Quantitative Thermal Analysis Research Articles

Compositionally gradient PVD CrAlSiN films: structural examination and oxidation resistance

The thermal stability and the resistance against oxidation of quaternary compositionally gradient CrAlSiN coatings deposited on steel substrate are investigated by examining their structural, morphological and chemical features before and after oxidation tests, as well as by quantitative thermal analysis. The as-deposited samples exhibit a columnar structure, with each column consisting of nanocrystals as fine as 20 nm. The as-deposited coating is mainly composed of CrxAl1−xN solid solution nanocrystals, which are embedded in an amorphous SiNx matrix. When exposed to high-temperature dry air environment the coated samples exhibit remarkable stability as they remained intact up to 800°C. Over 800°C, elements from the substrate outdiffused and modified the chemical content of the film, but still remain oxidation-resistant up to 900°C.

Advanced analysis of poly(3-hydroxybutyrate) phases based on vibrational heat capacity

The new quantitative thermal analysis of semicrystalline poly(3-hydroxybutyrate) (P3HB) phases based on vibrational, solid and liquid heat capacities has been presented. The apparent heat capacity of P3HB was measured using the standard differential scanning calorimetry, and temperature-modulated DSC and quantitative analysis allow for the study of any glass transition, melting/crystallization process and heat capacity of P3HB in the entire range of investigated temperature (183–465 K). The formation and description of phases during thermal processes of P3HB by advanced thermal analysis were examined. The mobile amorphous fraction, degree of crystallinity and rigid amorphous fraction were determined depending on the thermal history of semicrystalline P3HB included after isothermal and non-isothermal crystallization. The experimental, apparent heat capacity of P3HB in the non-equilibrium state was analyzed in reference to the solid and liquid heat capacities and all thermodynamic functions (enthalpy, entropy and Gibbs function) in the equilibrium state.

Application of infrared thermography for temperature distributions in fluid-saturated porous media

Infrared thermography has increasingly gained importance because of environmental and technological advancements of this method and is applied in a variety of disciplines related to non-isothermal flow. However, it has not been used so far for quantitative thermal analysis in saturated porous media. This article suggests infrared thermographic approach to obtain the entire surface temperature distribution(s) in water-saturated porous media. For this purpose, infrared thermal analysis is applied with in situ calibration for a better understanding of the heat transfer processes in porous media. Calibration is achieved with a combination of invasive sensors which are inserted into the medium and non-invasive thermal sensors in which sensors are not inserted to measure temperatures but it works through the detection of infrared radiation emitted from the surface. Thermocouples of relatively thin diameter are used to minimize the disturbance for flow. Thermocouples give the temperature values at specified positions inside the porous medium, and these values are compared with the values suggested by the infrared thermographic device at the same positions, in the calibration exercise. The calibration process was repeated for different temperatures and flow rates to get the temperature distributions of the whole material inside the system. This technique enables us to measure accurate two-dimensional temperature distributions, which is not possible by using thermocouples only. Continuous point heat sources at different flow rates and temperatures are studied experimentally. Additionally, it offers numerical simulations of the experiments utilizing a finite element-based model. A two-dimensional density and viscosity-dependent flow and transport model accounting for thermal dispersion is utilized to simulate the experimental results. Possible small heat losses from the surface are incorporated in the model according to the properties and thickness of the Plexiglass material used for the construction of the experiment tank. The numerical results agree well with the experimental observations.

