Spray pyrolysis ultrasonic atomization

Thermal treatment synthesis technique of mists formed from ultrasonic atomizer (Ultrasonic spray pyrolysis technique) Y203-Zr02, NiO, ZnS, BaTi03-SrTi03, MoS2, BiV04 [11-14]... 

The recent technique of nebulized spray pyrolysis (NSP) has been used to prepare aligned MWNTs bundles [62]. This technique consists in a spray generated by an ultrasonic atomizer. MWNTs with fairly uniform diameters, as well as ahgned MWNT bundles, have been obtained by using solutions of organometallic compounds, such as ferrocine, in benzene, toluene, and other hydrocarbon solvents. The advantage of NSP is the ease of scahng up to an industrial process where the reactants are fed into the furnace continuously. 

The morphology and size of particles prepared by the LPSP process are different from those produced by CSP using either an ultrasonic nebulizer or a two-fluid nozzle as atomizers under an atmospheric environment. For example, nickel oxide (NiO) nanoparticles can be formed via the LPSP route whereas, only submicronsized NiO particles are produced by ultrasonic spray pyrolysis [9]. It is evident that the nanoparticle formation mechanism in the LPSP process is different from that in the CSP process. The calculated particle size based on the ODOP principle is much larger than 100 nm, indicating that the nanoparticles are formed based on one-droplet-to-multiple-particles (ODMP). The reason can be attributed to the difference in operating pressures and aerosol formation mechanisms between the two types of aerosol generators. 

Purwanto, A. Lenggoro, I. W. Chang, H. W. Okuyama, K. Preparatirai of submicron- and nanometer-sized particles of Y2O3 Eu by flame spray pyrolysis using ultrasonic and two-fluid atomizers. Journal of Chemical Engineering of Japan 2006, 39, 68-76. 

The concept or the basis of spray pyrolysis method assumes that one droplet forms one product particle. To date, submicrometer- to micrometer-sized particles are typically formed in a spray pyrolysis process. A variety of atomization techniques have been used ftn- solution aerosol formation, such as ultrasonic spray pyrolysis, electrospray pyrolysis, low pressure spray pyrolysis using a filter expansion aerosol generator (FEAG), salt-assisted spray pyrolysis, two-fluid pyrolysis method, etc. [15-18]. These atomization methods differ in droplet size, rate of atomization, and... 

Finally, the ultrasonic atomization is shown as a very effective method for generating small droplets. The droplets produced by ultrasonic atomizer are 2-4 p,m, but atomization rate is limited to <2 cm /min. Ultrasonic spray pyrolysis method is the most convenient method to obtain spherically shaped fine particles. The droplets are formed from feeding solution by means of an ultrasonic oscillator with frequency in the order of several megahertz or shghtly less than 1 MHz [15,27]. 

Liu, T.Q., Sakurai, O., Mizutani, N., Kato, M. Preparation of spherical zirconia fine ZnO particles by spray pyrolysis method using ultrasonic atomization techniques. J. Mater. Sci. 21, 3698-3702 (1986)... 

A typical setup for spray pyrolysis consists of an atomizer, the precursor solution, the heated substrate and a temperature controller. Three types of atomizers are commonly used in spray pyrolysis compressed air (the solution is exposed to a beam of air) (Balkenende et al, 1996) ultrasound (short wavelengths are produced by ultrasonic frequencies, generating a very fine spray) (Arya Hintermann, 1990) electrostatic (the solution is exposed to a high electric field) (Chen et al., 1996). 

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