孙立梅
,
LI Ming-Yuan
,
林梅钦
,
GUO Ji-Xiang
,
彭勃
,
DONG Zhao-Xia
应用化学
doi:10.3969/j.issn.1000-0518.2008.08.019
利用动态光散射、黏度和聚沉值研究了合成的水溶性酚醛树脂的水化特性及反应条件的影响.结果表明,n(甲醛):n(苯酚)=3∶1、NaOH作催化剂、不同条件下制备的水溶性酚醛树脂,其水化形成的溶液澄清透明,10%溶液的黏度范围为1.529 1～6.064 7 mPa·s;50 mg/L的稀溶液中,分散单元的流体力学直径为2.1～21.1 nm,Zeta电位为-54.38～-10.07 mV;NaCl使酚醛树脂水化性能减弱而析出,不同产物的聚沉值档在0.014～0.099 mol/L范围内.不同反应条件产物的水化特性表明,随着预聚体质量分数、反应时间及反应温度的增加,产物的聚合度增加.因此产物的黏度和稀溶液中聚集体的流体力学直径增加,稀溶液的聚沉值和聚集体的Zeta电位降低.在上述反应条件下,预聚体质量分数对产物的影响较小,反应时间对产物的影响最明显,是控制反应产物的主要因素,而90℃之前不易发生缩聚反应.
关键词:
水溶性酚醛树脂
,
水化
,
黏度
,
流体力学直径
,
Zeta电位
,
聚沉值
Physical Review B
In a recent publication [S. Dong et al., Phys. Rev. Lett. 103, 127201 (2009)], two (related) mechanisms were proposed to understand the intrinsic exchange bias present in oxides heterostructures involving G-type antiferromagnetic perovskites. The first mechanism is driven by the Dzyaloshinskii-Moriya interaction, which is a spin-orbit coupling effect. The second is induced by the ferroelectric polarization, and it is only active in heterostructures involving multiferroics. Using the SrRuO(3)/SrMnO(3) superlattice as a model system, density-functional calculations are here performed to verify the two proposals. This proof-of-principle calculation provides convincing evidence that qualitatively supports both proposals.
关键词:
thin-films;weak ferromagnetism;superlattices;anisotropy;bifeo3;srruo3;model
中国腐蚀与防护学报
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关键词:
Europhysics Letters
Noncollinear magnetic investigations of the ground state in PrFeAsO have been performed by the density-functional theory. We calculated the total energy and made structure optimization, and the electronic density of states of PrFeAsO was analyzed. There are three different magnetic structures in PrFeAsO defined by experiments. Based on these magnetic structures, we studied four collinear and four noncollinear cases. The ground state is found to take the ordering proposed by Zhao, in which the FeAs plane is of stripe antiferromagnetism and Pr spins are perpendicular to Fe spins. The electronic density of states indicates that for PrFeAsO the increase of the electron Coulomb interaction leads to a decrease in conductivity. Copyright (C) EPLA, 2011
关键词:
high-temperature superconductivity;phase-diagram;oxypnictides;instability
刘建国
,
安振涛
,
张倩
,
杜仕国
,
姚凯
,
王金
材料导报
doi:10.11896/j.issn.1005-023X.2017.04.030
为评估氧化剂硝酸羟胺的热稳定性,使用标准液体铝皿于3 K/min、4 K/min、5 K/min加热速率下进行热分析.借助非等温DSC曲线的参数值,应用Kissinger法和Ozawa法求得热分解反应的表观活化能和指前因子,根据Zhang-Hu-Xie-Li公式、Hu-Yang-Liang-Xie公式、Hu-Zhao-Gao公式以及Zhao-Hu-Gao公式,计算硝酸羟胺的自加速分解温度和热爆炸临界温度,并对热分解机理函数进行了研究.设计了7条热分解反应路径,采用密度泛函理论B3LYP/6-311++G(d,p)方法对硝酸羟胺的热分解进行了动力学和热力学计算.计算结果表明,硝酸羟胺热分解的自加速分解温度TsADT=370.05 K,热爆炸临界温度Te0=388.68K,Tbp0=397.54 K,热分解最可几机理函数的微分形式为f(a) =17×(1-α)18/17.硝酸羟胺热分解各路径中,动力学优先支持路径Path 6、Path 5、Path 4和Path 1生成NO和NO2,其次是Path 2、Path 7和Path 3生成N2和N2O.温度在373 K以下时,Path 1'反应无法自发进行,硝酸羟胺无法进行自发的热分解.从热力学的角度来看,硝酸羟胺在370.05K以下储存是安全的.
关键词:
硝酸羟胺
,
热分析
,
热稳定性
,
热分解机理
,
密度泛函理论
