Mass-spectrometric study of molecular and ionic sublimation of gadolinium and terbium tribromides in Knudsen and Langmuir modes

Molecular and ionic sublimation of gadolinium and terbium tribromides in Knudsen and Langmuire modes was studied by the method of high-temperature mass-spectrometry. On the basis of obtained enthalpies of sublimation and ion-molecule reactions the enthalpies of formation of LnBr3 and Ln2Br6 molecules and LnBr4− and Ln2Br7− negative ions were determined. For the first time the electron work function for crystals of the studied tribromides was calculate

Study of Molecular and Ionic Vapor Composition over CeI3 by Knudsen Effusion Mass Spectrometry

The molecular and ionic composition of vapor over cerium triiodide was studied by Knudsen effusion mass spectrometry. In the saturated vapor over CeI3 the monomer, dimer, and trimer molecules and the negative ions I−, CeI4−, and Ce2I7− were identified in the temperature range of 753–994 K. The partial pressures of CeI3, Ce2 I6, and Ce3I9 were determined and the enthalpies of sublimation, Δ

Predictors of Early Retinal Changes in Diabetes Mellitus

Purpose. Determining the functional state of the outer and inner retina’s layers in patients with diabetes mellitus (DM) type 1 and 2 before the clinical manifestations and in the early stages of diabetic retinopathy (DR) using the methods of multifocal electroretinography (mfERG) and microperimetry (MP).Patients and methods. 91 patients were examined (182 eyes). The patients were divided into 4 groups: 1st — 23 people (46 eyes) with diabetes without DR (the duration of the disease is up to 2 years); 2nd — 22 people (44 eyes) with diabetes without DR (diabetes from 2 to 8 years); 3rd — 24 people (48 eyes) with NPDR on the background of diabetes; 4th — 22 people (44 eyes) of the control group (healthy eyes). In addition to the standard ophthalmologic examination, all patients were registered mfERG (FOK1) on the diagnostic equipment EP-1000 Multifocal (Tomey, Germany) and carried out MP using the device “MAIA” (CenterVue, Italy).Results. According to mfERG, it has been established that the components of mfERG, the biopotential density and the amplitude of P1, are most sensitive to diabetic changes. In groups with type 1 and type 2 diabetes, there is a significant decrease in the density of P1 in comparison with the control group (p < 0.005, Mann-Whitney test), as well as a decrease in the amplitude of P1 on almost all tested rings (p < 0.005). In all groups, there is an increase in the latency of P1 in the central ring (0–2.3°). According to MP data, it was found that patients with type 1 and type 2 diabetes showed a decrease in the average light sensitivity in comparison with the control group, however, our data are within the reference values, regardless of the presence or absence of clinical manifestations of PD.Conclusion. As a result of the study, early functional and morphological disorders of the neurosensory apparatus of the eye in diabetes were identified. It is proved that mfER and MP allow to detect violations at the preclinical stage of DR and are necessary studies for the dynamic control of the progression of DR

Thermodynamic Properties of Al-Cr-Fe Alloys: Experimental Investigation by Knudsen Effusion Mass Spectrometry

Vaporization of ternary Al-Cr-Fe and binary Al-Fe, and Cr-Fe alloys has been investigated in the temperature range 1234-1608 K by Knudsen effusion mass spectrometry (KEMS). The atoms Al, Cr, and Fe were found to be the only vapor species. Partial pressures of the elements were evaluated from the measured ion intensities and thermodynamic activities of the alloy components were determined by pressure ratio method (p/p°). Reliable partial and integral molar enthalpies, entropies and Gibbs energies for all the components have been obtained for the systems under investigation. The partial molar enthalpies and entropies were found to be nearly temperature independent over the wide temperature range investigated.</jats:p

Measurment of Thermodynamic Activity of Zirconia in Yttria-Stabilized Zirconia Electrolyte for Solid Oxide Fuel Cell Application

The Knudsen effusion mass spectrometry technique was applied to determine the activity of ZrO2 in 8 mol% yttria-stabilized zirconia (8YSZ) in the temperature range from 2200 K to 2500 K. The minor ZrO2+ ion current was used in calculations instead of the prevailing ZrO+ signal. The phase stability of the samples and their negligible interaction with the cell material was proved by XRD-analysis. The activity of ZrO2 was obtained to be 0.84 ± 0.04 independent of temperature. This fact allows estimating the same value of activity in the operating temperature range of solid oxide fuel cells (SOFCs)

