Knudsen Effusion Mass Spectrometry Research Articles

Thermodynamic properties of the Gd2O3-Y2O3-HfO2 system studied by high temperature Knudsen effusion mass spectrometry and optimized using the Barker lattice theory

The vaporization processes and thermodynamic properties of twenty samples in the Gd2O3-Y2O3-HfO2 system in a wide concentration range were studied by high-temperature Knudsen effusion mass spectrometry. At the temperature 2500 K the main vapor species were GdO, YO, and O. From the measured values of their partial pressures activities of the Gd2O3 and Y2O3 as functions of concentration were determined. The HfO2 activity was calculated by the Gibbs-Duhem integration. The resulting excess Gibbs energy function exhibited negative deviations from ideal behavior. For the optimization of the obtained thermodynamic functions of the ternary Gd2O3-Y2O3-HfO2 system the generalized Barker-Guggenheim theory of associated solutions was applied. In an alternative computing procedure the same model was used, but the optimization was based on the available literature data for the corresponding binary Gd2O3-Y2O3, Gd2O3-HfO2, and Y2O3-HfO2 systems. Thus, the Barker lattice model may be used for estimation of the thermodynamic functions of a ternary system on the basis of the data for the corresponding binary sub-systems.

A method for extracting calibrated volatility information from the FIGAERO-HR-ToF-CIMS and its experimental application

Abstract. The Filter Inlet for Gases and AEROsols (FIGAERO) is an inlet specifically designed to be coupled with the Aerodyne High-Resolution Time-of-Flight Chemical Ionization Mass Spectrometer (HR-ToF-CIMS). The FIGAERO-HR-ToF-CIMS provides simultaneous molecular information relating to both the gas- and particle-phase samples and has been used to extract vapour pressures (VPs) of the compounds desorbing from the filter whilst giving quantitative concentrations in the particle phase. However, such extraction of vapour pressures of the measured particle-phase components requires use of appropriate, well-defined, reference compounds. Vapour pressures for the homologous series of polyethylene glycols (PEG) ((H-(O-CH2-CH2)n-OH) for n=3 to n=8), covering a range of vapour pressures (VP) (10−1 to 10−7 Pa) that are atmospherically relevant, have been shown to be reproduced well by a range of different techniques, including Knudsen Effusion Mass Spectrometry (KEMS). This is the first homologous series of compounds for which a number of vapour pressure measurement techniques have been found to be in agreement, indicating the utility as a calibration standard, providing an ideal set of benchmark compounds for accurate characterization of the FIGAERO for extracting vapour pressure of measured compounds in chambers and the real atmosphere. To demonstrate this, single-component and mixture vapour pressure measurements are made using two FIGAERO-HR-ToF-CIMS instruments based on a new calibration determined from the PEG series. VP values extracted from both instruments agree well with those measured by KEMS and reported values from literature, validating this approach for extracting VP data from the FIGAERO. This method is then applied to chamber measurements, and the vapour pressures of known products are estimated.

Experimental thermodynamic investigation of the liquid Cu-Li-Sn system by Knudsen Effusion Mass Spectrometry

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.

Thermal analysis and Knudsen effusion mass spectrometry combined in a specially-adapted commercial skimmer coupled instrument (Netzsch)

The paper is aimed at informing on Netzsch STA 409 CD/3/403/5/G apparatus, a specially-adapted type of the commercial STA 409 CD - QMS 403/5 Skimmer Coupling Instrument combining methods of thermal analysis with Knudsen effusion mass spectrometry. Construction parameters as well as advantages and disadvantages of the instrument are presented. The instrument can be used for a broad spectrum of studies in materials field from which some of them, including e.g. thermodynamic and phase transformations studies, study of surface and catalytic processes, investigation of materials on multiscale level, are demonstrated. The new multifunction design as well as the instrument capabilities are discussed with respect to already published information.

