Oxygen Partial Pressure Gradient Research Articles

An Arteriovenous Bioreactor Perfusion System for Physiological In Vitro Culture of Complex Vascularized Tissue Constructs

Background: The generation and perfusion of complex vascularized tissues in vitro requires sophisticated perfusion techniques. For multiscale arteriovenous networks, not only the arterial, but also the venous, biomechanical and biochemical conditions that physiologically exist in the human body must be accurately emulated. For this, we here present a modular arteriovenous perfusion system for the in vitro culture of a multi-scale bioartificial vascular network. Methods: The custom-built perfusion system consisted of two circuits: in the arterial circuit, physiological arterial biomechanical and biochemical conditions were simulated using a modular set-up with a pulsatile peristaltic pump, compliance chambers, and resistors. In the venous circuit, venous conditions were emulated accordingly. In the center of the system, a bioartificial multi-scale vascularized fibrin-based tissue was perfused by both circuits simultaneously under biomimetic arteriovenous conditions. Culture conditions were monitored continuously using a multi-sensor monitoring system. Results: The physiological arterial and venous pressure- and flow-curves, as well as the microvascular arteriovenous oxygen partial pressure gradient, were accurately emulated in the perfusion system. The multi-sensor monitoring system facilitated live monitoring of the respective parameters and data-logging. In a proof-of-concept experiment, vascularized three-dimensional fibrin tissues showed sustained cell viability and homogenous microvessel formation after culture in the perfusion system. Conclusions: The arteriovenous perfusion system facilitated the in vitro culture of a multiscale vascularized tissue under physiological pressure-, flow-, and oxygen-gradient conditions. With that, it presents a promising technique for the in vitro generation and culture of complex large-scale vascularized tissues.

Multiplying Oxygen Permeability of a Ruddlesden-Popper Oxide by Orientation Control via Magnets.

Ruddlesden-Popper-type oxides exhibit remarkable chemical stability in comparison to perovskite oxides. However, they display lower oxygen permeability. We present an approach to overcome this trade-off by leveraging the anisotropic properties of Nd2 NiO4+δ . Its (a,b)-plane, having oxygen diffusion coefficient and surface exchange coefficient several orders of magnitude higher than its c-axis, can be aligned perpendicular to the gradient of oxygen partial pressure by a magnetic field (0.81 T). A stable and high oxygen flux of 1.40 mL min-1 cm-2 was achieved for at least 120 h at 1223 K by a textured asymmetric disk membrane with 1.0 mm thickness under the pure CO2 sweeping. Its excellent operational stability was also verified even at 1023 K in pure CO2 . These findings highlight the significant enhancement in oxygen permeation membrane performance achievable by adjusting the grain orientation. Consequently, Nd2 NiO4+δ emerges as a promising candidate for industrial applications in air separation, syngas production, and CO2 capture under harsh conditions.

Multiplying Oxygen Permeability of a Ruddlesden‐Popper Oxide by Orientation Control via Magnets

AbstractRuddlesden‐Popper‐type oxides exhibit remarkable chemical stability in comparison to perovskite oxides. However, they display lower oxygen permeability. We present an approach to overcome this trade‐off by leveraging the anisotropic properties of Nd2NiO4+δ. Its (a,b)‐plane, having oxygen diffusion coefficient and surface exchange coefficient several orders of magnitude higher than its c‐axis, can be aligned perpendicular to the gradient of oxygen partial pressure by a magnetic field (0.81 T). A stable and high oxygen flux of 1.40 mL min−1 cm−2 was achieved for at least 120 h at 1223 K by a textured asymmetric disk membrane with 1.0 mm thickness under the pure CO2 sweeping. Its excellent operational stability was also verified even at 1023 K in pure CO2. These findings highlight the significant enhancement in oxygen permeation membrane performance achievable by adjusting the grain orientation. Consequently, Nd2NiO4+δ emerges as a promising candidate for industrial applications in air separation, syngas production, and CO2 capture under harsh conditions.

Diffusion Barriers Minimizing the Strength Degradation of Reactive Air Brazed Ba0.5Sr0.5Co0.8Fe0.2O3-δ Membranes during Aging.

