基于液体静力称量法的纯水密度测量

分析了液体静力称量法测量密度的原理和体积测量中纯水密度的特性公式,推导了由己知密度的固体标准来测量液体密度的计算公式。利用固体密度基准量传装置,通过静力称量法为固体密度标准硅球赋值,其相对测量不确定度3×10^-6(k=2)。在20℃时利用高精度液体密度测量装置,通过静力称量法将固体标准(硅球)密度传递至纯水密度,与Tanaka模型比对,E_n值为0.059,比对结果等效。实验结果不仅验证了高精度液体密度测量装置,还验证了20℃纯水密度模型的理论值。     

基于液体静力称量法的玻璃浮计校准结果的不确定度分析

液体静力称量法是近年来在密度计校准中所采用的一种高准确度的测量方法,这种方法通过一套完整的基于静力称量法的密度计校准系统来实现。该系统依据阿基米德浮力原理,采用性能稳定的石英环作为参考标准固体密度,以密度稳定、表面张力低的正十三烷为工作标准液体,通过将浮计主体浸入标准液体至于管待测刻线,然后根据空气中和液体中两次浮计称重测量值,最终计算出当前刻线对应密度点的修正值。本文主要以122#(930)基准浮计的校准为例,对影响该基准浮计测量结果的各种因素作了详细的分析,并对各个分量所引入的不确定度进行了数值计算,最终得出该基准浮计对应密度测量范围校准结果的合成标准不确定度及扩展不确定度,进一步验证了该套校准系统的测量有效性和科学性。     

固体式密度天平校准系统的设计与实现

针对目前密度天平仅能在液体模式校准、无法在固体模式校准的情况,研制了一种挂钩式空腔玻璃砝码作为固体密度标准,对密度天平固体测量模式校准,并提出了一种称量式密度天平校准方法。对固体式密度天平的校准实验显示,校准结果的扩展不确定度为0.0016g/cm3(k=2)。     

橡塑密度计的校准

采用液体静力称量法测量橡胶标准样品的密度,并用该橡胶标准样品校准橡塑密度计。由于难以取得均匀分布的橡胶标准样品,采用了两种材料相结合的方法,通过调整两种材料的比例取得了全量程范围内均匀分布的密度标准样品。对该测量方法的不确定度做出了全面的分析,得出了影响测量结果不确定度的主要因素。     

解决表面张力对浮计法测量液体密度影响的方法

一、问题的提出浮计法是一种常用的液体密度测量方法，具有结构简单、量程较宽、直接读数、使用方便等特点。但是在使用浮计法时，表面张力往往会给测量结果带来较大误差，为此必须采取正确的处理方法才能保证测量结果的准确度。我们根据理论研究与实际工作经验，总结了一套行之有效的解决表面张力对浮计法测量液体密度影响的方法。二、表面张力的形成及其对淹作密度测量的影响表面张力是使液面缩小的一种力，其作用方向与液面相切，且与边界相垂直。当将细管插入液体中时，由于液体表面具有收缩趋势，在表面张力的作用下表面向上收缩成平面…     

液体静力称量法液体密度测量及其不确定度评定

介绍了液体静力称量法测量液体密度的原理并给出液体密度的计算公式,对影响测量结果的各种因素作了详细的分析,并对各个分量所引入的不确定度进行了数值计算,得出液体密度最终测量结果的合成标准不确定度.     

空气中双称量法砝码体积测量方法的研究

利用被测砝码和参考砝码在2种不同密度的空气介质中比较称量时,砝码间的质量差与空气密度差成线性变化这一特性,通过最小二乘法拟合质量差随空气密度差变化的曲线,提出了空气中双称量法砝码体积测量方法。基于空气中双称量法砝码体积测量数学模型和测量装置工作原理,分析影响测量结果的3个主要因素:2次测量的大气压变化范围,砝码表面解吸作用和质量比较仪计量特性。以10g~1kg OIML不锈钢砝码为例,将该方法测得的体积与液体静力比较法的测量结果比对,En值评定结果小于1。     

静力称量法测量重液密度计

本文介绍静力称量法测量重液密度计的测量原理和方法,并与直接比较法测量结果进行了比较。静力称量法测量重液密度计可以节约测量成本,提高测量效率,避免环境污染及有毒液体对工作人员的侵害。     

