【作者】 于雁武；

【导师】 刘玉存；

【作者基本信息】 中北大学 ， 武器系统与运用工程， 2010， 博士

【摘要】 本文采用炸药爆炸产生的冲击波直接作用于反应前驱体的方法对氮化碳的合成进行了系统的研究。对爆炸冲击波作用下氮化碳的微观合成机理进行了理论分析；实验研究了C2H4N4、CH3N5、CI4分别作为反应前驱体主要成分对氮化碳合成效果的影响；研究了前驱体中辅助N源对合成效果的影响；探讨了Cu粉在前驱体中延长压力、温度的作用机理。研究了液相氧化和气相氧化相结合的氮化碳提纯方法,并对提纯过程中杂质的去除机理进行了探讨。详细研究了冲击波压力、水保护介质、约束底座的强度和密度对氮化碳合成收得率的影响规律；通过具有强腐蚀性的混酸研究了氮化碳在常温和高温条件下的耐腐蚀性；研究了空气介质中氮化碳的热稳定性,以及在不同温度条件下内部结构的变化规律。利用Materials Studio软件分别模拟了α-C3N4和β-C3N4两种氮化碳结构的晶胞组成及XRD图谱,分析比较了理论模拟与实测图谱的差异及原因。通过XRD、FTIR、SEM、EDS、XPS等手段对氮化碳的物相组成、显微结构、元素比例及键合状态进行了表征,用TG-DTA分析了氮化碳的热稳定性。具体研究结果如下：利用冲击波引发物质相变的机理,分析得出氮化碳的合成机理。在一定强度的冲击波能量作用下,有机前驱体中含有的C=N和C≡N被打开,然后重组后形成C—N；无机前驱体中含有的C、N原子在经过瞬时高压压缩后,C、N原子的外层电子处于sp3、sp2高活性态,进而提高了C—N成键能力。采用DYNA程序建立了空气介质中炸药爆炸冲击及有机玻璃衰减理论模型,模拟了密度为1.604g/cm3的RDX和密度为1.800 g/cm3的HMX炸药柱的爆炸过程；计算模拟了两种炸药爆炸冲击波经过不同厚度有机玻璃板衰减后的冲击波压力及冲击波速度；通过模拟得到的冲击波压力及冲击波速度,计算了相应条件下的冲击波温度,为进一步的实验研究提供了理论依据。经过17.28 GPa冲击波作用后,以C2H4N4、CH3N5、CI4为主要成分的反应前驱体得到的氮化碳中C/N分别为1：0.75、1：2.98、1：1.02。CH3N5为主要成分的前驱体发生反应后,观测到了线度为2μm的六边β-C3N4晶粒。同时在合成的目标产物中发现了非晶SiO2、C3N4晶间相及金属硅酸盐共同构成的球形团聚体。不同前驱体方案经过17.28 GPa冲击波作用后,XRD图谱均显示出α-C3N4、β-C3N和石墨相C3N4的特征峰；FTIR图谱中观测到了较强的C—N衍射峰；XPS测试结果显示出氮化碳中的C、N两种原子分别以C—N(SP2)和C(Sp3)—N的形式成键。选用RDX和HMX作为冲击波源炸药,通过爆炸冲击波在有机玻璃中的衰减模型计算调节可以获得实验所需压力。冲击波压力为29GPa时,氮化碳收得率最高,可以达到3.8%。29GPa之后,冲击波压力的提高反而会使收得率降低。水保护介质的存在可以使氮化碳收得率提高25%。随着约束底座强度和密度的提高,氮化碳收得率呈上升趋势。氮化碳粉末常温下可以在王水中稳定存在48h以上,180—220℃高温时可以在混酸(HSO4:HNO3=2:1)中稳定存在6h以上。在空气介质中,氮化碳的氧化温度可以达到1000℃以上。模拟得出的α-C3N4、β-C3N4晶胞与理论预测结果吻合性较好；模拟得到的XRD图谱与实测结果的匹配程度可达60%以上。更多还原

【Abstract】 Carbon nitride was synthesized by shock-compression directly acting on the precursor. The microcosmic composite mechanism of carbon nitride was theoretically analyzed. Three kinds of precursors, such as C2H4N4、CH3N5 and CI4,were used to compose carbon nitride. The influence of additional N comprised in precursor was discussed. The mechanism of postponing compression and temperature by existence of Cu was investigated. Method of purification through the cooperation of liquid phase and gaseous phase was investigated, and the mechanism of eliminating impurities was studied. In terms of the yield of carbon nitride, shock-compression, water protective medium as well as the density and intensity of restraint potence were investigated, respectively. Under normal temperature and high temperature, the corrosion resistance of carbon nitride was researched through the using of mixed acid. The heat endurance in air and the mutative disciplinarian of micromechanism of carbon nitride were discussed. Crystal cells and the diffraction peaks ofα-C3N4 andβ-C3N4 were respectively simulated. The difference of simulant spectral line and the observed one was compared and analysed. The phase composition, microstructure, elements proportion, form of chemical bonds and heat endurance of carbon nitride were characterized with the help of XRD, FTIR, SEM, EDS, XPS and TG-DTA. The conclusion are the followings:Composite mechanism of carbon nitride was described after analysing the mechanics of phase change under shock-compression. Under special intensity of blast wave, the C=N and C≡N consisting in the organic precursors were disconnected and recombine the C-N. During the instantaneous shock-compression, the outer orbit electrons of C and N consisting in the inorganic precursors were excitateded and turn into a higher active energy level in which the C and N are in the sp3 or sp2 phase. The ability of bonding C-N was improved obviously.Theoretical model which describing the shock-compression of explosive detonation and the attenuation mechanism of plexiglass in the air was established through DYNA procedures. The explosive procedure of RDX and HMX which density is 1.604g/cm3 and 1.800 g/cm3, respectively was simulated. Shock wave pressure and shock wave velocity through the plexiglass plate with different thickness were simulated and calculated. Based on the shock wave pressure and velocity, the shock wave temperature was calculated. The calculating and simulating results provide the theoretical basis for further experimental study.Under the shock-compression of 17.28GPa, the ratios of C and N in the carbon nitride prepared from C2H4N4, CH3N5 and CI4 are 1:0.75,1:2.98 and 1:1.02, respectively. In the sample obtained from CH3N5, some hexagonal P-C3N4 particles of 2μm in size were observed. Some spherical aggregations which composed by amorphous SiO2, intergranular phases of C3N4 and metallic metasilicates were discoveried.In the samples prepared from different precursors under the shock-compression of 17.28GPa, the diffraction peaks ofα-C3N4,β-C3N4 and graphit C3N4 were detected. The feature peaks of C-N were found in the infrared picture and the C were mainly bonded with N by C-N(SP2) and C(SP3)-N.The appropriate shock-compression provided by RDX and HMX was calculated and regulated through using the attenuating regularity of detonation shock wave in the PMMA gap. Under the shock-compression of 29GPa, the highest yield of carbon nitride could reach 3.8%. The yield would reduce on the contrary after the shock-compression of 29GPa. The yield could be increased by 25% in the water protective medium. With the increasing of the density and intensity of restraint potence, the yield of carbon nitride was an upward trend. At room temperature, the carbon nitride could be stable in chloroazotic acid more than 48h, while at 180-220℃, the carbon nitride could be in a stable existence for more than 6h. In the air medium, the oxidation of carbon nitride could reach temperatures above 1000℃.The simulated crystal cells ofα- C3N4 andβ-C3N4 coincided very well with the prediction. Simulations of the XRD patterns with the measured results matched of up to 60%.更多还原