Thermal Emission of Alkali Metal Ions from Al30-Pillared Montmorillonite Studied by Mass Spectrometric Method

The thermal emission of alkali metal ions from Al30-pillared montmorillonite in comparison with its natural form was studied by mass spectrometry in the temperature range 770–930 K. The measurements were carried out on a magnetic mass spectrometer MI-1201. For natural montmorillonite, the densities of the emission currents (j) decrease in the mass spectrum in the following sequence (T = 805 K, A/cm2): K+ (4.55 · 10−14), Cs+ (9.72 · 10−15), Rb+ (1.13 · 10−15), Na+ (1.75 · 10−16), Li+ (3.37 · 10−17). For Al30-pillared montmorillonite, thermionic emission undergoes temperature-time changes. In the low-temperature section of the investigated range (770–805 K), the value of j increases substantially for all ions in comparison with natural montmorillonite (T = 805 K, A/cm2): Cs+ (6.47 · 10−13), K+ (9.44 · 10−14), Na+ (3.34 · 10−15), Rb+ (1.77 · 10−15), and Li+ (4.59 · 10−16). A reversible anomaly is observed in the temperature range 805–832 K: with increasing temperature, the value of j of alkaline ions falls abruptly. This effect increases with increasing ionic radius of M+. After a long heating-up period, this anomaly disappears and the lnj-1/T dependence acquires a classical linear form. The results are interpreted from the point of view of the dependence of the efficiency of thermionic emission on the phase transformations of pillars

Experimental Thermodynamics of New Electrode Materials for Li-Ion Batteries

Vaporization of five liquid binary Li-Sn alloys (molar fractions x Li = 0.1; 0.2; 0.3; 0.4; and 0.5) as well as pure Li have been investigated in the temperature range 576-1040 K by Knudsen effusion mass spectrometry (KEMS). The Thermodynamic activity of lithium was determined by the ratio of ion current intensities measured over the alloy and the pure metal. The activity of tin was determined by Gibbs-Duhem integration. The results were approximated by Redlich-Kister sub-regular solution model and compared with the available literature data.</jats:p

Experimental Thermodynamics of the Li-Sn System by Knudsen Effusion Mass Spectrometry

The vapourization of five liquid binary Li–Sn alloys (xLi = 0.1; 0.2; 0.3; 0.4 and 0.5) and three solid binary Li–Sn alloys (xLi = 0.71; 0.76 and 0.81) was investigated in the temperature range from 648 K to 1014 K by Knudsen Effusion Mass Spectrometry (KEMS). It is the first time that an intensive KEMS investigation was carried out for a wide composition range of this binary system. From the obtained temperature dependence of the thermodynamic activities, thermodynamic properties, such as mixing enthalpies and entropies, were calculated. In addition, sublimation enthalpies for pure lithium, recalculated to 0 K by the enthalpy increment functions of Li(c) and Li(g), demonstrated the stability and accuracy of the experimental setup. The obtained thermodynamic data agree with the corresponding literature data, thus showing the feasibility of this method for determining the thermodynamic data of lithium-ion battery materials

Experimental Thermodynamic Investigation of the Liquid Cu-Li-Sn System by Knudsen Effusion Mass Spectrometry 2

The thermodynamic activity of lithium was measured by Knudsen Effusion Mass Spectrometry (KEMS) within the Cu-Li-Sn system in the liquid region. For this purpose, eleven samples were studied between 773 and 1078 K in the Sn-rich part of the Cu-Li-Sn phase diagram. Mixing enthalpies, entropies and Gibbs energies were derived directly from the measured thermodynamic activity. The measured thermodynamic activities of Li were fitted to the Redlich-Kister-Muggianu (RKM) sub-regular solution model, by taking ternary interactions into account, using a mathematical regression procedure. Thereby, the partial and integral excess thermodynamic properties, the activities of Li, Cu and Sn and the ternary interaction L-parameters, as a function of temperature, were obtained