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Graphical abstract Highlights • Nanocalorimetry of specimens with different emissivities and thermal conductivities. • Comparison of measured heat capacity with detailed finite element analysis. • Quantification of the heat loss mechanisms during nanocalorimetry. • Strong impact of size effects on thermal radiation. Abstract We investigate the accuracy of a MEMS-based nanocalorimeter for determining specific heat in the temperature range from 300 K to 800 K. By comparing DC differential scanning measurements of materials of known specific heat capacities with detailed finite element studies, the dominant sources for heat losses and inaccuracies have been identified. The main source of error comes from radiative losses at elevated temperatures, but even near room temperature thermal gradients and thermal conductivity in the specimen lead to moderate discrepancies. Furthermore, studies on de-wetted Au films and Bi particles show that specimen emissivities differ strongly from literature values, presumably due to effects associated with the specimen dimensions being smaller than the thermal wavelength. By including the emissivity as a fitting parameter in the simulations, specimen heat capacities can be obtained to an accuracy of better than 7% over the entire temperature range. [ABSTRACT FROM AUTHOR]

Flash differential scanning calorimetry has been used to determine the glass transition response of the rapidly crystallizing energetic material, TNT. After heating at 600 K/s, it was found that for cooling rates from 1000 K/s to 10 K/s the glass transition changes from 247.5 K to 239.3 K. The dynamic fragility index was determined to be m = 62 ± 6 and the activation energy determined from the range of cooling rates in which vitrification occurred was found to be 290 ± 16 kJ/mol. Crystallization was found to occur during cooling at rates below 0.3 K/s, whereas cold crystallization was found on subsequent heating after cooling between 10 K/s and 30 K/s. At cooling rates of 100 K/s and above, and for the same heating rate of 600 K/s investigated, the glass transition event was observed, but cold crystallization during heating did not occur. Hence, the crystallization behavior of the fully amorphous TNT upon heating depends on the cooling rate and vitrification path. [ABSTRACT FROM AUTHOR]

Numerical simulation of DSC traces is used to study the validity and limitations of the Kissinger method for determining the temperature dependence of the crystal-growth rate on continuous heating of glasses from the glass transition to the melting temperature. A particular interest is to use the wide range of heating rates accessible with ultra-fast DSC to study systems such as the chalcogenide Ge 2 Sb 2 Te 5 for which fast crystallization is of practical interest in phase-change memory. Kissinger plots are found to show three regimes: (i) at low heating rates the plot is straight, (ii) at medium heating rates the plot is curved as expected from the liquid fragility, and (iii) at the highest heating rates the crystallization rate is thermodynamically limited, and the plot has curvature of the opposite sign. The relative importance of these regimes is identified for different glass-forming systems, considered in terms of the liquid fragility and the reduced glass-transition temperature. The extraction of quantitative information on fundamental crystallization kinetics from Kissinger plots is discussed. [ABSTRACT FROM AUTHOR]

The adaptation of segmented-flow technology to flow-through calorimetry was demonstrated by different kinds of newly designed chip calorimeters useful for liquids and suspensions as well as for solid samples. In segmented-flow technology, sample material is suspended in aqueous segments of nano- or microliter volume and transported by a water-immiscible carrier liquid. The analysis of the signal dynamics given by segmented samples in flow led to optimal settings of flow rate and sample volume for maximal throughput. For 12 μL sample segments, a cycle time of 4 min could be achieved. The protection of the measuring chamber of the calorimeters against biofouling caused by the water-immiscible carrier liquid was verified for segmented bacterial samples. The unique possibility to measure solid and aggregated samples in flow-through was demonstrated by the investigation of human hair follicles and fibroblast spheroids. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sample deposition by electrospray has been demonstrated for chip-based nanocalorimeter measurements. [•] Greatly simplifies sample deposition for small scale thermal analysis and expands applications for nanocalorimetry. [•] Samples include nanoparticles, nanofibers, chalcogenide Ge2Sb2Te5 (GST), ammonium nitrate and the lipid DPPC. [ABSTRACT FROM AUTHOR]

Abstract: In conventional bioreactors, the assessment of metabolic heat via heat balancing is difficult. The reason is the influence of inherent variables such as power input due to stirring, environmental heat loss and evaporation. Thus, the aim of this study is to present a newly designed chip calorimeter which can be linked to any kind of bioreactor. This chip calorimeter with a new integrated real-time sample dilution was developed and tested during batch fermentation of the bacteria Escherichia coli VH33 and the yeast Arxula adeninivorans CBS8244. The presented device is operable up to an upper limit of 4WL−1 for the volumetric metabolic heat production rate of these biological systems. [Copyright &y& Elsevier]

Abstract: Rules for the design of silicon chip based devices for liquid phase calorimetry are discussed. In contrast to the study of fast reactions the investigation of slow processes like the metabolic heat production requires sample volumes of at least a few micro-liters if a signal resolution in the mWl−1 range is necessary. On the other hand, increasing sensitivity gradients inside the reaction chamber and external temperature perturbations restrict its enlargement. Therefore, a careful optimization of the device with respect to the sample volume is necessary if one likes to use the advantages of chip calorimeters. The presented study was performed by use of a new designed flow-through chip calorimeter. [Copyright &y& Elsevier]

Abstract: Based on a new thermopile heat power sensor, which was developed in MEMS technology, a miniaturized flow-through calorimeter was constructed. The heat power sensor consists of a silicon chip with a thin film BiSb/Sb thermopile and a PMMA reaction chamber. To ensure high signal resolution the heat power sensor is mounted inside a high-precision thermostat, which has a temperature stability of less than 100μK. The heat power sensitivity of the calorimeter is 4–7VW−1 depending on the thermal conductivity of the liquid, the height of the chosen reaction chamber and the volume flow rate. A limit of detection of less than 50nW can be obtained for volume flows lower than 5μlmin−1. An important advantage is the low sample consumption of the calorimeter. For special applications the sample need for one measurement pulse does not exceed 20μl. [Copyright &y& Elsevier]