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In this work, crystallization, thermal expansion and wetting behavior of ZnO–Al 2 O 3 –SiO 2 (ZAS) glass were first investigated. The results showed that ZnAl 2 O 4 was precipitated from ZAS glass after crystallization treatment. Crystallization increased the coefficient of thermal expansion (CTE) of ZAS glass ceramic due to the high CTE of ZnAl 2 O 4. In addition, ZAS glass exhibited good wettability on the surface of MgAl 2 O 4 substrate. On this basis, ZAS glass was used to join MgAl 2 O 4 ceramic, and the microstructure and mechanical properties of joints obtained with different cooling methods were investigated. The flexural strength of joints was related to the content of ZnAl 2 O 4 crystals in the brazing seams. Additional nucleation and crystallization treatment during cooling process improved the crystallinity of brazing seam, resulting in better matching of the CTE of brazing seam with that of MgAl 2 O 4 ceramic. The maximum flexural strength of joints reached 201 MPa, which was equivalent to the strength of MgAl 2 O 4 ceramic. [ABSTRACT FROM AUTHOR]

The La 2 O 3 -SiO 2 -B 2 O 3 (LSB) glass filler with high softening temperature was first used to join MgAl 2 O 4 ceramic. An interfacial layer composed of Al 2 O 3 was formed due to the solubility difference of MgO and Al 2 O 3 in the LSB glass filler. As a result, the addition of Al 2 O 3 into the LSB glass filler caused the increase of interfacial layer thickness. On the contrary, the addition of MgO into the LSB glass filler led to the decrease of interfacial layer thickness. When the adding content of MgO was 6 wt%, the interfacial layer disappeared and completely amorphous brazing seam was obtained. The in-line transmittance of joints decreased with the increase of the thickness of interfacial layer. The optimal in-line transmittance of joint bonded with La 2 O 3 -SiO 2 -B 2 O 3 -MgO (LSB6M) glass filler reached 82.9% at 1000 nm. Meanwhile, the average flexural strength of joints was about 196.2 MPa, which was equal to the strength of MgAl 2 O 4 substrate. [ABSTRACT FROM AUTHOR]

A novel La 2 O 3 -Al 2 O 3 -SiO 2 (LAS) glass was used as filler to join transparent sapphire for obtaining high strength and high light transmittance joints. The results show that the LAS glass filler had compatible coefficient of thermal expansion (CTE) with sapphire and excellent wetting ability on sapphire. During the joining process, no interfacial reaction occurred and the brazing seams were in a completely amorphous state under fast cooling conditions (~50 °C/min). With increased joining temperature, the mutual dissolution and diffusion between sapphire and the LAS filler were enhanced. The flexural strength of joints first increased and then decreased with an increase in the joining temperature from 1400 °C to 1550 °C. The optimal flexural strength of joint reached 325 MPa, which almost was the same as the strength of sapphire substrate. At 500 nm, the in-line transmittance of this joint was 80.5%, which was close to that of sapphire (84.2%). [ABSTRACT FROM AUTHOR]

Transparent MgAl 2 O 4 ceramics were bonded by using CaO-Al 2 O 3 -SiO 2 (CAS) glass filler. The CAS glass filler exhibited the same thermal expansion behavior as MgAl 2 O 4 ceramic and excellent wetting ability on the surface of MgAl 2 O 4 ceramic. When the cooling rate of 15 °C/min was used, no interfacial reaction was observed and the amorphous brazing seam could be obtained. However, low joining temperature (1250 °C) led to the formation of pores and high joining temperature (1400 °C) resulted in the formation of cracks. Furthermore, the slow cooling rate of 5–10 °C/min induced the crystallization of CaAl 2 Si 2 O 8 and Mg 2 Al 4 Si 5 O 18 due to the dissolution of MgAl 2 O 4 substrate. The optimal flexural strength of 181–189 MPa was obtained when the joining temperature and cooling rate were 1300–1350 °C and 15 °C/min respectively. Moreover, the in-line transmittance of the joint at 1000 nm was 82.1%, which was slightly lower than that of MgAl 2 O 4 ceramic (85.6%). [ABSTRACT FROM AUTHOR]

• The crystal content increases and the crystal size decreases with the increase of TiO 2 content. • The CTE of NAS glass ceramics can be adjusted by the formation of Nd 2 SiO 5 with high CTE and Al 6 Si 3 O 12 with low CTE. • The NAS glasses possess excellent wettability on the surface of Al 2 O 3 , ZrO 2 and ZTA ceramic. The crystallization behavior, microstructure, crystalline phases, microhardness, coefficient of thermal expansion (CTE), and wetting behavior of Nd 2 O 3 -Al 2 O 3 -SiO 2 (NAS) glass ceramics with different TiO 2 content were investigated. The results show that the content of crystals increases and the size of crystals decreases with the increase of TiO 2 content. Moreover, the formation of Nd 2 SiO 5 leads to the increase and the precipitation of Al 6 Si 2 O 13 results in the decrease in the CTE value of NAS glass ceramics. As a result, the CTE of NAS glass ceramics can be controlled in the range of 4.2–9.2 × 10−6/℃. These values are suitable for matching bonding to most ceramics with different CTE. Indeed, contact angle measurement demonstrates that the NAS glasses with 3 %, 6 % and 9 % TiO 2 possess excellent wettability on the Al 2 O 3 , ZrO 2 and zirconia toughened alumina (ZTA) ceramic, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a novel Dy 2 O 3 -Al 2 O 3 -SiO 2 (DAS) glass ceramic was designed and prepared for joining zirconia toughened alumina (ZTA) ceramic. The crystallization, thermal expansion behavior and wetting behavior of the DAS glass filler were studied. The effect of cooling rate and joining temperature on the microstructure and flexural strength of joints was investigated. The results show that slow cooling rate (15 °C/min) leads to crystallization of brazing seam, which causes the formation of pores in the joints due to the large density difference between the glass and the crystalline phases. The dissolution of ZrO 2 from ZTA substrate into the filler during joining process improves the mismatch of the coefficient of thermal expansion (CTE) between the brazing seam and substrate. The maximum flexural strength of 535 MPa is obtained when the joining temperature and cooling rate are 1475 °C and 50 °C/min, respectively. [ABSTRACT FROM AUTHOR]

CaO–Al 2 O 3 –SiO 2 –TiO 2 glass ceramic filler with high crystallinity was used for joining alumina ceramic. The influence of joining temperature and crystallization treatment on the microstructure and flexural strength of joints was studied. The results demonstrated that a joining temperature higher than the melting temperature of crystals was essential to obtain dense joints. Furthermore, the formation of CaAl 2 Si 2 O 8 at the alumina/glass filler interface decreased the flexural strength of joints due to the mismatch of coefficient of thermal expansion (CTE) between CaAl 2 Si 2 O 8 and substrate. The maximum flexural strength of 256 MPa at room temperature was achieved when the joining temperature was 1260 °C. After crystallization treatment, a large number of fine CaTiSiO 5 was precipitated in the brazing seam. The flexural strength of joints after crystallization at room temperature was 221 MPa, and increased to 242 MPa at 800 °C. These results can be attributed to the change of CTE value of the brazing seam. [ABSTRACT FROM AUTHOR]