Elsevier

Materials Letters

Volume 142, 1 March 2015, Pages 52-55
Materials Letters

Open-celled porous Cu prepared by replication of a new space-holder

https://doi.org/10.1016/j.matlet.2014.11.152Get rights and content

Highlights

  • Rock candy particles were used as space-holders to prepare open-celled porous Cu.

  • A relaxational internal friction peak was found at around 260 °C.

  • The porous Cu has a significantly enhanced damping capacity compared with the solid Cu.

  • Mechanisms of the internal friction peak and damping enhancement were discussed.

Abstract

An open-celled porous Cu has been successfully prepared by using rock candy particles as space-holders. Resultant material exhibits uniformly distributed and interconnected pores. Results of damping test show that a relaxational internal friction peak arises at around 260 °C. Corresponding to the appearance of this peak the storage modulus has a softening valley. This peak has been ascribed to the sliding of grain boundaries under the applied stresses during damping test. It is also found that compared with the solid Cu, the damping capacity of the porous Cu has been significantly enhanced due to the effect of pores and the micro-plastic deformation in the Cu matrix.

Introduction

In the last few decades porous metals have been widely used in many fields because of their excellent properties [1], [2], [3], [4]. Porous metals can be categorized as close-celled and open-celled. In most cases, the functions such as filtration, separation, and sound or energy absorption require open-celled morphology. Thus, open-celled porous metals have a better application prospect.

Space-holder method is a very promising route for preparing open-celled porous metals [5], [6], [7], [8], [9], [10], [11]. The most outstanding technical advantage of this method is much wider range of structure parameters, thus providing more opportunities for resultant porous metals to meet the desired behaviors. At present, the commonly used space-holders for preparing high melting point porous metals mainly include the particles of NaCl, NaF, Al, Mg and SiO2, etc [9], [10], [11]. However, NaF has toxicity, and both the residual NaF and NaCl particles in the pores have corrosive action to the metal matrix. Al and Mg particles are usually separated from the metal matrix by evaporation at high temperatures. Potential reactions between them and the metal matrix will damage the structure of porous metals. SiO2 particles are dissolved in an aqueous solution of hydrofluoric acid. This will undoubtedly increase the population to the environment and create damage to the metal matrix. It is therefore necessary to develop new space-holders to offer a wider range of structures and properties. In the present study rock candy particles were used as space-holders to prepare open-celled porous Cu. It is generally believed that as a solid space-holder rock candy is not appropriate for preparing high melting point porous metals due to its low melting point. To overcome the difficulties in the preparation process arising from the difference of the melting point between the rock candy and Cu, in the present study the rock candy was removed firstly, and then the resultant porous pressed compact of Cu powders was sintered at appropriate temperatures. Using rock candy as space-holders possesses numerous advantages such as low cost, fast dissolution in water, no corrosive action to metals, free of toxicity, in addition to significant widening of structure parameters such as porosity, pore size and homogeneity of pore distribution, etc.

Section snippets

Experimental

The as-received raw materials are electrolytic Cu powders and domestic rock candy particles as shown in Fig. 1. The 200 mesh electrolytic Cu powders exhibit a typical dendritic shape, while rock candy particles are irregular in shape and around 0.4 mm in size. The rock candy particles were graded through a series sieves. The electrolytic Cu powders and rock candy particles were weighted using an electronic scale with a resolution of 10−2 g. They were blended together in a stirrer at a rotation

Results and discussion

Fig. 2 shows the morphologies of the porous Cu with a porosity of 70% and an average pore size of 0.4 mm. From Fig. 2(a) homogenous distribution in Cu matrix of interconnected pores can be clearly seen. Both the shape and size of rock candy particles are well replicated, suggesting that effective bonding between Cu particles had been achieved before immersing in boiling water, so the following dissolution process of rock candy and the convection of boiling water could not affect the shape of the

Conclusions

  • (1)

    An open-celled porous Cu has been successfully prepared by using rock candy particles as space-holders. Resultant material exhibits uniformly distributed and interconnected macroscopic pores.

  • (2)

    A relaxational IF peak is found at around 260 °C during heating. Corresponding to the appearance of this peak the storage modulus has a softening valley. This IF peak can be ascribed to the sliding of grain boundaries.

  • (3)

    The porous Cu shows greatly superior damping capacity to the solid one owing to the stress

Acknowledgements

The study was supported by the China Postdoctoral Science Foundation funded project (2014M551008) and the Natural Science Foundation of Hebei Province (no. E2012202015).

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