Vaporization behavior of Na2CO3 and K2CO3

Sodium and potassium carbonates are important components of high temperature materials. Therefore, information on gas phase is important for modelling of long term processes, where the stability of carbonates should be taken into account. In this study the vaporization behavior of Na2CO3 and K2CO3 has been studied with Knudsen Effusion Mass Spectrometry in the temperature range from 600 to 880 °C. It was established, that vaporization of sodium and potassium carbonates is close to congruent conditions at temperatures below 750 °C with the main species M, CO2 and O2 in the gas phase. The vapor pressures of these species are in a good agreement with the calculated values within an error of ± 30%, which are based on the available thermodynamic information including formation enthalpies of M2CO3(s) and M(g), CO2(g) and O2(g) and corresponding thermodynamic functions. At high temperatures above 750 °C incongruent vaporization was observed due to a disproportional increase of the vapor pressure of CO2. On this stage also Na2O+, K2O+ and K2CO3+ ions were registered in the mass spectra. Based on the analysis of fragmentation processes of M2CO3 molecules, the sublimation enthalpy ∆subH°298(K2CO3) is obtained to be 360 kJ/mol.

Vaporisation studies on Sn-Te-O system by Knudsen effusion mass spectrometry: Thermodynamic properties over (SnO2+SnTe3O8) biphasic region

Vaporisation studies along the pseudo binary line of SnO2–TeO2 (SnTe3O8 + SnO2) in the Sn-Te-O system were conducted by using Knudsen effusion mass spectrometry in the temperature range 843–968 K. SnTe3O8 vaporises incongruently and TeO2(g), TeO(g), Te2(g) and O2(g) were the neutral species observed over the equilibrium vapour. Partial pressure – temperature (p-T) relations of TeO2(g), TeO(g), Te2(g) over (SnTe3O8 + SnO2) “two phase” region were determined in the temperature range 843–968 K. Partial pressures of O2(g) were calculated by considering gas phase equilibrium reactions involving this species and TeO2(g), TeO(g), Te2(g). Using the p-T relations, enthalpy changes of the following reactions were evaluated: SnTe3O8(s) ⇌ SnO2(s) + 3TeO2(g); SnTe3O8(s) + 2TeO(g) ⇌ 4TeO2(g) + 0.5 Te2(g) + SnO2(s) and 0.5Te2(g) + TeO2(g) ⇌ 2TeO(g). Subsequently, the enthalpy and Gibbs energy of formation of SnTe3O8 phase at 298.15 K were deduced as ΔfHm° = −1613.7 ± 67.8 kJ mol−1 and ΔfGm° = −1386.7 ± 67.8 kJ mol−1. Knudsen effusion mass spectrometric studies on this system are being reported for the first time.

Measurement 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).

Study of thermal stability of CoSb3 skutterudite by Knudsen effusion mass spectrometry

Thermoelectric materials play an important role in the field of renewable energy for their ability of thermal energy conversion into electricity (thermoelectric generator) and reversibly electric energy conversion into thermal energy (thermoelectric heat pump or Peltier cooling). Doped CoSb3 based skutterudites represent one of the very promising categories for the development of highly efficient thermoelectric materials for the conversion of waste heat to electricity. The thermoelectric efficiency, however, is closely related to thermal and phase stability as the current materials contain volatile elements (Sb, Sr, Yb, etc.), which can evaporate at operation conditions and thus cause structure changes and damage the thermoelectric properties. For a better understanding of the thermal behaviour of complex multicomponent CoSb3 based skutterudite systems, a study of the thermal stability of primary CoSb3 skutterudite is necessary.In this work, the thermal and phase stability of primary CoSb3 skutterudite prepared by ball milling and hot pressing was investigated using thermal analysis and Knudsen effusion mass spectrometry performed on a Netzsch STA 409 CD/3/403/5/G apparatus, a specially-adapted type of the commercial STA 409 CD - QMS 403/5 Skimmer Coupling Instrument. Results, including data on phase transformations and those from vapour pressure measurements of antimony, supported by measurements of diffusion profiles and microstructure observations are summarized and used for evaluation of the long term thermal stability of the material.

Study of surface effects and catalytic properties of selected Ni-based bimetallic nanoparticles by Knudsen effusion mass spectrometry

Surface effects and catalytic properties of CuNi, AgNi and AuNi bimetallic nanoparticles having diameter 10–30 nm were studied by Knudsen effusion mass spectrometry. The nanoalloys were prepared by solvothermal synthesis using oleylamine. Gradual removing of the organic substances, present on the nanoparticles from the synthesis, accompanied by their oxidation was observed during slow heating. The nanoparticle catalytic activity leading to the oxidation of the organic surface layer to CO2 in final step depends on the selected element in the Ni-based nanoalloy. The CuNi system shows the highest catalytic activity while the AuNi system the smallest one. As demonstrated, the KEMS method can be applied with advantage as a progressive tool for the evaluation of the oxidation catalytic activity of metal nanoparticles. The surface effects and the catalytic properties are discussed in view of our previous studies.