Quantitative thermal analysis of α-C2SH as a precursor for low-energy cements

In this work, a combined method of using DSC, TG and XRD analysis in order to determine an amount of decomposed α-C2SH in its tribochemically activated mixture with quartz is presented. Furthermore, the influence of the grinding on the phase transition and heat flow during the hydration of this mixture is determined. The results showed that the product in which α-C2SH prevails is obtained after 12 h of the hydrothermal synthesis at 200 °C in stirred (50 rpm) suspensions. The purification of mentioned product using distilled water (water/solid = 500) for 5 min is enough to eliminate remaining Ca(OH)2. The stability of α-C2SH during the purification was confirmed using DSC and XRD analysis. A strong correlation between heat absorption values of the α-C2SH decomposition at 470 °C and its quantity in the mixture with quartz was noticed (R 2 = 0.9929). According to the plotted calibration curve, the amount of decomposed α-C2SH during the tribochemical activation was determined: within the first minute, it reaches 32.28 % and gradually increases to 48.73 % after 20 min. During the decomposition of α-C2SH, the semi-crystalline calcium silicate hydrates form, which recrystallize to wollastonite at 850 °C; meanwhile, the remaining α-C2SH transforms to larnite. The complex tribochemical and thermal activation of α-C2SH–quartz mixture leads to a vivid increment of its hydraulic activity: the heat flow of the main hydration reaction and the total heat values reached 3.1 mW g−1 and 104.48 J g−1, respectively.

Vibrational heat capacity of Poly(N-isopropylacrylamide)

The heat capacity of poly(N-isopropylacrylamide) (PNIPA) has been measured from (1.8–460) K using a quantum design PPMS (Physical Property Measurement System) and differential scanning calorimeters. The low-temperature experimental heat capacity below the glass transition temperature 415 K (141.85 °C) was linked to the vibrational molecular motions of PNIPA to establish the baseline of the solid, vibrational heat capacity. The vibrational heat capacity of PNIPA was computed based on group and skeletal vibrations. The group vibrational heat capacities were calculated based on the chemical structure and molecular vibrational motions derived from infrared and Raman spectroscopy. The skeletal heat capacity was fitted to a general Tarasov equation using sixteen skeletal modes to obtain three Debye characteristic temperatures Θ1 = 650 K and Θ2 = Θ3 = 68.5 K. The fit agreed well with the experimental data (±0.2%) from T = (1.8–250) K, and the vibrational heat capacity, which was extended to higher temperatures, served as a baseline of the solid heat capacity for quantitative thermal analysis of the experimental, apparent heat capacity data of PNIPA. The liquid heat capacity of fully amorphous PNIPA was approximated by a linear regression and expressed as Cpliquid(exp) = 0.3379 ⋅ T + 126.69 in J K−1 mol−1. This was then compared to the estimated linear contributions of polymers that have the same constituent groups. Using estimated parameters of transitions and solid and liquid heat capacities at equilibrium, the integral thermodynamic functions of enthalpy, entropy and free enthalpy as functions of temperature were calculated.

Reprint of “Heat capacity and transition behavior of sucrose by standard, fast scanning and temperature-modulated calorimetry”

The heat capacity (Cp) of crystalline and amorphous sucrose was determined using standard and quasi-isothermal temperature modulated differential scanning calorimetry. The results were combined with the published data determined by adiabatic calorimetry, and the Cp values are now reported for the wide 5–600K range. The experimental Cp of solid sucrose at 5–300K was used to calculate the vibrational, solid Cp based on the vibrational molecular motions. The calculated solid and liquid Cp together with the transition parameters for equilibrium conditions were used as references for detailed quantitative thermal analysis of crystalline and amorphous sucrose. Melting temperature (Tm) of the crystalline sucrose was identified in a broad 442–465K range with a heat of fusion of 40–46J/mol determined at heating rates 0.5–20K/min, respectively. The equilibrium Tm and heat of fusion of crystalline sucrose were estimated at zero heating rate as Tom=424.4K and ΔHof=32kJ/mol, respectively. The glass transition temperature (Tg) of amorphous sucrose was at 331K with a change in Cp of 267J/(molK) as it was estimated from reversing heat capacity by quasi-isothermal TMDSC on cooling. At heating rates less than 30K/min, thermal decomposition occurred during melting, while at extreme rate of 1000K/s, degradation was not observed. Data obtained by fast scanning calorimetry (FSC) at 1000K/s, showed that Tm was 483K and Tg was 364K. Superheating effects were observed during the melting with the maximum value around 46K at 1000K/s.

