Microcalorimetric Method Research Articles

Structural and optical properties of a new structural modification of Na3+3xYb2−x(PO4)3:1% Eu phosphate, where x = 0,1-0,5 and prospective thermometric applications of the compound

The powders of Na3+3xYb2-x(PO4)3: 1% Eu3+ (where x = 0.1, 0.2, 0.3, 0.4 and 0.5) have been synthesized using thermal method in solid state. Their structural and spectroscopic properties were investigated by powder X-ray diffraction, microcalorimetric method (DSC), Raman, infrared, absorption and luminescence studies. It was find that the studied materials belong to the NASICON-type compounds and crystallize in rhombohedral or monoclinic type of structure. Photoluminescence of investigated samples presents typical emission of Eu3+ ions with the dominance of electric dipole transitions and near-infrared bands attributed to Yb3+ ions. Efficient red and infrared emissions under the excitation of 395 nm can be attractive for LED lighting. The highest Yb3+ emission intensity has been registered for the sample with the Na3.9Yb1.7(PO4)3: 1% Eu3+ composition (x=0.3). Ytterbium excited level can be populated by the energy transfer from the Eu3+ ions and can be enhanced by sample heating. Due to the non-radiative processes, the Eu3+ luminescence decay times monitored at 619 nm were bi-exponental. Because of the strong influence of temperature on emission intensities, obtained compounds can be useful for non-contact temperature readout, especially in the high-temperature region (above 600 K). The maximum value of relative sensitivity Sr is equal 2.91%K-1 at 855 K for the sample Na3+3xYb2-x(PO4)3: 1% Eu3+ (x=0.3).

Physicochemical insight into the metal atom effect on magnetocaloric behavior of paramagnetic metalloporphyrins

To reveal the effect of coordinated organic and inorganic σπ-ligands on the magnetocaloric properties of metal ions at room temperature, we have synthesized paramagnetic (5,10,15,20-tetraphenylporphinato)cobalt(II), (chloro)(2,3,7,8,12,13,17,18-octaethylporphinato))manganese(III), their coordination complexes with 1-methyl-2-(pyridin-4′-yl)-3,4-fullero[60]pyrrolidine (1:3 and 1:2, respectively), and (ethoxy)(oxo)(5,10,15,20-tetraphenylporphinato)molybdenum(V) and have fully characterized their chemical structure by UV–vis, IR, 1H NMR, MALDI TOF spectral methods. Using the direct microcalorimetric method and DSC we have obtained, respectively, magnetocaloric effect, heat, change of enthalpy/entropy during the magnetization over the temperature range of 285 – 338 K in magnetic fields from zero to 1 T and the specific heat capacities in the temperature range from 270 to 400 К in zero fields for paramagnets synthesized. Involving the results of DFT calculations, we have shown that the electron structure of a central metal atom is the determining factor in the positive magnetocaloric effect in the complexes studied. The decrease in the MCE value is observed in the case of the intramolecular antiferromagnetic interactions in external magnetic fields (manganese(III) complexes) and additional axial bonding of the bulk fullerene-containing base.

Study on New Dental Materials Containing Quinoxaline-Based Photoinitiators in Terms of Exothermicity of the Photopolymerization Process.

Modern dentistry places great demands on the dental composites used for filling tooth cavities or treating cavitated tooth decay. The aim of the work was to modify the properties of composites by changing the initiators and co-initiators. This was achieved by using initiators based on a quinoxaline skeleton and co-initiators that are derivatives of acetic acid, which is an advantage of these photoinitiating systems due to the elimination of aromatic amines from the photocurable composition. The composites also differed in dental fillers. The effect of the compounds on the exothermicity of the photopolymerization process, the surface morphology of the obtained materials and the maximum compressive strength were determined. The photoinitiating capacity of the two-component systems was tested by the microcalorimetric method using the multifunctional monomer TMPTA, typical for dental filler compositions. The new photoinitiating systems show particularly good efficiency of free radical polymerization initiation, which occurs by the photoinduced intermolecular electron transfer (PET) mechanism. The comparison of the tested systems with camphorquinone, a photoinitiator traditionally used in dentistry, made it possible to observe a decrease in temperature during photopolymerization without a significant decrease in the polymerization rate or increase in photocuring time, as well as a better homogeneity of the surface of the obtained polymeric materials. This indicates that dye-acetic acid derivative systems may be useful in dental applications.