The separation of oxygen from air by means of inorganic ceramic membranes requires gas-tight ceramic-metal joints that enable reliable permeation operation in the oxygen partial pressure gradient at 850 °C. Reactive air brazing is a promising method to solve this challenge. However, reactive air brazed BSCF membranes suffer from a significant strength degradation that is caused by unhindered diffusion from the metal component during aging. In this study, we investigated how diffusion layers applied on the austenitic steel AISI 314 influence the bending strength of BSCF-Ag3CuO-AISI314 joints after aging. Three different approaches were compared as diffusion barriers: (1) aluminizing via pack cementation, (2) spray coating with NiCoCrAlReY, and (3) spray coating with NiCoCrAlReY and an additional 7YSZ top layer. Coated steel components were brazed to bending bars and aged for 1000 h at 850 °C in air prior to four-point bending and subsequent macroscopic as well microscopic analyses. In particular, coating with NiCoCrAlReY showed low-defect microstructures. The characteristic joint strength was raised from 17 MPa to 35 MPa after 1000 h aging at 850 °C. In addition, the dominant delamination fracture between the steel and the mixed oxide layer, observed in the reference series with uncoated steel, could be replaced by mixed and ceramic fractures of higher strength. The effect of residual joint stresses on the crack formation and path is analyzed and discussed. Chromium poisoning could no longer be detected in the BSCF, and interdiffusion through the braze was effectively reduced. Since the strength degradation of reactive air brazed joints is mainly caused by the metallic joining partner, the findings on the effect of the diffusion barriers in BSCF joints might be transferred to numerous other joining systems.

Multi-scale simulation of the fracture behavior of non-stoichiometric gadolinia-doped ceria solid electrolytes under the coupled mechanical and electrochemical field

Solid oxide fuel cell (SOFC) works in a complex working environment, which is affected by many factors such as temperature, load and electrochemical reaction. When there are cracks in the material, the multi-field coupling effect will cause the electrolyte performance degradation, even failure and damage. In this paper, the coupling effects of mechanical and electrochemical field on mechanical behavior of gadolinia-doped ceria (GDC) electrolyte are investigated by using the Atom-to-Continuum (AtC) multi-scale method combining molecular dynamics (MD) and finite element method (FEM). Based on the electrochemomechanical coupling theory, we derive the defect diffusion equation of the finite element form. The non-stoichiometry of the cracked GDC electrolyte is calculated, and it is found that the stress concentration at the crack tip will induce non-stoichiometric effects, causing further concentration of oxygen vacancy defects at the crack tip. Subsequently, the effect of electrochemomechanical coupling effect on the fracture toughness of GDC electrolyte is studied by using the AtC multi-scale method. At 800°C under oxygen partial pressure logPO2=−22, this multi-field coupling effect reduces the fracture toughness of 10GDC and 20GDC by 16.13% and 23.33%, and this effect is more apparent with the increase of oxygen partial pressure gradient and external load.

Multifactor theoretical study on ionic transport numbers of mixed oxygen ionic-electronic conducting oxides determined by the electromotive force method

The electromotive force (EMF) method is widely applied to measure the ionic transport numbers (ti) of mixed oxygen-ionic and electronic conducting oxides. However, the results determined by the EMF method are the average/apparent ti (tiapp), subjected to a given gradient of oxygen partial pressure (PO2), rather than ti at a specific PO2, making it challenging to reveal the accurate properties of materials. In this study, to clarify the impact of this issue, a precise defect distribution model of Gd doped CeO2 (GDC), considering defect equilibrium and local charge neutrality, is built. A multifactor theoretical analysis is conducted to compare tiapp and ti of the membrane at different sides. The modeling results reveal that a thick membrane is recommended for avoiding the influence of membrane thickness on tiapp. When there is a large difference of PO2 between two sides of the GDC membrane (PO2highPO2PO2lowPO2>1025), tiapp is inclined to ti at the side of high PO2. Only when both sides of the GDC membrane are reducing atmosphere, tiapp of the modified EMF method is approximately the average of ti at both sides. The findings of this study are instructive for the rational application of EMF methods.

