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1.
A novel La2O3-Al2O3-SiO2 (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%).  相似文献   

2.
The La2O3-SiO2-B2O3 (LSB) glass filler with high softening temperature was first used to join MgAl2O4 ceramic. An interfacial layer composed of Al2O3 was formed due to the solubility difference of MgO and Al2O3 in the LSB glass filler. As a result, the addition of Al2O3 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 La2O3-SiO2-B2O3-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 MgAl2O4 substrate.  相似文献   

3.
In this paper, a novel Dy2O3-Al2O3-SiO2 (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 ZrO2 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.  相似文献   

4.
《Ceramics International》2017,43(16):13810-13816
Glass system with compositions of 93.9% (xCaO-yAl2O3-zSiO2)−5% MgO-1% B2O3−0.1% Fe2O3 has been prepared by a conventional melt-quenching technique, and the glass forming region and the mechanical properties of the derived glasses were investigated. The approximate glass forming region was found to be x = 10~35%, y = 10~35% and z = 50~80%, while the rest of the area was crystallization zone or crack zone. As x = 10%, y = 25% and z = 65% (Sample 13), the investigated glass possesses the optimum volume density, bending strength, compression strength and modulus, which are 2.572 g/cm3, 74.05 MPa, 312.84 MPa and 163.96 GPa, respectively. Compared to sample 13, samples with different compositions have reduced the volume density, lowered the Raman intensity and improved the optical band gap. For the mechanical properties, with decreasing the contents of SiO2, the bending strength firstly increases, then decreases and finally shows a relatively small increasing trend. The dependence of compression strength and compression modulus on SiO2 content shows a similar trend to the bending strength. Moreover, the optical band gap and Raman spectrum of the sample 13 indicate that the number of oxygen bonds in the bridge reach the maximum, which could further confirm a significantly improvement on the mechanical properties.  相似文献   

5.
The influences of atmosphere during processes of melting and heat treatment, heat treatment temperature, Fe3O4 content and basicity on the magnetic properties of magnetite-based glass ceramics were investigated. For sample containing 20 % Fe3O4 melted in different atmospheres, the highest saturation magnetisation was realized in 20vol% air + 80 vol% Ar, due to the fact that ratio of Fe3+ to Fe2+ in melt obtained in this atmosphere was close to 2. However, it was found that the coercivity of glass ceramics was not affected by the melting atmosphere. A high sintering temperature led to the decrease of saturation magnetisation and the increase of coercivity. As increasing Fe3O4 content, the main crystal phase transformed from CaSiO3 to CaFe0.6Al1.3Si1.08O6 and finally to magnetite phase, accompanied by the increase of saturation magnetisation and coercivity. In addition, the increase of basicity caused the decrease of saturation magnetisation and the increase of coercivity.  相似文献   

6.
Fully dense and magnetically controllable glass ceramics was successfully synthesized by method of hot pressing using CaO-Al2O3-SiO2-Na2O glass powder and Fe3O4 powder as raw materials. The influences of sintering temperature and time, content and particle size of Fe3O4, as well as particle size of glass powder on the densification and magnetic properties of samples were investigated. It was found that the saturation magnetization gradually increased with increasing magnetite content. In addition, the samples containing smaller size magnetite particles had a higher coercivity. However, for samples using smaller size glass powder, magnetite particles could partially dissolve into the glass matrix, which led to the decrease of saturation magnetization and the increase of coercivity. It was also concluded that the precipitation of crystalline phase from smaller size glass powder caused the decrease of degree of densification, and after decreasing the sintering temperature, the degree of densification of product was enhanced.  相似文献   

7.
CaO-Al2O3-SiO2(CAS) glass ceramics were designed and prepared using a melt-quench approach. The coefficient of the thermal expansion (CTE) of the synthesized CAS (4.12 × 10−6 K−1) matched perfectly with that of the SiC ceramic (4.01 × 10−6 K−1). Thermal analysis of the CAS was conducted. Then the joining of the SiC ceramics by the CAS glass ceramics under various process parameters were conducted. The bonding temperature affects the fluidity of the CAS glass and the oxidation of the SiC substrate. The holding duration decides the infiltration of the CAS glass into the SiC substrate. The optimal bonding parameter is 1400 ℃/10 min and the corresponding highest shear strength of the SiC/CAS/SiC bonded joints in average was 56 MPa. Fracture observation was also conducted to help analyze the relationship between the interfacial microstructure and the joint strength. Finally, the formation mechanism of the SiC/CAS/SiC bonded joints was proposed.  相似文献   