A novel method for quantitative phase determination of cristobalite in ceramic cores using differential scanning calorimeter

The present research aims at developing a new quantitative thermal analysis method based on differential scanning calorimeter for determination of cristobalite phase content in ceramic cores. For this purpose, various control samples with different amounts of cristobalite phase were made based on the chemical composition of silica-based ceramic cores and analyzed via differential scanning calorimetry (DSC) technique. The surface area under the α → β cristobalite transition peak in the DSC curves was calculated via numerical integral of the peaks area, and the ratio of this area to the samples weight (A/W) was calibrated by cristobalite content of the samples. Afterward, for determining the cristobalite content of some industrial samples, the DSC patterns were plotted, and the A/W ratio of these samples was determined by the same method. Then the A/W ratios of the industrial samples were fitted on the calibration line, and the cristobalite content was derived using the equation of the calibration line. The method showed good accuracy, and the error values of the estimated cristobalite content of the industrial samples were below 2 %.

Heat capacity and transition behavior of sucrose by standard, fast scanning and temperature-modulated calorimetry

Abstract The heat capacity ( C p ) of crystalline and amorphous sucrose was determined using standard and quasi-isothermal temperature modulated differential scanning calorimetry. The results were combined with the published data determined by adiabatic calorimetry, and the C p values are now reported for the wide 5–600 K range. The experimental C p of solid sucrose at 5–300 K was used to calculate the vibrational, solid C p based on the vibrational molecular motions. The calculated solid and liquid C p together with the transition parameters for equilibrium conditions were used as references for detailed quantitative thermal analysis of crystalline and amorphous sucrose. Melting temperature ( T m ) of the crystalline sucrose was identified in a broad 442–465 K range with a heat of fusion of 40–46 J/mol determined at heating rates 0.5–20 K/min, respectively. The equilibrium T m and heat of fusion of crystalline sucrose were estimated at zero heating rate as T o m = 424.4 K and Δ H o f = 32 kJ/mol, respectively. The glass transition temperature ( T g ) of amorphous sucrose was at 331 K with a change in C p of 267 J/(mol K) as it was estimated from reversing heat capacity by quasi-isothermal TMDSC on cooling. At heating rates less than 30 K/min, thermal decomposition occurred during melting, while at extreme rate of 1000 K/s, degradation was not observed. Data obtained by fast scanning calorimetry (FSC) at 1000 K/s, showed that T m was 483 K and T g was 364 K. Superheating effects were observed during the melting with the maximum value around 46 K at 1000 K/s.

Quantitative chemical composition determination and thermal analysis for typical biomass ashes in China

ABSTRACTFor better use of biomass resources, a complete understanding of the chemical compositions for the biomass ashes is important. By the joint adoption of several analysis tools, the ashes of four typical biomass resources in rural areas of north China, i.e. corn stalk, wheat stalk, cotton branch, and poplar, were studied. It was found that after heating for 24 h at 450 and 850 °C, the biomass ashes exhibited quite different chemical and mineral compositions. At 450 °C, potassium salts (KCl, K2SO4, or K2CO3), carbonates, phosphates, and oxides (SiO2 and MgO) were the primary mineral phases; however, at 850 °C, all of the KCl and CaCO3 broke down, and the primary mineral phases became silicates, phosphates, and undecomposed potassium salts. The detailed mineral compositions of the biomass ashes were determined by carefully balancing the X‐ray fluorescence spectrometry and X‐ray diffraction results, which were then well confirmed by the thermal analysis via FactSage modeling and thermogravimetric analyses. The complete understanding of the chemical compositions and thermal properties of the biomass ashes will aid in their utilization or, in some cases, enable the avoidance of their negative effects. In addition, the joint analysis method here can be referred in the determination of mineral contents of any other biomass ash. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.

Thermal Imaging, a Potential Method for Microscale Quantitative Thermal Analysis – On Occasion of the 50th Anniversary of JCCTA Meeting –

Thermal Imaging, a Potential Method for Microscale Quantitative Thermal Analysis – On Occasion of the 50th Anniversary of JCCTA Meeting –

Heat capacity of poly(3-hydroxybutyrate)

