Oxide Ion Concentration Research Articles

High-Temperature Protonic Conduction in La2NiO4+ δ-Based Ruddlesden-Popper Type Oxides: Correlation with Concentration of Interstitial Oxide Ions.

Oxygen-excess La2NiO4+ δ (LNO) conducts oxide ions, electron holes, and hydroxide ions simultaneously on exposing to wet oxygen, exhibiting the potential as a cathode material in protonic ceramic fuel cells. Since the incorporation of protons in oxygen-excess LNO is via the hydration reaction assisted by interstitial oxide ions, in this work, the concentration of interstitial oxide ions is reduced and increased by substituting Ni with Cu and Co, respectively. A higher concentration of interstitial oxide ions leads to a high proton concentration, indicating the predominant role of interstitial oxide ions in the hydration reaction, different from that in the oxygen-deficient oxides, where protons are introduced by dissociative absorption of water molecules by oxygen vacancies. The theoretical calculation indicates that protons in Co-doped LNO prefer to locate between the interstitial oxide ions and unshared apical oxide ions. A trapping effect is found between protons and the oxide ions near Cu, leading to decreased proton mobility. Protonic conductivity at 400-575 °C is then directly measured by a Hebb-Wagner direct current polarization method with La0.99Ca0.01NbO4- δ as the blocking electrode, enabling the observation that Co-doped LNO has the highest protonic conductivity among the samples studied in this work.

Application of Cyclic Voltammetry with W Electrodes for Measurement of High CaO Concentration in Molten CaCl2

Molten CaCl2 is a useful electrolyte for certain pyroprocessing techniques, and the solubility of oxide ions in this salt is a critical characteristic of many of these techniques. CaO is a byproduct of direct oxide reduction (DOR), so the concentration of oxide ions can be used to determine the extent of these reactions. Using cyclic voltammetry (CV) with tungsten electrodes, the CaO concentration in the salt up to approximately 5 wt% was correlated to both oxidation peak height and power density values. This correlation was demonstrated in both equilibrium and transient conditions. CV is a promising method for the in situ real-time monitoring of CaO concentrations in DOR processes.

A dual-electrode oxide ion sensor for molten carbonates

• A simple sensor for detecting O 2– concentration in molten carbonate was proposed. • The sensor is applicable over both wide temperature and O 2– concentration ranges. • A fast response corresponding to varying O 2– activity can be achieved within a few seconds. • The electrochemical sensor is reliable and reusable with an excellent long-term stability. • The sensor can serve as an indicator for O 2– -involved (electro)chemical reactions. The concentration of oxide ions (O 2– ) determines the physicochemical properties of molten carbonates and modulates (electro)chemical reactions. However, it still lacks an efficient and reliable method to measure O 2– concentration in molten carbonates. Herein, we design a dual-electrode sensor to monitor the O 2– content in real time. For sensing O 2– in the target molten medium, we deliberately selected a Ni/NiO redox couple to serve as an O 2– -responding internal reference membrane electrode (RE in ) assembled in an yttrium-stabilized zirconia tube, which is accessible to achieve a stable and excellent response of O 2– from the bulk melt. To measure the membrane potential of RE in that is associated with the O 2– concentration in the bulk melt, we paired a Ag/Ag 2 SO 4 external reference electrode (RE ex ), which can indicate the potential difference between RE in and RE ex by measuring the open circuit potential (OCP), therefore figuring out the O 2– concentration based on Nernst equation. Taking molten Li 2 CO 3 -Na 2 CO 3 -K 2 CO 3 for example, the homemade dual-electrode sensor is well-responsive with a reliable linear correlation coefficient of R 2 = 0.9992 even the O 2– content is as low as 1.27 × 10 −4 mol kg −1 . The proposed dual-electrode gives clues to the rational design of anion sensor for relatively high-temperature systems.

