不同吊环组合对液体表面张力系数测量的影响

使用FD-NST-Ⅰ型液体表面张力系数测定仪,通过更换细铜丝加大吊环、细铜丝加小吊环、细棉线加大吊环、细棉线加小吊环四种组合的吊环测量了不同温度下纯净水和95%酒精的表面张力系数。由实验结果分析得到在使用细棉线加大吊环组合时,表面张力系数的测量结果相对于其他三种组合有最小的百分误差。     

液体表面张力系数实验装置的改进

对现有吊环法液体表面张力系数测量仪的水平调节装置、吊环升降装置存在的不足进行了改进,在原有仪器上增加了液体加热装置,以便对不同温度下的液体表面张力系数进行测量,实验说明新的实验装置更加科学合理.通过实验对比得出:新的实验装置操作方便、实验误差小、重复性好,有推广价值.     

对FD-NST-I型液体表面张力系数测量仪的改进

根据吊环法测量液体表面张力系数实验原理,针对现有的FD-NST-1型液体表面张力系数测量仪的不足进行改进.另外在仪器上增加样品加热装置,可以对不同温度下的液体表面张力系数进行测量.通过实验对比得出:改进后的实验装置操作方便、实验误差小,重复性好.     

对FD-NST-Ⅰ型液体表面张力系数测定仪附件吊环改进的设计

FD-NST-Ⅰ型液体表面张力系数测定仪附件吊环水平调试仅凭感觉判断吊环下沿是否水平，作者提出对吊环改进的设计，改进后的仪器成本增加不大，又能使得实验操作有科学依据，符合科学精神和科学态度。     

液体表面张力系数测定仪器的改进

对FD-NST-I型液体表面张力系数测定仪进行了改进,把单金属吊环改为用绝缘体接起的入水通电吊环,把玻璃容器更换为双层变温水池,利用STM32来进行力敏传感器数据的输出和对液体温度的控制,可以有效地减小误差和更好研究温度对此液体表面张力系数的影响.     

用吊环和∏型金属框拉膜测量液体表面张力系数的讨论

为了讨论拉脱法测量液体表面张力时用吊环和用∏型金属框拉膜的测量结果,在不同温度下分别对纯净水、乙醇和甘油三种常见液体的表面张力系数进行了测量,得出了吊环和∏型金属框各有优点,但用吊环测量的数据稳定性要优于∏型金属框。     

液体表面张力系数测量的分析

针对学生在利用FD-NST-I型液体表面张力系数测定仪测量液体表面张力系数时,对何时读取数字电压表的示数存在争议,通过对吊环离开液面后液膜拉脱过程的5个阶段的受力分析、液膜拉脱过程的数学讨论以及微观解释三个方面对该实验数据的最佳读取时刻进行分析讨论以及对实验数据的对比分析,得出在测量时应该读取的是数字电压表在吊环拉脱液膜过程中的最大值。     

拉脱法测表面张力系数测量值不稳定的原因分析与验证

拉脱法测量液体表面张力系数实验中,采用薄壁(0.6 mm)吊环和标准(1.0 mm)吊环,测量值相对稳定;但对于较厚壁(1.5,2.0,2.5 mm)吊环,每次测量值差别很大.通过手机拍摄视频,对不同时刻的液膜形状进行理论和实验分析,发现测量值不稳定的主要原因是颈缩突变,即拉伸过程中,液膜收缩从吊环外壁突变到内壁的程度不同,导致后续液膜断裂点的位置相差非常大,造成测量值的起伏不定.因此需将吊环平均直径替换为断裂时的液膜直径,对测量值进行修正.结果表明：修正后的表面张力系数与理论值的误差减小到了4.0%以内,验证了理论分析的正确性.     

提高液体表面张力系数测量准确度的方法

本文给出了提高液体表面张力系数测量准确度的实验方法.通过切削的办法,使得砝码盘的质量小于吊环的质量,保证了电压表的示数都在定标范围之内;通过分析得出为什么在液膜拉断瞬间读取电压值,使得测量更合理,结果更精确.     

液体表面张力系数测量实验的改进

在原有实验的基础上,采用控制液面下降法,将原实验仪器中的表面皿换成测量杯,利用放水阀控制液体流出速度,从而使数字电压表的示数在液膜拉断前后容易观察,另外在测量杯上标出水平线,以便于判断吊环与液面平行,这样测量出的液体表面张力系数更接近实际值。     

Surface free energies of solid metals: Estimation from liquid surface tension measurements

An equation is derived on semi-theoretical grounds which expresses the solid-vapour surface free energy as a function of the liquid surface tension and the solid-liquid interfacial free energy. A means of calculating reliable values for the solid-liquid energy is presented, which then allows an accurate estimate of solid surface energy at the melting temperature, T_m, to be made for the large number of elements for which dependable liquid surface tension data exist. A method of estimating surface entropy is presented, and has been used to calculate the energies typical of “average”, high-index surfaces at temperatures ranging from 0 K to T_m. It is felt that this paper describes the most accurate method presently available for the calculation of the surface energy of solids in the absence of direct experimental measurement.     

