Fast Differential Scanning Calorimetry Research Articles

A new experimental setup for combined fast differential scanning calorimetry and X-ray photon correlation spectroscopy.

Synchrotron-radiation-based techniques are a powerful tool for the investigation of materials. In particular, the availability of highly brilliant sources has opened the possibility to develop techniques sensitive to dynamics at the atomic scale such as X-ray photon correlation spectroscopy (XPCS). XPCS is particularly relevant in the study of glasses, which have been often investigated at the macroscopic scale by, for example, differential scanning calorimetry. Here, we show how to adapt a Flash calorimeter to combine XPCS and calorimetric scans. This setup paves the way to novel experiments requiring dynamical and thermodynamic information, ranging from the study of the crystallization kinetics to the study of the glass transition in systems that can be vitrified thanks to the high cooling rates reachable with an ultrafast calorimeter.

Continuous cooling and isothermal solidification analysis of AlSi10Mg using differential fast scanning calorimetry

This study investigates the solidification process of individual micro-sized AlSi10Mg particles using continuous cooling and isothermal differential fast scanning calorimetry (DFSC) methods at a range of cooling rates (from 500 K/s to 50,000 K/s) and temperatures (from 562 °C to 502 °C). The solidification microstructure consists of fine α-Al dendrites and (α-Al + Si) eutectics. Both dendrite arm spacing and eutectic spacing decrease with increasing cooling rate, as well as decreasing solidification temperature. The continuous cooling treatment exhibits finer microstructures compared to those observed in the isothermal treatment in the similar solidification temperature range. Overall, this study highlights the effectiveness of the DFSC methods, along with microstructure characterization, in analyzing the solidification process of individual powder particles over a wide range of cooling rates and temperatures.

Top-view analysis of ultrafast differential scanning calorimetry data

Ultrafast differential scanning calorimetry is the third-generation technique of differential thermal-analysis. It can fast heat up to 60000 K/s or fast cool down to 40000 K/s, so its temperature-changing rate spans five orders of magnitude, and permit repeating experiments on compounds or materials with a melting point lower than 1000 ℃. The unique rate of temperature change allows it to record structural changes of sample in milliseconds, producing a significant number of data. A “top-view” graph is suggested in this study for data analysis. It basically projects the heat flow onto a plane of variables such as temperature, rate or time and uses color contrast to describe the intensity change of heat flow. The issues with “side-view” graphs, where it is a challenge to discern rate or time from several curves, are successfully resolved by this novel technique. It can also realize a comparison of the kinetics among several co-existing physical events. Using an Au-based metallic glass as an example material, this work collects the data from four “side-view” graphs in literature, replots the data on “top-view” graphs, and compares pros and cons. Any substance or material to be examined by utilizing fast differential scanning calorimetry can be examined through using the “top-view” approach. It is useful not only for data analysis but also for constructing processing maps for novel materials, finding new structural transitions, and examining the kinetic behaviors of physical phenomena. All the data presented in this paper are openly available at https://doi.org/ 10.57760/sciencedb.j00213.00012.

Glass transition temperatures and crystallization kinetics of a synthetic, anhydrous, amorphous calcium-magnesium carbonate.

We report the first calorimetric observations of glass transition temperatures and crystallization rates of anhydrous, amorphous calcium-magnesium carbonate using fast scanning differential scanning calorimetry. Hydrous amorphous Ca0.95Mg0.05CO3 · 0.5H2O (ACMC) solid was precipitated from a MgCl2-NaHCO3 buffered solution, separated from the supernatant, and freeze-dried. An aliquot of the freeze-dried samples was additionally dried at 250°C for up to 6 h in a furnace and in a high-purity N2 atmosphere to produce anhydrous ACMC. The glass transition temperature of the anhydrous Ca0.95Mg0.05CO3 was determined by applying different heating rates (1000-6000 K s-1) and correcting for thermal lag to be 376°C and the relaxational heat capacity was determined to be Cp = 0.16 J/(g K). Additionally, the heating rate dependence of the temperature that is associated with the corrected crystallization peaks is used to determine the activation energy of crystallization to be 275 kJ mol-1. A high-resolution transmission electron microscopy study on the hydrous and anhydrous samples provided further constraints on their compositional and structural states. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 1)'.