Optimization of an ion transport membrane reactor system for syngas production

Ion transport membrane (ITM) reactor has been regarded as a promising novel technology for syngas production. To commercialize this technology, overall system designs and operating conditions should be optimized.In this study, a mathematical analysis of the ITM reactor system has been performed using Aspen Plus® to optimize its operations. Two-dimensional ITM reactor model developed in our previous study has been integrated into a system model to capture the system performance. The effects of air flow rates and gas inlet temperatures, which are the dominant factors determining both the ITM reactor performance and the system power consumption, have been investigated. To optimize the ITM reactor system, overall system power consumptions have been analyzed under various operating conditions. An optimal operation map has been presented that minimizes the power consumption and maximizes the syngas production. Simulation results show that dominant factors affecting oxygen permeability change according to the oxygen partial pressure gradient. When the local oxygen partial pressure gradients exceed 2, temperature is the most dominant factor. However, for local oxygen partial pressure gradients lower than 2, the oxygen partial pressure gradient is in turn the dominant factor. This study specifically provides the basic insight to establish the operating point and to grasp the effect of the internal oxygen partial pressure for commercialization of this technology.

Blood Supply and Oxygenation Status of the Liver: From Physiology to Malignancy.

To maintain a multitude of vital functions, blood flow to the normal liver and the hepatic oxygenation status has to be kept on a high level (1.0-1.2mL/g/min and 30-40mmHg, respectively). There is a longitudinal oxygen partial pressure (pO2) gradient within the liver sinusoids between periportal inflow and outflow into the central vein leading to a zonation of the O2 status, which is associated with a zoning of liver functions. Oxygenation of metastatic lesions of colorectal cancers in the liver is poor due to a dysfunctional vascularity and inadequate blood supply. Hepatocellular carcinomas (HCCs) are highly vascularised (arterialised), metabolically very active and present with a predominantly arterial blood supply. HCCs are generally believed to be very hypoxic. However,confirmation of severe hypoxia based on reliable, direct pO2 measurements in HCCs is still missing.

Blood Flow and Respiratory Gas Exchange in the Human Placenta at Term: A Data Update.

Reliable measurements using modern techniques and consensus in experimental design have enabled the assessment of novel data sets for normal maternal and foetal respiratory physiology at term. These data sets include (a) principal factors affecting placental gas transfer, e.g., maternal blood flow through the intervillous space (IVS) (500mL/min) and foeto-placental blood flow (480mL/min), and (b) O2, CO2 and pH levels in the materno-placental and foeto-placental circulation. According to these data, the foetus is adapted to hypoxaemic hypoxia. Despite flat oxygen partial pressure (pO2) gradients between the blood of the IVS and the umbilical arteries of the foetus, adequate O2 delivery to the foetus is maintained by the higher O2 affinity of the foetal blood, high foetal haemoglobin (HbF) concentrations, the Bohr effect, the double-Bohr effect, and high foeto-placental (=umbilical) blood flow. Again, despite flat gradients, adequate CO2 removal from the foetus is maintained by a high diffusion capacity, high foeto-placental blood flow, the Haldane effect, and the double-Haldane effect. Placental respiratory gas exchange is perfusion-limited, rather than diffusion-limited, i.e., O2 uptake depends on O2 delivery.

The thermal tolerance of a tropical population of blue crab (Callinectes sapidus) modulates aerobic metabolism during hypoxia.

The blue crab Callinectes sapidus is a widespread ectothermic species that supports large fisheries. Physiology of temperate and subtropical populations of blue crabs are well studied; however, a lack of information exists on tropical populations. Given the low locomotion capabilities of C. sapidus adult blue crabs, natural selection should favor traits that shape a particular thermal niche reflected through tolerance modulation to dissolved oxygen (DO). This study was designed to evaluate the thermal window and hypoxia sensitivity of the blue crab population in the southern Gulf of Mexico. The effect of acclimation temperatures from 20°C to 34°C on thermal preference (TP), critical thermal limits (CT), and thermal metabolic scope (TMS) was assessed in normoxia. Metabolic rate regulation over oxygen partial pressure (pO2) gradient was evaluated through oxygen consumption measurements at different degrees of acute hypoxia. Callinectes sapidus was observed tending to specialize towards higher temperatures, showing a mean TP from 26°C to 33°C. The lowest performance of aerobic pathways was observed at the coldest regimes and the highest at the warmest ones with mean TMS value being 35 % greater at 34°C than 20°C. Patterns for metabolic regulation were dependent on the interaction between environmental temperature and DO, in which the interval from 29°C to 34°C provoked a 50 % reduction in oxygen consumption when exposed to ∼20% air saturation levels. The results obtained showed that blue crabs distributed in the southern Gulf of Mexico could be close to their oxygen-temperature tolerance limits, which has important implications when climate change effects on species re-distribution is considered.

