Precursor Chemistry Effects on Development of Particulate Morphology During Evaporative Decomposition of Solutions
- PDF / 1,028,932 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 8 Downloads / 154 Views
PRECURSOR CHEMISTRY EFFECTS ON DEVELOPMENT OF PARTICULATE MORPHOLOGY DURING EVAPORATIVE DECOMPOSITION OF SOLUTIONS
TIMOTHY J. GARDNER,* D. W. SPROSON,** AND G. L. MESSING** *Organization 7472, Sandia National Laboratories, Albuquerque, ** Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802
NM 87185;
ABSTRACT Fine-grained, high surface area MgO, NiO and ZnO powders were synthesized by the evaporative decomposition of solutions (EDS) technique at 1000°C from acetate and nitrate salt solutions. The powder characteristics were similar in all cases; however, aggregated powders were obtained from the nitrate salts and aggregate-free powders were obtained from the acetate solutions when reacted in air. This difference is attributed to the oxidation of the acetate radical and/or its residue and that this process acts to disaggregate the salt droplet/particles that are formed during EDS.
INTRODUCTION The reliable fabrication of many electronic and structural ceramic- components requires high purity, fine-grained powders. Chemical methods to synthesize powders with these characteristics include freeze drying [1], sol gel [2], co-precipitation [3], and hydrolysis of organometallic compounds [4]. The product of these techniques is usually a salt or hydroxide that requires calcination to obtain the oxide powder. A powder synthesis technique that includes the control over powder characteristics afforded by chemical synthesis methods and the controlled decomposition of the product salt is the evaporative decomposition of solutions (EDS) technique [5]. EDS refers to a process in which a solution is atomized into a vertical furnace such that the solution droplets initially dehydrate to yield a finely divided salt which then subsequently decomposes to form the oxide powder before exiting the furnace. This process has been successfully utilized for both simple and multicomponent oxide powder production on an industrial scale [6]. It is obvious that the preparation of ceramic powders by EDS requires careful manipulation of the solution, atomizer and furnace parameters during the process. An often neglected aspect of EDS is the selection of a salt for solution preparation. Because the primary criterion for salt selection is water solubility, most research on EDS has bean "precursor specific" with only the metal nitrate and chloride salts being studied [5,6]. Recently, it was demonstrated [7,8] that the type of salt significantly affects the development of surface area, crystallite size and particle morphology in MgO powders synthesized under identical process conditions. Specifically, it was shown that magnesium acetate yielded an aggregrate-free powder whereas magnesium nitrate and magnesium chloride resulted in strongly aggregated powders. To determine whether this observation was specific to the magnesium salts, zinc oxide and nickel oxide powders were synthesized by EDS from their nitrate and acetate salts. The powder characteristics and the decomposition reaction path f
Data Loading...
