Production of stable and uniformly dispersed nanoparticles
This disclosure relates generally to production of stable and uniformly dispersed nanoparticles. Convention methods of nanoparticle production includes a two-step approach that utilizes additives or surface modifiers. The disclosed method avoids using any additives/surface modifiers owing to the environmental and economic implications. The method includes employing process conditions in a reaction to manipulate electrostatic double layer repulsive forces among nanoparticles to impart the dispersion stability of nanoparticles. The reaction includes pouring pH modifier dropwise into metal precursor solution with vigorous stirring forming metal hydroxide solution, while maintain ranges for concentration of metal precursor solution about 0.15M to 0.75 M, pH about 9 to 12, ionic conductivity about 50 to 200 mS/cm, stirring speed about 800 to 1200 rpm, aging time 6 to 24 hours. The metal hydroxide solution is heated with temperature maintained in range of 100 to 400° C. to obtain nanoparticle slurry comprising a stable suspension of the nanoparticles.
1 . A solvothermal synthesis method for production of stable and uniformly dispersed nanoparticles, the solvothermal synthesis method comprises:
employing a solvothermal reactor for enabling process conditions during a reaction resulting in production of the nanoparticles, the process conditions characterized by manipulating electrostatic double layer repulsive forces among the nanoparticles to impart dispersion stability of the nanoparticles produced as a result of the reaction, wherein the nanoparticles are produced without using one or more surface modifiers or one or more stabilizing agents in the reaction, wherein the reaction is a single step reaction process resulting in production of stable and uniformly dispersed nanoparticles, wherein the one or more surface modifiers or the one or more stabilizing agents includes one or more of surfactants, additives, polymers, organic ligands and dendrimers, wherein enabling the process conditions comprises:
enabling the reaction by pouring a pH modifier drop wise into a metal precursor solution with vigorous stirring resulting in formation of a metal hydroxide solution, concentration of the metal precursor solution maintained in a range of 0.15M to 0.75 M, pH in a range of 9 to 12, ionic conductivity of the metal precursor solution maintained in a range of about 50 to 200 mS/cm, and wherein a speed of stirring is about 800 to 1200 rpm, wherein aging time is in a range of 6 to 24 hours and the electrostatic double layer repulsive forces are manipulated by changing the ionic conductivity of the metal precursor solution, thereby interaction potential among nanoparticles' surface is manipulated by changing the ionic conductivity of the metal precursor solution to control dispersion stability of the nanoparticle solution; and
heating the metal hydroxide solution and maintaining a temperature of the solvothermal reactor at 200° C. for 24 hours to obtain a nanoparticle slurry comprising a stable suspension of the uniformly dispersed nanoparticles, wherein as the result of the reaction the nanoparticles produced are 2 to 5 percentage by weight of the nanoparticle slurry, wherein the metal precursor solution comprises a cerium nitrate solution and the pH modifier comprises a sodium hydroxide solution, and the metal hydroxide solution is a cerium hydroxide solution, and concentration of the cerium nitrate solution maintained in a range of 0.15 M to 0.3 M, wherein ceria mono-dispersed nanoparticles are produced in a particle size range in 20-30 nm;
wherein further interactions among the nanoparticles are manipulated by controlling temperature of the reaction, pressure of the reaction, initial concentration of the metal precursor solution, and rate of the reaction to obtain the nanoparticle slurry.
2 . The method of claim 1 , wherein the solvothermal reactor comprises an autoclave reactor, an electrical heater, a rotor attached with a motor through a magnetic drive, and a control panel.
3 . The method of claim 1 , further comprises preparing the cerium nitrate solution by adding cerium nitrate salt in double distilled (DD) water.
4 . The method of claim 1 , further comprises preparing the sodium hydroxide solution by adding sodium hydroxide salt in double distilled (DD) water.