Heat Conduction Microcalorimetry Research Articles

Specific heat and excess heat capacity of grout with phase change materials using heat conduction microcalorimetry

Microencapsulated phase-change-materials (PCMs) incorporated in cementitious grout can be used as a source of energy in an underground thermal energy storage system. Differential scanning calorimetry (DSC) is a widely used technique to measure the latent heat or specific heat of PCM-embedded cementitious materials. However, using milligram sample sizes (as required by DSC) of a cementitious material fails to represent the actual scale of cementitious components. This is the reason why, in the present paper, non-isothermal heat conduction microcalorimetry (MC) was evaluated as a tool for determining the thermal properties of PCM-embedded grout as well as pure PCM (three PCMs were used). An MC experimental protocol (using both single and 5–6 temperature cycles) was developed and used to measure latent heat and melting and crystallization temperatures, which were in good agreement with those reported for pure PCMs by the producers. In addition, the specific heats of the PCM-containing grout also agreed with measurements using the hot disk technique. Overall, the results show that the MC technique can be used as a potential standard method in determining thermal processes in complex systems, such as in PCM-embedded cementitious systems, where a large sample size is needed to represent the material.

Heat production in municipal and industrial waste as revealed by isothermal microcalorimetry

Self-ignited fires at municipal solid waste (MSW) storage sites are relatively common. The minimization of the phenomenon of self-heating in the waste can reduce the risks for smouldering combustion. The purpose of this work was to develop a method that can be used to measure and characterize the heat production in MSW. The method is based on isothermal heat conduction microcalorimetry (IMC). The heat production in MSW was determined based on sampling from two sites in two different geographical locations in Sweden. Both the original waste and milled/homogenised waste were tested. The heat production was measured at different temperatures together with gas analysis using micro-gas chromatography. The activity in the waste, in terms of its heat flow, increased when the temperature increased up to 60 °C and decreased at higher temperatures, e.g., 70 and 80 °C. The consumption of oxygen and the production of carbon dioxide, together with the heat production, indicated that aerobic metabolism was responsible for the heat production. This is further strengthened by the marginal heat production observed for ultraviolet treated waste. The results showed that IMC is a valuable tool for characterising the self-heating in municipal and industrial waste.

Synthesis and microcalorimetric determination of the bioactivities of a new Schiff base and its bismuth(III) complex derived from o-vanillin and 2,6-pyridinediamine

In this work, a new Schiff base [N,N′-bis(2-hydroxy-3-methoxyphenylmethylidene)-2,6-pyridinediamine, C21H19N3O4] and its bismuth(III) complex [Bi(C21H17N3O4)]Cl·2H2O were synthesized with o-vanillin and 2,6-pyridinediamine in ethanol and THF solvent, respectively. The compositions and structures of the two synthetic compounds were characterized by elemental analysis, chemical analysis, spectrum analysis (including MS, FT-IR, NMR, and UV–Vis), and thermogravimetric analysis. The thermogenic curves for the growth metabolism of Helicobacter pylori (H. pylori) and Schizosaccharomyces pombe (S. pombe) treated by different concentrations of the two synthetic compounds were determined by isothermal heat conduction microcalorimetry at 37.00 and 32.00 °C, respectively. Based on the thermogenic curves, some important thermokinetic parameters including the microbial growth rate constant (k), inhibition ratio (I), and half inhibition concentration (IC50) were calculated. The obtained results revealed that the Schiff base stimulated the growth of H. pylori, while the complex inhibited its growth. By contrast, both the Schiff base and the complex inhibited the growth of S. pombe, but the inhibitory effect of the complex was stronger than that of the Schiff base.