Rapid solidification of Al-Si alloys using differential fast scanning calorimetry

Tailoring microstructures and properties in metal alloys, e.g., in additive manufacturing, requires a deep understanding of its rapid solidification behavior. However, in many rapid solidification processes, in-situ investigations are difficult due to the lack of accurate measurements of cooling rates and nucleation undercooling. This study used differential fast scanning calorimetry (DFSC) to investigate the rapid solidification of micro-sized Al-Si alloy particles, with compositions including Al-Si1, Al-Si10, Al-Si12, and Al-Si20 (mass%), by employing controllable cooling rates ranging from 100 K/s to 95,000 K/s. Based on the analysis of nucleation undercooling and microstructure, the solidification sequence and different mechanisms of the α-Al phase formation were proposed. A modified model using classical nucleation theory (CNT), including surface heterogeneous nucleation, and interface/bulk heterogeneous nucleation for α-Al is employed. This study presents a practical approach to examining the rapid solidification behavior of metal particles, allowing the distinction between surface and interface/bulk nucleation.

The relation between the glass forming ability and nucleation kinetics of metastable quasicrystals in Mg–Zn–Yb liquid

Bulk metallic glass (BMG), metastable quasicrystals (QCs) and two types of approximant phases concurrently form from the melt during cooling at different rates in a Mg–Zn–Yb model alloy. Such an enriched phase competition between various metastable and stable crystals has also been found during the heating of Mg–Zn–Yb metallic glass between the glass transition and liquidus temperatures. Metastable QC acts as a transient phase that nucleates first from the melt and subsequently transforms into an equilibrium approximant phase. During heating, a metastable approximant phase transforms into the Mg-QC phase mixture which then transforms into the Mg and equilibrium approximant eutectic microstructure. Nucleation kinetics of QCs is critical to analyze for further understanding the relation between QC formation and glass forming ability of the alloy. For this purpose, a metastable phase diagram for QCs has been determined using a novel experimental strategy via fast differential scanning calorimetry (FDSC). Along compositional line binding Mg to Zn17Yb3, one stable eutectic point, i.e. Mg68.6Zn26.7Yb4.7 at 390°C, and one metastable eutectic composition, i.e. Mg64.6Zn30.1Yb5.3 at 350°C, were determined during interrupted heating experiments. We have demonstrated that the glass forming ability of Mg–Zn–Yb alloys strongly depends on the metastable phase diagram of QCs and their nucleation kinetics. Nucleation of metastable QCs limits the metallic glass formation, therefore the bulk metallic glass forming compositional region was found to be below metastable hypoeutectic compositions.

Fast differential scanning calorimetry to mimic additive manufacturing processing: specific heat capacity analysis of aluminium alloys

Eutectic AlSi12, commonly used in casting and in additive manufacturing, is investigated with Fast Differential Scanning Calorimetry to determine the impact of different cooling rates from the liquid state upon the apparent specific heat capacity on subsequent heating. A heat flow correction strategy is developed and refined for the reliable and precise measurement of sample heat flow using chip sensors and assessed by the evaluation of results on pure (99.999%) aluminium. That strategy is then applied to the study of the AlSi12 eutectic alloy, and rate-dependent perturbations in the measured apparent specific heat capacity are discussed in terms of Si supersaturation and precipitation. Several cooling rates were implemented from − 100 to − 30,000 K s−1, and subsequent heating ranged from + 1000 to + 30,000 K s−1. After rapid cooling, a drop in AlSi12 apparent specific heat capacity is found on heating above ~ 400 °C; even at rates of + 10,000 K s−1, a result which has high relevance in metal additive manufacturing where similarly fast temperature cycles are involved. The Literature data, temperature modulated DSC and CALPHAD simulations on the heat capacity of AlSi12 are used to provide comparative context to the results from Fast Differential Scanning Calorimetry.

Fast differential scanning calorimetry: new solutions in data treatment and applications to molecular glass-formers

Fast scanning calorimetry is an experimental technique very appreciated for its capability of suppressing reorganization processes, thanks to its wide interval of scanning rates, several orders higher than that of conventional calorimeters; nevertheless, drawbacks still exist. In this paper we propose a novel way to estimate the dynamical thermal lag by using the temperatures of maximum slope of the heat flow through the glass transition when we are not in the optimal conditions to apply the existing methods based on a reference material added on both cells of the chip or on the fictive temperature. Moreover, a novel interpretation of the heat flow losses due to the sample depending on the scanning rate sign is provided, in order to rescale the measured specific heat capacity to that from conventional calorimetry. Finally, the use of the glass to liquid transition measured on heating is shown as a new manner to reveal static thermal gradients.

