DMA/AOT摩尔比对非水微乳体系临界现象的影响

采用折射率法测定了非水微乳体系{N,N-二甲基乙酰胺(DMA)/二(2-乙基己基)琥珀酸酯磺酸钠(AOT)/正辛烷}在不同DMA与AOT摩尔比ωs时的温度-折射率(T-n)共存曲线, 并根据曲线推导出临界指数β和指前因子B. 结果表明, 临界组成φc(即DMA和AOT的体积之和在总体积中所占的分数)随ωs的增加而降低, 而临界温度Tc随ωs增加而增大; 临界指数β与ωs无关, 其数值趋近于Fisher重整化理论值(0.365); 与体系有关的指前因子B随ωs的增加而增大.     

DMA+AOT+正辛烷三组分非水微乳体系的临界现象

采用折射率法在离临界温度7 K的范围内测定N,N-二甲基乙酰胺(DMA)与二-(2-乙基己基)琥珀酸酯磺酸钠(AOT)摩尔比为3.46的非水微乳体系(DMA+AOT+正辛烷)的温度-折射率(T-n)共存曲线, 利用标准曲线转化为温度-体积分数(T-φ)共存曲线和温度-有效体积分数(T-ψ)共存曲线, 进而求得临界指数β. 研究结果表明, 该体系的临界指数β与已经报道的微乳液不同, 在较宽的温度范围内均符合Fisher重整化理论值0.365. 分析实验数据, 获得指数因子B、Wegner校正项因子B1和共存曲线的直径籽d, 并讨论所选择的序参量的优劣性.     

硝基苯与正十六烷在临界区域的液-液共存曲线

用折射率法在离临界温度10.5K范围内测定了硝基苯+正十六烷的温度-折射率(T, n)共存曲线, 通过标准曲线法转化得到温度-摩尔分数(T, x)和温度-体积分数(T, φ)共存曲线, 进而求得临界指数, 与理论值一致。分析实验数据, 给出描述三条共存曲线的方程, 并讨论了选定的序参量的有效性。     

超临界CO2与叔丁醇二元系统高压相平衡研究

采用固定体积可视观察法测量装置测定了CO2与叔丁醇在323.2~353.2 K温度范围内于不同压力下的平衡数据, 并运用Peng-Robinson状态方程(PR)和Van der Waals-2混合规则建立了相平衡模型, 通过非线性最小二乘法优化计算得到了不同温度下的模型参数. 并得到了模型参数与温度的表达式, 分别为k12=-199.2066+1.8136T-0.00548T2+5.50×10-6T3; n12=-384.5626+3.4960T-0.01056T2+1.06×10-5T3.获得了此体系在不同组成下的临界压力、临界温度、临界摩尔体积、临界压缩因子和临界密度等临界性质. 研究结果表明, CO2与叔丁醇二元体系的临界温度、临界压力和临界压缩因子均随着临界CO2组成的增加而降低.     

水+3-甲基吡啶+溴化钠三元溶液临界跨接现象

采用折射率法在较宽温度范围内研究了溴化钠、3-甲基吡啶和水的临界质量分数分别为0.240、0.192和0.568体系的临界性质, 发现在近临界点临界指数为0.365, 与Fishe重整化值一致. 有效临界指数随着温度逐渐远离临界点, 从0.365下降到0.20左右, 但当排除了“正规项”的影响后, 展现出向平均场理论值0.5单调跨接的行为.     

苯-水-乙醇三元溶液体系的临界行为

通过等体积滴定法测定了苯-水-乙醇三元部分互溶溶液体系的会溶点曲线；测定了29.00±0.05 ℃时,等溶点附近的等温共存曲线；拟合得到苯-水-乙醇体系序参量临界指数β= 0.38 ± 0.04,序参量临界指前因子K= 1.3 ± 0.2. 说明三元部分互溶溶液体系在等温会溶点附近有非经典临界溶液理论行为, 符合Fisher重正化模型.     

水-环己烷-二乙二醇丁醚三元体系的三液相相平衡

用改进的相体积法测定了水-环己烷-二乙二醇丁醚三元体系的相平衡, 给出了不同温度下平衡共存三液相的体积分数及平衡共存三液相的相密度的共存曲线. 实验结果表明, 在平衡共存三液相中, 水、环己烷和二乙二醇丁醚的体积分数随温度改变的变化曲线分别是倒“S”型, 正“S”型, “结”型; 将共存三液相的体积分数转化为对应的相密度后, 相密度随温度改变的变化曲线也是规整的倒“S”型; 而且, 3条“S”曲线形状均表现出不对称的特性. 因此, 密度也可以用作描述体系的相平衡, 而且在描述体系临界标度率时, 密度可能是一个很好的序参量.     