Phase Equilibrium System of CsCl–TbCl3–HCl(∼7.6 mass %)–H2O at 298.2 ± 0.1 K and Fluorescent and Thermal Properties of Its Solid-Phase Compounds in the System

The solubility data of the quaternary system CsCl–TbCl3–HCl(∼7.6 mass %)–H2O at 298.2 K were determined, and the corresponding phase diagram according to central projection data on the trigonal basal face CsCl–TbCl3–H2O was plotted. The diagram includes three invariant points and four crystallization fields corresponding to CsCl, Cs5TbCl8·6H2O, Cs2TbCl5·6H2O, and TbCl3·6H2O. Two new solid-phase compounds of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O, which are congruently soluble in the system, were isolated and characterized by the methods of powder X-ray diffraction, thermogravimetric, and differential thermal analysis. The standard molar enthalpies of solution for the two compounds of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O were measured to be (60.64 ± 0.28) and (14.08 ± 0.45) kJ·mol–1 by heat conduction microcalorimetry under the conditions of infinite dilution, and their standard molar enthalpies of formation were calculated to be −(5087.1 ± 1.7) kJ·mol–1 and −(3764.2 ± 1.0) kJ·mol–1. The fluorescence excitation and emission spectra of Cs5TbCl8·6H2O and Cs2TbCl5·6H2O were measured. The results show that upconversion spectra exhibit for Cs5TbCl8·6H2O at 500 nm and 545 nm and for Cs2TbCl5·6H2O at 495 nm and 545 nm excited at 750 nm, and the upconversion intensity increases with the increase of TbCl3 contents in CsCl.

Studying the compatibility of a metoclopramide-HCl–paracetamol mixture via IHCMC and establishing a validated RP-HPLC method for its determination in tablets

Currently metoclopramide hydrochloride (MCP-HCl) and paracetamol (PCM) are co-formulated together in a tablet form, which is widely used in relief of painful migraine. The purpose of this work was to investigate the physicochemical compatibility of this co-mixture in the solid form and in different media as well. A highly selective and sensitive RP-HPLC method was established to quantify MCP-HCl and PCM in the presence of their degradation products. Chromatographic separation was achieved on a C-8 column using phosphate buffer, acetonitrile and methanol (40 : 15 : 10, v/v/v, pH 3) as a mobile phase at a flow rate of 0.5 mL min−1 with UV detection at 220 nm. Isothermal Heat-Conduction Micro-Calorimetry (IHCMC) was used to investigate heat-flow caused by physico-chemical incompatibility. The method was linear within concentration ranges such as 20–80 μg mL−1 and 10–70 μg mL−1 for MCP-HCl and PCM, respectively. The LOD and LOQ of the method for determination of MCP-HCl and PCM were 0.501, 0.101, 1.67 and 3.39, respectively. Other analytical validation parameters such as accuracy, precision, selectivity and applicability of the method were evaluated using an external standard addition technique. The tablets containing MCP-HCl and PCM in the concentration ratio of 1 : 100 were analyzed by the method successfully via two concentration levels. Thermal analysis of solid mixtures of the drugs showed compatibility over short and long terms in contrast with their aqueous mixtures. So it is not recommended that this drug mixture be formulated in a liquid form.

Phase Equilibria in the Systems RbCl–TmCl3–HCl(22.12 %)–H2O and RbCl–LuCl3–HCl(21.37 %)–H2O at 298.15 K and Standard Molar Enthalpy of Formation of Rb2LuCl5·7H2O

The solubility in the RbCl–TmCl3–HCl–H2O and RbCl–LuCl3–HCl–H2O quaternary water–salt systems was studied along the ∼22 % hydrochloric acid section by the isothermal solubility method at 298.15 K, and corresponding equilibrium diagrams were constructed. The compositions of solid phases were established by the Schkreinemakers’ wet residue method. The quaternary system RbCl–TmCl3–HCl–H2O is a simple eutonic type, but the quaternary system RbCl–LuCl3–HCl–H2O is complicated, and one incongruently saturating complex phase is formed in this system: Rb2LuCl5·7H2O. The compound Rb2LuCl5·7H2O was identified and characterized by the methods of powder X-ray diffraction, thermogravimetric, and differential thermal analysis. The crystal water was lost at (308 to 499) K. The standard molar enthalpy of solution of Rb2LuCl5·7H2O in water was measured to be (6.04 ± 0.17) kJ·mol–1 by heat conduction microcalorimetry, and its standard molar enthalpy of formation was calculated to be −(4009.9 ± 1.3) kJ·mol–1.

