Si-B-C-N-H-Cl体系CVD过程的化学反应热力学研究

发布时间：2018-04-16 08:33

  本文选题：化学气相沉积 + 热力学　； 参考：《西北工业大学》2015年博士论文

【摘要】：连续纤维增韧非氧化物陶瓷基复合材料具有密度低、耐高温、优异力学、抗腐蚀和抗氧化性能,在航空航天领域获得广泛应用。Si-B-C-N系陶瓷备受关注,化学气相沉积(CVD)是制备陶瓷基复合材料界面、基体和涂层组元的有效方法。本文拟选择该体系有代表性的SiC、Si3N4、BN、SiBx和SiCN等作为陶瓷基复合材料界面、基体和涂层的候选材料。通过量子化学结合统计及经典热力学对相关体系进行热力学研究,充分理解CVD法制备上述材料的化学反应过程及其机理,对CVD Si-B-C-N系高温陶瓷材料制备工艺发展具有重要指导意义。本文对Si3N4、BN、SiBx、SiCN及SiBCN陶瓷的CVD先躯体体系涉及的热力学问题进行了系统计算,建立了相关产物的热力学数据库,包括分子在298.15K-2000 K的标准摩尔热容(Cθp,m),标准摩尔熵(Sθm)、标准摩尔生成焓(△fHmθ)和标准摩尔生成吉布斯自由能(△fGmθ)等。利用所得基本热化学数据,根据化学平衡(即系统的总化学势最小)原理,对相关各体系进行了热力学产物平衡浓度分布研究,计算得到CVD工艺参数与固相产物生成量之间的关系,并对部分结果进行了实验对比验证。主要研究内容和结果如下：(1)以BCl3-NH3-H2体系为先驱体制备氮化硼,确定了该体系可能存在的中间产物共144个,其中87个为新产物。通过计算获得其完整的热力学数据,包括分子结构,标准摩尔热容(Cθp, m),标准摩尔熵(Sθm)、标准摩尔生成焓(△fHmθ)和标准摩尔生成吉布斯自由能(AfGme)。利用所得基本热化学数据,根据化学平衡(即系统的总化学势最小)原理,计算了该体系在CVD典型工艺参数(1000 Pa总压,进气比BC13:NH3:H2=1:3:6)和温度范围为300 K-2000 K的产物平衡浓度图。结果表明,BCl3和NH3在300 K即可发生反应,高于2160 K可生成固相硼(B),1800K以下生成立方氮化硼(c-BN),1800 K以上生成六方氮化硼(h-BN)。而纤锌矿氮化硼(w-BN)在此工艺参数下则无法稳定存在。本文同样计算了体系相关固相产物(B, c-BN和h-BN)生成量与温度和先驱体进气比r= BCl3/(BCl3+NH3)的关系,热力学计算结果表明,生成固相产物BN的最佳进气比r=0.5。(2)同样计算获得SiCl4-NH3-H2体系在CVD过程可能涉及的118个(总共161个)新产物的热力学数据。基于所获数据,计算了该体系在CVD典型工艺参数(1000 Pa,总压,进气比SiCl4:NH3:H2=1:3:5和温度范围300 K-2000 K)的产物平衡浓度图。结果表明产生固相产物Si3N4的热力学温度为300 K-1560 K。同样计算了体系相关固相产物(Si和Si3N4)生成量与温度和先驱体进气比r=SiCl4/(SiCl4+NH3)的关系。热力学计算结果表明,生成固相产物Si3N4的最佳进气比r=0.5。(3)对于BCl3-SiCl4-H2-Ar体系,共涉及220个可能的中间产物。本文计算了其中128个新产物的热力学数据,以及该体系在CVD典型工艺参数(总压1atm,进气比BCl3:SiCl4:H2:Ar=4:1:5:5)和300 K-2000 K的产物平衡浓度图。同样还有固相产物(B, SiB6和SiB14)生成量与温度和先驱体进气比r= BCl4/(SiCl4+ BC13)的关系,热力学计算结果表明：固相B生成条件为进气比r0.8,SiB6的产生条件为0.1 r0.8,700 K T1550 K, SiB1i4的产生条件为r0.7且温度T1，，400 K。(4)对于SiCl3CH3-NH3-H2体系,总共涉及443个可能的中间产物。本文计算了其中99个新产物的热力学数据,以及该体系在CVD典型工艺参数(1000Pa总压,进气比SiCl3CH3:NH3:H2=1:3:5)和300 K-2000 K的产物平衡浓度图和固相产物(C, Si3N4和p-SiC)生成量与温度和先驱体进气比r= SiCl3CH3/(SiCl3CH3 +NH3)的关系。热力学计算结果表明,Si3N4可在300 K-1200 K生成,β-SiC生成条件为1200 K以上(5)计算了SiCl3CH3-BCl3-NH3-H2体系在气压1000 Pa,温度300-2000 K,先驱体进气比SiCl3CH3:BC13:NH3:H2= 5:1:4:50条件下的产物平衡浓度分布。热力学计算结果表明,在950-1100 K可实现C+SiC+Si3N4+BN的多相共沉积；高于1100 K可实现C+SiC+BN三相共沉积；在700 K-950 K则可实现C+Si3N4+BN的三相共沉积。(6)最后根据各体系的热力学计算结果,在热力学研究条件范围内,与动力学工艺参数的实验结果进行比对,结果表明两者基本相符。本文建立了Si-B-C-N-H-Cl体系所有可能的气相产物热力学数据库,利用该气相产物热力学数据库,结合相关体系的固相产物实验数据,即可计算得到任意工艺参数下的产物平衡浓度分布,这对指导相关材料体系的CVI工艺研究有重要意义。
[Abstract]:Continuous fiber reinforced non oxide ceramic matrix composites with low density, high temperature resistance, excellent mechanical, corrosion resistance and oxidation resistance, has been widely used to obtain.Si-B-C-N ceramics attention in the field of aerospace, chemical vapor deposition (CVD) was prepared by interfacial ceramic matrix composites, the matrix and the effective method of coating components in this paper. This system intends to select the representative of the SiC, Si3N4, BN, SiBx and SiCN as the interface of ceramic matrix composites, the candidate materials of substrate and coating. Through combining the statistical and quantum chemistry of classical thermodynamics thermodynamic study on the related system, fully understand the chemical reaction process and the mechanism of preparation of these materials by CVD, CVD Si-B-C-N the Department has an important guiding significance for high temperature ceramics preparation technology development. Based on Si3N4, BN, SiBx, SiCN and SiBCN thermodynamic problems involving CVD ceramic precursor system for the Department of The calculation, a thermodynamic database related products, including molecular in the standard molar heat capacity of K 298.15K-2000 (C 0 p m), the standard molar entropy (S theta m), the standard enthalpy of formation (fHm 0) and the standard molar Gibbs free energy (fGm 0). The use of the basic thermochemical data, according to the chemical equilibrium (total chemical potential is the minimum principle of the system), the thermodynamic equilibrium concentration distribution of the product, the calculated relationship between CVD production process parameters and solid products, and some of the results of the comparison test. The main research contents and results are as follows: (1) preparation of boron nitride precursor in the BCl3-NH3-H2 system, the intermediate product of the system may have a total of 144, including 87 new products obtained by calculating its complete thermodynamic data, including molecular structure, standard molar