Correlation between Differential Fast Scanning Calorimetry and Additive Manufacturing Results of Aluminium Alloys.

High-strength aluminium alloy powders modified with different nanoparticles by ball milling (7075/TiC, 2024/CaB6, 6061/YSZ) have been investigated in-situ during rapid solidification by differential fast scanning calorimetry (DFSC). Solidification undercooling has been evaluated and was found to decrease with an increasing number of nanoparticles, as the particles act as nuclei for solidification. Lower solidification undercooling of individual powder particles correlates with less hot cracking and smaller grains in the material produced by powder bed fusion of metals by a laser beam (PBF-LB/M). Quantitatively, solidification undercooling less than about 10–15 K correlates with almost crack-free PBF-LB/M components and grain sizes less than about 3 µm. This correlation shall be used for future purposeful powder material design on small quantities before performing extensive PBF-LB/M studies.

Comments on isothermal crystallization kinetics of polymers: Polypropylene at high supercooling

A robust procedure for isothermal kinetic evaluation of Differential Scanning Calorimetry (DSC) measurements of polymers using the Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation is proposed. This procedure takes into account the experimental uncertainties for short (initial deflection) and long (secondary crystallization) measurement times. This procedure is applied to the isothermal crystallization of various commercially available isotactic polypropylenes (iPP) in the temperature range between 10°C and 120°C. Further measurements are performed on unfilled iPP and iPP highly filled with calcium carbonate. The measurements were performed using Fast Differential Scanning Calorimetry (FDSC).Evaluation of the crystallization kinetics indicates homogeneous nucleation in the temperature range of mesophase formation below 60°C. With decreasing temperature, the crystallization is more affected by diffusion control and/or termination of growth at an early crystallization stageDuring α-phase formation (above 60°C), crystallization is heterogeneously nucleated. Depending on the sample, growth occurs at a constant rate or is diffusion controlled.Polypropylene highly filled with calcium carbonate shows an additional α-phase crystallization process. The KJMA evaluation indicates that this process is homogeneously nucleated.

Kinetics of the Glass Transition of Silica-Filled Styrene-Butadiene Rubber: The Effect of Resins.

Resins are important for enhancing both the processability and performance of rubber. Their efficient utilization requires knowledge about their influence on the dynamic glass transition and their miscibility behavior in the specific rubber compound. The resins investigated, poly-(α-methylstyrene) (AMS) and indene-coumarone (IC), differ in molecular rigidity but have a similar aromaticity degree and glass transition temperature. Transmission electron microscopy (TEM) investigations show an accumulation of IC around the silanized silica in styrene–butadiene rubber (SBR) at high contents, while AMS does not show this effect. This higher affinity between IC and the silica surface leads to an increased compactness of the filler network, as determined by dynamic mechanical analysis (DMA). The influence of the resin content on the glass transition of the rubber compounds is evaluated in the sense of the Gordon–Taylor equation and suggests a rigid amorphous fraction for the accumulated IC. Broadband dielectric spectroscopy (BDS) and fast differential scanning calorimetry (FDSC) are applied for the characterization of the dielectric and thermal relaxations as well as for the corresponding vitrification kinetics. The cooling rate dependence of the vitrification process is combined with the thermal and dielectric relaxation time by one single Vogel–Fulcher–Tammann–Hesse equation, showing an increased fragility of the rubber containing AMS.

Differential scanning calorimetry for authentication of edible fats and oils - What can we learn from the past to face the current challenges?

Fats and oils authentication has become an important issue recently, due to the growing interest in consumption of cold-pressed oils. Therefore, it is becoming more and more difficult to maintain official control over the growing assortment of new cold-pressed oils. Authenticity of plant oils is also an important issue for religious or cultural reasons.This review article focuses on the application of differential scanning calorimetry (DSC) in the field of assessing authenticity of various fats and oils (e.g. olive oil, palm oil, confectionery fats, butter). Extra virgin olive oil (EVOO) is the most comprehensively tested oil by means of the DSC technique in terms of the authenticity of origin as well as the adulteration with foreign oils. In most of the studies on DSC applicability for authentication, crystallization and melting curves were analyzed by the conventional DSC, although other modified DSC methods were also applied, such as isothermal freezing, modulated temperature DSC (MT-DSC) and fast DSC. However, the most promising are the melting profiles, which, due to the complexity of transitions, need advanced chemometric tools as well as tools for peaks deconvolution. The future prospect of using DSC in the authenticity assessment lies also in the use of DSC techniques along with other complementary chromatographic or spectroscopic techniques.

