摘要
为了研究1,1‑二氨基‑2,2‑二硝基乙烯(FOX‑7)在二甲基亚砜‑乙酸乙酯(DMSO‑EAC)混合溶剂中的结晶行为,促进FOX‑7球形化晶体制备工艺研究,利用激光动态法测定了298.15~333.15 K温度范围内FOX‑7在不同体积比DMSO‑EAC混合溶剂中的溶解度,建立了溶解度方程,估算了结晶热力学参数,并在DMSO‑EAC混合溶剂中进行了降温结晶实验。结果表明,FOX‑7在该混合体系溶剂中的溶解度随温度和DMSO含量的增加而增加;所有模型拟合结果良好,其中CNIBS/R‑K模型的关联结果最优;在VDMSO∶VEAC=1∶3体系中降温结晶所得晶体形貌规则、呈椭球状且粒度均匀。
图文摘要
The solubility of FOX‑7 in DMSO‑EAC mixed solvents were tested. The thermodynamic parameters, solid‑liquid surface tension and crystal surface entropy factor of FOX‑7 were estimated. The cooling crystallization experiment was carried out in DMSO‑EAC mixed solvent.
1,1‑二氨基‑2,2‑二硝基乙烯(FOX‑7)是一种综合性能优异的新型高能钝感炸药。自1998年首次合成以来,引起了含能材料研究者的高度重
含能化合物的晶体形貌不仅影响其工艺性能,而且对其物化性能、感度、热安定性和爆炸性能等均有着重要的影
国内外开展了FOX‑7结晶工艺研究。Kim
FOX‑7结晶热力学和动力学等研究是FOX‑7晶体形貌控制技术的基础。文献[
本课题组对FOX‑7在不同二元混合体系中的结晶进行研究时发现EAC是一种较好的非溶剂,因此提出以DMSO‑EAC为结晶体系,研究FOX‑7在其中的结晶行为。本研究采用激光动态法测定FOX‑7在不同体积比的DMSO‑EAC混合溶剂中的溶解度,用Apelblat、van′t Hoff和CNIBS/R‑K模型关联溶解度实验数据,计算FOX‑7的热力学参数、固液表面张力和晶体表面熵因子,为FOX‑7的结晶研究提供基础数据,进行降温结晶实验,获得了不同形貌的晶体。
FOX‑7,甘肃银光化学工业集团有限公司,经DMSO中重结晶纯化,纯度大于99.5%;DMSO和EAC,均为分析纯,西陇化工股份有限公司。
分析天平,AL104型,梅特勒‑托利多仪器有限公司;玻璃恒温水浴,SYP型,巩义市予华仪器有限责任公司;数显恒温磁力搅拌器,Jeio Tech Co.LTD;激光监测装置,JDW‑3型,北京大学物理系;水浴锅,SYD‑100型,杭州仪表电机有限公司;搅拌器,JJ‑1型,北京市永光明仪器有限公司;抽滤机,SHZ‑CA型,巩义市予华仪器有限责任公司;真空干燥箱,巩义市予华仪器有限责任公司;光学显微镜,XSP‑10A型,上海光学仪器厂。
本研究采用激光动态

图1 溶解度测定装置示意图
Fig.1 Schematic diagram of the solubility measuring equipment
1─激光发射器,2─结晶器,3─空气冷凝器;,4─酸式滴定管,5─磁力转子,6─磁力搅拌器,7─信号接收器,8─显示仪,9─超级恒温水浴
1─laser emitter, 2─crystallizer, 3─air condenser, 4─acid burette, 5─magnetic rotor, 6─magnetic stirrer, 7─signal receiver, 8─display instrument, 9─super constant temperature water bath
测定步骤:按
FOX‑7在二元混合溶剂中的溶解度(x)通过
(1) |
(2) |
式中,m1、m2、m3分别为FOX‑7、DMSO、EAC的质量,g;M1、M2、M3分别为FOX‑7、DMSO、EAC的相对分子质量。
FOX‑7在DMSO‑EAC混合溶剂中的溶解焓、溶解熵和溶解过程吉布斯自由能变化通过van’t Hoff方
(3) |
式中,x为FOX‑7的溶解度,mol·mo
FOX‑7的吉布斯自由
(4) |
溶解过程焓变和熵变对吉布斯自由能的相对贡献值%ξH和%ξ
(5) |
(6) |
固液表面张力()是代表晶体物理性质的主要物理量,表面张力的获得不仅使理论预测成核行为成为可能,而且可以促进对成核理论的深入理解。此外,固液表面张力很大程度上决定着晶体的生长机理。因此研究固液表面张力非常必要。Meresman
(7) |
式中,NA为Avogadro常数,6.02×1
晶体表面熵因子(f)可以通过溶解度数据及固液表面张力计算。f可以表征晶体表面在原子水平上光滑程度,f越大,晶体表面越光滑,晶体生长越困难。Barata
(8) |
(9) |
式中,V为分子体积,
FOX‑7在不同温度下不同体积比的DMSO‑EAC混合溶剂中溶解度的实验值如
xexp is the experimental solubility data, xcal is the correlated solubility data, RD is the relative deviation.
Apelblat方
(10) |
式中,x为FOX‑7的溶解度,mol·mo
通过实验数据回归得到的Apelblat方程的模型参数值如
A, B and C are the Apelblat equation model parameters, RMSE is the root‑mean‑square deviation,

