Low-pressure spray pyrolysis

PECULIARITIES OF NANOPARTICLES GROWTH IN LOW PRESSURE SPRAY PYROLYSIS... 

Recently it was experimentally proven that the highest yield of nanoparticles of different substances, including semiconductor and magnetic ones, is obtained in low pressure spray pyrolysis of special multicomponent solutions [1], During this pyrolysis micron size droplets of the multicomponent aqueous solution evaporate in a low pressure aerosol reactor. Additionally these droplets often have solid precursors of nanometer size, so we can consider every droplet as a colloidal solution. 

The aim of our work is to present simulation results to give a clear physical picture of interference of complex processes in the evaporating droplet during the low pressure spray pyrolysis. For different conditions the drop of temperature of an evaporating droplet is displayed in Fig. 1. The volatile components are water and ammonia. Total pressure in the aerosol reactor is 60 Torr. The initial droplet temperature is 300 K and its initial radius is about 2 pm. For the gas flow... 

Fig. 38.1 Experimental setup of a typical low-pressure spray pyrolysis (LPSP) process with a glass filter as the atomizer [9] copyright of Elsevier Limited, 2004...

W.-N. Wang, Y. Itoh, I. W. Lenggoro, K. Okuyama Nickel and nickel oxide nanoparticles prepared from nickel nitrate hexahydrate by a low pressure spray pyrolysis, Mat. Sci. Eng. B. Ill (1), 69-76 (2004). 

W.-N. Wang, I. W. Lenggoro, Y. Terashi, Y. C. Wang, K. Okuyama Direct synthesis of barium titanate nanoparticies via a low pressure spray pyrolysis method, J. Mater. Res. 20 (10), 2873-2882 (2005b). 

T. Ogi, F. Iskandar, Y. Itoh, K. Okuyama Characterization of dip-coated ITO films derived from nanoparticles synthesized by low-pressure spray pyrolysis, J. Nanopart. Res. 8 (3-4), 343-350 (2006). 

D. Hidayat, T. Ogi, F. Iskandar, K. Okuyama Single crystal ZnO Al nanoparticles directly synthesized using low-pressure spray pyrolysis. Mater. Sci. Eng. B. 151 (3), 231-237 (2008). 

T. Ogi, D. Hidayat, F. Iskandar, A. Purwanto, K. Okuyama Direct synthesis of highly crystalline transparent conducting oxide nanoparticles by low pressure spray pyrolysis. Adv. Powder Technol. 20 (2), 203-209 (2009). 

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... 

Yuan et al. used the technique of flame spray pyrolysis to prepare YSZ powder with a narrow particle distribution [6]. Zhang and Messing [7] demonstrated an important criterion for the synthesis of fine solid particles from the observation that the precipitated salt particles do not suffer plastic deformation or melt during heating, because of the formation of droplets from reservoirs with low permeability. Consequently, the residual solvent is trapped in the dried droplet, resulting in an increase in pressure, because then the solvent cannot evaporate... 

Spray pyrolysis was used by Li et al. (1993) to prepare a Pd-Ag alloy membrane on the outer surface of a porous alumina hollow-fibre substrate using spray pyrolysis of a Pd (N03)2 and AgN03 solution in an Hj-Oj flame. The mass fraction of silver in the membrane obtained at a substrate-surface temperature of 967-1067°C was as low as 0.04, while its fraction in the total metal mass dissolved in the spray solution was 0.1-0.4. This is explained by the higher partial pressure of Ag compared to that of Pd. An additional spray pyrolysis with a silver nitrate solution provided a proper silver content in the alloy membrane. The thickness of the alloy membrane was 1.5-2.0 mi, and the separation factor of hydrogen to nitrogen was about 24 at 500°C. The membrane surface was observed by high-resolution SEM, and the evolution of the morphology was discussed from the view of the deposition mechanism. 

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