8.
AlON was successfully brazed to BN-Si3N4 using a Ag-Cu-Ti filler alloy. SEM, TEM and XRD studies revealed that a TiN + TiB2 + Ti5Si3 reaction layer formed adjacent to the BN-Si3N4 while a (Cu,Al)3Ti3O layer formed adjacent to the AlON. In addition, Ag-Cu eutectic, Cu(s,s) and AlCu2Ti were observed in the brazing filler. The effect of brazing temperature on the microstructure and mechanical properties of the joints was investigated. As the brazing temperature increased, the reaction layers became thicker, while the thickness of the brazing seam decreased. Meanwhile, the amount and the size of AlCu2Ti intermetallic compounds decreased. The shear strength of the joints first increased and then dropped with increasing the brazing temperature. A joint with a maximum strength of 94 MPa was obtained when it was brazed at 850 °C for 15 min.  相似文献   

9.
In order to meet the sealing demands of SiC heat exchanger, the Ni-Mo filler alloy was designed, prepared and employed to braze SiC ceramics. Wetting behavior of the Ni-Mo filler alloy on SiC ceramics and interfacial microstructure of the brazed joints were systematically characterized using optical observation furnace and XRD, SEM, EDS, TEM, respectively. Flexural strengths of the brazed joints at room temperature and high temperature were measured with four-point flexural strength method. HCl immersion test was performed to evaluate the corrosion resistance of the joints. The Ni-Mo filler alloy exhibited excellent wettability on SiC ceramics. During the process of brazing, SiC reacted with element Ni of the Ni-Mo filler alloy, resulting in the formation of Ni2Si + graphite reaction layer adjacent to the SiC substrate. Ni3Mo3C and Ni2Si compounds were precipitated at the center of brazing seam. When the brazing temperature increased from 1250 ℃ to 1400 ℃, the thickness of Ni2Si + graphite layer increased gradually. The maximum room-temperature flexural strength of 174 ± 33 MPa was obtained when brazed at 1300 ℃ for 40 min. The joints also exhibited stable high-temperature strength and acid corrosion resistance. When the test temperature was 700 ℃, 800 ℃, 900 ℃, the joints gave the strength retention rate of 92.5 %, 79.8 %, 67.2 %, respectively. It was believed that the formation of high melting point phases played an important role. Residual strength of the joints after HCl corrosion exceeded 130 MPa, revealing a good potential for applications in corrosion environment.  相似文献   

10.
ZrB2-SiC ceramics and Nb alloy were brazed at 1160°C for 60 min with CoFeNiCrCuTix high-entropy alloy filler. The influence of Ti content on the interface structure and mechanical properties of ZrB2-SiC/Nb joint was systematically studied. It is found that the rich-Ti Laves phase was formed due to the addition of large atomic size Ti fill into the filler alloy or brazing joint, and its content increases with Ti content. The joint brazed by high-entropy alloys filler without Ti can be divided into a tooth-shaped Cr2B reaction layer and a central area composed of a eutectic mixed structure of FCC phase and rich-Nb lamellar Laves phase. Ti and Nb are mutual solid solution elements. The increase of Ti content in the joint makes the FCC phase and the rich-Nb lamellar Laves phase to transform into a big bulk Ti-rich Laves phase and the quadrilateral (Ti, Nb)B phase. The tooth-shaped Cr2B was disappeared. The residual stress generated in the joint during the brazing process tends to cause defects such as holes and microcracks in the bulk Ti-rich brittle Laves phase. Therefore, with the addition of Ti, the normal temperature performance of the joint decreases from 216 MPa to 52 MPa. However, with the increase of Ti, the high-temperature mechanical properties of the joint first decrease, and then increase. It was mainly due to the formation of rich-Ti Laves phase and quadrilateral (Ti, Nb)B with excellent high-temperature mechanical properties. When brazing with CoFeNiCrCuTi1.5 filler, the high-temperature performance of the joint reached 92% of its room temperature performance.  相似文献   

11.
《Ceramics International》2017,43(15):11668-11675
Ag-Cu-Ti/Cu/Ag-Cu multi-layered filler was successfully designed to braze porous Si3N4 and Invar alloy. To further reduce the CTE mismatch between the porous Si3N4 and brazing filler, Mo particles were introduced into Ag-Cu-Ti. The effects of the Mo addition on the microstructure and mechanical properties of the brazed joints were studied. The results showed that, the addition of Mo particles into Ag-Cu-Ti lowered the CTE mismatch and improved the joint strength to a certain degree. However, an excessive content was harmful. The Mo particles could absorb Ti at high temperature, causing Ti shortage in the reaction with the ceramic. When cooling down, the absorbed Ti was released. The released Ti could react with Cu to generate Cu-Ti phase. So, additional Ti was adopted in the brazing filler as a supplement. When the Ti content was 5 wt%, the reaction layer on the ceramic interface was too thin to transfer enough load. However, when it reached 15 wt%, the Cu interlayer dissolved completely and Fe-Ti and Ni-Ti phases appeared. The maximum joint shear strength (83 MPa) was obtained with 10 wt% Ti and 5 vol% Mo, which had exceeded 90% of the porous Si3N4 and was 56% higher than the joint brazed without Mo particles.  相似文献   