Oil-based magnetic fluids. Synthesis, properties, and application prospects

In this work, magnetite crude oil-based magnetic fluids have been synthesized and studied. Their physicochemical parameters (density, viscosity, magnetic phase particle size) have been determined. IR spectroscopy and thermogravimetric analysis have been performed. The magnetocaloric properties (magnetocaloric effect and heat capacity) of magnetic fluids have been determined by the microcalorimetric method in the temperature range of 278-350 K in the magnetic field changing its value from 0 to 1.0 T. The maximum value of the magnetocaloric effect of a magnetic fluid with a magnetic phase volume concentration of 0.08 is 0.0035 K at 310 K and at the magnetic induction to 1.0 T. The obtained samples of magnetic fluids have low production costs because crude oil is used as the carrier fluid and can be recommended for various applications of the petroleum and gas industry, for example, for well killing.

Mechanisms of hydration heat inhibitors on the early heat release process of cement

We evaluated the effects of hydration heat inhibitors on the early hydration heat release process of cement and its main mineral components. We used a microcalorimetric method to determine the effects of various proportions and properties of hydration heat inhibitors on the hydration of portland cement, tricalcium silicate, and tricalcium aluminate: concentration (C) = 40% m/m hydroxydiphosphonic acid (HEDP) (1-hydroxyethylidene-1,1-diphosphonic acid) and C = 40% m/m diethylene triamine pentonyphosphonic acid (DTPMPA) (diethylenetriaminepentamethylene phosphonic acid). We also analyzed and tested the heat release rate and cumulative heat release during the hydration of cement and its main mineral components. The hydration heat inhibitors decreased the heat release rate of cementitious materials by means of adsorption, chelation, precipitation, complex formation, and control of calcium hydroxide crystals. Among these materials, the hydration heat inhibitor had the most substantial effect on the composition of tricalcium silicate clinker, reducing the peak temperature at the initial stage of hydration and delaying its occurrence time. These results are pertinent to controlling and selecting the early hydrothermal release process of cement systems.

Differential bacterial ammonia oxidation patterns in soil particles from two contrasting forests: The importance of interfacial interactions

Soil inorganic nitrogen (N) deficiency limits forest productivity in subalpine regions. The traditional view holds that subalpine coniferous forests are characterized by lower soil inorganic N availability, and such differences are greatly affected by the diversity and abundance of ammonia-oxidizing bacteria. It is known that interfacial interactions between bacteria and solid particles in agricultural and aquatic ecosystems can alter bacterial metabolic activity and biogeochemical processes. However, whether bacteria-soil interfacial interactions induce different ammonia oxidation processes in distinct soil particles remain unknown. Herein, we collected soil particles of different sizes from two contrasting forest sites (a spruce-dominated natural forest and spruce plantation) and examined the effect of soil-Nitrosomonas europaea (a model ammonia-oxidizing bacteria) interfacial interactions on the oxidation of ammonium (NH4+-N) using batch adsorption and semipermeable membrane experiments. The metabolic activity of bacteria was also examined using an isothermal microcalorimetric method. Upon adsorption on soil particles, the ammonia oxidation rate and bacterial metabolism activity were slower than those of free bacteria. The inhibition effect ceased when the bacteria were physically isolated from the soil particles by a membrane, indicating the importance of interfacial interactions in the ammonia oxidation process. Additionally, clay particles were more effective than silts and sands in binding cells and greatly reduced the ammonia oxidation reaction. Across the two forests, natural forest soils exhibited a higher bacterial adsorption capacity but lower bacterial metabolic activity, resulting in a fewer loss of NH4+-N. Our results suggested that stronger bacteria-soil interfacial interactions (especially for clay fractions) were responsible for maintaining high soil inorganic N availability in forests, highlighting the need to incorporate interfacial interactions into biogeochemical models of N cycling in forest ecosystems.