The heat capacity of poly(3-hydroxybutyrate) (P3HB) has been measured using a quantum design Physical Property Measurement System (PPMS), differential scanning calorimetry (DSC), and temperature-modulated differential scanning calorimetry (TMDSC) over the temperature range of (1.9 to 460)K. The results within the range of (1.9 to 250)K were obtained using the quantum design PPMS, and established the baseline of the solid heat capacity. This experimental low-temperature heat capacity was linked to the vibrational molecular motion of P3HB. The solid heat capacity of P3HB was computed based approximately on groups of vibration and skeletal vibration spectra. The skeletal vibration heat capacity contribution was estimated by a general Tarasov equation with three Debye characteristic temperatures Θ1=549.1K and Θ2=Θ3=71.8K, and ten skeletal modes, Nskeletal=10. The experimental and calculated solid heat capacities agree with an error of ±0.2% over the temperature range from (5 to 250)K. The vibrational, solid heat capacity was extended to higher temperatures to judge additional contributions to the experimental heat capacity from other large-amplitude motion or latent heat during the quantitative thermal analysis of semi-crystalline P3HB. The liquid heat capacity of semi-crystalline P3HB above its melting temperature and of fully amorphous P3HB above the glass transition temperature was approximated by a linear regression and expressed as Cpliquid(exp)=0.1791 T+94.722 in units of J·K−1·mol−1. The calculated solid and liquid heat capacities can serve as equilibrium baselines for the quantitative thermal analysis of semi-crystalline P3HB. Also, the integral thermodynamic functions of enthalpy, entropy and free enthalpy for the equilibrium condition were calculated using estimated parameters of transitions.

Thermal analysis of cancerous breast model.

Breast cancer is one of the most common and dangerous cancers. Subsurface breast cancer lesions generate more heat and have increased blood supply when compared to healthy tissue, and this temperature rise is mirrored in the skin surface temperature. The rise in temperature on the skin surface, caused by the cancerous lesion, can be measured noninvasively using infrared thermography, which can be used as a diagnostic tool to detect the presence of a lesion. However, its diagnostic ability is limited when image interpretation relies on qualitative principles. In this study, we present a quantitative thermal analysis of breast cancer using a 3D computational model of the breast. The COMSOL FEM software was used to carry out the analysis. The effect of various parameters (tumor size, location, metabolic heat generation and blood perfusion rate) on the surface temperature distribution (which can be measured with infrared thermography) has been analyzed. Key defining features of the surface temperature profile have been identified, which can be used to estimate the size and location of the tumor based on (measured) surface temperature data. In addition, we employed a dynamic cooling process, to analyze surface temperature distributions during cooling and thermal recovery as a function of time. In this study, the effect of the cooling temperature on the enhancement of the temperature differences between normal tissue and cancerous lesions is evaluated. This study demonstrates that a quantification of temperature distributions by computational modeling, combined with thermographic imaging and dynamic cooling can be an important tool in the early detection of breast cancer.

Evolution of crystal and amorphous fractions of poly[(R)-3-hydroxybutyrate] upon storage

Quantitative thermal analysis of the evolution of crystal and amorphous fractions of poly[(R)-3-hydroxybutyrate] (PHB) upon storage at room temperature is detailed in this contribution. Conventional and temperature-modulated calorimetry were used to quantify the crystallinity, as well as the mobile and rigid amorphous fractions, of an initially partially crystallized PHB, subsequently maintained at 25 °C for various times. PHB undergoes progressive crystallization during storage, with an increase in crystal fraction (wC) from the initial wC = 0.35 up to wC = 0.71 attained after 1 year of storage. Crystallization is accompanied by vitrification of rigid amorphous segments, which leads to a noteworthy increase of the overall fraction of the material that is solid at room temperature, leaving only a mobile amorphous fraction wA = 0.04 after 1 year at 25 °C. The quantitative thermal analysis allowed to clarify the kinetics of evolution of both the ordered and unordered fractions of PHB upon storage, which leads to a severe deterioration of material’s properties.