Crystal Structures and Conduction Paths of Sc-Doped CaTiO3 Fast Oxide-Ion Conductors with Orthorhombic Symmetry

The crystal structures and electron density distributions (EDDs) of Ca-deficient Sc-doped CaTiO3 fast oxide-ion conductors, Ca0.97(Ti0.97Sc0.03)O3-δ (CTS3) and Ca0.96(Ti0.9Sc0.1)O3-δ (CTS10), were investigated in the temperature range of 298-1173 K in N2 to analyze the effect of composition on the perovskite structure and oxide-ion transport mechanism. CTS3 and CTS10 exhibited orthorhombic Pnma symmetry in temperature ranges of 298-1173 K and 973-1173 K, respectively, with CTS10 exhibiting lower symmetry and reduction in oxide-ion conductivity below 973 K. The EDDs of CTS3 and CTS10 at 1173 K indicated unique chemical bonds and conduction paths. CTS3 and CTS10 showed covalent bonds between (Ti,Sc) and O1 (or O2) sites. CTS3, with a lower oxide-ion conductivity than that of CTS10, exhibited pseudo-one-dimensional (1D) zig-zag curved conduction paths for oxide-ions along the a-axis, unlike previously reported curved migration paths along the b-axis in CaTiO3, and chemical bonds between Ca and O1 sites, indicating oxide-ion conduction suppression. In CTS10, additional conduction paths were observed along the a-axis, forming three-dimensional (3D) zig-zag curved conduction paths in the ac-plane and along the b-axis, with the weakening of the chemical bonds between the Ca and O1 sites. The oxide-ion conductivity and mobile oxide-ion concentration of CTS10 were 3.6 and 2.0 times those of CTS3, respectively, at 1173 K; the higher oxide-ion conductivity of CTS10 could be attributed to an increase in the mobile oxide-ion concentration and mobility with a 1D to 3D change in the conduction paths and a weakening of chemical bonds between the Ca and O1 sites.

Electrocatalytic Conversion of Methane to Ethylene Utilizing Highly Durable Barium Niobate Perovskites

Pursuing efficient conversion of methane to value-added products such as olefins and aromatics is a prospective use of natural methane feedstocks. The demand for on-site methane conversion has further increased due to the recent discoveries of shale gas reserves. Electrochemical methane conversion provides a means to control the surface oxide ion concentration, aiming to eliminate the over-oxidation of methane while also aiding in methane activation via applied potential. High temperature electrolysis processes provide improved reaction kinetics. Unfortunately, high temperature operation also leads to material degradation via sintering, crystal structure disproportion to thermodynamically more stable phases, and interfacial reactions that reduce performance. We demonstrated that the Sr2Fe1.5Mo0.5O6- d (SFMO) perovskite which was reported with desirable methane activation properties had poor chemical and electrochemical stability as it formed carbonates and coke under methane rich environments.[1][2] Here we present an exciting class of barium niobate perovskite materials with varying levels of Mg and Fe co-doping that show promising catalytic activity towards methane activation in the electrochemical and conventional heterogeneous oxidative coupling environment. The perovskite material was prepared by conventional solid-state methods and by microwave synthesis methods to compare the role of surface area. Thermogravimetric analysis and temperature programmed reaction measurements under methane show superior chemical stability in comparison to SFMO perovskites. These catalysts’ electrochemical properties are evaluated by cyclic voltammetry, impedance spectroscopy, and chronoamperometric measurements coupled with mass spectra analysis that demonstrate durable operation for five continuous days. A maximum ethylene production of 277 mmolcm-2h-1 with a faradaic efficiency of 20% at 1V was obtained. Stability determinations of our perovskite oxide electrocatalysts for EC-OCM offer an excellent example of our approach towards evaluation of materials durability under the highly carburizing environments. These perovskite materials could also serve as a support for a wide variety of catalyst materials for high temperature applications thus opening new possibilities.

Novel molten phase route for composite CO2 separation membranes

Alkali metal nitrates were successfully used as starting chemicals in the production of composite CO2 separation membranes. The easy conversion of nitrates into carbonates after high temperature annealing in CO2 is confirmed using techniques like FTIR (Fourier transform infrared) or selective NO3− electrodes. This conversion shows a step like increase at temperatures in the order of 600 °C, consistent with target utilization temperatures for these membranes. A second but equally relevant consequence of this novel route is the formation of significant concentrations of oxide ions in the molten phase, able to boost the membrane performance, where the ceramic phase modest oxide ion conductivity is rate determining. At 650 °C, a CO2 separation flux enhancement in the order of 60% was reached using nitrates as starting chemicals. A deep analysis of the oxide ion content in molten phases using a variety of analytical techniques, confirmed the specific features of the nitrates as starting chemicals but also showed that even when carbonates are used as precursors, the role of oxide ions in the molten phase can increase significantly the membrane performance.