Influence of Zinc-Saturated Zeolite on Portland Cement Hydration Kinetics

This work examines the influence of zeolite saturated with zinc (SZ) on the early hydration of Portland cement. The measurements and results indicate that the microcalorimetric method allows continuous observation and determination of SZ’s influence on kinetic processes in the early stages of hydration. According to the total heat released after 48 hours of hydration, higher SZ content results in lower heat values, while the maximum hydration occurs earlier. As SZ proportion increases, the rate of heat release and the degree of hydration decrease. Measured hydration degrees differ significantly from the calculated values when SZ is added to Portland cement, especially later in the hydration process.

Modification of magnetocaloric properties upon a change in the spin state of iron(III) in tetrapyrrole paramagnets

Porphyrin complexes of 3d-metals with an open electronic shell are ranked as molecular materials with both electronic functionality and paramagnetic behavior due to exhibiting a positive magnetocaloric effect (MCE) at the temperature close to the room. We have determined MCE, heat, and an enthalpy/entropy change during magnetization of chloride ligated pentacoordinated iron(III) 5,10,15,20-tetraphenylporphin, (Cl)FeTPP and dimethylformamide ligated sixcoordinated iron(III) mesoporphyrin IX, [(DMF)2FeMP]+Cl- at 278–338 K in magnetic fields from 0 to 1.0 T by the direct microcalorimetric method. The specific heat capacity in solid (Cl)FeTPP/[(DMF)2FeMP]+Cl- was directly determined depending on the temperature in zero magnetic fields using DSC. To improve understanding of the correlation between magnetic properties of the iron(III) complexes and its spin state, we have compared the magnetic behavior of paramagnets studied with those for manganese(III) porphyrins. Both the iron(III) spin state and the exchange (ferromagnetic or antiferromagnetic depending on functional substitution in a complex) between a paramagnetic ligand and the central ion are reflected in the magnetocaloric behavior of iron(III) porphyrins studied.

The first experimental evidence of room-temperature magnetocaloric effect in fullerenes

The aim of the study was the first characterization of fullerenes, organic molecular solids without a d or f metal/ion, as paramagnets with the magnetocaloric effect (MCE) displayed at the temperatures close to room. Direct determinations of MCE/magnetization thermodynamic parameters and a heat capacity of [60]fullerene (C60) and 1′-N-methyl-2′-(pyridin-4-yl)pyrrolidino[3′,4′:1,2][60]fullerene (PyC60) in aqueous suspensions were performed by means of original microcalorimetric method and differential scanning calorimetry, respectively. Both materials display positive MCE that has been determined to be 0.004 and 0.016 K at 278 K in C60 and PyC60, respectively, when the magnetic induction changes from zero to 1.0 T. The increase in PyC60 MCE is observed despite the fact that the molar heat capacities values of substituted fullerene are two times higher than that of C60. These results along with calculated full energies, bond lengths and a charge on atoms according to Mulliken in fullerenes (PM3 and the Hartree–Fock in the basis of 3-21G, using Gaussian03) are interpreted as a reflection of an aromaticity and antiaromaticity areas state in fullerenes.

Microcalorimetric evaluation of the effects of three anthraquinone derivatives from Chinese Rhubarb and the synergistic effect of the mixture on Staphylococcus aureus

In this study, a noninvasive and nondestructive microcalorimetric method was used to investigate the antimicrobial activity of three anthraquinone derivatives (emodin, aloe-emodin and physcion) from Chinese Rhubarb. Additionally, we observed a synergistic antibacterial effect of a mixture (emodin + aloe-emodin) on Staphylococcus aureus. Antibacterial effects were further evaluated through principle component analysis and the half-inhibitory concentration (IC50) according to the influence of the anthraquinone derivatives on eight quantitative thermokinetic parameters, which were measured by isothermal microcalorimetry and obtained from metabolic power–time curves of Staphylococcus aureus growth at 37 °C. The inhibitory actions of the anthraquinone derivatives varied at different concentrations. The antibacterial effect of the derivatives on S. aureus was as follows: emodin + aloe-emodin (E + AE) > emodin (E) > aloe-emodin (AE) > physcion. Based on these results, the combined effect of emodin and aloe-emodin was stronger than that of each anthraquinone derivative alone. The combination of emodin and aloe-emodin is a promising antibacterial agent, providing a novel avenue for antibacterial materials.