基于固体密度标准的砝码体积测量分析

正一、概述目前砝码体积的测量,国内主要采用液体静力法来实现。我国现有的测量设备均为进口仪器,直接由计算机给出测量结果,但是其测量结果的不确定度评定有别于现行砝码检定规程。本文给出基于固体密度标准的体积测量公式,其中包括液体密度的测量不确定度评估。     

静力称量法测量重液密度计

本文介绍静力称量法测量重液密度计的测量原理和方法，并与直接比较法测量结果进行了比较。静力称量法测量重液密度计可以节约测量成本，提高测量效率，避免环境污染及有毒液体对工作人员的侵害。     

基于静力称重法的玻璃浮计校准方法研究

采用单晶硅环作为参考标准固体密度,以密度稳定、表面张力低的正十三烷为标准工作液体,选用CCD图像测量系统进行玻璃浮计刻度和液面位置的对准,设计了玻璃浮计校准系统。根据空气中和液体中两次玻璃浮计称重测量值可以计算出当前刻度对应的修正值。对密度测量范围为770~790kg/m³,最小分度为0.2kg/m³的玻璃浮计进行了测量,并与德国国家物理技术研究院进行了双边比对,验证了玻璃浮计校准系统的有效性。     

基于压浮原理的单晶硅球密度比较测量方法研究

为了克服单晶硅球密度测量静力称重法精度受液体表面张力的影响,研究了压浮法进行单晶硅球密度精密比较测量方法和测量系统。在一定的温度下,调节压力,利用液体压缩系数控制液体密度使标准单晶硅球和被测单晶硅球稳定悬浮于工作液体中,通过温度、压力和悬浮高度的测量,计算出二者之间的密度差值。通过双层控温系统保证了液体温度长期波动在±0.25 mK内,利用标准单晶硅球在不同温度-压力悬浮条件线性关系计算出液体压缩系数。试验证明,压浮法测量装置实现了单晶硅球密度差值的精密测量,标准测量相对不确定度为2×10^-7。     

Thermophysical Properties of Undercooled Liquid Cu–Ni Alloys

Experimental data for the surface tension, density, and electrical resistivity of undercooled liquid Cu–Ni alloys of different compositions and at different temperatures are presented. The experiments were performed in facilities that combine the containerless positioning method of electromagnetic levitation with contactless measurement techniques. Although Cu–Ni alloys are rather simple from a chemical point of view, the data for density, surface tension, and electrical resistivity unveil the occurrence of short-range atomic order processes in the melt. For the density this manifests in a composition-dependent excess volume, for the surface tension in smaller values due to an increased surface segregation, and for the electrical resistivity in a deviation from the linear temperature dependence at low temperatures.     

High-Temperature Properties of Liquid Boron from Contactless Techniques

The density, surface tension, and spectral and total hemispherical emissivities of liquid boron obtained with contactless diagnostics are reported for temperatures between 2360 and 3100 K. It is shown that, contrary to previous expectations, liquid boron is denser than the solid at its melting point. It is also shown that the high total emissivity of 0.36 is not consistent with that of a liquid metal as recently claimed. Finally, good agreement is found with previously reported surface tensions and spectral emissivities of liquid boron.     