顺丁烯二酸二乙酯与正构烷烃二元溶液在临界区的关联长度和渗透压缩系数

测量了顺丁烯二酸二乙酯与正庚烷、正辛烷、正壬烷和正癸烷二元溶液在临界区域不同波长及温度下的浊度。与关联长度、渗透压缩系数、共存曲线相关的三个指前因子(χ~0,ξ~0,B)的比例关系为:R=ξ~0[B^2/(4k~BT~cχ~0)]^1^/^3(k~B和T~c分别为玻尔兹曼常数与临界温度),R的理论值为0.65-0.67。临界指数γ,ν和β服从指数和规则:3ν=2β+γ。用上述两个关系式及Ornstein-Zernike方程拟合浊度-温度-波长数据,得到γ与ν,在误差范围内与理论值一致。将γ与ν固定在理论值1.241和0.63,得到ξ~0和χ~0,结果表明ξ~0和χ~0可分别由ξ~0Φ~c^0^.^8^5∝M^n和χ~0Φ~c^-^1^.^2^0∝M^g表示(Φ是顺丁烯二酸二乙酯的临界体积分数,M是正构烷烃的摩尔质量),其中n=0.22±0.03,g=-0.07±0.09和我们最近提出的理论值0.18和-0.06吻合。     

顺丁烯二酸二乙酯与正构烷烃二元溶液在临界区的关联长度和渗 透压缩系数

测量了顺丁烯二酸二乙酯与正庚烷、正辛烷、正壬烷和正癸烷二元溶液在临界区域不同波长及温度下的浊度。与关联长度、渗透压缩系数、共存曲线相关的三个指前因子(χ~0,ξ~0,B)的比例关系为:R=ξ~0[B^2/(4k~BT~cχ~0)]^1^/^3(k~B和T~c分别为玻尔兹曼常数与临界温度),R的理论值为0.65-0.67。临界指数γ,ν和β服从指数和规则:3ν=2β+γ。用上述两个关系式及Ornstein-Zernike方程拟合浊度-温度-波长数据,得到γ与ν,在误差范围内与理论值一致。将γ与ν固定在理论值1.241和0.63,得到ξ~0和χ~0,结果表明ξ~0和χ~0可分别由ξ~0Φ~c^0^.^8^5∝M^n和χ~0Φ~c^-^1^.^2^0∝M^g表示(Φ是顺丁烯二酸二乙酯的临界体积分数,M是正构烷烃的摩尔质量),其中n=0.22±0.03,g=-0.07±0.09和我们最近提出的理论值0.18和-0.06吻合。     

硝基苯与正十六烷二元溶液在临界区域的浊度

测量了硝基苯与正十六烷二元溶液在临界区域不同波长及温度下的浊度, 结合与关联长度、渗透压缩系数、共存曲线有关的三个指前因子(x0, ξ0, B)的比例关系: R=ξ0[B^2/(4kBTcx0)]^1^/^3(kB和Tc分别为玻尔兹曼常数与临界温度)及R的理论值(0.65-0.67), 用Ornstein-Zernike方程拟合浊度-温度-波长数据, 得到临界指数γ与ν, 在误差范围内与值一致。将γ与ν固定在理论值1.241和0.63, 求得ξ0为0.168nm(R=0.65)和0.174nm(R=0.67), x0为2.81×10^-^9m^3.J^-^1(R=0.65)和2.85×10^-^9m^3.J^-^1(R=0.67)。     

Tricritical phenomena in quasi-ternary mixtures of water + n-decane + n-undecane + tert-butanol

Coexistence curves for the quasi-ternary system of water + n-decane + n-undecane + tert-butanol have been determined by measurements of the refractive index in three coexisting liquid phases. The binary mixtures of n-decane + n-undecane constructed the quasi-pure components in which the mass fraction beta of n-decane controls the approach to the tricritical point. The coexistence curves can be fitted to Scott's extended theory and can be extrapolated to a tricritical point at (44.1 +/- 0.3) degrees C and beta = 0.77 +/- 0.02 corresponding to an average n-alkane-carbon number of 10.19 +/- 0.02. The nonclassical critical amplitude ratio has been confirmed to be 4-5% smaller than the classical value, which is consistent with Fisher's prediction.     

