SiBCN陶瓷先驱体合成、固化动力学及陶瓷化产物性能研究

Study on synthesis, curing kinetics and ceramic product’s properties of SiBCN ceramic precursor

采用脱氢偶联聚合方法,以聚硅氮烷和环硼氮烷制备了四种低黏度SiBCN陶瓷先驱体,通过红外表征了SiBCN陶瓷先驱体的结构,通过非等温DSC研究了SiBCN陶瓷先驱体的固化动力学过程,通过超高温TG,XRD,XPS等手段表征了SiBCN陶瓷化产物的性能。结果表明:四种SiBCN陶瓷先驱体的室温黏度为198~275 mPa·S,固化温度范围为120~235℃。SiBCN陶瓷先驱体的固化过程为双放热峰,通过Kissinger, Ozawa, Crane方程对主放热峰进行分析得到SiBCN陶瓷先驱体P1、P2、P3、P4固化动力学参数,其中活化能Ea分别为96.9 kJ/mol、88.4 kJ/mol、119.5 kJ/mol、268.2 kJ/mol,反应级数n分别为0.933,0.930,0.940,0.943。SiBCN陶瓷先驱体P4经过1 300℃裂解后的SiBCN陶瓷结构为非晶态,其B含量为4.67%,分解温度高达1 651℃。四种SiBCN陶瓷先驱体裂解产物的分解温度与B含量表现出一定的关系:当B含量超过一定浓度时,陶瓷化产物的高温稳定性得到有效提高。

Four SiBCN precursors with low viscosity were synthesized by dehydrogenation of polysilazane and borazine.The precursor molecular structure,curing kinetics and ceramicized product’s properties of SiBCN precursorswere investigated by fourier transform infrared spectrometry(FTIR),differential scanning calorimetry(DSC),ultra-high temperature thermogravimetric analysis(TG),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS),respectively.The results show that four SiBCN precursors are the viscosity of 198~275 mPa·S at room temperature and curing temperature of 120~235℃.The curing process of SiBCN precursors make double exothermic peaks.The kinetic parameters of SiBCN precursor P1,P2,P3,P4 are calculated by Kissinger,Ozawa and Crane equations depended on main exothermic peak,where the results are summarized as follows:Apparent activation energy are 96.9 kJ/mol,88.4 kJ/mol,119.5 kJ/mol,268.2 kJ/mol with reaction order of 0.933,0.930,0.940,0.943.The XRD results indicate that the ceramic product of P4 maintains amorphous structure by sintering at 1300℃.The content of B in the ceramic product of P4 is 4.67%and decomposition temperature is higher than 1650℃.The decomposition temperature shows a certain relationship with content of B in ceramic product of SiBCN precursors:The high-temperature stability of the ceramic product is effectively improved when the B content of SiBCN precursor exceeds a certain concentration.