12.
The crystallization behavior, microstructure, crystalline phases, microhardness, coefficient of thermal expansion (CTE), and wetting behavior of Nd2O3-Al2O3-SiO2 (NAS) glass ceramics with different TiO2 content were investigated. The results show that the content of crystals increases and the size of crystals decreases with the increase of TiO2 content. Moreover, the formation of Nd2SiO5 leads to the increase and the precipitation of Al6Si2O13 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 % TiO2 possess excellent wettability on the Al2O3, ZrO2 and zirconia toughened alumina (ZTA) ceramic, respectively.  相似文献   

13.
《Ceramics International》2019,45(14):17258-17261
Ti3AlC2 ceramics were successfully joined with TiO2 and Nb2O5 respectively as interlayers via solid-state diffusion bonding at 1300 °C. The joints bonded with TiO2 and Nb2O5 exhibit distinct microstructures. Two continuous thin Al2O3 oxidation layers with a thickness around 1 μm were formed in the joints bonded with TiO2. Between the oxidation layers there exists a dense oxycarbide (TiC1-xOx) layer. For the joint bonded with Nb2O5, a dense bonding layer with Nb2AlC and Nb4AlC3 grains surrounded by thin Al2O3 oxidation layers at the grain boundaries were obtained. The shear strength of the final joints shows clear dependences on both the thickness and microstructure of the joints. Smaller joint thickness and the microstructure with complex phases favour for higher shear strength. Those result implies that bonding with oxides is a practical and efficient method for joining Ti3AlC2.  相似文献   

14.
The interfacial microstructure and mechanical properties of B4C-SiC-TiB2 composite joints diffusion bonded with Ti foil interlayer were investigated. The joints were diffusion bonded in the temperature range of 800–1200?°C with 50?MPa by spark plasma sintering. The results revealed that robust joint could be successfully obtained due to the interface reaction. B4C reacted with Ti to form nanocrystalline TiB2 and TiC at the interface at 800–1000?°C. Both the reactions between SiC and Ti and between TiB2 and Ti were not observed during joining. A full ceramic joint consisted of micron- and submicron-sized TiB2 and TiC, accompanied with the formation of micro-crack, was achieved for the joint bonded at 1200?°C. Joint strength was evaluated and the maximum shear strength (145?±?14.1?MPa) was obtained for the joint bonded at 900?°C. Vickers hardness of interlayer increased with increasing the joining temperature.  相似文献   

15.
《Ceramics International》2020,46(1):186-195
The Al2O3/SiO2–B2O3–Al2O3–Na2O glass/Al2O3 joints reinforced cooperatively by glass matrix and in-situ Al4B2O9 whiskers were obtained via a low-melting borosilicate glass braze. The composition of glass seam transformed from SiO2–B2O3–Na2O to SiO2–B2O3–Al2O3–Na2O due to continuous diffusion and dissolution of Al2O3. An appropriate amount of [AlO4] units introduced into the glass braze played a vital role in strengthening the glass network structure resulting to considerably improved mechanical strength of the glass seam. Meanwhile, plenty of in-situ Al4B2O9 whiskers growing from the Al2O3/glass braze interface to the center of glass seam in various directions generated. Three-dimensional crisscross structures were fabricated at the Al2O3/glass braze interface domains, where were enhanced by crack-bridging and pull-out effect of the whiskers. Generally, ascribed to the cooperative reinforcement of the glass matrix in the seam and in-situ Al4B2O9 whiskers at Al2O3/glass braze interface domains through reactions of Al2O3 and borosilicate glass braze, strength of the as-brazed joints was promoted prominently. The shear strength of the joints reached a maximum of 61 MPa brazed at 1050 °C for 60 min.  相似文献   

