超细镁铝尖晶石凝胶注模成型工艺研究

Gelcasting Process of Ultra-fine Magnesia Alumina Spinel

通过采用凝胶注模法对素坯进行成型,成型胚体经无压烧结制备得到透明镁铝尖晶石陶瓷材料。重点研究了超细镁铝尖晶石凝胶注模成型工艺中,单体、单体与交联剂比例、催化剂与引发剂添加量、陶瓷粉体固含量(vol.%)对素坯相对密度、微观形貌及材料光学性能的影响。实验结果表明:单体的质量分数过高或过低都会影响到素坯的相对密度和样品光学透过率。当单体的百分含量为15%时,素坯的相对密度取得最大值51.1%,其样品可见光波段的透过率最大为83%,近红外波段透过率最大为86%,且对尖晶石材料透过率的影响主要体现在可见光波段,对红外波段透过率的影响非常小;随着单体与交联剂比例的增加,素坯相对密度先增高后显著下降,且在m(AM)/m(MBAM)为20︰1时取得最大值。相比较而言,单体与交联剂比例对素坯的相对密度和尖晶石材料透过率的影响就要大得多;通过调节催化剂和引发剂的添加量可有效控制交联体系的开始固化时间和固化时长,但添加过多会使体系在较短时间内释放出大量热量,导致交联体系局部固化不均匀,影响素坯和材料性能,最终确定将引发剂添加量控制在1.5vol.%,催化剂添加量控制在1.0vol.%为宜;固含量越高,素坯的相对密度增大,但过高的固含量会影响素坯的均匀性,进而降低尖晶石材料透过率,所以必须将其控制在一定的范围内,一般选择固相量为45vol.%为宜。

Magnesium aluminum spinel(Mg Al2 O4)transparent ceramics were prepared by means of gel injection molding and pressure free sintering.Effects of monomer density,ratio of monomer to crosslinking agent,catalyst/initiator,ceramic powd er solid content(vol.%)on relative density,microstructure and optical properties of the final ceramics wer e systematically studied.It was demonstrated that relative density of the green body and transmittance of the ceramics were closely dependent on the mass fraction of monomer.When the monomer content was 15%,the relative density of the green body reaches a maximum of 51.1%,while the transmittance of the ceramics was 83%in visible band and 86%in near infrared band.Also,the influence of the monomer content on the transmittance of the spinel ceramics was mainly present in the visible band,while the tra nsmittance in the infrared band was nearly unchanged.As the ratio of monomer to cross-linking agent(m(AM)/m(MBAM))was increased,the relative density of green body was first increased and then decreased significantly,where the maximum was reached when m(AM)/m(MBAM)was 20:1.By adjusting the contents of the catalyst and initiator,the initial curing time and the curing time of the cross-linking system could be effectively controlled.However,excessive quantity of them would produce a large amount of heat in a relatively short time,resulting in uneven local curing of the crosslinking system and hence affecting the properties of the billet and materials.The optimal contents of the initiator and catalyst were 1.5 vol.%and 1.0 vol.%,respectively.The optimal solid content was 45 vol.%.