Vaporization studies on sodium oxide

The vaporization of pure Na2O(c) was investigated at temperatures of 900–1165 K with the method of Knudsen Effusion Mass Spectrometry (KEMS). Thermodynamic quantities of sublimation enthalpy, entropy and Gibbs energy were derived from the partial pressures of gaseous species Na and O2 over the pure sodium oxide reference samples. The sublimation enthalpies obtained for the reaction “Na2O = 2 Na(g) + ½ O2(g)” are for Na: ∆subH10000 = 243 ± 4, 2nd Law, and 241 ± 3, 3rd law. For O2: ∆subH10000 = 242 ± 2, 2nd Law, and 241 ± 2, 3rd law kJ mol−1. The Gibbs energy ∆subG10000 and entropy ∆subS10000 for sublimation were determined as 133 ± 5 kJ mol−1 and 110 ± 2 J mol−1 K−1 for sodium, and for O2: ∆subG10000=143 ± 4 kJ mol−1 and entropy ∆subS10000 = 100 ± 2 J mol−1 K−1.From the equilibrium constant for the reaction Na2O(c) = 2Na(g) + ½ O2(g) the enthalpy ∆rH10000 resulted in 605 ± 6, 2nd law, and 611 ± 9 kJ mol−1, 3rd law. The Gibbs energy ∆rG10000 and entropy ∆rS10000 were deduced as 342 ± 9 kJ mol−1 and 269 ± 5 J mol−1 K−1.

Sublimation enthalpies of terbium and lutetium triiodides and formation enthalpies of their monomer and dimer molecules

The sublimation of terbium and lutetium triiodides was studied by Knudsen effusion mass spectrometry. The temperature dependencies of partial vapor pressures [atm] of the monomer and dimer molecules were determined as: lnp(TbI3) = – (31.74 ± 0.24)× 103/T + (21.43 ± 0.29) for 743–906 K; lnp(Tb2I6) = – (38.66 ± 0.38)× 103/T + (25.63 ± 0.46) for 786–906 K; lnp(LuI3) = – (31.48 ± 0.25)× 103/T + (22.28 ± 0.30) for 721–951 K; and lnp(Lu2I6) = – (36.95 ± 0.37)× 103/T + (25.21 ± 0.43) for 796–950 K. On the basis of a joint analysis of all literature data, the sublimation enthalpies [kJ mol–1] at 298.15 K are recommended as 281 ± 3 (TbI3), 346 ± 30 (Tb2I6), 279 ± 12 (LuI3), and 340 ± 30 (Lu2I6). The standard formation enthalpies [kJ mol–1] of the gaseous species at 298.15 K are –343 ± 4 (TbI3), –902 ± 30 (Tb2I6),–326 ± 12 (LuI3), and –870 ± 30 (Lu2I6).

Review KEMS 2012 till 2017

Review on the main results on high temperature behavior of inorganic systems and materials obtained by the Knudsen effusion mass spectrometry (KEMS) during last five years is presented. The available information on vaporization processes and thermodynamic properties of these systems found recently is discussed with the indication of its great importance for the developing of advanced high temperature materials that may be used in the various fields of modern technologies such as space, nuclear and optical industries.

Study of thermal stability of p-type skutterudites DD0.7Fe3CoSb12 by Knudsen effusion mass spectrometry.

The temperature and phase stability of p-type skutterudites, DD0.7Fe3CoSb12, manufactured via various preparation techniques, all exhibiting a high ZT-level, have been studied by means of thermal analysis and Knudsen effusion mass spectrometry. The results from phase transformation measurements and characteristics of the evaporation of antimony, as the volatile element, supported by microstructure observations and by diffusion profiles are summarized and discussed in view of a full understanding of the degradation processes and knowledge of the long term operation stability of the bulk and nano-structured thermoelectrics studied. It was found out that the antimony evaporation is a complex diffusion kinetic process resulting in a stable Sb level dependent on the preparation route. The studied p-type skutterudites, DD0.7Fe3CoSb12, have proven their long term stability in thermoelectric devices at a maximum operation temperature of 600 °C. Complementary data on the structural, physical and mechanical properties of the materials are presented as well.