Synthesis, characterization and hydration analysis of a novel epoxy/superplasticizer oilwell cement slurry – Some mechanistic features by solution microcalorimetry

A new epoxy/polyacrylate-modified oilwell cement slurry was synthesized. The features of the new slurry were evaluated in relation to a standard cement slurry (w/c=0.5). The characterization of the slurries was performed by Raman, XRD, TG/DTG and solid-state diffuse reflectance spectroscopy. The main morphological features of the new slurry were preserved, even after long-term contact with HCl in aqueous solution. The hydration of the slurries was studied by heat-conduction microcalorimetry. The exothermic microcalorimetric outputs were well fitted to a three-parameter kinetic model. The analysis of both thermodynamic and kinetic results from microcalorimetry have pointed out that diffusional growth from non-stoichiometric mixtures is the main mechanistic feature of the hydration of the cement slurries. The results of this study underline the excellent features of the new epoxy/superplasticizer-modified cement slurry for using in severe acidic environments of oilwells.

Phase Equilibrium of the Ternary System Cadmium Chloride + l-Threonine + Water at 298.15 K and Standard Molar Enthalpy of Formation of Cd(C4H9NO3)Cl2·H2O

The equilibrium solubility of the ternary system cadmium chloride + l-threonine + water was determined at 298.15 K, and the corresponding equilibrium diagram was constructed. The ternary system is complicated with four equilibrium solid phases, CdCl2·2.5H2O, CdCl2·H2O, Cd(C4H9NO3)Cl2·H2O, and C4H9NO3, of which a new compound of Cd(C4H9NO3)Cl2·H2O was found to be incongruently soluble in the system. The new compound obtained was identified and characterized by the methods of FT-IR, elementary analysis, powder X-ray diffraction, single X-ray diffraction, and thermogravimetric and differential thermal analysis. It belongs to the monoclinic system, space group P2(1)/, with a = 0.7672(4) nm, b = 0.9166(5) nm, c = 1.3787(7) nm, β = 96.453(7)°, V = 0.9634(8) nm3, Dc = 2.188 g·cm–3, and Z = 2. The dissolution enthalpies of CdCl2, C4H9NO3, and Cd(C4H9NO3)Cl2·H2O in 2 mol·dm–3 hydrochloric acid were measured by heat conduction microcalorimetry. By designing an appropriate thermochemical cycle according to Hess’s la...

Combination of Silica Sol and Potassium Silicate via Isothermal Heat Conduction Microcalorimetry

AbstractIsothermal heat conduction microcalorimetry was utilized as a novel characterization method to investigate the polymerization processes of silica with both thermodynamic and kinetic parameters when the combination of silica sol and potassium silicate was stirred at temperatures of 25.0, 35.0, and 45.0°C. The silica polymerization was characterized by the greater enthalpy change at each higher temperature and by the reaction orders of the silica sol and potassium silicate, which varied rapidly, instantaneously, and constantly from low to high all the time, up and down in an alternate manner. When the reaction order of the silica sol and potassium silicate was 3.0, the maximum rate constant occurred at 25.0°C (k=1.22×10−4mol−2·dm6·s−1). The two temperature regions (25.0–35.0°C region with a faster rate and 35.0–45.0°C region with a lower rate) reflected a two‐stage oligomerization of silica monomers with different oligomers formed in a two‐step anionic mechanism. The measurements of particle size and pH value showed that the colloidal particles in the mixed silica sol and potassium silicate first dissolved, then "active" silica in the potassium silicate redeposited to make a distinct particle size distribution (Z‐average size, 33.0–14.9 nm at 25.0°C) influenced both by pH value (9.82–11.97 at 25.0°C) and the mass fraction (53, 65, 75, and 85 mass/%) of the silica sol in the mixture. The processes of combination of the silica sol and potassium silicate did not result from acid‐base neutralization reactions but from a complex polymerization of the "active" silica components which relate to silica monomers oligomerization with heat evolved (the total enthalpy changes, 1.6234–3.3882 J).