16.
Hexagonal boron nitride (h-BN) composite ceramics were fabricated by hot pressing using h-BN, La2O3, Al2O3 and amorphous SiO2 as the raw materials. The effects of La2O3-Al2O3-SiO2 addition on the bulk density, apparent porosity, microstructural evolution and room/elevated-temperature mechanical properties of h-BN composite ceramics were investigated. The results indicated that liquid phase generated by the reaction of La2O3-Al2O3 and SiO2 exhibited a good wettability with h-BN grains, contributing to fill the pores and improve the densification. Therefore, h-BN composite ceramics with synchronous introduction of La2O3-Al2O3 and SiO2 show the better mechanical properties compared with separate addition of La2O3-Al2O3 or SiO2. h-BN composite ceramic incorporated with 10 vol.% La2O3-Al2O3 and 20 vol.% SiO2 shows the highest room-temperature strength of 266.4 MPa and elevated-temperature strength of 389.0 MPa at 800 °C.  相似文献   

17.
《Ceramics International》2021,47(20):28904-28912
Novel glass ceramics for LTCC applications with high flexural strength can be achieved by CaO-MgO-ZnO-SiO2(CMSZ) glass cofiring with Al2O3. The sintering shrinkage behavior, crystalline phases, mechanical and dielectric properties, and thermal expansion of the CMZS/Al2O3 glass ceramic were determined. The X-ray diffraction results revealed that multiphases (CaMgSi2O6, Al2Ca(SiO4)2 and ZnAl2O4) formed in the sintering process of the CMZS/Al2O3 glass ceramic. The flexural strength of CMZS/Al2O3 glass ceramics first increases and then decreases with increasing Al2O3 content. The CMZS/Al2O3 glass ceramic with 50 wt % Al2O3 sintered at 890 °C for 2 h achieved the best performance, with a maximum flexural strength of 256 MPa, dielectric constant (εr) of 7.89, dielectric loss (tan δ) of 3.41 × 10−3 (12 GHz), temperature coefficient of resonance frequency (τf) of −29 ppm/°C, and the CTE value of 7.93 × 10−6/°C.  相似文献   

18.
Si3N4 ceramic/42CrMo steel joints were obtained by employing TiNp modified Ag–Cu–Ti active filler and subsequently the effect of TiNp content on the microstructure and mechanical properties of the joints was investigated. Microstructural examination revealed that TiN+Ti5Si3 reaction layer was adjacent to the Si3N4 ceramic while a TiC reaction layer was close to the steel substrate. With the increase of TiNp content, more fine grains and less Ag–Cu eutectic appeared in the joint and the reaction layers near the two base materials became thinner. The flexural strength of the joint obtained by four-point bending test climbed about 100% with the optimum TiNp content of 5 vol%, comparing with the case without TiNp. Thermal stress distributions in the joint were analyzed using finite element modeling computations, which accorded well with the bending test results.  相似文献   

19.
Ceramics and metal joinings have been widely employed in aerospace, dental implants, and the electronic packaging industry for fabricating multifunctional components. In this study, the 35Bi2O3-50B2O3-15ZnO (mol.%) glass has been employed for joining the ZrO2 ceramic and Ti-6Al-4V alloy. The effect of brazing temperature on the microstructure evolution, mechanical properties, and bonding mechanism of brazed joints has been analyzed. The microstructure of the ZrO2/glass/Ti-6Al-4V joints and the content of Bi4B2O9, Bi2O3 and Bi24B2O39 precipitated crystals in glass were found to be dependent on the brazing temperature. The reaction product of Bi4Ti3O12 was identified in the glass/Ti-6Al-4V interface because of the chemical reaction between the oxidized layer of Ti-6Al-4V alloy and glass. A maximum shear strength as high as 48.8 ± 5.2 MPa was obtained. Our work, thus, demonstrates that the 35Bi2O3-50B2O3-15ZnO glass is an effective bonding material for joining ZrO2 ceramic and Ti-6Al-4V alloy under low temperature in an ambient atmosphere.  相似文献   

20.
Joining of Y3Al5O12 garnet single crystal (YAG) was achieved by using a bismuth-borate based glass filler. The thermal properties of glass filler were experimentally determined and the wettability of molten glass on YAG was investigated. The YAG reacted with glass to form ZnAl2O4 particles and Y2O3 nanowires successively as joining temperature is above 625℃. ZnAl2O4 preferentially nucleated and grew on Y2O3 nanowires. The cooperative growth of the two phases accelerated YAG decomposition, which in turn led to cluster growth of Y2O3 nanowires and aggregation of ZnAl2O4 particles at elevated temperature. The microstructure evolution and reaction mechanism were studied. The highest shear strength of 29.6 ± 5.2 MPa was obtained for the joint brazed at 650℃. The fracture morphology demonstrated that the dispersive strengthening of ZnAl2O4 and stress relief by Y2O3 nanowire network contributed to the superior mechanical performance.  相似文献   

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