The density of liquid toluene has been measured over the temperature range −60 °C to 200 °C with pressures up to 35 MPa. A two-sinker hydrostatic-balance densimeter utilizing a magnetic suspension coupling provided an absolute determination of the density with low uncertainties. These data are the basis of NIST Standard Reference Material® 211d for liquid density over the temperature range −50 °C to 150 °C and pressure range 0.1 MPa to 30 MPa. A thorough uncertainty analysis is presented; this includes effects resulting from the experimental density determination, possible degradation of the sample due to time and exposure to high temperatures, dissolved air, uncertainties in the empirical density model, and the sample-to-sample variations in the SRM vials. Also considered is the effect of uncertainty in the temperature and pressure measurements. This SRM is intended for the calibration of industrial densimeters.
Measurements of density, speed of sound, and viscosity
have been
carried out on liquid certified reference materials for biofuels as
a function of temperature at ambient pressure. The samples included
anhydrous and hydrated bioethanol and two biodiesel fuels from different
feedstocks, soy and animal fat. The ethanol samples were measured
from a maximum temperature of 60 to 5 °C (speed of sound) and
to −10 °C (density and viscosity), respectively. The biodiesel
samples were characterized from 100 °C (density and viscosity)
and from 70 °C (speed of sound) to 10 °C (animal fat-based)
and 5 °C (soy-based). Densities were measured with two vibrating-tube
instruments of different accuracy. The speeds of sound were measured
with a propagation-time method in an acoustic cell that was combined
with one of the densimeters. Viscosities were measured with an open
gravitational capillary viscometer and with a rotating concentric
cylinder viscometer, according to Stabinger. The measurement results
are reported with detailed uncertainty analyses.
Nb 3 Sn superconducting wires made by the restacked-rod process (RRP ®) were found to have a dramatically improved resilience to axial tensile strain when alloyed with Ti as compared to Ta. Whereas Ta-alloyed Nb 3 Sn in RRP wires showed permanent damage to its current-carrying capacity (I c) when tensioned beyond an intrinsic strain as small as 0.04%, Ti-doped Nb 3 Sn in RRP strands exhibits a remarkable reversibility up to a tensile strain of about 0.25%, conceivably making Ti-doped RRP wires more suitable for the high field magnets used in particle accelerators and nuclear magnetic resonance applications where mechanical forces are intense. A strain cycling experiment at room temperature caused a significant drop of I c in Ta-alloyed wires, but induced an increase of I c in the case of Ti-doped strands. Whereas either Ti or Ta doping yield a similar enhancement of the upper critical field of Nb 3 Sn, the much improved mechanical behavior of Ti-alloyed wires possibly makes Ti a better choice over Ta, at least for the RRP wire processing technique. * Contribution of NIST, an agency of the US government, not subjected to copyright.
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