Phase Equilibrium in the System RbCl−NdCl3−HCl(13.26 %)−H2O at 298.15 K and Standard Molar Enthalpy of Formation of New Solid Phase Compound

The solubility of the quaternary system RbCl−NdCl3−HCl(13.26 %)−H2O at 298.15 K was determined, and the corresponding equilibrium diagram was constructed. The quaternary system consists of three equilibrium solid phases, RbCl, RbNdCl4·4H2O (1:1 type), and NdCl3·6H2O. The new solid phase compound RbNdCl4·4H2O was found to be congruently soluble in the system. The compound RbNdCl4·4H2O was characterized by X-ray diffraction, X-ray diffraction single crystal structure analysis, thermogravimetry, and differential thermogravimetry. It belongs to an orthorhombic system, with space group P21212, a = 0.6986(6) nm, b = 1.1319(1) nm, c = 0.6665(6) nm, Dc = 2.795 g·cm−3, and Z = 2. The compound loses its crystal water by one step at (370 to 474) K. The standard molar enthalpy of solution of RbNdCl4·4H2O in deionized water was measured to be −(26.97 ± 0.24) kJ·mol−1 by heat conduction microcalorimetry. Its standard molar enthalpy of formation was calculated to be −(2732.3 ± 1.0) kJ·mol−1.

Direct determinations of energetic parameters at chitosan/Cr(VI) interfaces by means of immersion heat-conduction microcalorimetry

Interaction parameters at epichlorohydrin-crosslinked chitosan beads/Cr(VI) interfaces from aqueous solutions was obtained by using immersion heat-conduction microcalorimetry. This technique permits simultaneous determinations of adsorbed amounts and interaction energies. The experimental variables evaluated were pH of the Cr(VI) solutions of 4.0 and 6.0, initial Cr(VI) concentration in solution of 0.50 and 5.00 × 10(-3) mol L(-1) and temperature of 25 and 45 °C. The calorimetric results were evaluated using a 2(3) full factorial design. The responses were the adsorption amounts (n(int)), the adsorption energies (Q(int)) and the adsorption enthalpies (Δ(int)H). The results indicated that all thermodynamic responses (adsorption energies and adsorption enthalpies) are all exothermic in nature. The initial Cr(VI) concentration in solution was the most important parameter in all responses evaluated in this study. Polynomial fits have pointed out that almost all interactive effects are statistically important on the values of n(int), Q(int) and Δ(int)H. It is concluded that the thermodynamical aspects of the Cr(VI) adsorption parameters are greatly influenced by the interactive factors and not by temperature changes alone.

Studies of mechanism of silica polymerization reactions in the combination of silica sol and potassium sodium waterglass via isothermal heat conduction microcalorimetry

Isothermal heat conduction microcalorimetry was adopted as a novel characterization method to investigate the polymerization processes of silica when the combination of silica sol and potassium sodium silicate was stirred at 25.0, 35.0, and 45.0 °C. Thermodynamic and kinetic parameters were simultaneously obtained. The enthalpy change was greater at each higher temperature. The reaction orders (m, n) instantaneously varied, up and down in an alternate manner. At 25.0, 35.0, and 45.0 °C, the rate constants were different; the maximum rate constant occurred at 25.0 °C. These phenomena reflect a two-stage oligomeric mechanism of silica monomers. The measurements of particle size showed the complex chemical composition of aqueous silicates, which can be qualitatively designated by the particle size distribution in two parts. The results further indicate that the colloidal particles in the mixed silica sol and silicates first dissolved. Then the “active” silica in the silicates redeposited to make a distinct particle size distribution influenced by K+ and Na+ ions as well as by temperature.

Phase Equilibrium System of Cadmium Chloride + dl-Alanine + Water at 298.15 K and Standard Molar Enthalpy of Formation of Cd3(Ala)2Cl6·4H2O

The equilibrium solubility of the ternary system cadmium chloride + dl-alanine (Ala) + water was determined at 298.15 K, and the corresponding equilibrium diagram was constructed. The ternary system is complicated with three equilibrium solid phases, CdCl2·2.5H2O, Cd3(Ala)2Cl6·4H2O, and Ala, of which a new compound of Cd3(Ala)2Cl6·4H2O was found to be congruently soluble in the system. The new compound obtained was identified and characterized by the methods of IR, elementary analysis, X-ray diffraction, X-ray diffraction single crystal structure analysis, thermogravimetry, and differential thermogravimetry. It belongs to the monoclinic system, with space group P2(1)/n, a = 0.70393(16) nm, b = 0.9074(2) nm, c = 1.6982(4) nm, β = 92.529(4)°, V = 1.0837(4) nm3, Dc = 2.434 g·cm−3, Z = 2. The dissolution enthalpies of Ala, CdCl2, and Cd3(Ala)2Cl6·4H2O in 2 mol·dm−3 H2SO4 were measured by heat conduction microcalorimetry. By designing a thermochemical cycle according to Hess’ Law and through calculation, we ob...