Magnetocaloric behavior of REE porphyrin-based paramagnets at room temperature

REE complexes with cyclic aromatic ligands are ranked as the molecular materials with both electronic functionality and a single-molecule magnet behavior at temperatures lower 80 K. At the temperature close to room, they display a positive magnetocaloric effect (MCE) often comparable with one in ferromagnetics. We were determined MCE during the magnetization of both (5,10,15,20-tetra(4-tert-butylphenylporphinato))ytterbium(III)chloride, (Cl)YbT[Formula: see text]BuPP and (5,10,15,20-tetraphenylporphinato)ytterbium(III)chloride, (Cl)YbTPP in their aqueous suspensions over the temperature range of 278–320 K and in magnetic fields from zero to 1 T by the direct microcalorimetric method. Specific heat capacity in the solid of (Cl)YbT[Formula: see text]BuPP/(Cl)YbTPP has been directly determined in zero magnetic fields using differential scanning calorimetry. Thermodynamic parameters of ytterbium(III) complexes magnetization namely enthalpy/entropy change was determined. To improve understanding of the correlation between (Cl)YbT[Formula: see text]BuPP/(Cl)YbTPP magnetic properties and its electronic structure, we have compared magnetic behavior of paramagnets studied with those for (Cl)MTPP where M = Gd, Eu, Tm.

Investigation on flower-shaped Ni-doped Fe3O4/SnS2 formation mechanism through a microcalorimetric method and catalytic property as a Fenton-like catalyst

Flower-shaped Ni-doped Fe3O4/SnS2 composite was synthesized by a one-pot solvothermal method, where nanosized Ni-doped Fe3O4 particles were dispersed on the SnS2 sheets and these sheets built the flower-shaped structure. A microcalorimeter was employed to study the Ni-doped Fe3O4 formation processes with the SnS2. The experimental results indicated that the Ni-doped Fe3O4 formation mechanism is similar with and without the SnS2. Different endothermal processes demonstrated that the interaction between the cations (Fe3+, Fe2+ and Ni2+) and S2− induced various morphologies of the Ni-doped Fe3O4. Cluster-shaped Ni-doped Fe3O4 was synthesized without SnS2. The composite exhibited more excellent Fenton catalytic activity than the Ni-doped Fe3O4, SnS2, and the mixture is composed of the Ni-doped Fe3O4 and SnS2 with the same composition as the composite for the degradation of rhodamine B (RhB). RhB could be removed about 95% in 120 min at natural pH of the RhB solution (6.64) without irradiation for the Ni-doped Fe3O4/SnS2 composite as the catalyst. The present SnS2 enhanced adsorption capacity for RhB and the dispersed nanosized particles of Ni-doped Fe3O4, and the interaction between cations (Fe3+ and Fe2+) and S2− enhanced the conversion from Fe3+ to Fe2+, which induced excellent catalytic activity of the composite.

New paramagnets based on nanocarbon and cobalt(II)porphyrin: Magnetocaloric effect and specific heat capacity

Abstract This article represents the first unique data about a new paramagnets based on a carbon nanoform composited with cobalt(II) porphyrin with both a photoinduced electron transfer and a room-temperature magnetocaloric effect. Magnetocaloric effect values/magnetization thermodynamic parameters and specific heat capacity have been directly determined for the donor-acceptor triad derived from cobalt(II)5,10,15,20-(tetra-4-tert-butylphenyl)21H,23H-porphyrin and 1′-N-methyl-2′-(pyridin-4-yl)pyrrolidino[3′,4′:1,2][60]fullerene via axial coordination and compared with those for C60 and the precursors. The studies were performed by the original microcalorimetric method developed by us and differential scanning calorimetry. The samples display the positive magnetocaloric effect that has been determined to be equal, to 0.004 (C60), 0.016 (PyC60), 0.028(porphyrin complex), and 0.007 K (triad) at 278 K and 1.0 T. The magnetocaloric effect values observed are comparable with those in metal-based magnetic materials but unlike those, the studied triad demonstrates a photoinduced electron transfer. The contributions of aromatic electron systems to the magnetization thermodynamic parameters have been analyzed.