图2 不同温度下Apelblat方程关联FOX‑7溶解度的曲线
Fig.2 Solubility curves of FOX‑7 at different temperature, correlated by the Apelblat equation
Van′t Hoff方
(11) |
式中,x为FOX‑7的溶解度,mol·mo
通过实验数据回归得到的van′t Hoff方程的模型参数值如
A and B are the van’t Hoff equation model parameters, RMSE is the root‑mean‑square deviation,

图3 不同温度下van′t Hoff方程关联FOX‑7溶解度的曲线
Fig.3 Solubility curves of FOX‑7 at different temperature, correlated by the van′t Hoff equation
CNIBS/R‑K模
(12) |
式中,x为FOX‑7的溶解度,mol·mo
通过实验数据回归得到的CNIBS/R‑K模型的模型参数值如
B0,B1,B2,B3 and B4 are the CNIBS/R‑K equation model parameters, RMSE is the root‑mean‑square deviation,

图4 不同浓度下CNIBS/R‑K模型关联FOX‑7溶解度的曲线
Fig.4 Solubility curves of FOX‑7 at different concentration, correlated by the CNIBS/R‑K equation
前述模型均用相对误差(RD)检验结果的一致性;用均方差(RMSE)评估相关方程的拟合效果,见式(
(13) |
(14) |
式中,xexp为实验值;xcal为计算值;N代表实验点的总数。
从
从
FOX‑7在DMSO‑EAC混合溶剂中的热力学参数值见
is the solution enthalpy of FOX‑7, is the solution entropy of FOX‑7, is the Gibbs free energy for the solution process of FOX‑7, %ξH is the relative contributions by enthalpy toward the solution process, %ξS is the relative contributions by entropy toward the solution process.
FOX‑7在DMSO‑EAC混合溶剂中的固液表面张力和晶体表面熵因子见
采用光学显微镜对FOX‑7在不同比例的DMSO‑EAC混合溶剂中降温结晶所得的晶体形貌进行表征,如

a. VDMSO∶VEAC=3∶1

b. VDMSO∶VEAC=2∶1

c. VDMSO∶VEAC=1∶1

d. VDMSO∶VEAC=1∶2

e. VDMSO∶VEAC=1∶3
图5 FOX‑7在DMSO‑EAC混合溶剂中的晶体显微照片(×40)
Fig.5 The crystal micrographs of FOX‑7 in DMSO‑EAC mixed solvents (×40)
(1)采用激光动态法测定了298.15‑333.15K温度范围内FOX‑7在不同体积比的DMSO‑EAC混合溶剂中的溶解度。结果表明,FOX‑7在混合溶剂中的溶解度随温度的升高和DMSO含量的增加而增大,其溶解为吸热过程。
(2)用Apelblat、van′t Hoff 和CNIBS/R‑K模型对实验溶解度数据进行拟合,得到溶解度计算值和实验值相对误差均比较小,最大不超过2%,所有模型拟合结果良好;建立了溶解度方程,三种关联模型所得方程计算得到的溶解度数值均与实验值吻合度高,其中CNIBS/R‑K模型对实验数据的关联结果最优;FOX‑7的溶解度数值与关联模型可作为基础数据与模型应用于FOX‑7的结晶过程控制。
(3)计算获得了FOX‑7在DMSO‑EAC混合溶剂中的溶解焓、溶解熵和吉布斯自由能等热力学参数。以平均温度315.65 K计算,FOX‑7的溶解焓和吉布斯自由能在DMSO‑EAC混合溶剂中都为4~8 kJ·mo
(4)利用实验溶解度数据估算了FOX‑7的固液表面张力和晶体表面熵因子。FOX‑7在VDMSO∶VEAC=1∶3体系中的固液表面张力和晶体表面熵因子最大,晶体生长最慢,降温结晶得到的椭球状晶体,生长方式为螺旋位错生长模式。
(责编: 高 毅)
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