in between the reactant powder will expand.
To reduce thrust you should work with dried and high purity reactants.
Working in a vacuum chamber may also reduce the trust (as less gas is heated). This also avoids the fly-off from escaping the chamber, which may help to recover the reaction products.
It looks like your process is too intensive. To decrease the intensity I would try to add some "ballast". For example to provide solution combustion or to substituеe a portion of glycine for another fuel (citric acid). Also you can lower the initiation temperature
You can do several different things to improve the yield of the combustion reaction: try to play with different fuels (using simple thermodynamic assumptions, you can predict the amount of heat during the reaction), you can try to adjust fuel to oxidizer ratio, and change the ignition temperature. Sometimes the opening of the door to add a bit moreoxygen during the reaction, helps with the yield.
The problem here is powder fly off and thereby you get lower yield. Put a stainless steel mesh and cover it. You can get more than 95% yield. I came across through this issue in my research. In fact, you can work on any stoichiometry of fuel to oxidant ratio with better yield, using this method.
I have two patents about combustion synthesis of ceria powder and the reactor( in my list of publication) which can produce it. You can get it from patent office. It can help you.
Design of reactor and control of temperature of combustion reaction are important for high yield.
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