Thermal properties of new copper matrix composite reinforced by β-eucryptite particulates

Abstract

Cu matrix composites with different volume fraction of Ag coated β-eucryptite particulates were successfully fabricated by powder metallurgy method. Low thermal expansion coefficient and high thermal conductivity were attained simultaneously in the new Cu matrix composite. The microstructure of β-eucryptite–Cu composite was studied by scanning electron microscope and transmission electron microscope. The thermophysical properties of β-eucryptite–Cu composites were analysed by means of thermal dilatometer and diathermometer. No interfacial reaction products between β-eucryptite and Cu were found in the composite. The research indicates that β-eucryptite, which has a negative coefficient of thermal expansion, is a useful reinforcement, which can remarkably reduce the coefficient of thermal expansion of Cu matrix composite. The effects of volume fraction of β-eucryptite particulates on the thermal expansion coefficient and thermal conductivity of the composite were investigated.

Phase-Transformation-Induced Extra Thermal Expansion Behavior of (SrxBa1–x)TiO3/Cu Composite

“…In addition, the compressive stress and the tensile stress are simultaneously induced on the SBT particles and on the Cu matrix, respectively, when the composite is cooled from a high temperature because the CTE of the SBT particles is lower than that of the Cu matrix 14 15 . The tensile stress acting on the matrix can be relaxed upon heating, and K m is much smaller than K p in the SBT/Cu composite; therefore, it can be concluded that the CTE of the composite decreases during this process on the basis of Equation (1) and our previous studies 16 17 25 .…”

“…In the last decade, many studies have investigated negative-CTE ceramics to reinforce MMCs with a low CTE and high TC, such as β-eucryptite (AlLiSiO 4 )14151617 and ZrW 2 O 8 181920. However, the CTE of β-eucryptite (approximately −0.7 × 10 −6  K −1 ) is not as low as expected and microcracks are easily formed in the bulk β-eucryptite ceramics due to its poor strength.…”

“…Generally, it is convenient method to utilize ceramic reinforcement with a low or negative CTE to reduce the ceramic volume fraction in Ceramic/Cu composite, and then a low CTE and high TC can be simultaneously obtained for the composite. In the last decade, many studies have investigated negative-CTE ceramics to reinforce MMCs with a low CTE and high TC, such as β-eucryptite (AlLiSiO 4 ) 14 15 16 17 and ZrW 2 O 8 18 19 20 . However, the CTE of β-eucryptite (approximately −0.7 × 10 −6 K −1 ) is not as low as expected and microcracks are easily formed in the bulk β-eucryptite ceramics due to its poor strength.…”

A novel Ag based sealant for solid oxide cells with a fully tunable thermal expansion

“…A more promising approach to lower the braze CTE is to introduce a negative thermal expansion (NTE) filler material, which contracts upon heating [32][33][34][35][36][37][38]. A practically important NTE material is LiAlSiO 4 , which has an anisotropic CTE (α a = 8.21 × 10 -6 K -1 and α c = -17.6 × 10 -6 K -1 , 0-1000 °C).…”

“…Xue et al [35][36][37][38] successfully employed LiAlSiO 4 particles to lower the thermal expansion of Al and Cu matrix composites. The same group also showed that the wettability between Cu and LiAlSiO 4 can be improved by coating the LiAlSiO 4 particles with Ag [38]. Thus, these findings suggest that LiAlSiO 4 is suitable for lowering the thermal expansion of Ag-Cu composite brazes.…”