heat capacity (C 0 p m), Standard molar entropy (S - M), the standard enthalpy of formation (fHm 0) and the standard molar Gibbs free energy (AfGme). By using the basic data, according to the chemical equilibrium (total chemical potential is the minimum) principle, typical process parameters in the CVD system the calculation (1000 Pa total pressure. The inlet temperature range than the BC13:NH3:H2=1:3:6) and the product of the equilibrium concentration of figure 300 K-2000 K. The results showed that BCl3 and NH3 reacted at 300 K to above 2160 K can be produced by solid boron (B), 1800K generation of cubic boron nitride (c-BN), more than 1800 K to generate six boron nitride (h-BN). Wurtzite boron nitride (w-BN) on these parameters are not stable. This paper also calculated the relative solid system (B, c-BN and h-BN products) generation and the temperature and precursor intake than r= BCl3/ (BCl3+NH3) the relationship between the thermodynamic calculation results show that the formation of solid products and the best BN Intake than r=0.5. (2) also obtained 118 SiCl4-NH3-H2 system in the CVD process may involve (161 in total). The thermodynamic data of new products based on the data obtained in the CVD, the typical process parameters of this system were calculated (1000 Pa, total pressure, inlet temperature range than SiCl4:NH3:H2=1:3:5 and 300 K-2000 K) product the equilibrium concentration diagram. The results show that the thermodynamic temperature of solid products of 300 Si3N4 K-1560 K. also calculated the related product solid system (Si and Si3N4) generation and the temperature and precursor intake than r=SiCl4/ (SiCl4+NH3). The relationship between the thermodynamic calculation results show that the ratio of r=0.5. optimal intake produced by solid products of Si3N4 (3) for BCl3-SiCl4-H2-Ar system, involving a total of 220 possible intermediates. This paper calculated the thermodynamic data among the 128 new products, as well as the CVD system in the typical process parameters (inlet total pressure 1atm, BCl3:SiCl4:H2:Ar =4:1:5:5) and the product of the equilibrium concentration of figure 300 K-2000 K. There is also solid products (B, SiB6 and SiB14) generation and the temperature and precursor intake than r= BCl4/ (SiCl4+ BC13) the relationship between the thermodynamic calculation results show that the solid B formation conditions for the intake than r0.8, producing conditions for 0.1 r0.8700 K T1550 SiB6 K, SiB1i4 and r0.7 for generating conditions of temperature T1400 K. (4) for the SiCl3CH3-NH3-H2 system, involving a total of 443 possible intermediates. This paper calculated the thermodynamic data among the 99 new products, as well as the CVD system in the typical process parameters (1000Pa total pressure, inlet ratio SiCl3CH3:NH3:H2=1:3:5) and 300 K-2000 K product balance the concentration maps and solid phase products (C, Si3N4 and p-SiC) generation and the temperature and precursor intake than r= SiCl3CH3/ (SiCl3CH3 +NH3). The relationship between the thermodynamic calculation results show that the Si3N4 can be generated at 300 K-1200 K, beta -SiC generated a For more than 1200 K (5) SiCl3CH3-BCl3-NH3-H2 system in the 1000 Pa pressure calculation, temperature 300-2000 K, precursor concentration distribution of SiCl3CH3:BC13:NH3:H2= intake than the product balance under the condition of 5:1:4:50. The thermodynamic calculation results show that in the 950-1100 K C+SiC+Si3N4+BN can realize multi phase co deposition; above 1100 K can achieve C+SiC+BN phase co deposition in 700; K-950 K can achieve C+Si3N4+BN phase co deposition. (6) the final results according to the thermodynamics of each system, in the range of thermodynamic research conditions, and the dynamic parameters of the experimental results were compared, the results showed that both the basic line. This paper establishes a Si-B-C-N-H-Cl system of all possible gas phase thermodynamic database, product thermodynamic database by using the experimental data of gas, solid products combined with the related system, calculation of product balance parameters can be arbitrary The concentration distribution, it is important to study the CVI process to guide the related material system.

【学位授予单位】：西北工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ174.758.2


本文编号：1758137