BFFO的热安全性和凝固特性

为了探究双呋咱并[3,4-b:3′,4′-f]氧化呋咱并[3″,4″-d]氧杂环庚三烯(BFFO)的熔铸工艺性能,通过DSC实验并结合长时恒温试验,对BFFO的热安全性进行了研究;通过X光透射成像、扫描电镜形貌分析、DSC控制凝固测试等对其凝固性能进行了研究,并与3,4-二硝基呋咱基氧化呋咱(DNTF)进行了对比。结果表明,BFFO熔融峰温84.7℃,95~135℃的恒温长时加热未见变色发烟,显示良好的熔铸工艺热稳定性。BFFO的起始分解温度为251.8℃,分解峰温339.5℃,β→0时热爆炸临界温度(T_b)为270.8℃,显示出良好的熔铸工艺热安全性。BFFO具有一种特殊的凝固结晶特性,能以小时为单位,长时间保持熔融状态,显示出非常缓慢的凝固速率。BFFO熔融液相密度为1.659g/cm³(95℃),自然凝固体积收缩率为11.3%。其凝固缺陷集中于药柱顶部补缩区,成型部分整体均匀致密,凝固成型密度1.774g/cm³,达到理论密度的94.9%,显示出良好的熔铸凝固成型性能。相比DNTF,BFFO的熔融峰温降低24.8℃,具有更好的熔融工艺性;分解峰温提高62.6℃且分解过程相对缓和,具有更优的热安定性。BFFO的凝固速率显著低于DNTF,具有更好的凝固补缩性能,可以降低铸件的内部缺陷,使凝固成型相对密度较DNTF提高7.8%。

Thermal Safety and Solidification Characteristics of BFFO

In order to explore the melting and casting process performance of bifurazano[3,4-b:3′,4′-f]furoxano[3″,4″-d]oxacyclohetpatriene(BFFO),the thermal safety of BFFO was studied by DSC test and long-term constant temperature test,and the solidification properties were studied by X-ray transmission imaging,SEM morphology analysis and DSC controlled solidification test,whcih were also compared with 3,4-bis(3-nitrofurazan-4-yl)furoxan(DNTF).The experimental results show that the melting peak temperature of BFFO is 84.7℃,and there is no discoloration and smoke when heated at 95—135℃for a long time,showing good thermal stability of the melting and casting process.The decomposition peak temperature of BFFO are 251.8 and 339.5℃,respectively.The critical temperature of thermal explosion(T_b)whenβ→0 is 270.8℃,and there is no discoloration,which shows good thermal safety of melting and casting process.BFFO has a special solidification and crystallization characteristics,which can maintain the molten state for a long time in hours and show a very slow solidification rate.Moreover,the experiment of solidification shrinkage shows that the density of molten liquid phase of BFFO is 1.659g/cm³(95℃),and the volume shrinkage of natural solidification is 11.3%.The solidification defects are concentrated in the feeding area at the top of the grain,and the forming part is uniform and dense as a whole.In contrast,the solidification forming density is 1.774g/cm³,reaching 94.9%of the theoretical density,showing good melting and casting solidification forming performance.The melting peak temperature of BFFO is 24.8℃lower than DNTF,which makes it have better melting processability.The decomposition peak temperature is 62.6℃higher than DNTF,and the decomposition process is relatively mild,which makes it have better thermal stability.The solidification rate of BFFO is significantly lower than DNTF,which makes BFFO have better solidification and feeding performance.In addition,it can reduce the internal defects of castings,and the relative density can be increased by 7.8%compared with DNTF.