Statistical research on phase formation and modification of alite polymorphs in cement clinker with SO3 and MgO

The design of experiments (DoE) was adjusted in cement clinker chemistry, with alite polymorphisms in the clinker taken into account. The additions of SO3, MgO, as well as two other factors, sintering temperature and time, were included to study clinker formation and alite polymorphisms. XRD quantitative analyses and thermal analysis (DSC–TG) were used to collect quantitative data from the samples and to investigate the clinkerization of the raw meal. The central composition design was used to design the experiments and the response surface methodology was used to evaluate the results. The addition of SO3 inhibited the formation of alite in the clinker, while MgO compensated for any negative effects caused by the SO3. A contour plot interpreted the combination effects of these four factors. The amount of C4AF was then increased with a likewise increasing SO3 content. MgO favored the formation of M3 type alites, while SO3 stabilized the M1. Alite modification, which is related to hydration properties, could be helpful for efficient use of high MgO content calcite in cement production.

Apparent heat capacity measurements and thermodynamic functions of d(−)-fructose by standard and temperature-modulated calorimetry

The qualitative and quantitative thermal analyses of crystalline and amorphous d(−)-fructose were studied utilising methods of standard differential scanning calorimetry (DSC), quasi-isothermal temperature-modulated differential scanning calorimetry (quasi-isothermal TMDSC), and thermogravimetric analysis (TGA). Advanced thermal analysis of fructose was performed based on heat capacity. The apparent total and apparent reversing heat capacities, as well as phase transition parameters were examined on heating and cooling. The melting temperature, Tm, of crystalline d(−)-fructose shows a heating rate dependency, which increases with raising the heating rate and leads to superheating. The equilibrium melting temperatures: Tm∘(onset)=370K and Tm∘(peak)=372K, and the equilibrium enthalpy of fusion ΔfusH°=30.30kJ·mol−1, of crystalline d(−)-fructose were estimated on heating for the results at zero heating rate. Anomalies in the heat capacity in the liquid state of d(−)-fructose, assigned as possible tautomerisation equilibrium, were analysed by DSC and quasi-isothermal TMDSC, both on heating and cooling. Thermal stability of crystals in the region of the melting temperature was examined by TGA and quasi-isothermal TMDSC. Melting, mutarotation, and degradation processes occur simultaneously and there are differences in values of the liquid heat capacity of d(−)-fructose with varied thermal history, measured by quasi-isothermal TMDSC. Annealing of amorphous d(−)-fructose between the glass transition temperature, Tg, and the melting temperature, Tm, also leads to crystallization of the sample and shows changes in the total apparent heat capacity. The experimental, apparent heat capacity of fully crystalline and fully or partially amorphous d(−)-fructose was analysed with reference to the solid (vibrational) and liquid heat capacities based on the ATHAS scheme.

Melting, glass transition, and apparent heat capacity of α- d-glucose by thermal analysis

The thermal behaviors of α- d-glucose in the melting and glass transition regions were examined utilizing the calorimetric methods of standard differential scanning calorimetry (DSC), standard temperature-modulated differential scanning calorimetry (TMDSC), quasi-isothermal temperature-modulated differential scanning calorimetry (quasi-TMDSC), and thermogravimetric analysis (TGA). The quantitative thermal analyses of experimental data of crystalline and amorphous α- d-glucose were performed based on heat capacities. The total, apparent and reversing heat capacities, and phase transitions were evaluated on heating and cooling. The melting temperature ( T m) of a crystalline carbohydrate such as α- d-glucose, shows a heating rate dependence, with the melting peak shifted to lower temperature for a lower heating rate, and with superheating of around 25 K. The superheating of crystalline α- d-glucose is observed as shifting the melting peak for higher heating rates, above the equilibrium melting temperature due to of the slow melting process. The equilibrium melting temperature and heat of fusion of crystalline α- d-glucose were estimated. Changes of reversing heat capacity evaluated by TMDSC at glass transition ( T g) of amorphous and melting process at T m of fully crystalline α- d-glucose are similar. In both, the amorphous and crystalline phases, the same origin of heat capacity changes, in the T g and T m area, are attributable to molecular rotational motion. Degradation occurs simultaneously with the melting process of the crystalline phase. The stability of crystalline α- d-glucose was examined by TGA and TMDSC in the melting region, with the degradation shown to be resulting from changes of mass with temperature and time. The experimental heat capacities of fully crystalline and amorphous α- d-glucose were analyzed in reference to the solid, vibrational, and liquid heat capacities, which were approximated based on the ATHAS scheme and Data Bank.