Generalized Poisson-Nernst-Planck-Based Physical Model of the O2∣LSM∣YSZ Electrode

The paper presents a generalized Poisson-Nernst-Planck model of an yttria-stabilized zirconia electrolyte developed from first principles of nonequilibrium thermodynamics which allows for spatial resolution of the space charge layer. It takes into account limitations in oxide ion concentrations due to the limited availability of oxygen vacancies. The electrolyte model is coupled with a reaction kinetic model describing the triple phase boundary with electron conducting lanthanum strontium manganite and gaseous phase oxygen. By comparing the outcome of numerical simulations based on different formulations of the kinetic Eqs. with the results of EIS and CV measurements we attempt to discern the existence of separate surface lattice sites for oxygen adatoms and surface oxides from the assumption of shared ones. Moreover, we show that the mass-action kinetics model is sensitive to oxygen partial pressure unlike exponential kinetics models. The resulting model is fitted to a dataset of EIS and CVs spanning multiple temperatures and pressures, using various relative weights of EIS and CV data in the fitness function. The model successfully describes the physics of the interface around the OCV.

Investigation of Regeneration Mechanisms of Aged Solar Salt.

The scope of our study was to examine the potential of regeneration mechanisms of an aged molten Solar Salt (nitrite, oxide impurity) by utilization of reactive gas species (nitrous gases, oxygen). Initially, aging of Solar Salt (60 wt% NaNO3, 40 wt% KNO3) was mimicked by supplementing the decomposition products, sodium nitrite and sodium peroxide, to the nitrate salt mixture. The impact of different reactive purge gas compositions on the regeneration of Solar Salt was elaborated. Purging the molten salt with a synthetic air (p(O2) = 0.2 atm) gas stream containing NO (200 ppm), the oxide ion concentration was effectively reduced. Increasing the oxygen partial pressure (p(O2) = 0.8 atm, 200 ppm NO) resulted in even lower oxide ion equilibrium concentrations. To our knowledge, this investigation is the first to present evidence of the regeneration of an oxide rich molten Solar Salt, and reveals the huge impact of reactive gases on Solar Salt reaction chemistry.

Electroanalytical Measurements of Oxide Ions in Molten CaCl2 on W electrode

The electrochemical interaction of oxide ions with tungsten electrodes in molten calcium chloride (CaCl2) was analyzed by combining electroanalytical techniques with X-ray photoelectron spectroscopy. During a cyclic voltammetry (CV) scan, the oxide ions appear to interact with the tungsten working electrode via a multi-step oxidation and reduction process. The overall redox peaks behave reversibly up to 750 mV s−1. This electrochemical process enables the oxide ion concentration to be correlated to CV oxidation peaks. The resulting correlation agrees well (8.8% difference) with back titration measurements and can be used to monitor oxide content in the salt in real-time during CaCl2 based pryoprocesses.

Fundamental analysis for electrochemical removal and monitoring of oxide impurities in lead lithium using LiCl-KCl melt

• The liquid LiPb alloy is expected to be used in the blanket system. • The oxide impurities in the LiPb is forcused in this research. • LiCl-KCl is useful for the transfer of oxide impurities. • The oxide impurities in the molten salt can be extracted by applying voltage. The electrochemical treatment using chloride molten salt was focused as a method for removal and monitoring of oxide impurities in the liquid breeder materials. The anodic reactions on a glassy carbon electrode in a LiCl-KCl eutectic melt contacting with Li-Pb eutectic melt without and with Li 2 O addition were investigated. The transfer of oxide impurities to the molten salt from liquid metal was proved by the change of the concentration of oxide ions in the molten salt estimated from the cyclic voltammetry. The content of oxide impurities in the Li-Pb can be estimated by calculating backward from the transfer ratio and this technique may also be applied to monitoring. The visual observation and the weight loss of the anode indicated that the oxide impurities transferred to the molten salt could be removed as gases such as CO 2 by applying a voltage between an anodic glassy carbon rod in the molten salt and the Li-Pb used as a cathode.