Demonstration of a ceria membrane solar reactor promoted by dual perovskite coatings for continuous and isothermal redox splitting of CO2 and H2O

The direct one-step CO2 and H2O splitting using an oxygen-transport membrane (OTM) reactor was investigated as a potentially ideal way to generate renewable fuels from concentrated solar energy. The solar-driven thermolysis of CO2 (or H2O) was promoted by in-situ oxygen removal across nonstoichiometric ceria-based membranes. A new solar membrane reactor integrating a tubular densified membrane made of either pure ceria or perovskite-coated ceria was designed and operated under high-flux concentrated solar radiation. A continuous flow of inert gas on the permeate side was used to create the required oxygen partial pressure gradient (driving force) and ensure continuous oxygen permeation via oxygen ion diffusion across the densified ceria membrane. The continuous OTM solar operation at high temperature was demonstrated through testing under various operating conditions. The CO and O2 production rates were sharply enhanced by increasing the operating temperature (up to 1550 °C). The increase of CO2 concentration or oxidant gas flow rate also enhanced the process performance. Unprecedented fuel production rates (>0.07 μmol s−1 cm−2 at 1550 °C) were achieved with a pure CO2 stream on the feed side and flowing Ar on the sweep side of the reactive ceria membrane. An original composite membrane integrating two different perovskite coatings on each side of the ceria membrane, with a sandwich-like structure, was designed and tested under concentrated sunlight. Thin layers of La0.5Sr0.5Mn0.9Mg0.1O3 on the inner side and Ca0.5Sr0.5MnO3 on the outer side were added to enhance oxygen ion transfer. With such a membrane configuration, a remarkable production of CO (>0.13 μmol s−1 cm−2) and oxygen (with CO:O2 ratio of 2) was obtained simultaneously, respectively on the inner and outer sides of the OTM. These results outperform the production rates achieved with the uncoated ceria membranes, and demonstrate the benefits of using composite membranes composed of a densified core material coated with (or sandwiched in between) redox active perovskite materials.

Thermochemical solar-driven reduction of CO2 into separate streams of CO and O2 via an isothermal oxygen-conducting ceria membrane reactor

• Demonstration of single-step CO 2 thermolysis in a novel solar-driven membrane reactor. • In-situ separation of CO and O 2 via lattice oxygen transfer through ceria dense membrane. • Continuous and isothermal operation of the MIEC tubular membrane reactor at 1450–1550 °C. • Increasing the temperature, CO 2 concentration or flow rate enhanced CO and O 2 production rates. • The fuel production rate was up to 4.26 μmol/cm 2 /min at 1550 °C under pure CO 2 feeding. CO 2 single-step thermolysis was achieved using oxygen permeable MIEC (mixed ionic-electronic conducting) membranes made of ceria for separate production of CO on the feed side and O 2 on the sweep side. The CO 2 -dissociation reaction was driven by concentrated solar energy as a renewable thermal energy source and by applying a chemical potential gradient between both membrane sides. A continuous oxygen transfer across the membrane was achieved thanks to a flow of inert gas on the permeate side. This created the required oxygen partial pressure gradient and favored oxygen permeation via oxygen ion diffusion through the ceria membrane thickness. A novel solar chemical reactor integrating the reactive ceria membrane was designed and tested under real concentrated solar radiation, with operating temperatures up to 1550 °C. The reactive part of the tubular redox membrane was located inside a well-insulated cavity receiver for homogeneous heating, which was fed with a carrier argon flow on the sweep side to facilitate the transport and removal of the permeated oxygen. The dynamic response of the solar fuel production upon changing the operating conditions (temperature, CO 2 mole fraction, and feed gas flow rate) in the membrane reactor was investigated by quantifying the evolved gas production rates. Continuous CO 2 dissociation was achieved on the feed side inside the tubular membrane with in-situ spatial separation of O 2 and CO streams across the membrane. Reliable solar membrane reactor operation under real concentrated sunlight was successfully demonstrated for the first time, with stable and unprecedented CO production rates up to 0.071 μmol/cm 2 /s at 1550 °C and CO/O 2 ratio of 2.

Inhibiting in situ phase transition in Ruddlesden-Popper perovskite via tailoring bond hybridization and its application in oxygen permeation

Inhibiting in situ phase transition in Ruddlesden-Popper perovskite via tailoring bond hybridization and its application in oxygen permeation

Investigation of cardiorespiratory effects of the selective 5-HT4 agonist BIMU-8 in etorphine-immobilised goats (Capra aegagrus hircus) in a randomized, blinded and controlled trial.