Critical phenomenon of nonaqueous microemulsion (AOT/DMA/decane)

The critical phenomenon of nonaqueous microemulsion was studied for the first time. The coexistence curves of (T,n), (T,phi), and (T,psi) (n and phi are refractive index and volume fraction, respectively; psi is defined as psi=phi/[phi+phi(c)(1-phi)/(1-phi(c))]) for a ternary microemulsion [phi (AOT-DMA)+(1-phi) decane] at constant pressure and a constant molar ratio (omega=2.86) of DMA to AOT have been determined within about 7 K from the critical temperature T(c) by measurements of refractive index. The critical exponent beta has been deduced from (T,n), (T,phi), and (T,psi) coexistence curves within 1 K below T(c). They all were 0.329+/-0.005 and were consistent with the 3D Ising value. The experimental results in a temperature range of (T(c)-T)<7 K also have been analyzed to obtain critical amplitudes and the Wegner correction terms, to examine the diameters of the coexistence curves.     

假二元微乳液体系标度律

微乳液是在表面活性物质存在下形成的油 -水混合热力学稳定体系 ,在一定条件下 ,表面活性剂双 -2 -乙基己基硫代琥珀酸钠 (AOT) -水 -正构烷烃可形成油包水型微乳液体系 ,其中分散颗粒的大小仅由水与 AOT的物质的量比 x确定[1] .这类微乳液体系有一个低临界温度 Tc,当温度高于 Tc时体系分成两相 ,两相中分散颗粒的大小相同 ,但颗粒浓度不同 ,因此 ,可看成一个假二元体系 .近年来 ,有关这类微乳液体系在临界区域与温度相关的标度律是否符合 3 D-Ising模型方面存在争论 [2～ 4 ] .本文通过精确测量 AOT-水 -正构烷烃假二元微乳液体系在…     

Effect of polymer chain in coexisting liquid phases by refractive index measurements

The behavior of polyethylene oxide (PEO, molecular weight, M(w) = 9 x 10(5), as an impurity) was studied in the critical binary mixture of nitroethane (NE) + 3-methylpentane (MP) by refractive index measurements. The measurements were performed at three different PEO concentrations (C = 0.373, 0.759, and 1.509 mg/cc) in the near critical composition of NEMP. We observed that the coexisting phase region shifts down with increasing PEO concentration and the critical temperature (T(c)) decreases linearly with C. At temperatures T close enough to T(c), the critical exponent beta [defined by the relation (n1-n2) proportional (T(c)-T)beta, with n1 and n2 being the refractive indices of the coexisting phases] was found to decrease from 0.456 to 0.372 when the PEO concentration changes from 0.373 to 1.509 mg/cc. These values are higher than that of 0.345+/-0.015 of pure NEMP, which is compatible with the three-dimensional Ising value beta = 0.325. It appears that the shape of the PEO in NEMP coexistence curves is similar from that of pure NE + MP.     

Critical Behavior of {Water + AOT + Decane} Microemulsion with Small Molar Ratio of Water to AOT

The coexistence curves of (T,n), (T,φ) and (T,ψ) (n,φ,ψ are the refractive index, the volume fraction, and the effective volume fraction, respectively) for a ternary microemulsion system of {water + sodium di(2-ethylhexyl) sulfosuccinate (AOT) + n-decane} with the molar ratio 25.1 of water to AOT have been determined at constant pressure within about 7 K from the critical temperature T _c by measurements of refractive index. The critical exponent β has been deduced from the (T,n), (T,φ) and (T,ψ) coexistence curves within 1 K above T _c . They were 0.323, 0.327, and 0.329, respectively, and were consistent with the 3D-Ising value. Furthermore, the experimental results have been analyzed to obtain critical amplitudes B and the Wegner-correction terms B ₁, to examine the diameters of the coexistence curves and to discuss the goodness of density variables for constructing order parameters.     

The liquid–liquid coexistence curves of {x dimethyl adipate + (1 − x) n-octane} and {x dimethyl adipate + (1 − x) n-nonane} in the critical region

The liquid–liquid coexistence curves of (dimethyl adipate + n-octane) and (dimethyl adipate + n-nonane) have been determined within about 10 K from the critical temperatures, from which the critical amplitudes and the critical exponents are deduced. The critical exponents corresponding to the coexistence curve β are consistent with the 3D-Ising values. The experimental results have been analyzed to determine Wegner-correction terms and to discuss the asymmetric behaviour of the diameters of the coexistence curves by the complete scaling theory. Molar mass-dependences of the critical amplitude and the critical volume fraction have been shown to be consistent with the theoretical prediction.