A study of Eu2O3 solubilization in K2SrCl4 melt at 973 K under the action of CCl4 vapor

A comparative study of carbochlorination processes (treatment with CCl4 vapor in argon flow) of K2SrCl4 melt and K2SrCl4+Eu2O3,solid mixture at 973 K was performed by the potentiometric method with the use of Pt(O2)|ZrO2(Y2O3) membrane oxygen electrode as reversible to oxide ion.Solid Eu2O3 interacts with K2SrCl4 melt that results in partial transformation of the oxide into oxochloride, EuOCl (the degree of Eu2O3 transformation is 0.54) and the process is completely suppressed at oxide ion (SrO) concentration ca. 3∙10−3 mol kg-1; here the melt becomes saturated with respect to both Eu2O3 and EuOCl. The course of interaction of Eu2O3 with K2SrCl4 melt at 973 K obeys the Shchukarev equation.The analysis of van’t Hoff diagrams for these processes showed that the stage of Eu2O3 solubilization under the action of CCl4 is clearly detected. The data corresponding to the finishing of Eu2O3 solubilization in K2SrCl4 melt allowed to estimate the solubility product of Eu2O3 as 1.2·10−22 mol5·kg-5 in molality scale and 3.2·10-26 in mole fractions. The corresponding values for EuOCl are 1.47·10-7 mol3·kg-3 (mCl-= 13.1 mol kg-1) or 1.05·10-9 (mole fractions).An application of the Shreder-Le Chatelier equation for the recalculation of some literature data on the solubilization of rare-earth metal oxides and oxochlorides at different temperatures allowed us to compare them with the results obtained in this work. It was confirmed that the running of the carbochlorination process at low oxide ion concentrations was determined by the rare earth oxide (oxochloride) dissolution similarly to the situation observed in other chloride melts where HCl was used as a chlorinating agent. The literature data and data of this work expressed in units of oxoacidity function Ω and reduced to the same temperature (973 K) are in a good agreement.

Structural optical and electrical properties of RE4Zr3O12 (RE = Dy, Y, Er, and Yb) nanoceramics

Concentration of oxide ion vacancies and its ordering in crystalline lattices play an important role in the structural, optical and ionic transport properties of RE2O3–MO2 (RE (Rare earths), M = Ti, Zr, Hf) systems. Rarely investigated rare earth zirconate system, RE4Zr3O12 (RE = Dy, Y, Er, and Yb) exhibiting the polymorphic structural forms, was chosen for the present study. RE4Zr3O12 nanoceramics were prepared through an auto-ignited combustion method; thereafter, dense bulk ceramics were derived from them at relatively low temperatures. X-ray diffraction studies carried out on the nanoceramics as well as bulk ceramics suggest defect fluorite structure for RE = Dy, Y and Er whereas δ-phase rhombohedral structure for RE = Yb ceramics. Extent of oxide ion ordering and the structural variations due to the replacement of rare earth ions in the crystalline lattices were analyzed by Raman and infrared spectroscopy. UV–Visible and photoluminescence spectroscopy were employed to investigate the optical properties of the nanoceramics. Impedance spectroscopic studies carried out on the bulk ceramic materials show that the oxide ion hopping conduction mechanism in the bulk ceramics was affected by the structural factors and free mobile oxide ion concentration. Increase of total electrical conductivity of the dense ceramics with the increase of temperature was in accordance with the Arrhenius relation. Electrical conductivity of fluorites was higher than the δ-phase ceramics, which was attributed to the decreased activation energy and increased available number of mobile oxide ions in the fluorite structure.

PHYSICO-CHEMICAL BASES OF ELECTROLYTIC SYNTHESIS OF CARBON NANOMATERIALS FROM MOLTEN SALTS. Part 1

An analysis of the decomposition potentials of lithium, sodium, potassium, calcium, barium, and magnesium carbonates with different versions of cathode products (elemental carbon, carbon monoxide, metal and carbide) in the range of 300-1900 K showed that for K2CO3 deposition of alkali metal on the cathode is most energetically profitable process at all temperatures. For Na2CO3 it is possible to obtain carbon at T < 1000 K. With temperature increase, the predominant process is the reduction of alkali metal. For Li2CO3, CaCO3, BaCO3, MgCO3 at T < 950 °C carbon deposition will be more advantageous, at higher temperatures reduction up to CO will be more advantageous. The decomposition of CO2 flows at more positive potentials compared with carbonate systems. However, low activity of CO2 in carbonate-containing melts will prevent the significant contribution of this reaction to the electrode process. Thermodynamic calculations of the dependence of the carbon deposition potentials from carbonate anion on the acidity of the melt (concentration of oxide ions) show the possibility of displacing this potential up to 0.8 V by changing the acid-base properties of the melt. On the basis of the analysis of binary phase diagrams, Me–C and MeC–C, criteria for selecting the cathode material for generation of the tubular structure of graphite are established. The diagrams should contain: (1) – solid solutions of C–Me at a temperature of 700–900 °C and sufficient solubility of carbon (up to ~ 1 at.%) in the metal should be observed; (2) – after saturation of the solid solution with carbon, the precipitation (precipitation) of graphite from the metal should occur without the formation of intermediate carbide phases; (3) – in the case of the formation of carbides, the diffusion of carbon in the solid solution С–Ме and in the carbide phase MeС should flow with high speed and quickly reach the concentration of carbon saturation for graphite deposition.