Synthesis and characterization of three-dimensional sea urchin-like AgBr/TiO2 microspheres with enhanced antibacterial and visible-light photocatalytic performance

Three-dimensional (3D) AgBr/TiO2 microspheres with remarkable sea urchin-like architectures were prepared by a solvothermal-hydrothermal two-step process. The products have been characterized through XRD, SEM, HRTEM and Nitrogen adsorption–desorption analysis. The antibacterial activity of the 3D AgBr/TiO2 microspheres against Escherichia coli (E. coli) was investigated quantitatively by microcalorimetric method for the first time. Meanwhile, the visible-light photocatalytic performance of the 3D AgBr/TiO2 microspheres was also evaluated for the degradation of rhodamine B (RhB). As a contrast, the same tests were carried out for the conventional AgBr/P25 (TiO2). The results show that the 3D AgBr/TiO2 microspheres prevent better antibacterial and visible-light photoctalytic performance than the conventional AgBr/P25. It revealed that unique morphology effect, the extraordinary visible-light responses of AgBr and various oxidative radicals produced by visible light irradiated 3D AgBr/TiO2 microspheres are responsible for improved antibacterial and photocatalytic performance.

Heats of exchange of chloride with pyridinecarboxylate ions in Dowex-1 anion exchanger

The heats of exchange of chloride with pyridinecarboxylic acids anions in Dowex-1 strongly basic anion exchanger was obtained by the microcalorimetric method at 298 K. Nicotinic acid, isonicotinic acid, dipicolinic and cinchomeronic acids as pyridinecarboxylic acids were selected. It has been revealed that the sorption of pyridinecarboxylic acid anions by Cl form of Dowex-1 anion exchanger from aqueous solutions is the endothermic process. The standard enthalpy values of the exchange of chloride by pyridinecarboxylate ions in Dowex-1 anion exchanger calculated via microcalorimetric experimental data are in the range of 3–14 kJ mol−1. The standard enthalpies of model reaction that simulated the anion exchange process were determined via quantum chemical calculations of the reagent formation enthalpies in vacuum in the framework of the MOPAC2016 program. The enthalpies of both ion exchange of chloride by pyridinecarboxylate and the model reaction increase in the sequence: nicotinate, isonicotinate, anion of dipicolinic acid, anion of cinchomeronic acid.

Exploring an in situ LED-illuminated isothermal micro-calorimetric method to investigating the thermodynamic behavior of Chlorella vulgaris during CO2 bio-fixation.

Much endeavor has been dispensed recently to evaluate the potential of CO2 mitigation by microalgae. We introduce an alternative, novel, LED-illumination isothermal microcalorimetric method to assess the thermodynamic behaviors of microalgae for better understanding of their carbon sequestration capacity. Microalgae thermodynamic behaviors were recorded as power-time curves, and their indices such as total heat evolution (QT), maximum power output (Pmax) and heat generated by per algae cell (JN/Q) were obtained. The values for highest (74.80gL-1) and control sample (0.00gL-1) of QT, Pmax and JN/Q were 20.85 and 2.32J; 252.17 and 57.67μW; 7.91 × -06 and 8.80 × -07Jcell-1, respectively. According to the values of QT, a general order to promote the CO2 sequestration was found at 74.8gL-1> 29.92gL-1> 14.96gL-1> 7.48gL-1> 0gL-1 of C sources, which directly corresponded to carbon availability in the growth medium. Chlorella vulgaris GIEC-179 showed the highest peak Pmax at 74.8gL-1 concentration which was directly transformed to their biomass during bio-fixation of CO2 process. This study is applicable for better understanding of CO2 fixation performance of algae.

Physicochemical and catalytic properties of Pd/MoO3 prepared by the sonophotodeposition method

Molybdenum trioxide-supported palladium catalyst Pd/MoO3(SPD) is prepared by the sonophotodeposition procedure (SPD). This method combining sonication with ultraviolet irradiation is used at room temperature and atmospheric pressure and does not require the use of chemical reducing agent. For comparison, the Pd/MoO3 catalysts are also prepared by the ultrasound irradiation and traditional impregnation - H2 reduction methods. The Pd/MoO3 catalysts are characterized by X-ray diffraction (XRD), electron microscopy (SEM, TEM, HRTEM), energy dispersive (EDS, STEM) analysis and X-ray photoelectron spectroscopy (XPS). The SPD treatment improves the platelets-like morphology of the MoO3 oxide grains making more difficult formation of hydrogen bronzes HXMoO3 (x > 0.9) studied by microcalorimetric method. The “in situ” reduction of precursor ions during the SPD treatment generates much better dispersed Pd-nanoclusters than other preparation methods. It results in much higher activity of Pd/MoO3(SPD) catalyst for the cinnamaldehyde hydrogenation than its MoO3-supported counterparts and Pd/SiO2, a reference catalyst.

