Facile joining of SiC ceramics with screen-printed polycarbosilane without pressure

Highlights

• Joining of SiC ceramics was successfully achieved at a relatively low temperature of 1500 °C without any pressure using pure polycarbosilane (PCS) as the joining material.

• The ultra-thin interlayer contributes to the average shear strength of 105.8 ± 10.4 MPa.

• The screen printing method using PCS as the joining material has good practicality in SiC ceramics joining.

Abstract

Joining of SiC ceramics was successfully achieved at a relatively low temperature of 1500 °C without any pressure using pure polycarbosilane (PCS) as the joining material, which was distributed homogenously on the surface of SiC monolith through a screen printing method. The XRD pattern shows that the pyrolysis product of PCS is single-phase SiC. The interlayer thickness of the SiC joint is approximately 2 μm. This ultra-thin interlayer with lower possibility of the existence of defects contributes to the average shear strength of 105.8 ± 10.4 MPa, higher than that of other works using other preceramic polymers to the best of our knowledge. Due to the simplicity, low cost and high joining strength, the screen printing method using PCS as the joining material has good practicality in SiC ceramics joining.

Introduction

Silicon carbide (SiC) ceramics have prominent comprehensive performance with high temperature resistance, high strength as well as hardness, and excellent corrosion resistance [[1], [2], [3], [4]], which makes SiC ceramic components widely used in the areas of aerospace industry, electronics and advanced nuclear systems [[5], [6], [7], [8]]. However, it is difficult to obtain SiC ceramic components with large and complex geometry because of their brittleness and high rigidity, which restricts practical application. In order to overcome this, it is necessary to develop the joining techniques of SiC ceramics. With the continuous efforts of researchers, many joining techniques have been developed to join SiC ceramics, such as nano-infiltration and transient eutectic-phase (NITE) joining [[9], [10], [11]], diffusion bonding [12,13], MAX-phase (M, early transition metal; A, A-group element; X, C or N) joining [14] and brazing joining [[15], [16], [17]]. Kim et al. adopted SiC tape to join SiC ceramics at 1850 °C under 20 MPa, and the flexural strength was reported to be 343 ± 53 MPa [11]. Chen et al. reported that the inactive AgCu filler metal was used to join chromium pre-coated SiC ceramics at 900 °C, leading to a shear strength of approximately 29.6 MPa [15]. In addition, joints produced by applying SiC preceramic polymers such as PCS, polysilazane (PSZ), polymethylsilane (PMS) and allylhydridopolycarbosilane (AHPCS) have some advantages over the ones using other joining techniques [[18], [19], [20], [21], [22]]. For example, the main composition of the joining interlayer is SiC, in accordance with the parent material, so the joint has good stability at high temperature, less stress concentration and excellent radiation resistance, especially favorable for the application in nuclear systems [19]. Zheng et al. reported the green state joining of SiC using mixture of PCS and SiC powder at 2000 °C, and the flexural strength of the joined samples increased from 180 to 250 MPa when the applied pressure on the green compacts increased from 35 to 138 MPa [18]. Colombo et al. adopted PCS to join SiC ceramics pressurelessly at 1200 °C, and the shear strength was reported to be less than 1 MPa [23]. Jeong et al. used PCS to join SiC composites at 1750 °C and 20 MPa, and the joints with flexural strength of about 120 MPa [24]. Khalifa et al. reported that the polymer AHPCS was used to join SiC ceramics at 1500 °C, leading to a shear strength of approximately 80 MPa [25]. In this paper, we adopted the precursor PCS of SiC as the joining material, via a facile screen printing method to join SiC ceramics at a relatively low temperature of 1500 °C without pressure.