Analysis of phase transition by variation of oxide ion content in BaFe0.9In0.1O3−δ as oxygen storage material using Mössbauer spectroscopy – Discovery of magnetic phase transition with cubic structure maintained

Perovskite-type BaFe0.9In0.1O3−δ (BFI010) with random distribution of oxide ion vacancy was prepared by Pechini method with sintering under O2 flow (BFI010-O2) and N2 flow (BFI010-N2). Although crystal structures of the obtained specimens could be explained as the same cubic perovskite, the large variation in oxide ion vacancy content δ was observed between these specimens. Relationship between chemical state of Fe ions and δ was evaluated using Mössbauer spectroscopy at room temperature. It was revealed that valence of Fe was mixture of Fe3+ with isomer shift, I.S., of 0.260 mm/s and Fe4+ with I.S. of −0.073 mm/s with paramagnetic property in BFI010-O2. Mössbauer spectrum of BFI010-N2 could be explained that only Fe3+ with antiferromagnetic interaction existed, indicating different phases could be obtained by variation of δ in BaFe0.9In0.1O3−δ in spite of the same cubic crystal structure. It was concluded that oxygen storage phenomenon due to redox variation of Fe ions occurred between the two different phases without variation of crystal structure.

High oxide ion conductivity below 500∘C in the garnets LaxY3−xFe5O12+δ

We address the issue of achieving high oxide ion conductivity at low temperatures $(\ensuremath{\le}500{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C})$ in stable electrolytes for solid oxide fuel cell (SOFC) techonology. We report here a high oxide ion conductivity $(\ensuremath{\sim}{10}^{\ensuremath{-}2}\phantom{\rule{0.16em}{0ex}}\mathrm{S}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1})$ in the La substituted yttrium iron garnets $\mathrm{L}{\mathrm{a}}_{x}{\mathrm{Y}}_{3\text{\ensuremath{-}}x}\mathrm{F}{\mathrm{e}}_{5}{\mathrm{O}}_{12+\ensuremath{\delta}}$ at low temperatures $(\ensuremath{\sim}450{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C})$. The judicious substitution of high electropositive $\mathrm{L}{\mathrm{a}}^{3+}$ ions in the yttrium iron garnet $(x\ensuremath{\le}0.45)$ affords continuous and easy oxide ion conduction pathways through polyhedral networks even at a low temperature of $\ensuremath{\sim}127{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$. The conduction pathways have been visualized from the maximum entropy method analyzed soft bond valence sum distribution, obtained from neutron diffraction data. Our study also shows that these iron garnets have high structural stability over a broad range of temperature (at least over $27\text{--}800{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C})$, and compatible thermal expansion coefficient $(\ensuremath{\sim}10.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}{\mathrm{C}}^{\ensuremath{-}1})$ with that of the commonly used interconnect and electrode SOFC materials. We reveal that the oxide ion conduction in the present garnet is based on an excess oxide ion concentration mechanism. The observed high oxide-ion conductivity at low temperatures in the present trivalent substituted garnets is a remarkable finding for the development of an efficient SOFC technology.

Investigation of the course of K2SrCl4 melt deoxidization with CCl4 vapor

The course of deoxidization (removal of oxide ions) of molten K2SrCl4 using tetrachloromethane vapor was investigated by a potentiometric method using Pt(O2)|YSZ oxygen electrode for the detection of current (equilibrium) oxide ion concentration. The course of the chemical stage of the ‘CCl4–O2−’ interaction in the studied melt at 923, 973 and 1023 K is characterized by pseudo-second order kinetics (with respect to O2−). The values of the rate constants determined at the said temperatures give the possibility to estimate the activation energy of the carbochlorination process as 208 kJ mol−1, which agrees with the similar parameters for other studied chloride mixtures. The final oxide ion concentration after the purification decreases from 4.90 × 10−7 mol kg−1 at 923 K to 1.23 × 10−8 mol kg−1 at 1023 K.