Vaporization Thermodynamics of Polymeric Cadmium Pivalate

The vaporization of cadmium pivalate CdPiv2 with a polymeric structure was studied by the Knudsen effusion mass spectrometry of the gas phase. The sublimation of this complex was found to be congruent and to be accompanied by thermal dissociation with the formation of metal atoms and organic compounds due to its polymeric character. The standard enthalpies of vaporization were found, and the standard formation enthalpy of condensed cadmium pivalate was calculated. Highly volatile cadmium compounds could be synthesized via the introduction of additional ligands able to saturate the coordination sphere of the central atom.

Synthesis, structure, stability and phase diagrams of selected bimetallic silver- and nickel-based nanoparticles

An overview of the research on silver-based (Ag-Sn, Ag-Cu, Ag-Ni) and nickel-based (Cu-Ni, Au-Ni, Ni-Pt) bimetallic nanoparticles is presented. The investigated nanoparticles in this review are formed by elements that represent an important group of metals revealing fcc lattice under macro-sized conditions (with the exception of Sn). The effects of surface stabilizing layer of the alloy nanoparticles are also described. Our experience with synthesis, characterization and stabilization of alloy nanoparticles is summarized. The development of the nanoparticle synthesis represents an important and mandatory part of the experimental nanoalloy research. Main synthetic routes under focus are the low temperature borohydride reduction method, the high temperature oleylamine synthesis, and the high pressure method in autoclave. The subsequent structural studies are focused on both nanoparticle core and outer stabilizing layer. The cores of the nanoparticles are studied mainly by electron microscopy techniques. The phase stability of the nanoparticle core is investigated by thermal analysis. The Knudsen effusion mass spectrometry was applied for studies of stabilizing organic molecules that can be found on the surface of the nanoparticles. The presented overview of the experimental results is complemented by thermodynamic calculations of phase diagrams by the CALPHAD method.

Thermodynamics of the heterogeneous equilibria in the In2O3–ZnO system by Knudsen effusion mass spectrometry

A thermodynamic study of the In2O3–ZnO quasi-binary system was performed by Knudsen effusion mass spectrometry in isothermal conditions at 1428 K. The Zn7In2O10 and Zn5In2O8 compounds which are stable at that temperature were determined to vaporize incongruently so that only ZnO transfers into the gas phase. The vapor composition and partial pressures of the vapor species were determined and the component activities were computed in different phase fields of the system. Standard Gibbs energies and standard enthalpies of some heterogeneous reactions involving Zn7In2O10 and Zn5In2O8 as well as the standard enthalpies of formation of the compounds were calculated.

Ion-molecular equilibria in lanthanide triiodide vapors and formation enthalpies of LnI4− and Ln2I7− ions (Ln = La, Ce, Pr, Gd, Tb, Tm, and Lu)

Ion-molecular equilibria LaI4– + LnI3 = LnI4– + LaI3, Ln2I7– = LnI3,cr + LnI4– (Ln = Ce, Pr, Gd, Tb, Tm, and Lu), and 3LaBr4– + 4LaI3 = 3LaI4– + 4LaBr3 in vapors over the LaI3-CeI3-PrI3-GdI3, LaI3-GdI3-TbI3-TmI3, and LaI3-LaBr3 mixtures and the pure lanthanide triiodides were studied in the temperature range of 700–1050 K by Knudsen effusion mass spectrometry. The equilibrium constants were measured and the reaction enthalpies were calculated by the techniques of the second and third laws of thermodynamics. The standard formation enthalpies of ions, ΔfH°(298.15 K) (in kJ mol–1), were determined to be –832 ± 21 (LaI4–), –834 ± 23 (CeI4–), –834 ± 25 (PrI4–), –812 ± 24 (GdI4–), –813 ± 25 (TbI4–), –817 ± 23 (TmI4–), –806 ± 25 (LuI4–), –1399 ± 45 (La2I7–), –1402 ± 46 (Ce2I7–), –1417 ± 47 (Pr2I7–), –1356 ± 47 (Gd2I7–), –1365 ± 47 (Tb2I7–), –1366 ± 46 (Tm2I7–), and –1322 ± 47 (Lu2I7–).

