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Abstract
Reading and co-workers introduced a new technique a few years ago called Modulated Differential Scanning Calorimetry or MDSC. Here the first part of a theoretical analysis for this technique is given. A simple mathematical model for modulated differential scanning calorimetry in the form of an ordinary differential equation is derived. The model is analysed to find the effect of a kinetic event in the form of a chemical reaction. Some possible sources of error are discussed. A more sophisticated version of the model allowing for spatial variation in a calorimeter is developed and it is seen how it can be reduced to the earlier model. Some preliminary work on a phase change is also presented.
Abstract
This article is a review of some of the results we have obtained by studying various kinds of emulsions using techniques from the simplest one, a home-made differential thermal analysis to elaborated ones such as differential scanning calorimetry commercial devices. These techniques were used not only to determine energetic values but also essentially to show and quantify physical chemical phenomena such as undercooling, freezing, melting, mass transfer between droplets and solid formation involved in hydrate formation.
Photosynthetic energy conversion in the diatom Phaeodactylum tricornutum
Measuring by calorimetry, oxygen evolution and pulse-amplitude modulated fluorescence
measure the heat related to photosynthetic processes by calorimetry is provided in [ 11 ]. To our knowledge, only two studies dealt with the influence of NPQ on the photosynthetic energy balance measured by calorimetry [ 12 , 13 ]. There exist two methods
Abstract
Semi-batch reactors are widely spread in the fine chemicals and specialties industry. The reason is that, compared to the pure batch operation, the feed of at least one of the reactants provides an additional way of controlling the reaction course, which represents a safety factor and increases the constancy of the product quality. Process temperature and feed rate can be optimized to satisfy safety constraints, i.e. cooling capacity and allowable accumulation. An economically better way of operating a semi-batch reactor is to adapt the feed rate to the allowed accumulation of reactants. An experimental method based on calorimetry will be presented and illustrated by an example.
Modulated differential scanning calorimetry in the glass transition region
II. The mathematical treatment of the kinetics of the glass transition
Temperature-modulated differential scanning calorimetry (TMDSC) is based on heat flow and represents a linear system for the measurement of heat capacity. As long as the measurements are carried out close to steady state and only a negligible temperature gradient exists within the sample, quantitative data can be gathered as a function of modulation frequency. Applied to the glass transition, such measurements permit the determination the kinetic parameters of the material. Based on either the hole theory of liquids or irreversible thermodynamics, the necessary equations are derived to describe the apparent heat capacity as a function of frequency.
Abstract
The physico-chemical properties of poly(ethylene) glycol solutions in water have been studied with use of pressure perturbation calorimetry. The three PEGs of average molecular mass (M r) 6000, 10000, 20000 were used. The concentration of polymers was changed in the range 0–30% mass per volume (w/v%). On the basic of VP-DSC measurements with use of PPC technique the dependencies of thermal expansion coefficient (α) and excess specific heat capacity (C p,exc) on temperature were determinated for PEG–water solutions.
Abstract
The melting and crystallization of a sharply melting standard has been explored for the calibration of temperature-modulated differential scanning calorimetry, TMDSC. Modulated temperature and heat flow have been followed during melting and crystallization of indium. It is observed that indium does not supercool as long as crystal nuclei remain in the sample when analyzing quasi-isothermally with a small modulation amplitude. For standard differential scanning calorimetry, DSC, the melting and crystallization temperatures of indium are sufficiently different not to permit its use for calibration on cooling, unless special analysis modes are applied. For TMDSC with an underlying heating rate of 0.2 K min−1 and a modulation amplitude of 0.5–1.5 K at periods of 30–90 s, the extrapolated onsets of melting and freezing were within 0.1 K of the known melting temperature of indium. Further work is needed to separate the effects originating from loss of steady state between sample and sensor on the one hand and from supercooling on the other.
solution by nitrogen and thiol functionality grafted to silica gel measured by calorimetry . Thermochim Acta 450 : 12 – 15 10.1016/j.tca.2006.06.012 . 17. Lima , IS , Airoldi , C 2004 A
determined on a Perkin-Elmer 1700 FTIR spectrometer using KBr pallets. Differential scanning calorimetry (DSC) thermograms were obtained with the use of a DSC Netzsch 204 calorimeter (Netzsch, Günzbung, Germany). All DSC measurements were carried out in
. Gawlicki , M , Nocuń-Wczelik , W , Bąk , Ł 2010 Calorimetry in the studies of cement hydration. Setting and hardening of Portland cement–calcium aluminate cement mixtures . J Therm Anal Calorim 100 2 571 – 576 10.1007/s10973