Determining and modelling a complete time-temperature-transformation diagram for a Pt-based metallic glass former through combination of conventional and fast scanning calorimetry

State of the art fast differential scanning calorimetry (FDSC) is used to complement conventional differential scanning calorimetry (DSC) studies about the isothermal time-temperature-transformation (TTT) diagram of the bulk metallic glass forming liquid Pt42.5Cu27Ni9.5P21 to allow a comprehensive study of the crystallization kinetics of this system over a broad temperature range. FDSC and DSC data align well in the low-temperature region of the crystallization nose but show distinct discrepancies in the high-temperature region as the FDSC studies reveal faster crystallization times. The results are mathematically described and discussed based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. Thereby, either homogeneous or heterogeneous nucleation is assumed, depending on the respective experimental conditions in FDSC and DSC studies. With this approach, the complete TTT diagram can be modelled as superposition of two sequential JMAK fits.

A tale of two polyamides: Comparing the crystallization kinetics of a hot-melt adhesive and a PA 6/66 copolymer

In this work, the isothermal and non-isothermal crystallization kinetics of two polyamides, a polyamide-based hot melt adhesive with the trade name of Technomelt PA 6910 and a copolymer of PA 6 and PA 66, are studied using Fast Scanning Calorimetry (FSC) and Differential Scanning Calorimetry (DSC). While both of these materials exhibit good performance as feedstocks for material extrusion additive manufacturing, their crystallization behavior and kinetics differ substantially. Technomelt PA 6910 crystallizes much slower than the PA 6/66 due to the lower density of hydrogen bonding within Technomelt PA 6910’s structure. The low glass transition temperature encourages room temperature crystallization of Technomelt PA 6910. PA 6/66 is a random copolymer whose faster crystallization is attributed to a high density of hydrogen bonding accompanied by a sheet-like structure of the hydrogen bonding within the melt, which favors high-temperature crystallization. The kinetic results from this study enable coupling the crystallization kinetics of these materials with thermal models for processing techniques including material extrusion additive manufacturing.

Kinetics of structure formation in the vicinity of the glass transition

The structural stability of a gold-based bulk metallic glass (Au49Ag5.5Pd2.3Cu26.9Si16.3) was investigated by fast differential scanning calorimetry (FDSC). A chemically homogeneous glass (CHG) containing no quenched-in nuclei was produced using sufficiently fast cooling from the melt. To characterize the stability of this glass, the structural variations during annealing in the glassy state were investigated and a sequence of five different events observed. These are structural relaxation, an incubation period, nucleation, crystallization, and finally reorganization. The kinetics of these processes and the stability of the crystalline structures are discussed.

Fast Differential Scanning Calorimetry: New Solutions in Data Treatment and Applications to Molecular Glass-Formers

Fast Differential Scanning Calorimetry: New Solutions in Data Treatment and Applications to Molecular Glass-Formers

Dependence of mechanical properties and microstructure on solidification onset temperature for Al2024–CaB6 alloys processed using laser powder bed fusion

The addition of a sufficient amount of the potent heterogeneous nucleating agent CaB6 enables the fabrication of crack-free specimens from the solidification-crack susceptible high-strength 2024 (Al–Cu–Mg) aluminum (Al) alloy using laser powder bed fusion (LPBF). The present work investigates the effects of varying addition contents of CaB6 nanoparticles (0.0–2.0 wt%) on the alloys' solidification behavior as well as the specimens’ solidification-crack volume, microstructure, and mechanical properties.The findings of X-ray microscopy (XRM) analyses on LPBF specimens and in-situ differential fast scanning calorimetry (DFSC) analyses on single powder particles at LPBF-like high heating and cooling rates reveal decreasing crack volumes with decreasing solidification supercooling. A CaB6 content of equal to or greater than 0.5 wt% effectively suppresses solidification cracking. 1.0 wt% is defined as the optimum CaB6 content in terms of mechanical properties. With this content an average grain size of 0.77 μm, an ultimate tensile strength (UTS) of 478 ± 4 MPa and an elongation (A) of 13.2 ± 0.1% are achieved. When the CaB6 content is further increased, the alloy's average grain size asymptotically approaches a minimum size of ∼0.7 μm for the given process parameters. This value corresponds to the nucleation-free zone (NFZ), within which the CaB6 nanoparticles present are not activated as nucleating agents, resulting in deposition along the grain boundaries.