Surface tension and density data for Fe–Cr–Mo,Fe–Cr–Ni,and Fe–Cr–Mn–Ni steels

The temperature dependence of surface tension and density for Fe–Cr–Mo (AISI 4142), Fe–Cr–Ni (AISI 304), and Fe–Cr–Mn–Ni TRIP/TWIP high-manganese (16 wt% Cr, 7 wt% Mn, and 3–9 wt% Ni) liquid alloys are investigated using the conventional maximum bubble pressure (MBP) and sessile drop (SD) methods. In addition, the surface tension of liquid steel is measured using the oscillating droplet method on electromagnetically levitated (EML) liquid droplets at the German Aerospace Centre (DLR, Cologne). The data of thermophysical properties for Fe–Cr–Mn–Ni is of major importance for modeling of infiltration and gas atomization processes in the prototyping of a “TRIP-Matrix-Composite.” The surface tension of TRIP/TWIP steel increased with an increase in temperature in MBP as well as in SD measurement. The manganese evaporation with the conventional measurement methods is not significantly high within the experiments (?_Mn < 0.5 %). The temperature coefficient of surface tension (dσ/dT) is positive for liquid steel samples, which can be explained by the concentration of surface active elements. A slight influence of nickel on the surface tension of Fe–Cr–Mn–Ni steel was experimentally observed where σ is decreased with increasing nickel content. EML measurement of high-manganese steel, however, is limited to the undercooling state of the liquid steel. The manganese evaporation strongly increased in excess of the liquidus temperature in levitation measurements and a mass loss of droplet of 5 % was observed.     

Physical property measurements for the mathematical modeling of fluid flow in solidification processes

Measurement methods are being developed to provide values for the density, viscosity, heat capacity, enthalpy, fraction solid, surface tension, and thermal diffusivity and conductivity of commercial alloys in the liquid and mushy states. These data are needed for the mathematical modeling of heat and fluid flow in solidification processes. This paper briefly describes the present state of development of apparatus for the measurement of density by the levitated drop and hydrostatic probe methods and viscosity by the oscillating viscometer in our laboratory. Paper presented at the Fourth Asian Thermophysical Properties Conference, September 5–8, 1995, Tokyo, Japan.     

Effect of molten gallium on the surface tension of solid cadmium

The method of zero-creep was used to measure the surface tension of solid cadmium in the presence of small quantities of gallium. The average surface tension of pure cadmium at 280° C is 650 erg/cm², which is in agreement with data for liquid cadmium. It was shown that gallium reduces the surface tension of cadmium, both in the case of adsorption, i.e., excess concentration of the adsorption-active component (gallium) in the surface layers of solid cadmium, and in the limiting case, i.e., at the interface between solid cadmium and liquid gallium.     

A Comparison of Surface Tension,Viscosity, and Density of Sn and Sn–Ag Alloys Using Different Measurement Techniques

This work is aimed at comparing several methods for the measurement of physical properties for molten Sn and Sn–Ag alloys, namely, surface tension, density, and viscosity. The method used for viscosity in this work is the modified capillary method. For surface tension and density, the data used for comparison were previously measured using the maximum bubble pressure method and the dilatometer technique, respectively, for four Sn–Ag alloys having (3.8, 32, 55, and 68) at% Ag. The results are compared with those obtained using a new method based on a fluid draining from a crucible under the influence of gravity, designated the Roach–Henein (RH) method. This new method enables the determination of these three physical properties in one set of measurements. Liquid Sn was used as well as two liquid Sn–Ag alloys having (3.8 and 34.6) at% Ag with the RH method. It was determined that the RH method may be used to simultaneously obtain surface tension, viscosity, and density and that the errors associated with these measurements were similar to those obtained using traditional and separate techniques. Comparisons of the measured viscosity and surface tension to those predicted using thermodynamic models will also be presented. Finally a comparison of mixing model predictions with the experimentally measured alloy surface tension and viscosity is also presented.     

Oxygen influence on ceramics wettability by liquid metals: Ag/α-Al2O3—Experiments and modelling

A renewed interest in the effects of oxygen on the wetting of solid oxides has recently risen in connection to the development of the technique of “air brazing” which makes use of the strong effect of oxygen to increase the wettability of oxides by means of processes running in air or in atmospheres with high oxygen content. Adsorption of oxygen not only at the liquid–vapour surface but also at the solid–liquid interface has been postulated by many previous researches, mainly on the basis of thermodynamic considerations. Along the same line, new results of the wetting behaviour in the system Ag/α-Al₂O₃ as a function of oxygen partial pressure are presented, with the simultaneous measurement of the liquid surface tension. These results are compared with the existing ones, and discussed on the basis of thermodynamic principles. The resulting work of adhesion is compared with the “work of separation” computed by the density functional theory (DFT) approach. DFT calculations are also employed, at variance with previous models, to investigate the structures that are formed at the interface upon addition of oxygen in different sites energetics, atomic and electronic properties of this oxygen-rich interface are discussed together with the connection with experiments.