Cement–epoxy/water interfaces – Energetic, thermodynamic, and kinetic parameters by means of heat-conduction microcalorimetry

Hydration phenomena at cement/water interfaces drive the characteristics of oil-well cement slurries. In this study, new epoxy-modified cement slurries were synthesized. The slurries characterization has suggested the presence of low amounts of portlandite in the slurry with the higher content of polymerized epoxy resin. The hydration processes of the cement slurries were studied by heat-conduction microcalorimetry. The energetic and enthalpic hydration data were all exothermic in nature. The cumulative heat release curves have shown the presence of multilinearity of the kinetic processes. The hydration microcalorimetric data were well fitted to the multistep Avrami kinetic model. It was found that the epoxy-modified cement slurries present a good potential to be used in environmental-friendly oil-well operations.

Using heat conduction microcalorimetry to study thermal aggregation kinetics of proteins

The thermally induced irreversible aggregation of a monoclonal antibody in different pH buffers was investigated using different techniques such as micro-differential scanning calorimetry (micro-DSC), size exclusion HPLC (SEC) and isothermal microcalorimetry. The kinetics of aggregation of the protein was analyzed in terms of a Lumry–Eyring model proceeding via a non-native conformational state. The rate constants and reaction enthalpies of unfolding and consequent aggregation were obtained by fitting the isothermal microcalorimetric and SEC data based on proposed aggregation mechanisms. The consistency of rate constants obtained via isothermal microcalorimetry and SEC indicates it is possible to deconvolute the observed microcalorimetry power–time data obtained from thermally induced protein aggregation.

Phase equilibrium system of RbCl-PrCl3-HCl(12.86 mass %)-H2O at 298.15 K and standard molar enthalpy of formation of new solid-phase compound

The equilibrium solubility of the quaternary system RbCl-PrCl3-HCl-H2O was determined at 298.15 K and the corresponding equilibrium diagram was constructed in this paper. The quaternary system is complicated with three equilibrium solid phases, RbCl, RbPrCl4 · 4H2O (1:1 type) and PrCl3 · 6H2O, of which the new compound RbPrCl4 · 4H2O was found to be congruently soluble in the system. The new compound obtained was identified and characterized by the methods of X-ray diffraction, thermogravimetry, and differential thermogravimetry. The compound loses its crystal water by one step at 343 K to 453 K. The standard molar enthalpy of solution of RbPrCl4 · 4H2O in deionized water was measured to be −24.53 ± 0.22 kJ mol−1 by heat conduction microcalorimetry. Its standard molar enthalpy of formation was calculated to be −2743.20 ± 1.09 kJ mol−1.

Investigation on the Equilibrium Phase Diagram of the Ternary System TmCl3−CdCl2−H2O at 298.15 K and Standard Molar Enthalpy of Formation of Cd3TmCl9·15H2O

Equilibrium phase relation and solubility data for the rare earth trichloride TmCl3·6H2O and cadmium chloride in aqueous media were investigated. The corresponding equilibrium phase diagram in the ternary system TmCl3−CdCl2−H2O at 298.15 K was constructed. The results showed that the system was complicated and consisted of four stable equilibrium solid phases [CdCl2·2.5H2O, CdCl2·H2O, Cd3TmCl9·15H2O (3:1 type), TmCl3·6H2O]. The new compound Cd3TmCl9·15H2O was found to be congruently soluble in the system. The 3:1 type compound obtained was identified and characterized by the method of X-ray diffraction, X-ray diffraction single-crystal structure analysis, thermogravimetry, and differential thermogravimetry (TG, DTG). It belongs to a monoclinic system, with space group P2(1)/n, a = 1.2267(4) nm, b = 2.0034(7) nm, c = 1.2321(4) nm, β = 113.793(5)°, V = 2.7706(17) nm3, Dc = 2.554 g·cm−3, Z = 4. The standard molar enthalpy of solution of Cd3TmCl9·15H2O in deionized water was measured to be (29.73 ± 0.40) kJ·mol−1 by heat conduction microcalorimetry. Its standard molar enthalpy of formation was calculated to be −(6747.2 ± 1.2) kJ·mol−1.

