Microstructure Evolution of Alumina/Alumina Joint Bonded by Boron Oxide–Alumina Nonmetal Powder Interlayer

Abstract

Alumina was successfully joined to itself in air environment by B2O3 + Al2O3 powder mixture as the interlayer to synthesize aluminum borate whiskers in the joint. The microstructure evolution was analyzed by means of scanning electron microscope (SEM) and X‐ray diffraction (XRD). The possible mechanism of microstructure evolution was also discussed. The effects of parameters such as heating cycles and temperature on the microstructure as well as the 3‐point flexural strength of the joint were investigated. It was found that heating the specimen for several heating cycles instead of holding at a constant temperature for a long time can eliminate the voids among the whiskers to achieve a dense microstructure, and the phenomenon that higher temperatures can accelerate the reaction was also observed. The highest strength of the joint reaches 90.29MPa with the heating temperature of 800°C after four heating cycles.

Preparation and characterization of aluminum borate whiskers reinforced ceramics with MnO2 addition

“…Aluminum borate (AB) has two stable compound forms of Al 18 B 4 O 33 and Al 4 B 2 O 9 in the Al 2 O 3 -B 2 O 3 binary with a variety of excellent properties, such as high strength, low thermal expansion coefficient, high melting point, high stability, and low cost. [1][2][3][4][5] Thus, AB are widely applied in ceramic-based composites that have potential uses in many fields, such as heterogeneous or ceramic-based materials brazing joints, [6][7][8][9] aerospace, 10 refractory, 11 cracking catalyst, and filtering materials. 12,13 There are many different ways to heterogeneous materials joining.…”

Microstructure and mechanical properties of Al2O3 ceramic joints achieved by Ag‐SiO2 braze in air

“…14 Glass and glass-ceramic braze, which comprise various kinds of oxide components, possess superior durability in oxidation atmosphere and favorable wettability on a ceramic surface. [15][16][17] Various glass braze systems, such as CaO-Al 2 O 3 -SiO 2 , MgO-Al 2 O 3 -SiO 2 , and Bi 2 O 3 -B 2 O 3 -ZnO, have been successfully used for joining Al 2 O 3 in air. 18,19 One of the main advantages of glass sealants is that their sealing and thermal properties can be tuned by tailoring their composition.…”

Joining Alumina and Sapphire by Growing Aluminium Borate Whiskers In-Situ, and the Whiskers’ Orientation Relationship with the Sapphire Substrate

“…Recently, a novel method was developed to join alumina by in-situ growing aluminium borate whiskers between the two substrates [14,15]. Since the difference in CTE between the whiskers (4 × 10 −6 K −1 ) [16] and alumina is smaller than that between the metal brazing alloy and alumina, the residual stress in the joint can be reduced and the reliability of the joint can thus be improved.…”

“…Lo et al [14] realised the bonding of alumina by growing aluminium borate whiskers between the substrates and the bending strength of the joint reached 155 MPa. Cao et al [15] also achieved the joining of alumina by synthesising aluminium borate whiskers and nanowire in the joint and the bending strength of the joint reached 92.8 MPa. Aluminium borate whiskers have outstanding high temperature resistance.…”