Elsevier

Materials Letters

Volume 264, 1 April 2020, 127360
Materials Letters

Enhancing interface bonding strength of Ti-ZrO2 joints using graphene as brazing materials

https://doi.org/10.1016/j.matlet.2020.127360Get rights and content

Highlights

  • Ti-ZrO2 have been jointed using graphene as brazing material.

  • After brazing, Ti-ZrO2 joints exhibited significantly improved bonding strength.

  • Graphene sponge interlayer acts as carbon sources and anti-diffusion barrier.

Abstract

Ti-ZrO2 joints with a graphene sponge interlayer were prepared and the interface bonding was characterized by three-point flexural strength. Compared with direct Ti-ZrO2 jointing showing a formation of monoclinic TiO2 and ZrTiO4 at interface and a negligible bonding, interfacial strength of Ti/graphene sponge/ZrO2 joints has been significantly increased up to 48.5 ± 7.0 MPa without any new interfacial phase formation. The enhanced interface bonding can be ascribed to the preferred interstitial diffusion of carbon atoms originated from the decomposition of graphene sponge interlayer at high temperature. The carbon diffusion reduces the available interstitials and vacancies for Ti, O and Zr diffusions, which retards the interdiffusion between titanium and zirconia, achieving a preferred diffusion bonding to enhance the strength of Ti-ZrO2 joints.

Introduction

With the remarkable synergy of titanium and zirconia, Ti-ZrO2 materials have been bursting out enormously potential biomedical and electronic applications, such as bone transplantation and encapsulation of electronic devices [1], [2], [3], [4], [5]. However, poor interface bonding strength between titanium and zirconia hinders these promising applications on account of the reaction between titanium and zirconia which happens easily at high temperature, possibly causing interfacial phases such as TiO2 and ZrTiO4, which results in a negligible joints strength [4], [5], [6]. As Correia et al. proposed, diffusion bonding is an appealing choice for enhancing interface strength in Ti-ZrO2 materials [4]. The formation of TiO2 and ZrTiO4 implies an intensive interdiffusion between Ti and ZrO2 [5] which however deteriorates the joint strength. Therefore, achieving a proper diffusion to avoid the formation of interfacial phases would be a feasible strategy for improving joints strength. Bearing these in mind, we utilized a scheme of brazing zirconia to titanium with a graphene interlayer which has good affinity with both [7], [8], so as to control the diffusion. Compared with other carbon forms, graphene is nonporous and two-dimensional layered with high specific surface, which is conducive to covering much more contact surface under the same carbon consumption, and avoiding the direct contact between Ti and ZrO2.

Section snippets

Experimental

3 mol% Y2O3-stabilized zirconia (3Y-TZP) discs in dimension of Φ60 mm × 2 mm (34.3 g), with a nominal composition of >99.9 wt% ZrO2 + HfO2 + Y2O3, 5.2 wt% Y2O3, <0.01 wt% Fe2O3, <0.02 wt% SiO2, <0.04 wt% Na2O (Feifan Ceramic Co., China), consisting of 83.6 vol% tetragonal ZrO2 (t-ZrO2) and 16.4 vol% monoclinic ZrO2 (m-ZrO2), were well polished. Titanium discs of Φ60 mm × 2.5 mm (31.8 g) showing a nominal composition of 99.9 wt% Ti, 0.03 wt% Fe, 0.05 wt% O, 0.01 wt% N, 0.005 wt% C, 0.005 wt% H

Results and discussions

Interfaces with enough strength for cross-sectional metallographic preparation were obtained only at GS joints. However, negligible bonding strengths were observed in TZ joints, similar with the previous work [4]. Additionally, a change in the color of zirconia in both types of joints from white to black, indicates oxygen diffusion from ZrO2 into Ti, causing black oxygen-deficient zirconia (ZrO2−x) [9].

From Fig. 2(a, b), the generation of monoclinic TiO2 (PDF#48-1278) and ZrTiO4 hindering

Conclusions

Graphene sponge interlayer was inserted into Ti-ZrO2 joint to improve the poor interfacial bonding. After the interlayer doping, the only existence of α-Ti solid solution and t-ZrO2−x at interface indicated that the strong diffusion between titanium and zirconia had been retarded. Decomposition of graphene sponge interlayer at high temperature provides carbon sources and plays the role of anti-diffusion barrier for titanium and zirconia interdiffusion. A preferred diffusion bonding rather than

CRediT authorship contribution statement

Yong Xian: Conceptualization, Methodology, Writing - original draft. Xiaoshan Zhang: Investigation, Writing - review & editing. Yichao Ding: Data curation. Jing Wang: Validation. Hongyuan Huang: Visualization.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors appreciate the financial support from Natural Science Foundation of Sichuan Province (No. 2018JY0278) and Chunhui of Ministry of education project (No. Z2017064).

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