一种测量液膜高度的方法

给出一种测量液膜高度的新方法,利用此方法测定液体表面张力系数时发现,计算液膜重量时,液膜厚度不能用金属丝直径代替,否则液体表面张力系数会出现负值。     

The surface tension of polymer liquids

An experimental and theoretical review of the surface tension of polymer liquids is presented. New experimental methods for polymer surface tension measurement are reviewed. Numerous theoretical and empirical approaches are briefly described. Strong emphasis is placed on the accuracy and limitations of the thermodynamic information which are used as input to many of if not all these theories. It is shown that, by using accurate thermodynamic bulk properties for these liquids including polar polymers, one can use a simple corresponding states principle to describe the temperature and molecular weight dependences of the surface tension with no adjustable parameters to within a few per cent, even though the actual surface tensions may vary by a few hundred per cent. Any small inaccuracies in the predictions arise from conformational entropic effects or because one cannot accurately compute the 'real' cohesive energy density of a polymer liquid from thermodynamic properties alone. The results of recent measurements on high molecular weight polymers are compared with previous work on lower molecular weight liquids. We use the polyethylene and polytetrafluoroethylene oligomeric series to illustrate the uses and limitations of thermodynamicdata for the prediction of surfacetension. The temperature and molecular weightdependences of the surface tensions of these polymers are dominated by the dependence of the bulk thermodynamic properties on temperature and molecular weight. Limited discussion is also given to studies of copolymers and blends using surface tension and complementary techniques.     

Size effect on surface tension of liquid binary alloy droplets

A simple model for size-dependent surface tension of liquid binary alloy droplets has been established based on Bulter’s equation and our model for size-dependent surface tension of pure liquid component. As an example, the surface tension of liquid Bi–Sn alloy droplets are calculated and discussed. The results show that as the size of the liquid alloy droplets decreases, the corresponding surface tension decreases. The component with lower surface tension is enriched in the surface layer at all times while relatively more another component with higher surface tension appear in the surface region when the size decreases. The effect of decreasing size on liquid alloy surface tension is like that of increasing temperature. When size is larger than about 12 nm, the size effect is small and negligible.     

Surface tension and density of liquid Bi–Pb,Bi–Sn and Bi–Pb–Sn eutectic alloys

Surface tension and density measurement of liquid Bi₅₆Pb₄₄, Bi₄₃Sn₅₇ and Bi₄₆Pb₂₉Sn₂₅ eutectic alloys was carried out by using the large drop method over the temperature range of 380–750 K. The regular solution model has been used in conjunction with Butler's equation to calculate the surface tension of binary and ternary alloys of the Bi–Pb–Sn system, while the surface tension of ternary alloys has also been predicted by using geometric models. The new experimental results were compared with the calculated values of the surface tension as well as with the data available in the literature.     

The surface tension of liquid Cu-Fe-Sb alloys

The results of study on the influence of temperature and iron and antimony on the surface tension of liquid ternary Cu-Fe-Sb systems are presented. The measurements were carried out with the sessile drop method, in a broad range of the alloy additions concentration (Fe and Sb). It was demonstrated that the surface tension varies as a linear function of temperature and concentration of iron. It was also demonstrated that antimony, in examined alloys, shows the properties characteristic of a surface-active substance, significantly reducing the surface tension value. The changes of the surface tensions as a function of concentration of antimony were described with the Szyszkowski's equation. Composition of surface layer, enriched with an antimony, was determined basing on the model, which used data regarding properties of binary systems. The surface tension values of Cu-Fe-Sb systems was also computed from model and compared with experimental data. A good agreement was obtained.     

基于悬滴法的纳米燃油表面张力测量与分析

以柴油为基液、溴化十六烷三甲基铵(Cetyltrimethyl Ammonium Bromide,CTAB)为助溶剂,通过两步法配制CNT(Carbon Nanotubc)、CeO₂及Co₃O₄纳米燃油。采用悬滴法测量柴油与纳米燃油的表面张力,探究纳米物质种类、粒径、质量分数及温度对纳米燃油表面张力的影响。研究发现,在纳米燃油液滴气液界面层内,纳米粒子与柴油分子之间的吸引力使液固分子体系总体的内聚力增强,因而表面张力增大;纳米燃油的表面张力随着粒子质量分数增加而增强,但随着温度升高而线性下降。大粒径的纳米粒子表面电荷密度降低,对表面电子束缚减小,电子游离所产生的与柴油分子之间的极化静电相吸作用更强,使液粒之间的范德华力增强,表面张力增大。在相同质量分数的条件下,非金属CNT的密度较小,纳米燃油中的粒子数目较多,此外其得电子能力更强,极易使周围柴油分子极化形成静电吸引,液粒间范德华力增强,因此CNT纳米燃油的表面张力最大;同为金属氧化物,Co₃O₄的分子量大于CeO₂而表现出较低的分子极性,其与基液燃油分子间的静电作用力也较弱,因而Co3O4纳米燃油的表面张力较低。本文测量了多种纳米燃油的表面张力,探讨了不同物质种类、浓度、尺寸的纳米介质及环境温度对燃油表面张力的影响,为纳米燃油在发动机缸内的液滴破碎与着火燃烧过程提供了重要的基础数据和理论支持。     

表面光散射法正十六烷高温热物理性质研究

为拓展高温下流体黏度和表面张力的测量,改进了原有的表面光散射实验系统,将实验的温度区间拓展至570K,改进后的系统在整个温区内测量黏度和表面张力的扩展不确定度分别为2%和1%(k=2)。利用新的实验系统研究了正十六烷在353~547 K温度范围内的黏度和表面张力,并利用实验数据分别拟合了温度倒数多项式和van der Waals方程,在全温度范围内实验值与方程的偏差均在1%之内。在较宽的温度范围内获得的正十六烷的高精度黏度和表面张力数据和方程,可以作为参考数据和方程,用于相关仪器的标定和检验。     

拉脱法测量液体表面张力系数α实验误差分析

在液膜拉脱过程中,对吊环的受力以及受力的变化情况进行分析,以便正确测量求得液体表面张力,减少α的实验测量误差。