Vaporization features of CeO2[sbnd]ZrO2 solid solutions at high temperature

Ceria-zirconia solid solutions are the important materials for the application in catalysis and the energy conversion. However, the existing data on the thermodynamic properties of ceria-zirconia solid solutions which is used to distinguish their stability is controversial. In the present work, equilibrium ceria-zirconia solid solutions with 90, 50, 24 and 9 mol.% CeO2 were manufactured using the original sol-gel reverse co-precipitation method with further prolonged thermal treatment for 5–50 h at 973–1373 K. Comprehensive characterizations of the precursor powders obtained were performed via SEM, STA, XRD, ESCA and PSD-analysis. According to XRD observations combined with Rietvield refinement and ESCA the equilibrium solid solutions without an admixture of Ce3+ in the condensed phase were obtained after the calcination of samples at 1373 K. Knudsen effusion mass spectrometry was used to study the vaporization processes and the thermodynamic properties of solid solutions in the CeO2ZrO2 system at 2150 K. Similar dependence of the CeO2 activity on the condensed phase composition was obtained for solid solutions with various ceria contents, which ensured the equilibrium evaporation. The schematic evaporation process for xCeO2-(100-x)ZrO2 solid solutions at 2100–2500 K was suggested for the first time. It was found, that high temperature behavior of CeO2ZrO2 system significantly differs from its behavior at lower temperatures, i.e. 873–1373 K, when Ce (IV) to Ce (III) reduction takes place.

MASP-1 and MASP-3 play independent roles in activation of the lectin and alternative complement pathways

A thermodynamic study of the In2O3–ZnO quasi-binary system was performed by Knudsen effusion mass spectrometry in isothermal conditions at 1428 K. The Zn7In2O10 and Zn5In2O8 compounds which are stable at that temperature were determined to vaporize incongruently so that only ZnO transfers into the gas phase. The vapor composition and partial pressures of the vapor species were determined and the component activities were computed in different phase fields of the system. Standard Gibbs energies and standard enthalpies of some heterogeneous reactions involving Zn7In2O10 and Zn5In2O8 as well as the standard enthalpies of formation of the compounds were calculated.

Thermodynamic properties of gaseous cerium molybdates and tungstates studied by Knudsen effusion mass spectrometry.

CeO2 -WO3 and CeO2 -MoO3 catalysts have shown excellent performance in the selective reduction of NOx by ammonia (NH3 -selective catalytic reduction) over a wide temperature range. Strong interaction between CeO2 and WO3 or MoO3 might be the dominant reason for the high activity of these mixed oxides. Studies of ceria-containing gaseous salts involve considerable experimental difficulties, since the transition of such salts to vapor requires high temperatures. To predict the possibility of the existence of gaseous associates formed by cerium and molybdenum (tungsten) oxides it is important to know their thermodynamic characteristics. Until the present investigation, gaseous cerium oxyacid salts were unknown. Knudsen effusion mass spectrometry was used to determine the partial pressures of vapor species and the equilibrium constants of gas-phase reactions, as well as the formation and atomization enthalpies of gaseous cerium molybdates and tungstates. CeO2 was evaporated from molybdenum and tungsten effusion cells containing gold metal as a pressure standard. A theoretical study of gaseous cerium gaseous molybdates and tungstates was performed by several quantum chemical methods. In the temperature range 2050-2400 K, CeO, CeO2 , XO2 , XO3 , CeWO3 , CeXO4 , CeXO5 (X = Mo, W) and CeMo2 O7 were found to be the main vapor species over the CeO2 - Mo (W) systems. On the basis of the equilibrium constants of the gaseous reactions, the standard formation enthalpies of gaseous CeWO3 , CeXO4 , CeXO5 (X = Mo, W) and CeMo2 O7 at 298 K were determined. Energetically favorable structures of gaseous cerium salts were found and vibrational frequencies were evaluated in the harmonic approximation. The thermal stability of gaseous cerium oxyacid salts was confirmed by high-temperature mass spectrometry. Reaction enthalpies of the gaseous cerium molybdates and tungstates from gaseous cerium, molybdenum and tungsten oxides were evaluated theoretically and the obtained values are in reasonable agreement with the experimental one.