Calorimeter

About: Calorimeter is a research topic. Over the lifetime, 5878 publications have been published within this topic receiving 77157 citations.

The heat capacity of pure silicon and germanium and properties of their vibrational frequency spectra

Abstract: Heat capacities of pure silicon and germanium have been measured between 2.5° and 300°K. The estimated accuracies of the measurements are ±0.5% for 10° 20°K. The results for silicon were anomalous in the region T <7°K; it is suggested that this behaviour resulted from adsorption and desorption of exchange gas in the calorimeter vessel. No anomalies were observed in the measurements on germanium; their accuracy at the lowest temperatures is estimated to be ±2%. The results for both substances are significantly different from previously published values. The temperature variation of ΘD of both silicon and germanium below about T= ΘD/3 is consistent with general harmonic theory, but at high temperatures ΘD decreases with increasing temperature. This appears to be a clearly marked anharmonic effect of a type that cannot be explained by change of volume alone. The results for T < ΘD/3 are therefore extrapolated to high temperatures to give a heat capacity consistent with h...

Thermodynamic Properties of 1-Butyl-3-methylimidazolium Hexafluorophosphate in the Condensed State

Abstract: Thermodynamic functions for 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) are reported in a range of temperatures from (5 to 550) K, based on new measurements by calorimetry. Heat capacities of the crystal, glass, and liquid phases for [C4mim][PF6] were measured with a pair of calorimeters. A vacuum-jacketed adiabatic calorimeter was used at temperatures between (5 and 310) K, and a heat bridge-scanning calorimeter was used from (300 to 550) K. With the adiabatic calorimeter, the fusion Tfus = 283.51 K, = 19.60 kJ·mol-1, and the glass transition Tg = 190.6 K were observed. The [C4mim][PF6] test sample was determined to have a mole fraction purity of 0.9956 by a fractional melting analysis. Densities of the liquid were measured in a range of temperatures from (298 to 353) K with a pycnometer equipped with a capillary neck. An unexpected endothermal transition, with a very small enthalpy change of 0.25 J·g-1 (0.071 kJ·mol-1), was observed in a range of temperatures from (394 to 412) K. He...

Calculations of the Heat Release Rate by Oxygen Consumption for Various Applications

Abstract: The calculation of heat release rate by oxygen consumption is based on the assumption that all materials release approximately the same amount of heat per unit mass of oxygen consumed. This technique is now being employed to determine the heat release rate of materials in various heat release rate calorimeters. Other uses include the heat release rate of assemblies in the fire endurance furnaces and the total heat release rate in room fire tests. These different applications lead to different experimental procedures which require different formulas. The experimental choices or constraints include open or closed systems, paramagnetic or high temperature oxygen analyzers, CO analyzers or CO traps, and the use of a gas burner whose heat release rate must be deducted from the total. Various assumptions about CO levels in the exhaust duct and vitiation and humidity in the incoming air are made. General formulas for the heat release rate by oxygen consumption are developed in this paper from which the formulas for specific applications can easily be derived.

Thin film microcalorimeter for heat capacity measurements from 1.5 to 800 K

Abstract: A new microcalorimeter for measuring heat capacity of thin films in the range 1.5–800 K is described. Semiconductor processing techniques are used to create a device with an amorphous silicon nitride membrane as the sample substrate, a Pt thin film resistor for temperatures greater than 40 K, and either a thin film amorphous Nb–Si or a novel boron‐doped polycrystalline silicon thermometer for lower temperatures. The addenda of the device, including substrate, is 4×10−6 J/K at room temperature and 2×10−9 J/K at 4.3 K, approximately two orders of magnitude less than any existing calorimeter used for measuring thin films. The device is capable of measuring the heat capacity of thin film samples as small as a few micrograms.

X‐ray detection using a superconducting transition‐edge sensor microcalorimeter with electrothermal feedback

Abstract: We have developed a new type of x‐ray detector based on a superconducting transition‐edge thermometer operated near 100 mK. A superconducting quantum interference device is used to measure the current through the thermometer, and negative electrothermal feedback is used to improve the energy resolution and shorten the thermal time constant. We have used a detector mounted on a scanning electron microscope to measure the energy of titanium Kα (4.5 keV) fluorescence x rays with a resolution better than 14 eV full width at half‐maximum. Using two other devices, we have measured an energy resolution for Joule heat pulses of 2.6 eV at 1 keV and 0.2 eV at 4 eV, the best reported for any calorimeter. An electrical noise equivalent power of 3×10−18 W/√Hz was also measured, suggesting the use of these detectors as infrared bolometers.