| With the rapid development of optoelectronic technology,microelectronic technology and aerospace technology,the precision,miniaturization and lightweight of functional devices have become a mainstream development trend.Aerospace connectors and other components urgently need to use lightweight aluminum alloys instead of high-density Kovar,steel,copper and other materials.In recent years,The Bi2O3-B2O3-ZnO glass system with a low melting point?350500??and a high thermal expansion coefficient(1013×10-6/?)has become a research hotspot of aluminum alloy sealing for the characteristics of aluminum alloys with low melting point?660??and high thermal expansion coefficient(1224×10-6/?).In order to further increase the thermal expansion coefficient of Bi2O3-B2O3-ZnO glass system,this paper introduced alkali metal oxide and alkaline earth metal oxide to replace ZnO and destroyed the glass network structure to achieve the purpose of increasing the glass thermal expansion coefficient.In this paper,Bi2O3-B2O3-ZnO glasses were prepared by melt quenching method.The effect of alkali metal oxides and alkaline earth metal oxides replacing ZnO on the glass structure and properties was systematically studied.FTIR and Raman spectroscopy were used to study the structural changes of the glass;differential scanning calorimetry?DSC?and thermal expansion were used to investigate the glass transition temperature?Tg?,initial crystallization temperature?Tx?,thermal stability??35?T?,coefficient of thermal expansion?CTE?and softening temperature?Tf?;crystallization of glass was studied by X-ray diffraction?XRD?and scanning electron microscope?SEM?;chemical stability?acid resistance,alkali resistance,water resistance?of the glass was studied by weight loss method.Finally,the Bi2O3-B2O3-ZnO glass with excellent comprehensive performance and silicon aluminum alloy were selected for matching sealing experiments.The main work and results of the paper were as follows:1)The effects of the replacement of ZnO by alkali metal R2O on the structure,thermal properties,crystallization behavior,and chemical stability of 40Bi2O3-30B2O3-?30-x?ZnO-xR2O glasses?R is Li,Na,K,abbreviated as LBBZR?were studied.Studies have shown that R2O destroys the glass network structure through network disconnection,causing[BiO6]to[BiO3],[BO4]to[BO3].Tg and Tf of LBBZR glasses were reduced by20?compared to 40Bi2O3-30B2O3-30ZnO base glass.The maximum CTE of LBBZNa-5glass was 11.11×10-6/?.However,with the destruction of the glass network structure,the chemical stability of LBBZR glasses have deteriorated and the weight loss rate has increased.In order to further increase the CTE of the glass,Tg and Tf of the LBBZNa glasses gradually decreased and the CTE gradually increased by increasing the substitution amount of Na2O to further enhanced the network disconnection.Among them,the lowest Tg and Tf of LBBZNa-15 glasses were 338.2?and 346.6?,respectively,and the highest CTE was 12.94×10-6/?.However,with the further destruction of the glass network structure,Tx and?35?T of the LBBZNa-15 glass were reduced to 456?and 117.8?,respectively.The glass was more prone to crystallization,the chemical stability was further deteriorated,and the weight loss rate was further increased.In order to further improve the comprehensive performance of LBBZNa glasses,the substitution amount of Na2O was determined to be 5mol%and the content of Bi2O3/B2O3 was further adjusted.Tg and Tf of BBZNa glasses did not change significantly.The maximum CTE of BBZNa-60 glass was12.71×10-6/?,Tx and?35?T significantly decreased to 399?and 63.1?,and the chemical stability deteriorated sharply.Relatively speaking,LBBZNa-5 glass has good comprehensive properties:Tg was 367.2?,Tf was 380.7?,Tx was 522?,?35?T was154.8?,CTE was 11.11×10-6/??30300??,Water resistance,Alkali resistance and acid resistance were 6.29×10-7g/?cm2·min?,5.15×10-5g/?cm2·min?,1.17×10-5g/?cm2·min?.2)The effects of substitution of ZnO by alkali metal YO on the structure,thermophysical properties,crystallization behavior and chemical stability of40Bi2O3-30B2O3-?30-x?ZnO-xYO glasses?Y is Ca,Sr,Ba,abbreviated as LBBZY?were studied.Studies have shown that YO destroys the glass network structure through network disconnection,leading to the transition of[BiO6]to[BiO3],[BO4]to[BO3],Tg and Tf of LBBZY glasses were not significant compared to 40Bi2O3-30B2O3-30ZnO base glass.The maximum CTE of LBBZSr-10 glass was 11.14×10-6/?.By changing the substitution amount of SrO to further adjust the CTE of LBBZY glasses,Tg and Tf of LBBZSr glasses did not change significantly,and the improvement of CTE was small.In order to further improve the comprehensive performance of LBBZSr glasses,the SrO substitution amount was determined to be 10 mol%,and the content of Bi2O3/B2O3 was further adjusted.As the content of Bi2O3 increased,Tg and Tf of BBZSr glasses gradually decreased,and the maximum CTE of BBZSr-60 glass was 11.95×10-6/?,Tx and?35?T decreased significantly to354.5?and 109.5?.Relatively speaking,LBBZSr-10 glass has good comprehensive properties:Tg was 384.9?,Tf was 398.4?,Tx was 544?,?35?T was 159.1?,CTE was11.14×10-6/??30300??,Water resistance,Alkali resistance and acid resistance were8.37×10-7g/?cm2·min?,6.97×10-5g/?cm2·min?,1.68×10-5g/?cm2·min?.3)LBBZNa-5 glass and LBBZSr-10 glass with excellent overall performance have been selected for sealing with silicon aluminum alloy?AlSi50?,respectively.LBBZNa-5glass and AlSi50 alloy could be sealed at 450?for 30 minutes to obtain a well sealing effect.The glass precipitated Bi4B2O9 crystal phase,did not react with the matrix,the sealing interface was complete,and there were a few pores.With the extension of the holding time,a large amount of Bi4B2O9 crystal phase would be precipitated in the LBBZNa-5 glass,and the crystal phase would gradually grow.LBBZSr-10 glass and AlSi50 alloy could maintain excellent sealing effect at 425?for 30 minutes.The glass has not crystallized or reacted with the substrate,the sealing interface was complete,and there were no defects such as pores or cracks.With the extension of the holding time,the LBBZSr-10 glass would precipitate the Bi4B2O9 crystal phase,which was conducive to the improvement of mechanical properties. |
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