Thermodynamic description of condensed phases

Phases may be smaller than visible to the human eye. In order to characterize a microphase, a phase smaller than 1 μm, one must consider surface area and free energy in addition to the standard thermodynamic functions. As one approaches nanometer sizes, one also needs to know the changing thermodynamic functions within the phases. The Gibbs–Thomson equation can be used to characterize microphases, but not nanophases. For the latter, the glass transition is needed to assess the properties in the interior. In order to classify condensed phases as liquid, solid, mesophase, or crystal, one needs to consider the molecular motion in addition to the molecular structure. Most important are large-amplitude displacements in form of translation, rotation, and conformational motion. An operational definition based on experiments and an updated classification of the phases is given. The surprising result is the observation that crystals, earlier assumed prime examples of solids, can have order–disorder transitions to more mobile mesophases, as well as a glass transition without change in crystal structure, i.e., under certain condition, they cannot be identified as a solid. To these observations, one has to add the fact that large-amplitude motion may start gradually to a more mobile phase without abrupt changes in structure. These observations limit the usefulness of the 80-year-old classification of transitions as being of first or second order. Quantitative thermal analysis is shown to be an important tool to identify the possible total of 57 different condensed states in terms of their macroscopic properties as well as molecular structure and motion.

Note: Three-omega method to measure thermal properties of subnanoliter liquid samples

There are growing needs to measure the thermal properties of small-volume liquid samples in various fields of bioengineering and microfluidics. Accordingly, there have been efforts toward miniaturization of the sensing device without substantially sacrificing the sensitivity. The minimum sample volume required for quantitative thermal analysis is currently in the 10 nl scale. In this work, we describe microfabricated sensors and a modified three-omega data-analysis scheme to determine the thermal conductivity k and volumetric heat capacity rhoc(p) of samples of a few hundred picoliters. In experiments using several reference liquids, the technique measured k and rhoc(p) of 750 and 375 pl samples. The measurement accuracies were approximately 10% for k and approximately 15% for rhoc(p).

Study of crystalline and amorphous phases of biodegradable poly(lactic acid) by advanced thermal analysis

Abstract The qualitative and quantitative thermal analysis of biodegradable poly(lactic acid) PLA is presented. The glass transition, melting process, and heat capacity of a semi-crystalline poly(lactic acid) are studied utilizing the differential scanning calorimetry and temperature-modulated DSC. The mobile amorphous fraction, W a degree of crystallinity, W c and rigid-amorphous fraction, W RAF were estimated depending on the thermal history of semi-crystalline PLA. From qualitative thermal analysis, the glass transition of rigid-amorphous phase was observed as a broadening from the changes of heat-flow-rate between mobile glass transition temperature and melting temperature. The amount of the rigid-amorphous fraction (RAF) was evaluated from W RAF = 1− W c − W a and graphically was presented as the result of a deflection from the linearity of the dependence of the change of degree of mobile amorphous phase ( W a ) vs. the degree of crystalline fraction ( W c ) for semi-crystalline PLA with different thermal history. The degree of crystallinity of semi-crystalline samples of PLA can be discussed in terms of a two- or three-phase model. In contrast, the quantitative thermal analysis of the experimental apparent heat capacity of semi-crystalline PLA did not show any appearance of RAF in the examples of analyzed samples. The experimental heat capacity of PLA was analyzed in reference to the solid and liquid equilibrium heat capacities of poly(lactic acid) found in the ATHAS Data Bank.

Semi solid metal processing: The fraction solid dilemma

One of the most challenging aspects in semi solid metal (SSM) processing is to determine the actual volume fraction of the solid at the processing temperature. The fraction has great impact on the SSM slurry viscosity and the subsequent filling of the mold in the casting stage. Three methods, namely quantitative metallography, thermodynamic calculation, and thermal analysis are employed to investigate and clarify the contradictory open literature reports about the real value of the volume fraction of primary particles. It is reported that the discrepancies between the results obtained by different methods are caused mainly by variations in cooling rates and by coarsening of the primaries during the quenching process.