Toxic effects of binary toxicants of cresol frother and Cu (II) on soil microorganisms

As the scale and intensity of mining increase, the application of mineral agents raises concerns about its environmental impact, but little information is available on the combined toxic effect of cresol frothing agent and Cu2+ on the soil microbial activity. In this work, microcalorimetric method, enzyme activity and Illumina HiSeq 2500 high throughput sequencing technology were combined to determine the effect of binary toxicants on soil microorganisms. The dose-toxicity relationship obtained from microcalorimetry experiments indicated that an increase in dosage was associated with a decrease in metabolic rate constant k (or an increase in the inhibitory ratio). The ratio of 400/0.08 (mg·L−1/mg·g−1) of Cu2+/cresols stimulated the growth of microorganisms in soil. Urease and fluorescein diacetate esterase activities upon the exposure of binary toxic mixture showed a negative impact and the toxicity order followed: Cu2+/p-cresol > Cu2+/o-cresol > Cu2+/m-cresol. By Illumina HiSeq 2500 high throughput sequencing technology, the results of microbial communities in 3 soil samples showed no significant differences, and Proteobacteria, Acidobacteria, Gemmatimonadetes and Bacteroidetes phyla were the dominant species as Gram-negative bacteria.

Effect of CO2 dilution on propane–air isothermal catalytic combustion on platinum

The present work aims to investigate several kinetic aspects of catalytic combustion of the stoichiometric propane–air mixture on a platinum wire in the presence of progressive CO2 dilution, using a micro-calorimetric method. The method allowed the determination of the induction periods and of the reaction rates during transient and steady-state regimes at different initial pressures P 0 (10–101 kPa), wire temperatures T w (470–575 K) and gas-phase composition. The kinetic parameters were evaluated from regression analysis using empirical and mechanistic models. The dilution with CO2 of the stoichiometric propane–air mixture (4.02% propane) was 10, 20, 30, 40, 50%. For additions equal to or greater than 23%, the gaseous system is outside the flammability limits reported in the literature. The kinetic characteristics of the catalytic combustion remain similar for the whole range, even for 50% CO2 addition when the propane concentration in mixture diminishes to 2%, a concentration smaller than the lower explosion limit in air in normal conditions.

Reactivity of t-butyl hydroperoxide and t-butyl peroxide toward reactor materials measured by a microcalorimetric method at 30 °C

To investigate the oxidation of isobutane to t-butyl hydroperoxide (TBHP) for the first time as a two-phase process in a microreactor in a broad range of flow rates (isobutane flow rate: 15–188 µL min−1, oxygen: 0.1–1.5 mL min−1), temperatures (75–150 °C) and pressures (25–100 bar), a study has been performed to select the most appropriate construction materials for the experimental facility, especially for the microreactor but also for fittings, sealings, sensors, pumps, tubes, the sampling unit, etc. TBHP, as most hydroperoxides, is quite reactive and reacts with most metals, polymers, acids and bases. Therefore, the materials most appropriate had to be determined to minimize losses of TBHP in the initiator pump and in the reaction mixture of the sample at ambient temperature. As TBHP decomposes very slowly under such conditions, a microcalorimetric method has been used to measure the heat production of TBHP in contact with selected materials at 30 °C. Among those materials, various metals, e.g., copper, gold, silver, zinc, aluminum, titanium, tantalum, normal steel, Hastelloy C276, Hastelloy C-2000, V4A steel, and semiconductors like silicon and silicon carbide have been tested. Furthermore, several polymers like nitrile butyl rubber, PEEK, silicone, Chemraz® and PTFE have been studied. Moreover, the role of metals and metal ions as catalysts for the decomposition of TBHP and DTBP is discussed. The experiments showed that silver and copper are the most reactive metals of the investigated substances and silicon the most suitable coating material for the reactor. The most stable polymers were found to be PEEK and PTFE.