Additive manufacturing of a precious bulk metallic glass

For the first time, a high-density amorphous and crack-free bulk metallic glass (BMG) based on a precious metal (PdCuNiP) was produced via additive manufacturing (AM). Laser powder-bed fusion (LPBF) was used for the fabrication of the samples, and led to a density of 99.6%. Excellent mechanical properties such as high hardness and compressive strength were achieved, overcoming the limitations usually found for precious metals in jewelry and watchmaking. Furthermore, without any post-processing, a mirror-like smooth and brilliant surface was directly obtained, which is highly beneficial for applications where surface finish or aesthetics matters. The effect of the main processing parameters, such as laser power and laser-scanning speed, on the shape of single tracks was investigated by laser confocal microscopy (LCM). Following the single-track experiments, highly amorphous LPBF samples were produced. The samples were characterized by optical microscopy (OM), scanning electron microscopy (SEM), conventional and synchrotron X-ray diffraction (XRD), micro-computed tomography (μ-CT), compression tests, and microhardness. The crystallization kinetics of the powder alloy was investigated via fast differential scanning calorimetry (FDSC). A small quantity of the powder (< 70 g) was used for the fabrication of samples, alleviating the cost of the process. Efficient production of precious metal parts with enhanced mechanical properties is demonstrated.

Nucleation Behavior of a Single Al-20Si Particle Rapidly Solidified in a Fast Scanning Calorimeter.

Understanding the rapid solidification behavior characteristics, nucleation undercooling, and nucleation mechanism is important for modifying the microstructures and properties of metal alloys. In order to investigate the rapid solidification behavior in-situ, accurate measurements of nucleation undercooling and cooling rate are required in most rapid solidification processes, e.g., in additive manufacturing (AM). In this study, differential fast scanning calorimetry (DFSC) was applied to investigate the nucleation kinetics in a single micro-sized Al-20Si (mass%) particle under a controlled cooling rate of 5000 K/s. The nucleation rates of primary Si and secondary α-Al phases were calculated by a statistical analysis of 300 identical melting/solidification experiments. Applying a model based on the classical nucleation theory (CNT) together with available thermodynamic data, two different heterogeneous nucleation mechanisms of primary Si and secondary α-Al were proposed, i.e., surface heterogeneous nucleation for primary Si and interface heterogenous nucleation for secondary α-Al. The present study introduces a practical method for a detailed investigation of rapid solidification behavior of metal particles to distinguish surface and interface nucleation.

Nucleation behaviour and microstructure of single Al-Si12 powder particles rapidly solidified in a fast scanning calorimeter

The understanding of rapid solidification behaviour, e.g. the undercooling versus growth velocity relationship, is crucial for tailoring microstructures and properties in metal alloys. In most rapid solidification processes, such as additive manufacturing (AM), in situ investigation of rapid solidification behaviour is missing because of the lack of accurate measurement of the cooling rate and nucleation undercooling. In the present study, rapid solidification of single micro-sized Al-Si12 (mass%) particles of various diameters has been investigated via differential fast scanning calorimetry employing controllable cooling rates from 100 to 90,000 K s−1 relevant for AM. Based on nucleation undercooling and on microstructure analysis of rapidly solidified single powder particles under controlled cooling rates, two different heterogeneous nucleation mechanisms of the primary α-Al phase are proposed. Surface heterogeneous nucleation dominates for particles with diameter smaller than 23 μm. For particles with diameter larger than 23 μm, the nucleation of the primary α-Al phase changes from surface to bulk heterogeneous nucleation with increasing cooling rate. The results indicate that at large undercoolings (> 95 K) and high cooling rates (> 10,000 K s−1), rapid solidification of single particle can yield a microstructure similar to that formed in AM. The present work not only proposes new insight into rapid solidification processes, but also provides a theoretical foundation for further understanding of microstructures and properties in additively manufactured materials.