Isothermal microcalorimetry (IMC) is a laboratory method for real-time monitoring and dynamic analysis of chemical, physical and biological processes. Over a period of hours or days, IMC determines the onset, rate, extent and energetics of such processes for specimens in small ampoules (e.g. 3–20 ml) at a constant set temperature (c. 15 °C–150 °C).
IMC accomplishes this dynamic analysis by measuring and recording vs. elapsed time the net rate of heat flow (μJ/s = μW) to or from the specimen ampoule, and the cumulative amount of heat (J) consumed or produced.
IMC is a powerful and versatile analytical tool for four closely related reasons:
All chemical and physical processes are either exothermic or endothermic—produce or consume heat.
The rate of heat flow is proportional to the rate of the process taking place.
IMC is sensitive enough to detect and follow either slow processes (reactions proceeding at a few % per year) in a few grams of material, or processes which generate minuscule amounts of heat (e.g. metabolism of a few thousand living cells).
IMC instruments generally have a huge dynamic range—heat flows as low as ca. 1 μW and as high as ca. 50,000 μW can be measured by the same instrument.
The IMC method of studying rates of processes is thus broadly applicable, provides real-time continuous data, and is sensitive. The measurement is simple to make, takes place unattended and is non-interfering (e.g. no fluorescent or radioactive markers are needed).
However, there are two main caveats that must be heeded in use of IMC:
Missed data: If externally prepared specimen ampoules are used, it takes ca. 40 minutes to slowly introduce an ampoule into the instrument without significant disturbance of the set temperature in the measurement module. Thus any processes taking place during this time are not monitored.
Extraneous data: IMC records the aggregate net heat flow produced or consumed by all processes taking place within an ampoule.
Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.
vignette|Un calorimètre différentiel à balayage. La calorimétrie différentielle à balayage (en anglais, Differential Scanning Calorimetry ou DSC) est une technique d'analyse thermique. Elle mesure les différences des échanges de chaleur entre un échantillon à analyser et une référence (par exemple l'alumine ou encore l'air). Elle permet de déterminer les transitions de phase : la température de transition vitreuse (T) des matériaux amorphes : polymères, verres (Inorganiques, organiques ou métalliques) et des liquides ioniques ; les températures de fusion et de cristallisation ; les enthalpies de réaction, pour connaître les taux de réticulation de certains polymères.
Couvre la calorimétrie isotherme, une méthode pour mesurer le taux de production de chaleur dans des matériaux comme le ciment, en discutant de son importance et de ses applications pratiques.
Explore les identités thermodynamiques, les changements d'entropie et l'efficacité des machines thermiques, y compris les cycles Carnot et Otto, les pompes à chaleur et les méthodes de chauffage.
Phase transitions in AuCu alloy are investigated using in situ temperature XRD and mechanical spectroscopy. The measurements are carried out from room temperature up to 973 K starting from the ordered phase AuCuI. Using a temperature ramp rate of 1 K/min, ...
ELSEVIER SCIENCE SA2019
, , ,
In this study, a protocol for synthesising beta-C2S using K2SO4 as a dopant has been reported. Quantitative X-Ray diffraction was used to characterise synthesised samples. It was observed that it is possible to synthesise beta-C2S with high purity (>96 wt% ...
PERGAMON-ELSEVIER SCIENCE LTD2023
, , ,
Although supplementary cementitious materials (SCMs) are now commonly accepted and widely used, consensus has not been reached for methods to test their chemical reactivity. A multitude of test methods exist but often fall short on one or more of the key f ...