Study of the carbohalogenation process in molten KCl–NaCl equimolar mixture

The process of the removal of oxide ions to the gaseous phase from molten KCl–NaCl equimolar mixture using tetrachlorometane vapor was studied by a potentiometric process using Pt(O2)|YSZ oxygen electrode for the detection of oxide ion concentration. The chemical stage of the interaction of CCl4 with oxide ions (carbohalogenation) in the molten KCl–NaCl equimolar mixture at 953, 973, 1000 and 1023 K is characterized by second order kinetics with respect to oxide ions. The temperature dependence of the rate constant is described by the equation: ln k = 43 (±4) − (24,800 ± 3800) T−1, which permits the estimation of the activation energy as 206 ± 30 kJ mol−1. The purification limit of molten KCl–NaCl equimolar mixture from oxygen-containing admixtures in the studied temperature range decreases from 2 × 10−9 to 3 × 10−10 mol kg−1 of O2− with the rise of the melt temperature from 953 to 1023 K.

High-temperature and Corrosion Behavior of Nitrate Nitrite Molten Salt Mixtures Regarding their Application in Concentrating Solar Power Plants

Abstract We deeply investigated the chemical reaction network of molten nitrate / nitrite salt mixtures at high temperatures (> 450 °C) and proved530 °C as maximum operating temperature of HITEC® in CSP application with potential for further temperature increase by implementation of technical measures. Particularly the level of oxide ion concentration and the gas atmosphere havesignificant effects on thermal stability and corrosion behavior. It could be shown that the corrosive depletion of standard steels is within technical limits up to the thermal stability limit of the salt mixture. Low chloride concentration of the melt is crucial for low corrosivity.

Interaction of oxide species with CCl4 in liquid BaCl2-KCl (0.26:0.74)

Kinetic parameters of ‘oxide ion – CCl4’ interaction (carbochlorination) on the background of liquid BaCl2-KCl (0.26:0.74) in 943–1023 K temperature range have been determined by a potentiometric method. A cell with the membrane oxygen electrode Pt(O2)|ZrO2(Y2O3) was used for detection of O2‒ concentration during the interaction. The chemical reaction in the solution is found to become limiting at relatively low oxide ion concentrations (less than 10−5 mol·kg−1), and it is characterised by the second kinetic order with respect to oxide ion. The purification process stops at equilibrium concentrations of O2− within (1 – 2)·10−7 mol·kg−1. The polythermal study allows to estimate the activation energy of the carbochlorination as 238 ± 30 kJ·mol−1.

Oxidative parameters and expression of 70kDa heat shock proteins in pig heart tissue after transport and slaughter.

In view of the significant role of Hsp70 in protecting the organism against the destructive effects of stress, and the possibility of using this protein as a marker of the infarction process in the heart, the aim of this study was to conduct an evaluation of the expression of 70kDa heat shock proteins (Hsp70) and the concentration of TBARS (thiobarbituric acid reactive substances) and nitric oxide ions (NO), determined as nitrite ions, as markers of oxidative stress in hearts obtained from healthy pigs following slaughter and pigs which had died during or immediately after transport with symptoms of sudden cardiac death. The material consisted of hearts obtained from 90 pigs following slaughter and from pigs which had died. Oxidative stress was determined in heart lysates based on the concentration of TBARS and nitrite ions. Expression and concentration of Hsp70 were determined using SDS-PAGE, Western blotting, and ELISA. Expression of Hsp70 was observed in hearts lysates obtained from slaughtered pigs and from those which had died with symptoms of sudden death. The strongest reaction in the Western Blotting was noted in hearts lysates from pigs with no pathological changes. The highest TBARS concentration was observed in lysates from hearts in pigs which had died during or immediately after transport. The highest concentration of NO ions, determined as nitrite ions, was noted in hearts from pigs with myocardial infarction lesions. The significant decrease observed in Hsp70 concentration in heart tissue obtained from the pigs which had died in comparison to the hearts from healthy pigs indicates the important role of this protein in protecting the heart muscle against the destructive effects of stress, which limits the occurrence of post-stress cardiomyopathy in pigs following transport.