Opioid-induced respiratory compromise remains a significant challenge in etorphine-immobilised wildlife. Serotonergic agonists offer a potential avenue for preventing or treating opioid-induced respiratory compromise. We therefore aimed to determine whether the selective 5-hydroxytryptamine receptor 4 (5-HT4) agonist, BIMU-8, reverses opioid-induced respiratory compromise in etorphine-immobilised goats. Seven healthy adult goats were immobilised with etorphine, then treated with BIMU-8 or sterile water 5 minutes later in a randomised, prospective cross-over study. Cardiorespiratory variables were measured at 1-minute intervals from 4 minutes before etorphine to 15 minutes after its administration. Arterial blood gas analyses were also performed before and after etorphine administration and the respective treatments. Intravenous injection of BIMU-8 attenuated etorphine-induced respiratory compromise, as indicated by improvements, compared to baseline and between treatments, in respiratory rate (fR ), peripheral arterial blood oxygen saturation (SpO2 ), partial pressure of arterial oxygen (PaO2 ) and the alveolar-arterial oxygen partial pressure gradient (P(A-a)O2 ). BIMU-8 caused an increase in heart rate and a temporary decrease in arterial blood pressure. Mild movements and slight muscle spasm occurred but BIMU-8 did not reverse immobilisation. Our results indicate that BIMU-8 may be a potential drug candidate for the treatment, or prevention, of etorphine-induced respiratory compromise in immobilised ungulates.

Oxygen permeation and oxidative coupling of methane with NiFe2O4-Gd0.1Ce0.9O2-δ composite membrane

Oxygen permeability and oxidative coupling of methane (OCM) characteristics of a 30 vol.% NiFe2O4-70 vol.% Gd0.1Ce0.9O2-δ (NFO-GDC) composite membrane were systematically investigated by varying operational conditions for oxygen permeation and OCM experiments. The NFO-GDC membrane showed the maximum oxygen permeation flux of 2.24 mL∙cm−2∙min−1 under an Air/He gradient at 900 °C, and flux increased with increasing oxygen partial pressure gradient in the order He < CH4 < H2. The maximum OCM yield and C2H4/C2H6 ratio were observed at 900 °C and for CH4 flowing at 12.5 mL∙min-1, respectively, and the yield and ratio both increased with increasing temperature in the range 700–900 °C. The overall coupling yield was notably enhanced by applying a Mn/Na2WO4/SiO2 catalyst to the permeate side of the composite membrane. The NFO-GDC membrane with the Mn/Na2WO4/SiO2 catalyst exhibited the maximum yield and a C2H4/C2H6 ratio of 8.6% and 3.21, respectively.

Transport Properties of Film and Bulk Sr0.98Zr0.95Y0.05O3−δ Membranes

In electrode-supported solid oxide fuel cells (SOFCs) with a thin electrolyte, the electrolyte performance can be affected by its interaction with the electrode, therefore, it is particularly important to study the charge transport properties of thin electrode-supported electrolytes. The transport numbers of charged species in Ni-cermet supported Sr0.98Zr0.95Y0.05O3−δ (SZY) membranes were studied and compared to those of the bulk membrane. SZY films of 2.5 μm thickness were fabricated by the chemical solution deposition technique. It was shown that the surface layer of the films contained 1.5–2 at.% Ni due to Ni diffusion from the substrate. The Ni-cermet supported 2.5 μm-thick membrane operating in the fuel cell mode was found to possess the effective transport number of oxygen ions of 0.97 at 550 °C, close to that for the bulk SZY membrane (0.99). The high ionic transport numbers indicate that diffusional interaction between SZY films and Ni-cermet supporting electrodes does not entail electrolyte degradation. The relationship between SZY conductivity and oxygen partial pressure was derived from the data on effective conductivity and ionic transport numbers for the membrane operating under two different oxygen partial pressure gradients—in air/argon and air/hydrogen concentration cells.

Determination of Oxygen Diffusion and Surface Exchange Coefficients of Mixed Ionic-Electronic Conductors by Oxygen Semi-Permeation Methods

The understanding of oxygen transport mechanisms through mixed ionic-electronic conductors is of great interest for the development of electrochemical devices at high temperature for energy conversion applications. This study is focused on the determination of two coefficients—the oxygen diffusion coefficient and the surface exchange coefficient which are key parameters for the electrochemical performance of a material. These coefficients can be largely impacted by the measurement conditions. The oxygen semi-permeation method is an adequate method to determine these two fundamental coefficients close to the working conditions of the material, i.e., under small or large oxygen partial pressure gradients.

