First, I would ask you for the reasons for making such a structure.  Second, I see a bunch of problems.  You'll not evaporate the water from a LiOH mixture - I think a high temperature azeotrope (LiOH.H2O) is formed and this withstands 250C. The LiOH will dissolve the silica at such temperatures.  If you were successful then the hydroxide would pick up CO2 from the air and form the carbonate.  I think your Tower is leaning...

I'm afraid this question is outside my research field. In wish you success with your research

Thank you Dr. Alan F Rawle for your answer and thank you Dr. Paolo Neri for your wishes. I am trying to produce LiOH-SiO2 nanoparticles with narrow size distribution because I will produce porous pellets starting from the LiOH-SiO2 nanopowders and ZnO ones, then leaching the sacriphical phase (ZnO), and finally calcinating at 600°C the desired phase to produce Lithium Orthosilicate porous pellet. I already obtained SiO2 NPs with narrow size distribution by means of Stober method. I checked time ago about the LiOH-Water system, and the BPE is about 6 °C in saturated condition. In order to avoid the SiO2 dissolving, I will operate under vacuum conditions (0.2-0.25 bar), so that the LiOH solubility in water is 1.3 times lower than the one at 100 °C and consequently the pH value will be lower. I will operate under N2 flow in order to avoid Li2CO3 formation. Furthermore I will operate under intense stirring in order to create an as much as possible uniform system and with a low rate of evaporation, in order to avoid as much as possible the omogeneous nucleation which would cause the unwanted LiOH pure NPs formation.

Do you think it will be so difficult for me to obtain shell-core structure?

I believe it will be impossible to make such a core-shell structure.  Please prove me wrong - I learn more that way.....

Thank you Gaser Nagah Abdelrasoul for answering.

I have been working in the NPs field for 1 month, because I am doing the final project to achieve the Master Degree in Chemical Engineering, so I am reading as much as I can about NPs synthesis, so forgive me if I will make some mistakes.

I will try to disperse SiO2 NPs in LiOH saturated Ethanol solution, in order to avoid the severe condition that would occur in the case of a LiOH saturated aqueous solution (even if the SiO2 should not be interact with OH- in LiOH aqueous saturated condition, but Ethanol is better for different reasons).

I am currently reading papers about producing NPs by means of microemulsion. I am thinking to produce the LiOH-SiO2 shell-core structure by creating a microemulsion, where the SiO2 NPs are incorporated in the droplets, and the droplets phase is saturated with LiOH. It is very important to create a good affinity between the droplets and the SiO2 NPs, and to create repulsion between the continuous phase and the SiO2 NPs. Then, by varying the temperature or by evaporation, the supersaturation of LiOH inside the droplets leads to the precipitation of the LiOH (mainly on the SiO2 surface, being careful about the variation temperature rate or evaporation rate).

I noticed two main problems in this coating way: first, in order to obtain narrow size distribution of LiOH-SiO2 shell-core NPs (starting from SiO2 monodisperse NPs), ideally only 1 nanoparticle should be contained in each droplet (to avoid the aggregation); second, the collisions among the droplets, due to the Brownian motion, could cause the aggregation of a fraction of droplets, increasing the number of NPs inside each droplet.

In the first case, I could act on the droplet size, by choosing the suitable ratio among the components of the microemulsion. In the second case, I could act by choosing the suitable surfactant, in order to avoid as much as possible the aggregation of the droplets due to the Brownian motion ( maybe a steric stabilization is the best choice).

Do you think it may be a good way? Are there further issues in this coating process that I didn't take into account?

Thank you all very much for your suggestion