Elsevier

Ceramics International

Volume 43, Issue 11, 1 August 2017, Pages 8531-8533
Ceramics International

Short communication
Synthesis of yttria precursor nano-powders using a symmetrical alternating current assisted precipitation method

https://doi.org/10.1016/j.ceramint.2017.03.124Get rights and content

Abstract

Symmetrical alternating current (SAC) was applied during yttria precursor nano-powder precipitation. The effects of SAC on the morphology and grain size of the yttria precursor were investigated via scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found the precursor to be transformed from irregular platelets/spheres to uniform spheres due to the SAC vibration effect. High frequency and density of SAC exerted greater influence on the morphology and grain size of the yttria precursor than weaker one.

Introduction

It is well recognized that precipitation method provides considerable advantages of simple operation, inexpensive raw materials and high-purity in the nano-powder fabrication processing [1]. Unfortunately, droplets of the precipitator tend to distribute inhomogeneously even under the action of strong stirring due to variations in super-saturation in the solution, eventually leading to non-uniform powder size distribution.

Applying a current in the material preparation process can help to improve the performance of molten metal and ceramics [2], [3], [4]. Electrophoresis and/or electroosmosis may occur when direct current (DC) or alternating current (AC) is applied [5], [6] to colloid and nano-powders of these types of suspensions; double electron layers appear and surround the nuclei in the aqueous solution under these conditions. Sarkar et al. [7], for example, observed distortion and thinning of double electron layers under a DC field which made it easier for the particles to deposit on the electrodes. Riahifar et al. [8] found that when symmetrical alternating current (SAC) was used in a stable suspension, the net displacement of a particle was zero in one cycle. Other studies have suggested that compared to DC, the electrolysis of water as well as particle deposition rate are greatly reduced under SAC [9]. To this effect, it is reasonable that fewer particles would deposit on the electrodes in the SAC-based precipitation process. Further, considering the vibration of nuclei and coexisting ions under SAC, the homogeneity of the suspension may be improved and the particle size might be better controlled.

The purpose of this study was to determine the effects of SAC on yttria precursor morphology and grain size in the precipitation process.

Section snippets

Experimental

Yttrium nitrate hexa hydrate (Y(NO3)3·6H2O) (99.99% purity) and ammonium hydrogen carbonate (NH4HCO3, A. R. grade) were used as raw materials in the preparation of yttria precursor nano-powders. Fig. 1 schematically illustrates the experimental apparatus used to prepare yttria precursor by SAC assisted precipitation method. The main experimental apparatus includes a current pulse generator, constant water bath, peristaltic pump, stirrer and pH measurement system.

In the experiment, Y(NO3)3·6H2O

Results and discussion

The XRD patterns of the yttria precursor are shown in Fig. 2. The main composition the precursor is Y2(CO3)3·2H2O (JCPDS card No. 01-081-1538). Peaks for precursors prepared with SAC are apparently lower than those prepared without SAC. High frequency and density of current have more exerted greater influence on the intensity of the yttria precursor, for example, in the Fig. 2(d), where the intensity of the XRD pattern is very weak.

Fig. 3 shows the morphology of yttria precursor powder samples

Conclusions

In this study, yttria precursor nano-powders were prepared using yttrium nitrate as the starting salts and ammonium hydrogen carbonate as the precipitant. An SAC was applied in the chemical precipitation process to explore the vibration effect (dielectrophoresis) on the formation of yttria precursor nano-powders. The action of SAC made the size and morphology of the yttria precursor nano-powders grow spherical and more uniform and the effects were more obvious in cases with high frequency and

Acknowledgments

This work was financially supported by the “National Natural Science Foundation of China” (Grant No. 51304039, No. 51674073), “The Fundamental Research Funds for the Central Universities” (Grant No. N130402021, N150202003).

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