Breathing with fins: do the pectoral fins of larval fishes play a respiratory role?

Convective water flow across respiratory epithelia in water-breathing organisms maintains transcutaneous oxygen (O2) partial pressure (Po2) gradients that drive O2 uptake. Following hatch, larval fishes lack a developed gill and the skin is the dominant site of gas transfer, yet few studies have addressed the contribution of convective water flow to cutaneous O2 uptake in larvae. We hypothesized that the pectoral fins, which can generate water flow across the skin in larvae, promote transcutaneous O2 transfer and thus aid in O2 uptake. In zebrafish (Danio rerio), the frequency of pectoral fin movements increased in response to hypoxia at 4 days postfertilization (dpf), but the response was blunted by 15 dpf, when the gills become the dominant site of O2 uptake, and was absent by 21 dpf. In rainbow trout (Oncorhynchus mykiss), Po2 measured at the skin surface of ventilating larvae was lower when the pectoral fins had been surgically removed, directly demonstrating that fins contribute to convective flow that dissipates cutaneous Po2 boundary layers. Lack of pectoral fins compromised whole animal O2 consumption in trout during hypoxia, but this effect was absent in zebrafish. Overall, our findings support a respiratory role of the pectoral fins in rainbow trout, but their involvement in zebrafish remains equivocal.

Oxygen permeation through single-phase perovskite membrane: Modeling study and comparison with the dual-phase membrane

Dual-phase Ce0.85Sm0.15O1.925-Sm0.6Sr0.4Al0.3Fe0.7O3-δ (SDC-SSAF) mixed ionic-electronic conducting (MIEC) membrane, which is highly stable in CO2-rich atmosphere, is a promising candidate for oxyfuel applications. Here, the oxygen permeation behavior of the single-phase perovskite Sm0.6Sr0.4Al0.3Fe0.7O3-δ (SSAF) membrane is analyzed in comparison to that of SDC-SSAF. The oxygen permeation resistances and kinetic constants of a 0.5 mm-thick SSAF disk were regressed using the Zhu model. At 950 °C and under an oxygen partial pressure (PO2) gradient of 0.21 bar/0.02 bar, the characteristic thickness (Lc) was 0.443 mm. Oxygen permeation in SSAF is generally limited by a mixture of surface exchange reactions and bulk diffusion between 800 and 950 °C at 0.21 bar/0.02 bar (feed/permeate). Overall, temperature is more dominant than PO2 gradient to enhance the oxygen permeation flux. A surface exchange-bulk diffusion transition region that exists between 850 and 875 °C in SDC-SSAF case is absent in SSAF case since oxygen permeation through SSAF is governed by mixed bulk diffusion and surface exchange.

Structure and electrical properties of YSZ-rGO composites and YSZ ceramics, obtained from composite powder

Despite zirconia based ceramics is technologically important and applied as a solid electrolyte, the studies for new compositions with enhanced performance are carried out continuously. Zirconia-graphene composites are regarded as promising oxygen transport membranes having a cross-flow of ionic and electronic charge carriers under oxygen partial pressure gradient and as an alternative to perovskite-based SOFC interconnects. In the work 92ZrO2-8Y2O3 (mol.%, YSZ) ceramics and YSZ-rGO composite ceramics (where rGO is reduced graphene oxide) were obtained from composite precursors by the calcination at 1823 K in air and in vacuum, respectively. In order to determine the optimal amount of rGO addition to the ceramic precursor simple mathematical model was suggested for the first time which is scalable for any ceramics-graphene derivative and metal-graphene derivative systems. Using SEM, EDX, XRD, Raman spectroscopy and Impedance spectroscopy data the effect of rGO and the annealing ambiance on the structure, temperature dependencies of grain and grain boundary conductivities of YSZ ceramics rGO-YSZ and composites were revealed for the first time. The rGO additive acts as grain growth inhibitor, which is completely removed from ceramics during annealing in air resulting in ceramics with the refined microstructure and coinciding temperature dependencies of grain and grain boundary conductivities in all temperature range. Vacuum annealing results in YSZ-rGO composites with high ionic conductivity and high crystallinity.