Zirconia ceramic ferrules and ceramic sleeves are the core components of optical fiber connectors. Generally, the insertion loss of the connector is required to be less than 0.20 dB. The technical indicators of the ceramic sleeve must meet the following requirements. For example, Zirconia ceramic sleeve: Outer diameter: Φ3.20±0.01mm, inner diameter: Φ2.495±0.002mm, length: 11.4±0.1mm. The process flow of the zirconia sleeve is: Raw materials – mixing – granulation – molding (injection molding or isostatic pressing) – sintering – end surface processing – rough hole repair – concentricity processing – fine grinding of the inner hole – fine grinding of the outer circle – slotting – brushing – cleaning the technical key of zirconia sleeve is as follows:
1. Zirconia ceramic production technology. Mainly includes: zirconia raw material preparation, mixing material preparation, and molding technology.
2. Precision processing technology of ceramic parts. Inner hole fine processing, outer circle fine processing, slotting, brushing. High-quality zirconia nanopowder can greatly improve the breakage of zirconia ceramic sleeves during use and extend their service life.
For ceramic ferrules or sleeves produced with unqualified zirconia powder, the end face of the ferrule will become rough after long-term use, which will greatly increase the insertion loss of the ferrule); and the sleeve will be damaged due to aging strength.
The basic requirements for zirconia powder for ceramic sleeves are sintering temperature less than 1500℃, sintering density greater than 6.0g/cm3, and three-point bending strength greater than 900MPa; the basic requirements for zirconia powder for ceramic ferrules are sintering temperature less than 1400℃ (preferably 1350℃), sintering density greater than 6.0g/cm3, and three-point bending strength greater than 800MPa. After further research and development, the sintering density at 1350℃ reached 6.03 g/cm3, and the sintering density at 1450℃ reached 6.05 g/cm3.
Analysis of the damage to zirconia ceramic sleeves:
The damage to ceramic sleeves during actual use is the biggest product quality problem. The reasons for the breakage of ceramic sleeves during use are very complicated, which can be summarized as follows:
1. The strength of the ceramic sleeve is too low and cannot withstand the stress generated when the core is inserted.
2. The ceramic sleeve is broken due to static fatigue.
3. Under high temperature and humidity for a long time, the zirconia ceramic sleeve produces a large amount of spontaneous martensitic phase transformation from a tetragonal phase to a monoclinic phase, which causes aging and greatly reduces the strength of the sleeve.
4. Artificial abnormal plugging and unplugging causes local stress concentration in the ceramic sleeve.
5. The quality of metal or non-metallic flanges is unqualified.
From the above analysis, it can be seen that the strength of the ceramic sleeve itself becomes the main factor affecting its damage.
In addition, the results of dynamic fatigue and cyclic fatigue tests on zirconia materials show a slow crack expansion behavior in zirconia ceramics, that is, there is a possibility of fatigue failure of the ceramic sleeve. The study of the strength-fracture probability-life prediction diagram shows that when the maximum force of the zirconia sleeve is assumed to be 200MPa (actually, the finite element analysis shows that the force of the sleeve during normal use is less than 100MPa), the probability of the ceramic sleeve being damaged after 20 years of use is less than one in ten thousand.
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