Phase Equilibrium System of RbCl−SmCl3−HCl(12.84, 22.66 % by Mass)−H2O at 298.15 K and Standard Molar Enthalpy of Formation of RbSmCl4·4H2O

Solubility of the quaternary system RbCl−SmCl3−HCl(12.84, 22.66 % by mass)−H2O was determined at 298.15 K, and corresponding equilibrium diagrams were constructed. The quaternary system is complicated with three equilibrium solid phases RbCl, RbSmCl4·4H2O (1:1 type), and SmCl3·6H2O. The solubilities of RbCl, RbSmCl4·4H2O, and SmCl3·6H2O decreased with an increase of the concentration of HCl. The crystallization field decreased for RbCl and SmCl3·6H2O and increased for RbSmCl4·4H2O with an increase in the HCl concentration. The new solid-phase compound RbSmCl4·4H2O was found to be uncongruently soluble in the system. The compound RbSmCl4·4H2O was characterized by the methods of X-ray diffraction, thermogravimetry, and differential thermogravimetry. The compound loses its crystal water by one step at (359 to 457) K. The standard molar enthalpy of solution of RbSmCl4·4H2O in deionized water was measured to be −(29.40 ± 0.26) kJ·mol−1 by heat conduction microcalorimetry. Its standard molar enthalpy of formation was calculated to be −(2725.3 ± 1.0) kJ·mol−1.

Phase Equilibrium System of HoCl3−CdCl2−HCl(7.52 %)−H2O at 298.15 K and Standard Molar Enthalpy of Formation of Cd4HoCl11·14H2O

The equilibrium solubility of the quaternary system HoCl3−CdCl2−HCl−H2O was determined at 298.15 K, and the corresponding equilibrium diagram was constructed. The quaternary system is complicated with three equilibrium solid phases, CdCl2·H2O, Cd4HoCl11·14H2O (4:1 type), and HoCl3·6H2O, of which the new compound Cd4HoCl11·14H2O was found to be congruently soluble in the system. The new compound obtained was identified and characterized by the methods of X-ray diffraction, thermogravimetry, and differential thermogravimetry. The standard molar enthalpy of solution of Cd4HoCl11·14H2O in deionized water was measured to be (15.74 ± 0.18) kJ·mol−1 by heat conduction microcalorimetry. Its standard molar enthalpy of formation was calculated to be (−6864.7 ± 1.3) kJ·mol−1. The standard molar enthalpy of formation, the solubility data, and the phase diagram of the quaternary system could provide the fundamental basis and serve as a guide for the preparation of Cd4HoCl11·14H2O.

Phase Equilibrium System of RbCl−LaCl3−HCl(12.60 Mass %)−H2O at 298.15 K and Standard Molar Enthalpy of Formation of RbLaCl4·4H2O

Solubilities of the quaternary system RbCl−LaCl3−HCl−H2O were determined at 298.15 K, and the corresponding equilibrium diagram was constructed in this paper. There are three equilibrium solid phases, RbCl, RbLaCl4·4H2O (1:1 type), and LaCl3·7H2O in the quaternary system. The new compound RbLaCl4·4H2O was found to be congruently soluble in the system. The compound RbLaCl4·4H2O was characterized by the methods of X-ray diffraction, thermogravimetry, and differential thermogravimetry. The compound loses its crystal water by one step at (358 to 449) K. The standard molar enthalpy of solution of RbLaCl4·4H2O in deionized water was measured to be (−19.61 ± 0.24) kJ·mol−1 by heat conduction microcalorimetry. Its standard molar enthalpy of formation was calculated to be (−2750.4 ± 1.1) kJ·mol−1.